How to process astrophotography images : Image processing

hello everybody welcome back to another episode of AV astronomy and tonight's video I wanted to go over my basic workflow this is not going to be an exhaustive lesson as there are some different approaches you will take with different images you know some images you'll be working with will have a much higher dynamic range than others but I'm gonna use m42 as an example since it is a higher dynamic range target and it the principles that I use here will apply to many many other images so first thing you want to do you've taken your data right you've taken your light frames you've taken at least some flat files and bias files now I know a lot of people are big on doing dark files doing darks I personally don't just because mainly I don't know how accurate they're gonna be anyway with the temperature difference with a DSLR and not having a cool camera so I leave those out and really with modern day digital SLRs the dark current is so low anyway I don't think it is a huge deal breaker when it comes to overall image quality if you're if you're doing dithering like you should be and and taking multiple frames you know 4050 frames or so 60 frames you're gonna get some some relatively clean pretty nice and clean images so let's get started [Music] first thing we're gonna do is open up deep sky stacker you have not downloaded this it is a free stacking software for your images there are some others that you can use pics insight has one built into it and I know there's some others out there but this has been working great for me so this is what I'm using go to open picture files and navigate to the folder that you're wanting to stack right so I have this is how I label my file system I do bias edited flats stacked and raw so we go to raw height frames so we select all the light frames okay and you want to check all then get your flat files control a selects all and then of course hit control to deselect and click to deselect the ones that you don't need there you want to do at least 20 flats that's that's what I go even more is better but I do 20 flats and then bias the same thing select all and you've got these all checked the next thing you want to do under settings your register settings you want to you want to play with this slider to make sure it can detect a fair amount of stars I go for 100 to 200 that usually works pretty well so you can play around with that to get the star threshold that works for you wouldn't overthink this program too much it really is pretty straightforward light frames flat files and bias frames okay now you want to go to register check pictures now I do a under settings here sorry backing parameters standard mode Kappa Sigma clipping and what that does is in the event you had a meteor or satellite or any other plane whatever anything that just flew across your imaging frame that will cancel it out it's a really really good feature to initiate to use okay flats to do average bias average alignment automatic all this other stuff honest they have just left alone I don't touch it you do want to create output file on the folder for the reference frame autosave TIFF and use all available processors these should be on by default but that's what you want hit OK under advanced this is here you can check you hit compute and you can check to see how many stars that detects in the image and yeah what we've got 200 something that's plenty of stars to make sure this is aligning properly register already registered and then hit okay I've already stacked this so I'm not gonna go through put it but this many images it's gonna take about you know 5-10 minutes depending how fast your computer is to get this all stacked okay so you hit OK all right after your image has stacked you're gonna get some result right here okay it's gonna display right here and once you get this one this is once this is fully loaded on you want to go to safe picture to file label it choose where you want it to save right and don't you know make sure none is clicked for compression and this right here embed adjustments in the saved image but do not apply them that's very important do not do not click this you want it to be embedded into the image okay then you click Save now you've got an image to work with in Photoshop Photoshop is the program I use again there's there are a fair amount of options for editing your photos I like Photoshop because it's what I'm used to and it's produced some really good results there are some other software's like pic since I astral pixel processor there's some other other ones out there as well but anyway this is what I use and it's it served me well so we want to open up go to that stacked image okay and here it is that's the short stack here it is so this is what your stack image is gonna look like coming out of deep sky stacker doesn't look like much of anything the first thing I do is duplicate the frame control J it's the shortcut for that and I do an initial stretch so I go over here to action and we're gonna go to curves and just do a nice stretch on this image and you want to keep that line from hitting the ceiling the top here so this might be a little too aggressive for the first stretch just pull this down just a tad there we go we'll go with something like that okay that's the first stretch then flatten another thing this image is because I did drizzle on it is huge it's like 500 megabytes so that's something to keep in mind I usually go ahead and just change the image size take this bad boy down to like a 20 by 13 at 300 dpi and that brings it down to 137 megabyte file instead of the 500 and something so something to keep in mind if you use drizzle it's going to make the file much larger because it's interpolating the data to try and enhance resolution do the same thing let's get another stretch out of this so duplicate layer ctrl J hit the curves and let's drag from the center up again you can see starting to nebulosity starting to come through the same thing and don't worry about the core right now you're gonna blow the heck out of this core while we're stretching we'll we'll recover that later when we're doing the short frames those 15 sync second frames that I took right now we're just trying to squeeze out as much nebulosity and interstellar dust and detail that we can right here layer flatten now you can use a star mask to keep these stars from bloating I have not quite mastered that yet the settings on that I do use them sometimes and in some images I can get away with one iteration usually if I do more than one iteration of the star mask with a star mask stretch the the stars themselves get these dark halos around them they can be very difficult to remove so I'm sure it's just a matter of setting tweaking to minimize that but I have found just letting the stars kind of do their thing has not been so bad I have a different technique will incorporate here in a moment using the minimize option to minimize those stars alright so now that we've done two stretches here it looks like we could we could get away with one more so let's flatten this out control-j stretch alright that's obviously way too crazy but we're gonna go to about right here okay let's pull this down some I'm pretty satisfied with that we're getting some decent nebulosity detail the core is blown out but there's still good amount of detail here and you're starting to see some of the dust lanes and interstellar dust outside of it to stretch to this degree you really got to have I would say at least 40 30 to 40 the more the merrier the cleaner your image is going to be differed frames and if you're not sure what differing is dithering I could do a whole lesson on that but it essentially what it is is it's slightly changing the composition of your image while imaging so what I mean by that is after in your apt capture software will do this for you is after it takes an image it slightly moves its angle of view of the current target and by doing so the color noise that is produced becomes random and therefore it is averaged out and it cleans up the images beautifully it really does a good job so the more images you can do dither the better now that we've done this let's go ahead flatten it and you see this some of this light pollution that I'm dealing with and I've used a CLS Sky Tech CLS filter with this there's still some light pollution that bleeds through and there's several techniques out there for removing it the light pollution the easiest and one of the I think most effective ways I have found of doing this is by duplicating the layer going to the dropper over here and sampling the area that appears to it's more of this greenish here right let's pull this out I do you know 5 by 5 or 11 by 11 average you want to get an average of the area boom right there okay hold down alt backspace and it makes a solid grading it that color you just sampled then you're going to click on the image here under the layers tab to make sure that's active go to image apply image and you're gonna go to subtract and I do an offset of 30 you can change this 25 30 35 40 to your liking you'll see it changed down here it may make it a little grayer or darker I think 30s kind of been a good sweet spot for the offset so that's what I go with and then I just delete this that's gone now look at that your light pollutions been pulled out and there's really not a whole lot of gradient issue going on here I'm gonna do a control J do another layer you always want to work in layers that way if you screw something up you can delete the layer that you screwed up and you've still got the image that didn't doesn't have any tweaks done to it that you may have messed up but anyway so what we're gonna do now is gradient reduction I'm gonna go into RC Astro this is a plugin this is on Russell Crowe Minh site and it is an excellent plugin it works 90% of the time and there's different levels of it that you can use but you like you know you can go to fine detail medium coarse and these are aggressiveness tabs I usually just stick with medium medium and balance the background and let it run it stain and boom now on this particular one I don't really like this little halo thing that it did on here so first of all let's undo that and what you can do as well is selectively choose using a lasso where you want the gradient reduction to take place so let's say you just want it to do everything but then let's feather this I don't know 20 30 pixels select inverse because we want it to just perform that gradient reduction on that everything but that nebula and let's see what happens here we'll go with medium medium again and see what happens now you notice here it was a much better result it left the nebula itself alone but it did a great job of reducing those gradients there was a good bit more than I thought and neutralized all that gradient out of there alright so now we're gonna flatten this and at this point what I would do is start working on blending in the core so that's gonna be our next step here another thing I wanted to mention in this type of situation where you're gonna be blending multiple images together you you don't want to make any crops or adjustments it's okay to change this as long as this is activated because it'll automatically adjust that to be proportionate okay but you don't want to actually come in here with the crop tool and crop out certain sections it'll never line up properly trust me I've been there done that it doesn't work so for the time being we're gonna leave this like this and now we're going to open up the other image which is the short stack okay this is this this is the stack of 15-second images okay and I think I did 30 of these that were stacked with the same flat and bias frames and just a quick note on that if you're not sure what a flattened bias frame is again that's probably a no hold another video lesson on how to take those but essentially a flat frame is kind of a grayish looking image that helps with Vinnie adding and the bias frames help with artifacts and noise as well you take the bias frames by setting putting the lens cap on your camera and setting it to the fastest shutter speed it can and take you you know 20 30 40 frames there the idea is to get them as black as possible and you do this at the same ISO that you used when you imaged your target same thing with the flats although in this case what you'll do is most people put a white t-shirt and that's what I do to aim it at a clear part of the sky and you're going for you know something about in the middle of the histogram maybe a little on the darker side that's worked well for me and take about 20 or 30 of those okay that's in a little that's just a little tidbit on that in a nutshell but really there's more to it okay so just like with the other one we're gonna duplicate our layer control J and we're going to stretch this bad boy boom and the first couple stretches are not gonna look like much of anything because this was a really short exposure but the idea here is we're just trying to bring out the core okay so let's flatten that that looks good to me ctrl + to zoom in so you can get a closer look to make sure you're not blowing this core out as you start to stretch this so ctrl J we're gonna we're gonna give it another go and adjustments herbs and let's swing that up so we don't want to go that high we don't want to lose that detail in the middle let's just go right about there it's bring that down preserve some of that okay that's looking pretty good there let's flatten that control J again I think we can get away with one more stretch here guys curves and that's that much we're losing the core we want to retain that core detail I'll bring this back a bit see that there we go right about there that's good okay this is what we're gonna work with so let's flatten this layer flatten control - that zoom out here okay and let's make this respective to the size of the other image 20 same thing here 300 pixels boom now it's the exact same size all right if you notice the orientation of this and this is not the same so we need to fix that so we got to flip this horizontally and vertically where was it rotation vertical okay now we're good alright so here's where the magic happens we're going to copy this image paste it on this image make a layer mask and then paste this back on top I'm going to show you dad step-by-step here okay so first thing we're gonna do is press ctrl-a on your dark image okay in control C to copy it and you're gonna click on this to activate this layers panel and you're gonna paste that right on top control V okay it puts it right on top then we can just kind of move this aside now what you want to check for is that it pasted it exactly where it needs to be and the way you check for that is you go into opacity and lower it maybe not that much enough - oh okay you can see it now look at that see it's not it's not perfectly lined up so use your arrow keys OOP to make adjustments to get these aligned properly because if they're not aligned right and it's you're gonna lose resolution okay it's gonna soften your image and it's not gonna look right you can check again there let's write about there I should had some good reference stars right here yeah right no okay that's pretty well centered all right so let's put that back 200% no those are aligned pretty well what we're gonna do now is create a layer mask by pressing this tab right here this little button here okay press ctrl a ctrl C alt click ctrl V and there it is okay there's a mask now when you see it combined like this obviously that's that's not what you're going for so you've got to make some adjustments here and you do that you adjust the mask you can press deselect here get that away marching ants you you go to blur you're gonna use Gaussian blur okay to soften this mask okay and you're gonna just this again zoom in but you're gonna adjust this to your liking you know obviously that looks pretty horrible so we want to just preserve the core we don't want it too soft just enough to bring that core back right so we play around with the slider see what looks good to your eyes that that looks pretty good to me there so I'm gonna go with 101 pixels on that now another thing you can do to help bring back some of that detail is do a curves layer on this so first ctrl M to bring up curves and drag the slider on the bottom here down see what that does now you want to be careful here you want to do it that much but you can bring back some of that detail you lose right about there looks pretty good to me okay we're gonna hit okay then we're gonna flatten all this and now you can crop all this awfulness now you'll notice here on this particular image I did not use a focal reducer and if you've ever wondered what happens when you don't use a focal reducer on a telescope that doesn't have a perfectly flat field this is what you get this like warp-speed field curvature here and it's pretty severe you can see I mean it's it's pretty wide now we can mitigate some of this in Camera Raw filter which I'm gonna do right now we're gonna go in a Camera Raw filter okay under filter tab camera off I'm breaking my own rule here let's back that up control J let's copy that layer alright Camera Raw filter and we are going to go to the lens correction tab and we're gonna go to distortion okay and what we're gonna do is see if you go this way it makes it even worse but if you go the opposite way actually I know it looks kind of weird in the middle but it's correcting a lot of those stretch stars on the outer edge now you don't want to go too far with it obviously get a kind of a weird effect there but you want to keep the stars that looks about right there we're gonna to crop some of that out but that that does help a good bit on the on the field curvature there so I'm gonna go with that okay before and after see how that fixes that we're gonna flatten it and now we're gonna crop out the garbage or the the areas that just don't look all that great okay which includes all these oval-shaped stars and that looks pretty good right there now you got all these in this particular image Orion is not a super busy as in like super star busy picture so there's that you're there's not a whole lot of adjustments you need to make here but we're gonna do a minimum pass on this thing so we're gonna control J copy the layer alright we're gonna go into select color range and we're gonna go to highlights cuz we're wanting to just dim these guys down right and we're gonna just this slider so that we get most of the stars selected we want a good bit you know that's probably good right about there and we don't want too much the nebulosity but at the same time you don't want to lose on those stars so let's say right about there okay now you notice it's selected some of the nebula we don't want it to mess with that so what you do is just go to your go to your elliptical tool and you're gonna press you can zoom in and you're gonna actually I use the poly you're gonna go to your polygonal lasso that's what I use some people use others but and you're going to press hold alternate while you click around the areas you don't want it to cover see that and it deletes it it's the same thing let's we wanted to keep it around that okay and we get a little better here okay you get the idea let's leave this little alone here too we can always reselect stars but you really do want to take the time it doesn't take long to deselect the nebulosity you don't want to mess with that with the minimum filter I'm even going here but you get the idea so you want to make these a little more refined the selection more refined there and that's leaving the nebula alone all right you want to go to select and this next step you want to go to select modify expand and I do usually do with something like this about two pixels but you're gonna probably want to experiment again to your liking but what this does is this expands the selection that you already have here okay so we're gonna expand that and if it picks up nebulosity remember you don't want it to do that so let's get rid of this okay I think we're good here a little bit in the running man got messed with got selected we really don't need all those they're so small as it is okay let's run with that and select modify feather you should do half the amount that you expand this just that's what I do works for me and let me just say you know this is not a you know the I'm not touting this as the absolute best way to process am it is I'm still learning as well but you know from what I've learned reading online cloudy night forums YouTube videos and books that I've read you know these are a lot of the techniques that are used in Photoshop all right so just to recap there I went to modify feather and selected one and hit okay all right so now what we want to do is minimize these stars here's the fun part filter other minimum and you really want to do a small selection but you can get a preview of what it does now I might do and you want this to be on preserve roundness because you want your stars to remain round but let's put two pixels on here see what happens look at that look at that let's zoom in a little bit see what happens to these stars those really tiny one it's just pretty much disappear in the larger ones shrink down just just ever so slightly but enough to you know this is all to taste guys you know really you're you're trying to you know if you're really just trying to emphasize the nebula that's where this really comes in handy I don't think I'd go even that heavy I like the stars in this particular picture cuz it's not two star heavy anyway so I probably do just like a a one pixel on this it okay deselect and there you go here's a before and after look at that for after now these really big ones if this bothers you let's flatten this first control J if they these bigger stars bother you you can shrink them individually as well and one of the ways I do that first thing we actually wanna do is make your selection and I use the elliptical tool here for this zoom in control plus make your selection like let's just strength this guy down he's just a little too big right it's getting centered it right about there filter distort spear eyes and watch what happens here when we drag this slider down mmm-hmm now you notice you go all the way down with it you kind of get this weird halo but you know from here to right about there it's good and look at that it just chops it down and you can do that with multiple stars here and he was a before-and-after see that now this image the date the signal miss came and came through so well I haven't even done it color saturation on this yet adjustment as you've seen I would probably just go you know again that's the taste but for me I would just make a mild adjustment and the way I do this is it going to press control you to bring up the hue/saturation just on this particular one I mean we're talking maybe ten fifteen I don't want to go too heavy here let's just go fit ten let's go ten okay change your mode to color filter blur Gaussian blur two pixels and hit OK alright then you're gonna click the background layer so what you want to do here is bring up the curves adjustment and you want the output to be two five five yeah on the input and the output to 45 okay and then you want to click right in the middle will make sure that these read 128 128 and there you go that's how you make a color adjustment without adding noise flatten that now you could stop here I would take this a little further there still we haven't done noise reduction yet we haven't done sharpening yet and we have done HDR toning yet so that's what we're going to hit on to next so let's bring up the Camera Raw filter again because that's where I like to do my sharpening in noise reduction it does a beautiful job of cleaning up images and you do that when you pull up Camera Raw filter you're gonna go to this tab here detail tab okay let's zoom in now this image really I mean look how clean this is it's really not a whole lot of noise in this image in the first place but there's some let's go to here there's a little bit there the color noise is not horrible you can just drag this slider you can see it though there's some green and blue coming in through there that shouldn't be there and look at that it's gone I just dragged up to a five you see that from there to five gone luminance noise this if you go too heavy it will soften your image but it'll help get rid of that luminance noise which see how that softens up but you want to be care if you don't want to soften image too much but I'd say right about there and that cleans up the noise very nicely same thing with sharpening you want to get more detail out of this maybe lost city you just you know playing around with these sliders see what you get don't go too heavy let's let's go to 45 on the sharpening let's see what happens when we pump that radius up two pixels detail you know go to extremes shoot see what it looks like just see what it does masking let's go down here not too heavy these adjustments are slight it just enhances the sharpness they're ever so slightly that's what I like about Camera Raw filter but that takes care of that now if you go to this tab we can do some minor adjustments to vibrance and saturation as well just drag that up a little bit and get a little more color vibrance clarity adds a little more detail as well it's almost like a sharpening agent see that look how much that that's all the way down that's all the way up which it's a little garish they're a little over the top but you know something like this right here it's nice and you get you can really start to see all this dust around the nebula I like that let's go with that boom okay let's flatten that and let's go do some HDR toning on this thing and see what happens there so I've duplicated the layer and you want to do this under image adjustments HDR toning and yeah let's just go ahead and flatten it because it does that anyway okay so obviously that's just crazy blown out right there so we got to play with these you want to make sure all these are active so you have full control over this okay let's start with the highlights obviously that's that's blowing out our core we don't want to lose core detail so let's there we go let's bring that back right there vibrance is a little little creek huh actually vibrance wasn't bad let's leave the color there saturation is okay you could bring it up even more but that's just getting kind of crazy it's just unnatural so let's that's good there shadow then we lose all of our dust lines and it's just over at the top so let's put this somewhere right about here to bring out those dust lines a little better all right tone and detail ooh that's nuts but you see you see what you can do with this thing it's crazy host to rise it to blur it out let's make some small adjustments here just see what happens if we want to add a little sharpness but I would not mess with exposure slider gamma this can had some details well bring out some detail in contrast all right and again this is all to your liking but you you want to keep the core in control you want to try and bring out some of this detail surrounding the nebula which it's done a pretty good job and there you go I mean you can you can keep tweaking this you can go back and make more curves adjustments to try and bring out more detail because there's a little more there but you gotta be careful once you can only stretch this so far once you get beyond a certain point of what is what data is actually there and how clean your images are you know you start pushing the boundaries of what's gonna leave you with a good image so for me I would just leave this here I'm pretty satisfied with that I think that's that's coming out pretty darn good so that's it guys that is we would flatten this out flatten this image out save it as TIFF JPEG whatever posted online blasted Bragg and that in a nutshell is how I do my image editing in Photoshop I'm sure there's other things that can be done as well you can go in here and something that I'm gonna continue to work on is working on layer masks not just with HDR images like the m42 but really all my images because when you work in masks it just gives you so much more control over each item be it the stars the background you can selectively choose and mask which areas you want to bring the detail out in so more to come on that later guys if you enjoyed the video you felt like you got something good out of it please like and subscribe don't forget to hit the notification bells so you don't miss out on any future videos that we'll be covering tutorials gear and imaging sessions and until next time there's [Music]

Channel: A.V.Astronomy

Views: 24,715

Keywords: Image processing, how to process astrophotos, astrophotography image processing, photoshop for astrophotography, deep sky stacker, deep sky stacker for astrophotography, nebula image processing, M42, Nebula, Deep Sky

Id: uLVZanCDgDA

Length: 37min 46sec (2266 seconds)

Published: Tue Jan 07 2020