Tracker vs. No Tracker for ASTROPHOTOGRAPHY (Shooting the Pleiades)

It's a beautiful winter night here in New  England and if I look due east I can very   quickly find one of my favorite deep sky objects.  The Pleiades star cluster is one of the only deep   sky objects that most people can spot just with  the naked eye. It typically doesn't even require   star hopping to find. Just look in the right  direction (for us in the northern hemisphere   right now that would be east at nightfall)  and look for a compact little dipper of stars.   And if you're still having trouble finding it  look for Orion's belt which is you know really   evident and make an imaginary line between Orion's  belt and Aldebaran which is the brightest star   in Taurus and then just keep following that  imaginary line until you find the Pleiades.   If you have exceptional eyesight and if you you've  allowed your eyes to adapt under a very dark sky   you may see seven or even more stars in the  cluster. Here on the East Coast of the US   typically i see at most six stars. But tonight  instead of just looking at it, which is fun,   we're gonna photograph it and we won't just  be photographing the stars themselves but   the beautiful blue reflection nebula that  is intertwined all around the star cluster.   A reflection nebula is literally interstellar dust  lit up by starlight and the pleiades are very hot   B-type stars that shine blue which is why  the Pleiades reflection nebula takes on its   characteristic electric blue color seen here.  We will photograph the Pleiades with a stock   10 year old DSLR, the Canon 60d right here and a  telephoto lens with 200 millimeter focal length.   To make this even a bit more fun though i'm going  to show photographing the Pleiades two ways:   First just on a stationary tripod  like this with no star tracking   and Second with a popular star tracker  called the Sky-watcher Star Adventurer.   We will compare all aspects of the  two ways of photographing the cluster,   as well as the final results, in a  showdown of: tracker versus no tracker.   Hello, my name is Nico Carver and i'm an  astrophotographer astrophotography simply   means photographing the night sky and there are  many different ways to go about it tonight i'm   going to go over the steps of photographing  the pleiades in two common ways first with   just my camera and lens on a fixed tripod and  second i'm going to add a star tracker device   in between the tripod and the tripod's ball head  and this device is going to slowly counteract the   earth's rotation just by slowly moving the camera  like this and this will allow us to shoot longer   exposures than we could on a fixed tripod we're  going to capture a total of 30 minutes with each   setup process them the exact same way and then  compare the results at the end which should be   interesting before we get started i just want to  very quickly say that this channel is supported by   my patrons over on Patreon if you'd like to join  it starts at just one dollar a month and i truly   appreciate all the support that i get over there  we're going to start tonight with an overview   by going through just quickly what's the same and  what's different about shooting the pleiades with   a star tracker versus without one just on a tripod  if you don't understand all this terminology now   uh and you're new to astrophotography don't worry  because after this overview i'm gonna explain   everything in depth when we go through step by  step okay so the first thing in the overview is   we need a dark moonless sky this is really  a necessity for a blue reflection nebula so   yes right now we are shooting from a dark sky  location on new moon with both setups number   two camera settings we want raw file format no  noise reductions no lens corrections no auto   rotate all of that any camera settings other than  exposure length we're going to set the exact same   number three polar alignment and balance this  is something we only have to do with the star   tracker setup and these techniques do require  a bit of practice and time to get down i want   to emphasize though that they are necessary with  the tracker you can't skip them but i will say the   wider your lens the less accurate you can be with  your polar alignment for instance if i was using a   24 millimeter lens rather than a 200 millimeter  lens then a rough puller alignment even with a   laser pointer would be fine but at 200 millimeters  i really want to take my time at the polar scope   and get this polar alignment step as precise  as i can to get good results with a tracker   number four focus i'm not going to sugarcoat  it focusing on the stars is difficult it's   going to be more difficult than focusing  during the day you can't use autofocus   one thing that makes it a little easier is an  inexpensive Bahtinov mask and i'll show that but   focusing is going to be basically the same with  both setups the only thing with the star tracker   is you have to be careful when focusing not to  bump your tripod and mess up your puller alignment   number five exposure length this is a the biggest  difference probably to calculate exposure length   with no tracker but just on a tripod we're going  to use the NPF rule which i've talked about in   other videos and that's going to tell us at 200  millimeters we want to take one second exposures   with a tracker instead i usually do tests and  and i started around 30 seconds if 30 seconds   looks good i look at the histogram i'll just  go with that if i if i push it to one minute   and the stars aren't just round then i'll then  i'll back down to 30 seconds it's it's it's more   of a trial and error process okay and the number  six is number of exposures or we also call these   lights and here again it's a big difference when  you do deep sky to photography you typically take   many exposures of this of the deep sky object and  you stack all of these exposures or light frames   same thing together to bring down the noise  and to make this comparison fair we're going   to stack enough lights to get to 30 minutes total  integration on each setup but to get there without   a tracker at just one second each it's going to  take about 2 000 lights while to get there with   a tracker at 30 seconds each let's say it'll  only take 60 lights number seven calibration   frames bias darks and flats if you haven't  heard these terms before don't worry we're   going to go over exactly what they mean but we  want at least 40 of each kind these are going to   be take them the exact same way with both setups  the only difference is with the tracker the darks   will take a little longer to create because  they have to match the length of the lights   and finally processing we're going to do the exact  same so i'm only going to show it once and then we   can compare the results at the end and see if we  can see any difference between the tracked results   versus the untracked results given 30 minutes  total integration on both so that was just a quick   overview of what this video is now i'm gonna jump  into each of these eight topics in order and show   you how to do them in detail so you can follow  along and do this yourself when they're done the   same way with each setup like calibration frames  are gonna be done the same way then i'm only gonna   show it once but whenever there are differences  i'm going to show it first with the tracker setup   and then with the no tracker setup and so we  can compare and contrast any differences in   using these two different systems the first step  in our adventure of photographing the pleiades   is for both setups we want a dark moonless clear  sky and to find such a sky let's look at some free   websites i use to plan out my night the first  one is light pollution map dot info and i've   pulled it up right here it gives you a pretty good  general idea of where dark skies may be located in   your area so it has a full world map you can  just drag it around you can zoom in and out and you can search for your area  right up here under search places   it uses satellite data so this is a particular  survey called the world atlas 2015 that's the   default one on here i typically switch between  that one and just whatever the latest survey is   and they give you slightly different colors but  the key thing is that cooler colors like blue   and black um and green are your darker skies and  warmer colors like yellow orange red and pink   and white are your light polluted skies and so you  can see here these are cities this is the city of   boston this is the city of new york i live right  here in Somerville Massachusetts so close to the   worst location you can find for light pollution  so what i typically do is i drive a couple hours   away from here to a green zone or a blue zone if  i can to do my astrophotography one thing i want   to point out is just because a dark site exists  near you so like we could go out here and and   know that we're under a dark sky doesn't mean  that that spot is going to be good for doing us   astronomy because it might be like a forest  where when you look up all you see is the   tree branches and leaves so you need  a you need to find like a big field or   overlooking an ocean or something like that  where you have a nice horizon and this can   be sort of tough actually a lot of times though  if you look for parks that have parking lots or   fields like athletic fields those are good places  to go if you do find a park so if you zoom in and   you find a good park that to go to that's in  a nice dark spot make sure to call that park   ahead and make sure they allow and can give you  permission to be there overnight another strategy   other than calling up park departments is ask  around at a local astronomy club so most major   metropolitan areas have astronomy clubs and  then they may have a spot outside of the   city that you could go to either just places  where they've made arrangements with people   or sometimes astronomy clubs will have land that  they have for club members okay so that's light   pollution last thing i'd say about it is for  instance here where i am in somerville if i have   my camera pointed this way to the northwest that's  my best direction so any deep sky objects that are   over in the northwest will be in a slightly darker  sky or substantially darker sky than if i point   my camera to the south east where i'm shooting  right into the light dome of the city of boston so   it's another thing to just when you're looking at  this map think about the direction that your deep   sky object is in the sky as well and then look and  see if there's going to be something interfering   with that okay now once we found our dark site we  actually have to think about the day that we're   going to or night that we're gonna go shoot  for a blue reflection nebula like i mentioned   we want this to be during the new moon phase or  when the moon has set behind the horizon so for   both the new moon phase week and for  finding out when it's going to be clear   i recommend clearoutside.com i think this works  worldwide at least it seems to when i type in   different um places up here and i like it because  it does a number of things pretty well it gives   a forecast i'll talk about the accuracy that  forecast in a minute but it also just lists   the moon phase right here it does a full week  which i like and you can quickly scan it to see   you know green is good green is when it's supposed  to be clear red is bad orange is bad so i can   see tonight if i open this up tonight it seems  that for my location it's supposed to be clear   for the next you know or clear-ish for the next  four hours then three hours of clouds and then   another four hours of clear so we'll see if that  actually happens i just looked outside a moment   ago and i did not think that uh only 14 of the sky  was obscured by clouds i think it was more like 80   so you have to take these forecasts these  cloud forecasts with a grain of salt even   the day of they're often wrong which is why  i usually check multiple different sites in   addition to clearoutside.com i'm usually  checking meteoblue that has this under   outdoor sports it has a special astronomical  seeing forecast which also gives you a cloud   forecast broken up into low mid and high clouds so  according to meteoblue right now about 76 percent   of the sky is obscured by clouds which actually  is much more accurate to what i just observed   and my only hour of somewhat clear skies is going  to be the 10 o'clock hour according to this one   so um typically yeah i check multiple forecasts  they're never always correct there's not one   that's definitely more correct than the others  i'll just mention one more i think it's north   america only but it has a really nice interface  astrospheric.com yes this is for north american   astronomers one thing i like about this one  is it has a cloud map so i can sort of see   when the clouds are coming and where  they're predicted to go and that's just   sort of nice because i can maybe sort of get  an idea for multiple locations i might go to   just in one quick glance with this one if i did  want to change the location on this one you just   can either search or you can click on the map and  change it okay so three things to look for again   are a dark sky a moonless sky and a clear  sky and so to find that we need to look at   light pollution maps we need to look at the moon  phase and we need to look at cloud forecasting okay moving on to camera settings we're  going to start with the camera's quick   menu and i'm using a canon 60d but hopefully  you'll be able to follow along with   whatever kind of camera you're using and the  quick menu is basically just your commonly used   settings so we have shutter speed aperture and  iso up here at the top and i'm going to talk about   how to set the iso and shutter speed in a little  bit later in the video but in terms of aperture   we just want to set this to the lowest number  possible the aperture is a fraction so this   means 1 over 2.8 which means a wider aperture  meaning more light coming into the sensor and so   whenever you have a choice just make it as low as  possible and generally for this technique we want   f4 or lower so if you have a choice of different  lenses and one of them the minimum is f 6.3 but   then on another lens you can go down to f4 or f  2.8 choose that at one that has the wider aperture   okay other thing i'm going to turn on before we  leave is i'm going to turn on the two second timer   this is really useful when you're taking test  shots so that you can press the shutter button   and then it waits two seconds before actually  taking the picture so your test shots aren't   ruined by vibration now once we actually are going  to start our sequence of exposures we would want   to turn this back to just single shooting so that  it doesn't add two seconds every time we take a   picture i'm going to go into the big menu now  and the most important setting camera setting   that if you if you forget about anything else you  want to make sure this one is set correctly is you   want it set to raw you don't want to have your so  if it was set to jpeg only it would look like that   right that would just be a jpeg and so if we just  shoot jpeg our calibration isn't going to work   and so we don't get the benefit of calibration  frames and we don't get the benefit of   the raw file space which gives us more information  to work with so because it's not pre-stretched by   a curve within the camera's computer so  i'm going to go ahead and fix this here   and just have it set to raw basically every other  camera setting is really just about disabling   stuff so i disable the beep i disable the image  review now when you're doing some tests you may   want to keep this on but i i prefer just to go to  playback mode rather than just see the image for a   couple seconds you really want to be able to go to  playback mode and zoom in and all that so i don't   find the image review helpful and it just drains  the battery so i just leave that off any kind of   other you know reduction red eye reduction disable  that picture style white balance don't actually   matter for shooting raw but i usually just set the  white balance to daylight because it's a question   i get often again a color space doesn't really  matter for shooting raw but i just have mine   set to adobe rgb exposure simulation i think you  want to enable that because that makes the screen   um brighter okay here's an important one auto  rotate make sure to turn that off that has   screwed some people up because when you're when  the camera is changing position all the times if   it has that auto rotate setting sometimes it can  that can really screw up because your calibration   frames and your lights uh your actual pictures  the night sky don't match uh geometry anymore   and and i've seen people have issues with that  so i would definitely turn that one off format   i'll just mention quickly here i'm starting with  a fresh 64 gigabyte card um but if you're not   go you would want to make sure to back up the card  to your computer or hard drives and then format it   so you have a nice fresh slate to go with you  could do a sensor cleaning before you start   but i would recommend disabling the auto cleaning  while you're doing astrophotography so then if   for some reason you know you have to change  the battery or something it doesn't change   the position of the dust for between your  lights and your flats so i would maybe just   uh clean at the beginning of your  session and then just make sure that that   is that the auto cleaning is disabled and my  camera is so old that it doesn't have different   noise reduction options but if your camera does  have any kind of noise reduction options go   ahead and turn those off as well okay and that's  really it for camera settings just disabling most   things but making sure that the image quality  is set to raw and then again in the quick menu   i like to turn on the timer and just familiarize  myself with where the shutter speed the aperture   and the iso are make sure the aperture is  set as wide as it will go for your lens   one last thing i'll just mention about the quick  menu is sometimes when i'm doing my test exposures   i'll turn this iso up to as high as it will go  because you'll get a brighter image that way   one more thing actually about bright images is if  your camera does support changing the brightness   of the screen itself make sure you can turn  that screen brightness all the way up which is   going to help you focus and see stars and things  like that when you're doing your test shots then   when you actually start your sequence of exposures  to save battery life you can turn the brightness   of the screen back down i don't think my  camera has that setting so i'm just going to   mention it here in case your camera does okay next  camera setting uh we have to calculate or find out   for our camera is the camera's iso and uh this is  something that causes a bit of confusion when you   get into deep sky astrophotography the reason  is is because with daytime photography iso is   something that's often misunderstood and people  uh basically say falsehoods about it because   to simplify or because they don't know any  better people often say well higher isos   add noise and the truth is the higher isos aren't  adding any noise but when you go to a higher so   you are typically reducing the exposure time   and so you're capturing less light um and so  you're good when you're capturing less light   you're going to see more noise you're going to see  more of the camera's uh noise patterns and uh so   anyways i don't want to get too much of an aside  here but uh basically just what you've learned   about iso is probably wrong if you think that high  isos create noise and um i'm going to give you   my two cents using a source that i trust which is  bill class photons to photos you go here you go to   the fourth link down which is the input referred  read noise chart and this plots read noise versus   iso you click on your camera over here so i'm  going to pick the canon 60d and you just find   an iso where this read noise starts to level off  so for me that would be iso 1600 i could go up to   3200 which is sort of what i recommend if you're  doing uh astrophotography without a tracker   so basically where it starts leveling off you  can sort of see is around iso 1600 we don't we   definitely wouldn't want to pick one of these isos  because the read noise is substantially higher   so for tracked astrophotography i usually pick  the lowest iso where it really starts leveling   off and for untracked astrophotography  or photography just on a fixed tripod   i pick the next one up so um in our case uh for  this test for the tracked astrophotography the   one that we're doing on the skywatchers  star adventure i'm going to use iso 1600   and for the untracked astrophotography the one  just on the tripod i'm going to use iso 3200   we we could even go up to 6400 but we wouldn't  want to go up to this 12 800 you can see   that all of these have these little circles  these filled in circles but this one has a   triangle and that means that it's a scaled  setting um just if you see the triangle   avoid that iso setting um you want a natural  one where it's it's just using the camera's uh   natural amplifier and isn't doing any kind of data  scaling which this triangle represents okay um let   me just mention quickly here that one reason to  get a newer camera which you've probably heard   is that they have lower noise and this is true  like if i plot the canon 6 the canon 90d a much   newer camera you can see it has substantially  lower read noise across the whole iso range and nikon and sony's often  have very low noise as well and one other thing that's sort of interesting  here is you can see with canon cameras they have   this sort of stair step uh down until the until  the read noise sort of levels out well with a   nikon camera with a sony sensor it's pretty even  all the way across so with something like that   it's harder i think to pick the right iso value  it's not as clear you know where you would   where you would pick on this one but generally for  something like a reflection nebula and stars if   i had a nikon crop sensor camera that had much  more flat chart like this i would pick a quite   low iso setting maybe like 400 if i was doing  tracked and i would still probably go with 1600   or 3200 for untracked for just on a tripod but  with this particular camera the highest i would go   is maybe 1600 or two thousand because after  that you can see the the little symbol changes   to triangles which means they're doing some  raw data scaling which is what we want to   avoid so stick with the range where it's in the  little circles and with just on a tripod you're   running good wanting to go to a higher iso and  if you have a tracker with this camera i would   probably go lower like iso 400 to recover more  dynamic range okay this has just been a brief   primer on how to use this site i'm not going  into a lot of depth with this and explaining what   read noises and everything else but if you have  questions you can always ask them in the comments   this is this site's also cool and that you can  compare you know different cameras and see how   they compare in terms of read noise which is  an important noise term in terms of deep sky   astrophotography and cameras the next thing  we're talking about is polar alignment and   balance which only applies to the sky watcher star  adventure or whatever star tracker you're using   i like to balance first and at least get the  the approximate balance then polar line and then   very carefully put my whole payload back onto  the mount because i find that if in balancing   it's very likely that you're going to throw  off the polar alignment if you're trying to   do too much after you've fully aligned if  this makes sense hopefully it will once   once we go through it here so to balance this  mount we're going to release the ra clutch here   and you can see immediately it starts turning  when i release our the right ascension clutch   and i can tell right away that it's camera  heavy because the the camera side up here   is falling see and then the counterweight  side is going up like that so all i'm going   to do is i'm going to take the counterweight  right here i'm going to gradually lower it   until i find balance so it seems to be right there  and i'm just going to make sure that that holds   in any direction that i put the camera  and it does so you can see i can now put   the camera on lens anywhere and it's still  balanced and basically the point of of   balancing like this is so that the the gears  can work a lot smoother as it's just turning   this more effortlessly if everything is  balanced if there's a lot of unbalance   then you'll have more slippage and problems so  this is a really important step with star trackers   especially the heavier that your payload up here  gets the closer you get to the payload limit   the more important this is and also the longer  the focal length if you're working with a wide   angle lens then this balance step wouldn't be  quite as important okay now that we have that   balance we want to mark or just remember exactly  where this declination bracket is clamped in here   so that after we pull it aligned we can very  carefully put it back in not disturb the polar   alignment and don't have to rebalance which  might throw off the polar alignment let's go   ahead and move on to polar alignment so to  do this i'm going to go ahead and take out this whole piece here so i'm going to take out the declination bracket with the counterweight  shaft the counterweight the camera   the ball had everything that's on top there and  i've just covered the polar scope with a little   piece of tape because i lost the cap that comes  with it basically we we uncover the polar scope   here we take this cap off here so that we can look  through the polar scope which goes right through   the axis of the mount and the first step is  we want to find polaris and i can see it right   there and i'm going to line up just by actually  lifting up my tripod and moving the whole thing   okay so now i have the this mount roughly lined  up with polaris right there if you're not sure   where polaris is in the night sky um you can  just use a compass like on your smartphone   or if you have a magnetic compass and just point  find north and then you should see polaris it   should be a bright star that's you know it's the  end star in the little dipper not too hard to find   uh once you get a little bit used to looking at  the constellations so this is the first step we're   gonna visually line it up okay the next step i'm  going to go ahead and set my latitude on the the   base here so i'm just going to go ahead and loosen  this up and then i can go up and down right here   and so i can set this to our latitude right now  which should be around 43 degrees and then i can   tighten it back up and so now this is nice  and tight and we're not having any movement   uh that way now we might and so you know see  if i do this it doesn't actually go up and   down you have to loosen this one and then  you can use this one to do the adjustment   now we're probably gonna have to return to this  adjustment when we actually do the polar alignment   the other adjustment i'll just point out right  now since we're right here when we actually do   the polar alignment is this knob right here so  this is the azimuth and this is the altitude   and so we're going to basically you can think  of the altitude as up down and the azimuth is   left right and so to use these later you always  have to loosen one and then tighten the other and   that can move it left and right so if you need to  move it you know left in the view you loosen one   you tighten the other and so forth it's just  a push-pull system against a pin in there   same thing with this you you loosen one and then  you can tighten the other it's a push-pull that   way okay so now i'm finally ready to actually look  through the scope and when i'm looking through the   scope i also have open an app that i'm going to  look at and this app tells me given my location   which it finds using the phone's gps and the  time of day it tells me where polaris should sit   in this circle that we see this is the reticule  so we're going to see the same kind of reticule   in the polar scope and we can see that polaris  we should position right at around 5 30 if you   think of this as a clock and so that's where i'm  going to aim for when i'm actually adjusting it if you don't see polaris in the view you can  just pick up the whole tripod and just and just   readjust until you see it in there the one other  thing i'll say is for me personally i like to   start with the tracker off because as soon as you  turn it on it will put on a red light in the polar   scope and to me i find that red light distracting  at first i might turn it on at the very end but   for the most part i like to do this just in the  dark my eyesight is good enough that i can sort of   make out the reticule just from the starlight  but if you might be different your iso might   be different so you might want to turn on the  mount and then it will illuminate the the polar   scope with a red light on most trackers and  mounts so i just showed you polar alignment   and balance with the tracker setup and i just want  to reiterate here that with the no tracker setup   polar alignment and balance is not applicable  or is not a necessary step because with a fixed   tripod there's no need to do it so that's the  end of step three moving right on to step four i'm just centering up the pleiades in my live  view screen here and once i have it centered i'm   just moving the ball head to do this on either  setup we can start focusing and let's start by   just trying focusing without any kind of  aid so all i do all i've done is turn the   manual focus switch to manual focus on the lens  and i've racked the focus all the way to infinity   and then we're going to zoom in on live view on  the pleiades and here's what the stars look like   and i can tell these are out of focus uh if you  are new to this you might not know that these are   out of focus the the dead giveaway for me here is  that they look sort of like donuts with a brighter   ring around the edge and then they're more dim  in the center and so let me rack focus and you   see how it can change change when i'm doing that  and one thing i want you to notice is that when i   get into focus here a lot more stars pop into view  also so these dimmer stars are coming into view as   well as the brighter stars are getting a lot more  concentrated and have a bright core and so this   is what you're looking for when you're manually  focusing with a 10 times zoom in on live view here   now i just also want to show you if you do  have a Bahtinov mask what to look for so let   me put the Bahtinov mask on the front of the  lens and we're going to do the same thing here   and basically it's going to be hard for me  to show in video but i can see that there is   a little x pattern there let me go ahead and  take a test picture though and then go into   playback mode and then you can really see the  x pattern quite clearly so here it is you can   see on all the stars there's an x pattern  but it's really evident on the bright stars and then we just have to remember when if  we do use a Bahtinov mass to take it back   off from the front of the lens before  continuing it's really just an aid   for focusing you don't want to leave it on to figure out the best exposure time for uh  tracked astrophotography you have to sort of know   the limits of your particular gear and so if you  have a really excellent equatorial mount that's   nice and heavy and you know that you can do five  minute long exposures without any star trailing   then you might be able to go with five minute  exposures and that would work really well   for a star tracker like this i generally am  pretty conservative and at 200 millimeters   i would start at somewhere around 30 seconds  and 30 seconds though is plenty to give you nice   exposures you can see that  we can see nice reflection   nebula showing up even in a single 30 second  exposure this is what dark skies gets us and so   i can tell there's going to be lots of nice detail  from this even in a 30 second exposure but i can   also see that these stars are right on the edge of  starting to trail even at 30 seconds i did go up   to 60 seconds and they were starting to trail more  so i know this is the limit of my mount right now   i know that you know some people may  not want to hear this some people   probably get better results than i do  on a star tracker but it's really just   about figuring out for yourself where  your limits are with your equipment   okay the other rule though that i want to  mention for judging exposure on a tracking system   is the histogram rule and so it's not it's  not so much a rule is just a useful tip here   figure out on your camera how to bring up  the histogram and playback mode on my canon   camera i can press info twice and bring up the  histogram like that and this uh gives me um   all of the information that's in the picture all  the pixel values and it charts it on this little   uh graph here and i can see that that histogram  peak is almost at one quarter of the way over   and it has plenty of separation from the left  hand side that's the most important thing is   we don't want it squashed up right on the left  hand side we want a little bit of separation   from the left hand side so we're getting away from  the noise floor of the camera the other thing to   look at if we hit the info button again is the  different color channels and you can see that   all three color channels look pretty healthy  there they're all moved over from the left   now typically a advice you'll often  hear is get this histogram peak   one quarter over from the left or one third  over or even one half over and so those are   all good too you'll get plenty of data that way  i'm not convinced that we actually need to get it   much further over than what i'm showing right now  but one quarter over is is a good rule of thumb   um and so uh the histogram is really helpful  to look at for judging exposure if you   if i could get longer exposures and still have  nice round stars i would probably push them a   little bit further to get this histogram peak  about one quarter of the way over from the left   now when we stack many exposures together we're  going to recover a lot of dynamic range and   and so you don't have to think that this single  exposure is what your final picture is going to   look like because when we bring the noise floor  down we can stretch the image quite a bit more   okay enough said let's look at the  npf rule for untracked exposures   okay next we're going to look at how to calculate  the shutter speed or exposure time for each light   when we are doing untracked astrophotography  just with a tripod and for this i recommend the   npf rule it's available on this free website which  from this french astronomy society and the website   is in french but if you're using something like  google chrome you can just automatically translate   it to english there's a little thing up here in  the address bar to do an auto translation or you   could probably translate it to whatever language  you speak this website has been updated recently   it makes it a little bit simpler in some ways and  harder in other ways but i'm going to show the new   website just because i don't know how long the  old website is going to be available through the   wayback machine so with this new website instead  of giving us a full list of different camera   models it only gives us four different choices so  if you have a full frame camera choose full format   if you have a canon crop sensor camera you choose  canon aps-c if you have a crop sensor camera from   another brand you choose that and if you have a  micro four thirds camera you would choose that   and this gives it a general idea of the size and  pixel size of the camera so you could probably   just go with that but if you want to be more exact  you can enter in things over here so let's find   out exactly what the pixel size and resolution of  the canon 60d that we're going to be using is so   i'm just going to google canon 60d pixel size and  one of the first results here is digicam database   and it tells me right here pixel pitch same thing  as pixel size is 4.29 um or round up to 4.3 and   this sensor resolution i'm going to use this max  image resolution right here so the width is 5184   pixels because it always goes with by height okay  so 4.3 and 5184 so we're going to enter those in perfect and so now it knows the actual camera data  for our camera so you would just do the same thing   just google your camera plus pixel size figure  those out from a website like digicam database   the opening would be the same thing as the  aperture ours is going to be 2.8 but you can   change this right here the focal length we're  going to be using is 200 millimeters because   that's the focal length of our lens where it  says precision of formula you want to change it   to point stars okay and then we have declination  this is something you'd want to look up in like a   stellarium or a planetarium app for  whatever you're shooting i'm shooting   the pleiades and i just looked it up in my app on  my phone and it says the declination is 24 degrees okay so we have everything entered now and this  results part automatically updates and um usually   what i go for is the full mfn or npf that for  some reason it translates it to mfn but we want   the full npf rule uh the calculation for was right  below right here and it gives us 0.7 seconds and   i always just round up to the full second so  0.7 i'm going to round up to 1. um if it said   1.5 i would round that up to 2. so i just round  up and that works well enough for me i'll just   mention briefly here this calculator is also built  into the photopills app and that app does have a   camera database so you can just quickly find your  camera and don't have to find out this information   on your own um so that might be an option too  if you want to check out that app photo pills   next the number of exposures so for this  constrained test we're going to try to keep   these two systems equal in terms of total  integration which just means the total time   when you add up all of the different exposures  that you take and so we're going to do about   30 minutes total integration for each system  for the just the tripod and for the tracker   but 30 minutes is actually a fairly scant  integration in terms of deep skies to photography   really uh you want to go if you have a tracker i'd  recommend you know as many hours as you can um you   know the best astrophotographers will typically  you know not even show you an image of theirs   unless they've gotten something like 20 hours over  multiple nights i know we're talking about sort of   advanced things now but the point i'm trying to  make is the more the better always because you   can always keep bringing that noise down which is  going to reveal fainter and fainter detail as you   bring the noise in the picture down by taking  more and more pictures of the same thing so   for this test we're doing 2000 around 2000  on the tripod and around 60 on the tracker   it's just so that we can compare you know apples  to apples to 30 minutes here 30 minutes here we now want to take calibration  frames so in addition to the light   frames we also want these calibration  frames and we're going to start with   dark frames for dark frames we want to leave  all the settings alone same iso same shutter   speed all we have to do is cover the lens with the  lens cap so that no light is hitting the sensor   now i'm sure many of you are wondering can't  we just take these later on after we go home   the answer is no these need to be taken at the  same temperature as the lights so you really do   need to take them here on the field but with such  short exposures these are really quick to take   we'll just we just want 50 so we'll just leave the  same setting on the intervalometer and we're going   to do one second each so we're going to cover the  lens hit start on the intervalometer and that's it   next up is bias frames you can technically take  these anytime but we might as well take them now   all we want to do is change the shutter speed i'm  going to change it from one second down to as fast   as the shutter can go on your camera for my camera  here that's 1 8 000 of a second and let's take 75   bias frames okay and last up is flat frames and  it's important to take these very soon before or   after you take your light frames because we want  everything to be the same in terms of focus and   any dust particles on the lens or the sensor so  i wouldn't even recommend turning your camera off   if you can help it we just want to take these  as soon as possible to take these we take the   lens cap back off and we point the lens straight  up and i'm going to rubber band a clean white   t-shirt to the lens hood you want it to be taut  with no wrinkles then we place a white screen on   top and this can be any pure white screen if you  have an ipad you can set to white or a laptop you   can set to white that will work if you want to buy  something just for this purpose what i'd recommend   is an led tracing panel these go for about  30 bucks and they're powered with a usb cable   so whatever you have that produces a white light  just put that on top and now we're going to move   the shutter speed up and down with the dial here  until this exposure meter at the bottom of the   screen is telling us we're properly exposed  to check that we just push the shutter down   halfway and i'll tell you right here so for my  particular setup here it's showing proper middle   exposure at 1 40 of a second so i'm just going  to set my intervalometer to take 50 and hit start   okay i'm now on my computer this is a windows  laptop that i'm using um so that i can use deep   sky stacker and i've moved my files both my 60  lights and my calibration files to the computer   so i can uh stack them using deep sky stacker and  i'm just going to show this once with the tracked   results but the only difference with the untracked  results is you would need a lot more space on some   hard drives to do this process because if you're  doing 2000 lights and a few hundred calibration   frames that's going to take up many many gigabytes  of space and then it's going to take up even   more for the process because deep sky stacker  does use a lot of hard drive space while it's   working and puts that all into a temp folder and  so what i do is i use external hard drives to   manage all of this because a lot of times like on  my laptop here it it has a ssd that's not very big   so i need to use external hard drives to make this  process work especially with the untracked results   where i have so many files but anyways i've just  organized my files copied them off the camera's sd   card into these folders lights which are again  the um actual pictures of the night sky flats   which are the flat frames which correct dust  bunnies and optical problems like vignetting darks   which match the lights in length and temperature  and bias which are very very short dark exposures and i'm going to be using a  free program you can download   online called deep sky stacker it is windows  only but if you are a mac or linux user i'll have   future videos in this series which show programs  for those systems let me find it here there we go   okay and i guess i'm not on the latest  version but i doubt much has changed   this is what the interface should look like if it  doesn't look like this if you're seeing something   radically different be aware that deep sky stacker  is packaged with another program called deep sky   stacker live for live stacking so make sure that  you're clicked into the regular deep sky stacker   it should say up here deep sky stacker four point  something and it should look just like this okay   anyways let's go ahead and start and you basically  just go down this left-hand side um going through   these different commands the one thing that  i like to do um first before i do any of that   is just set up my temporary folder  um and i think this is under settings   stacking settings yes here we go so um i've  actually i think i've already actually set it up   but uh what you would want to do and it will  remember this setting if you've said it before is   click into settings and then it'll say temporary  files folder and you just want to click on these   three little dots and tell it where to put the  temporary folder so like i mentioned before i   don't have much space on the computer here i only  have six gigabytes so the process of stacking   would definitely fail while on my external hard  drive i have 164 gigabytes free and so i use that   as my temporary folder okay with that done we can  now load up our pictures so we're just going to go   up here into the upper left and click on open  picture files and my folder is on the desktop and i'm going to start by bringing in all  my lights so i'm just going to click on one   press control a to select all and then click open okay and it brings in all of our light  frames here but if we look right up here   in this blue bar it says light frames zero  and the reason for that is it only registers   pictures that are checked and for some reason  the first time you bring in some picture files   it doesn't check them so i'm just going  to click check all over here on the left   and somehow i thought i took 60 but it  only took in 59 that's okay close enough i might have deleted one that was bad or  something um so we have 59 light frames and then we're going to add our dark  file so we just go down the list here   and go into the darks folder  and again select all open and now it starts checking them so i have 49  dark frames and then we'll bring in our flats   we're going to skip over dark flat files  so called these are files that would be   darks that match your flat frames but since  our flat frames are very short and we are   using bias frames we don't we don't need dark  flats uh they would be to correct uh thermal   noise in your flat frames if you were using  very long darks like with narrow band filters   or something like that so i'm going to skip  over those i am going to add bias files though ctrl a click open okay so we  have everything loaded up here   about 40 flats 50 dark 60 bias 60 lights okay and  you know these numbers don't have to be exactly   your numbers you know yours may be different  i would just always recommend at least 30 of   each calibration file and as many light frames as  possible the other thing we can do is we can just   quickly scroll through here and looking over in  this far right hand column i can see that these   all are registering as the same size which is  good if you have any with incorrect geometry   you know mean a different size that might stop  the process okay this is all looking good and   i can also see that they're all cr2s which  is the canon raw file which is what we want okay that looks good so now we just have to  check a few settings and then we can start   the process and it just does its thing  and then we have a picture at the end   um one thing i will point out here is you  can look through your files right here and so if you haven't already  looked through your light frames   i would recommend looking through them  and just making sure that they all have   fairly round stars um and that you know there  aren't that have have any like huge streaks or   you know stars that look really bad um or clouds  or things like that if you do find any with clouds   or anything you can just uncheck them and then  it wouldn't include them in the stacked result okay let's go ahead and click on register   checked pictures over here on the left  you can see there's a link right there   and i'm going to click into advanced and  click compute the number of detected stars   okay and it found 2088 stars that's perfectly fine  i just want to show you if we take down the star   detection threshold then it will find more stars  and if we take up the star detection threshold   it will find fewer stars because it  will treat a smaller little things as   noise um and so really it it anywhere from you  know a few percent to 20 percent it really doesn't   i can't tell you exactly where to set  this but the point is you want it to   be confident that it's finding enough stars and i  i often get the question well even when i set my   you know threshold to one percent it  says it's only finding three stars   if that's the case then something went wrong  with your capture because it should never have   that much trouble finding stars and it's the  usual problems are that you weren't tracking or   using the npf rule correctly so you have stars  that aren't round or you are out of focus and   then it can't find the stars because it finds the  stars based on their star cores and if it can't   if they're really out of focus and it can't find  those star cores i'm going to select the best 100   of pictures and stack them because i've already  looked through these pictures and i also want to   get as close to a half an hour of data for each uh  setup so we can make this a fair test i am going   to click stack after registering and let's go into  the recommended settings and look through these these all look good if it was  if it was finding anything   weird and then i'm going to click on  stacking parameters and just check this oh this is another thing i hear people talk  about well why not enable one of these drizzles   it's going to make the picture bigger i'm not  going to get into what drizzling is but i'm   going to say if you if you don't know about  drizzle if you haven't read about it don't   check these because drizzle is a specific  algorithm that you really need well dithered data   for it to work correctly and so i would not check  one of those unless you know what you're doing okay and then i just use sort of the recommended  different stacking parameters through all of these and one thing i'll note here is it will create  an output file in the lights folder called   autosave.tiff you can certainly use that  it's a 32-bit tiff file or when you're all   done you can just click save picture to file  and save it as a 16-bit tiff file which will   work with basically any processing software  we use after this like [ __ ] or photoshop okay this is all good i'm going to go  ahead and click ok and click ok again   it will give me a summary of everything and this  all looks good and it tells me right down here   how much space this process will temporarily use  6.5 gigabytes now keep in mind that is going to   be much much higher with the unstacked process  where we're stacking like like 1800 lights so   just keep that in mind that this is one advantage  of using a tracker is your file sizes will be   a lot more reasonable okay i'm going to click  ok and let it start doing its thing and so now   it's very automated it goes through all these  different steps like creating calibration masters   calibrating your light frames registering  your light frames stacking them   in in the end what you have is one calibrated  registered stacked um light uh so basically   it's it's all of this stuff all of these  hundreds of uh pictures are used to make one   final picture and then we take that and bring it  into the next program okay so we'll let it do its   thing and then move on when it's done with that  final autosave.tiff or like i said you can also   save the tiff off as a 16 bit file with  this save picture to file command over here   and then we'll bring it into the next program  i've taken our output from deep sky stacker   the 16-bit tiff file dss.tiff and i've  brought it here into adobe photoshop   if i go into image mode i can see that  it's rgb color and 16 bits per channel   if you are just using the autosave.tiff you may  consider changing it from 32 bits to 16 bits   there's you know some discussion about whether  it's better to do this before or after the stretch   in my experience it doesn't matter too much but  if you are trying to get the very most out of   your image you might want to leave it in 32 bits  per channel do a stretch and then switch it over   to 16 bits but a lot of things don't work if  it's in 32-bit mode so that's why i recommend   for photoshop at least the 16-bit mode so we  can actually see our histograms and things   like that okay first thing i want you to do is  go ahead and duplicate the layer so you can see   that right now it just says background over  here in the layers panel go ahead and right   click on that and choose duplicate layer i'm  going to call this new layer first stretch and then i want you to open up the histograms  panel if you don't see a little histogram panel   over here on the right side go ahead and go to  window and find histogram to open it up and then   yours will probably look something like  this and i want you to change it to all   channels view so you can see red green and  blue just like mine okay next we're going   to start stretching the image so we're  going to go to image adjustments levels   and i'll note here that when you access something  from one of photoshop's menus like we just did   image adjustments levels it will give you the  keyboard shortcut right over here since i'm on a   mac the keyboard shortcut for levels is command  l if you're on a windows computer it would be   control l and so l is for levels and this is  just handy so instead of having to go to the   menu each time and finding this we can just hit  command l or control l on windows to bring up   the levels because we're going to be opening  up this adjustment window a number of times   okay here it is and the first thing  that i want to do is i just want to   move the values here off the left hand  side so i'm going to do that by taking   this middle slider the midtone slider and  dragging it well over here over to the left and saying okay okay and now you can see that  we have some separation some of the stars are   coming out in the image and we're just going  to do that same thing one more time so we're   going to take this and we're going to move  it even further over we're going to move   that mid tone slider to the left again and all  three channels will get moved out like this   okay and i can see that we actually have really  nice color balance because the left edge of these   three channels is lining up quite nicely now you  might see up here that there is a bit more blue   in the highlights but that is completely natural  because we are dealing with a blue reflection   nebula so you don't you wouldn't want to correct  this because this is is already correct because   there's going to be more blue highlights when  you're dealing with a blue nebula so this is quite   good we don't have to do any color balancing if  these were more out of whack though because you're   maybe dealing with more light pollution than me  what you would do is when you bring up that levels   command you would just want to line up the left  edge of these three by changing the channel from   rgb to any individual channel and then you can see  that you can move the channels around to line them   up better just by grabbing one channel and moving  it relative to the other ones so we can do some   color balancing while stretching and if you are  new to this i'd recommend watching some of my   other tutorials where i do a bit more with color  balancing for this data we don't really need it   because like i said it already is well balanced  okay i'm going to continue stretching here and basically what i'm trying to do is in  addition to bringing this this curve over   i'm not really trying to bring it  too much further over now but just   widening it and the way we widen it is by taking  the shadow slider and moving it to the right   and taking the mid-tone slider and  moving that to the left and every   time we do that we're going to widen  out the curve and stretch the data more okay until we have something like this and you  can see there is lots of really cool dust in   this now uh in this tracked shot we'll have to see  well to compare this at the end to the untracked   shot but i'm not so sure if we're going to get  this much dust away from the central region here this also looks quite clean even  just for a half an hour of data   and what i mean by clean is there's not a lot  of noise even when we zoom way in like this   you can see there's not much noise here it  looks really smooth okay so all we've done   so far is a stretch and it already looks  really nice but from here we may want to   do some saturation boosts so we could click  on this hue saturation adjustment layer   and one thing about just boosting the saturation  globally like this is you can see it also is   boosting the saturation of the sky background  and so it's making the sky background very   sort of bluish i guess and so we could correct that by just  bringing up curves and you know resetting   the blue point the blue's black point actually  that worked really well i didn't expect it to work   that well so this is actually an excellent point  when you're really when you're working with uh   nice data with data that is really well captured  and done on a tracker uh even simple adjustments   like that just work incredibly well i guess  i've gotten used to working with uh with   astrophotography untracked which is always more  difficult in the processing i might actually just   stop right there that looks really nice what  else could we do here with it well there seems   to be maybe a little bit of a green to magenta  shift i've noticed this dust over here looks a   little greenish and over here the sky looks a  little bit too magenta so let's see if we can   do some color correction on that what i'm going  to do is i'm going to bring up a selective   color adjustment layer i'm going to start with my  blacks and i'm just going to take a little bit of   magenta out of the blacks which i think let's  turn this off and on yeah i think that correct   i'm looking mostly looking over here i know that  the dust got really green by doing that but we're   going to correct that second so looking over here  i think that did help correct that magenta tone   and now i'm going to go back into that  adjustment and i'm going to go into my neutrals   and i'm going to add a little bit of  magenta back and just take out a tiny bit   of yellow okay i do like that so uh here's sort of  where i ended up with the neutrals color balancing   you know it might not need so much a lot of  times i'll back off of these a little bit after   it just needs to be a little brighter now  sorry i'm sort of mumbling to myself let's see   okay so i'm going to go back here  into my curves and i'm just going to   add a couple points on this curve to brighten  that up and then i'll go into my blue curve   okay do i like what i just did as a whole i'm  going to go into my history panel and see here yes i do like that okay so i'm actually happy with  this image as it looks right now i might crop it   down a little bit but um just to make this a fair  comparison and because i want to do the processing   the same with both images and i feel that the the  one that i just do on the tripod is going to need   it i'm going to make a starless version of this  with star net plus plus and then recombine it   with this version the stars version so let's  do that so i'm going to make a new layer from   visible so i'm going to do command option shift  e or that would be control alt shift e on windows it just pastes a new layer from exactly what  we have here and i'm just going to call this   stars and then i'm going to save  that i'm going to go to file save as we want the srgb color profile we want to turn  off layers so it saves as a copy and i'm going to   call it stars.tiff and save it to the desktop then  what i'm going to do is i'm going to google star   net plus plus this is a standalone program that's  useful for removing stars from astrophotography   and i'm going to download it from this sourceforge  page and if you go to files up here at the top   and then go into version 1.1 they have a nice  zip file for each main type of operating system   so since i'm on a mac i'm going to download the  mac version okay once that's downloaded i'm just   going to move the entire starnet macos folder  onto my desktop here and open it up and then   i'm just going to open up this run rgb starnet  dot sh file with a text editor i'm just going   to change these two file names be the first one  being the input file so we called that stars.tiff   and then i'm going to change the output file  to m31starlist.tiff this number is the stride   and typically i use a lower stride when i'm at a  lower focal length and a higher stride when i'm   at a higher focal length um it starts at 128 but  you can go down to 16. i'm going to change it to   64 for this image and typically the the lower the  stride number the longer the process takes so if   you wanted to see what will happen if you run  it quicker you can leave it on the default 128.   okay then i just have to move this stars.tiff  into the same directory okay with that shell   file edited like this and the stars.tiff file in  the same directory we now just have to run this   file a terminal command so i'm just going to open  up terminal and we have to get into this folder   so the command for that is cd for change directory  space and then i'm just going to drag this folder   over and hit enter and then we just want to run  this command or this sorry this shell script which   calls on the actual program so to run it i'll have  to do is just drag it over and hit enter and it   starts running it gives us a little information  about the file it tells us how many different   tiles it's going to break it the image up into  to analyze that's what the stride number is so   the slower the stride number the more tiles  it will break the image up into and then   the longer it'll take and then it gives us a  percentage finished so this will take some time   probably 20-30 minutes on my laptop with  an image this size star net plus plus is   finished and i just brought in the starless  result here back into photoshop so now we   have two different files we have the stars file  and the starless file right and so i'm going to   go ahead and clean this up a little bit  and what i mean by that is sometimes   these dark spots where it removed the bigger  stars can pose problems later on so what i   usually do is i just grab my spot healing brush  tool and make it about the same size as the the dark spot and this will just usually either get  rid of them completely or just brighten   them up a little bit so they won't be as  noticeable once we add back in the stars   now you want to be careful when you're doing  this not to mess up the nebulosity too much so you wouldn't want to do it right in here  because there's a lot of fine nebulosity in there   that could get disturbed if you were to use this   but there's so much detail in here that i  don't think that we're going to notice these   artifacts so i'm just going to  do them do this in areas where they're away from the main action there's  different ways actually to clean these up   you could also use the clone stamp  which would be a little bit more sometimes work a little bit better  because you have a little bit more   control but i'm just sort of going  for the the quick and dirty here okay and let's do that one   okay then i'm going to go ahead and just um do a  curve here and just reset the black point on this and maybe just do a slight s curve like  that okay i'm gonna get rid of these guys   over here i'm probably gonna crop these  away anyways but i'll just grab them anyways okay and then uh this is looking pretty good  the one thing i noticed is that we have a little   bit of a gradient where uh even with the dust i  think that it's a little bit too bright over here   so i'm just going to do another curves layer   and just bring it down just a little bit and  then that made this side way too dark we don't   want it to apply to this side so i'm just  going to draw a gradient right on that curves   mask and i want it to go from black to white  from this side to this side because i want the   curves adjustment to not apply to this side so  this should be black and this should be white   right and so that just evened it out  a little bit you can see here's before and there's after okay good and now let's go ahead and copy this i'm  going to do command a command c or that would be   control a control c on windows and command v or  control v on windows to paste it in so we just   took this entire thing the stars image selected  it with command a copied it with command c   and pasted it onto here with command v and then  let's go ahead and change the blend mode and we're   going to change it from normal to screen okay and  then at this point i usually zoom in and i look   at those bright stars where there were possible  artifacts and i see if there's anything left over   that looks funky this looks pretty good one thing  i will note about this tracked result is that it   does really bring out the chromatic aberration on  this lens especially probably because i shot wide   open that's all this sort of magenta pinkish halos  on the stars so if you wanted to get rid of that   there is a good way we could go  into camera raw filter and under   optics we can raise up this purple amount  here and you can see if i turn this off and on   that's before see how it's sort of pinkish and  that's after so that's the easiest way to get rid   of it is just go into camera raw filter optics  defringe and take away purple and then click ok all right what else i think now the  picture is too bright so let's go ahead   and reset the black point  again just with another curves i'm just going to do something like that and it looks just a little bit too red in the  background so let me open up that curve again   and i'm just going to open up my red curve  and just bring that over a little bit too do the same thing with green i  like it right about there okay   so i'm gonna call that done um there is one weird  sort of black uh ridge down here and i don't know   if that is is right or if that's something some  artifact from the sensor or the lens or something   but that looks a little weird to me other than  that this looks really cool i like all of the   extended dust and stars and the star color looks  really nice especially after we got rid of that   fringing i'm going to now try to process my  untracked uh picture from deep sky stacker   exactly the same way i did this one i may find  that i have to do something with that picture   that will adjust what i did in the processing  here so the final result may not look exactly   like this when we do the comparison don't be  alarmed if that's the case um but i'm going   to try to keep these processes as similar uh as i  can and then we'll jump into the final comparison and here we are the final result so uh we  have the tracked result on the left and the   untracked or fixed tripod result on the right  and these again were both about a half an hour of   data this one 1800 single exposures at one second  each and this one 60 exposures at 30 seconds each   and so i think this does show that in  this at least in this extreme example   having longer single exposures uh even if  you get to the same total integration can   be a huge help in resolving uh finer details and  uh dimmer uh signals um so all this really faint   nebula and stuff and all these beautiful star  colors come through a lot better than they do over   here even though these were shot under the same  sky again 30 hour 30 minutes integration on each   and i think the reason has to do with noise really   because at one second long you're just really  not beating the the noise of the camera so you're   you're stuck down in the noise of the camera and  you the the signal really just never has a chance   well at 30 seconds you like when we look to those  histograms they were they were off the left-hand   side so they weren't down in the noise and uh  that really just helps in the final result here   now if you imagine this is just uh 30 minutes  with the tracker if we went two hours or three   hours or 10 hours you can just imagine how  how good this would look because if we zoom in   you can see there is still quite a bit of noise  in both images you know they're both pretty noisy   but if we look at the fine details in the pleiades  see how it comes out quite uh well over here this   is you know the brightest part of the image looks  really good even just with 30 minutes of data here   well here you can still just see that a lot of  that detail is getting lost in the noise from the   camera now one interesting result that i didn't  expect is that with the longer uh sub-exposures   chromatic aberration on the stars this sort  of fringing around the all the stars uh was   a lot worse in the uh version with the tracker  over here uh we don't have we don't see that   chromatic aberration but on the other hand the  stars are not very colorful compared to this   so i think i would rather have more uh colorful  stars and have to deal with a little bit of that   fringing rather than just have stars that  are are a little bit subdued and mostly white oh one last thing that i want to mention is that  i did this crop because this was as much usable   frame as i could get out of the untracked result  because i you know was reframing it pretty uh   regularly about once a minute but even so a lot  of the frame was not usable due to registration   artifacts because when you're reframing um you  know the outside of the outer parts of the picture   don't get nearly as much data as the inner as the  center and so but with the tracked result i could   actually have done a much bigger crop than this  and i probably would have i'll show that now so i do like this close crop but i probably would  go for a little bit bigger crop on this one okay this has been Nico Carver from  nebulaphotos.com i will just mention again   that i do have a Patreon you can support me in a  number of ways you can subscribe to the channel   you know watch the videos like and comment but  you can also if you want to support me financially   i have some links down in the description  including my Patreon link where you can set   up a monthly or yearly donation and you're about  to see all of my patrons names over on Patreon   they're in the credits of any long video and i  really do appreciate all of the support that they   give me because it allows me to make cool videos  like this one that do take a lot of time to make   all right till next time this has  been Nico Carver. Clear Skies!

Channel: Nebula Photos

Views: 275,371

Keywords: astrophotography, astronomy, skywatcher star adventurer, canon photography, canon astrophotography, dslr astrophotography, dslr astrophotography for beginners, no tracker astrophotography, the pleiades, the seven sisters, suburu, m45, messier 45, stars, star photography, star cluster, night sky photography, fixed tripod astrophotography, nebula photos, nico carver, nico carver astrophotography, nico nebula photos

Id: mYucAuUrdTs

Length: 84min 46sec (5086 seconds)

Published: Thu Jan 14 2021