Vexatious Light Worms & Where to Find Them: Getting Clearer, Cleaner Globular Clusters

lightw worms disgusting right nah at this moment you're probably thinking what the heck are light worms and if you don't know well that's completely normal because it's my own term for well these things let's take a closer look at them lightw worms are what I call the knot of serpentine shapes that often come to infest images of star clusters they are fundamentally artifacts that appear because star clusters may contain con hundreds of thousands to half a million or more stars within a small region of space that is tens of thousands of light years away simply too far away for most small telescopes to resolve clearly the camera doesn't know quite what to do with them and so that Haze gets resolved as these light worms they give the illusion of dust and gas and globular clusters but globular clusters are virtually dust and gas- free so light worms are artifacts that don't belong there to illustrate let's take a look at some clusters that are perfectly portrayed by NASA this is the great cluster in Hercules and as you can see no light worms instead we have beautiful Clarity of the individual stars and the luminescence created by the thick field or Haze of the stars in the core of the star cluster here is another NASA image of NGC 362 once again we have a haze of luminescence created by the thick field of stars toward the core of the cluster but no light worms and this is NG C 6380 another beautiful star cluster with as always an increasingly bright Haze of light toward the core but once again no light worms NASA is able to avoid light worms by time Spence Imaging to build a good signal to noise ratio using telescopes with large apertures for better resolution and shooting in space which avoids atmospheric turbulence what this means though is that lightw worms don't belong in Star clusters but if you go look at images to be found among astrophotographers on the internet on sites like astrain and elsewhere you're going to find a lot of light worms which in my opinion is unfortunate because they aren't difficult to get rid of and today I'm going to show you how so let's go Exterminating the technique I'm going to show you for getting rid of lightw worms is remarkably straightforward but with some star clusters it's a little bit more difficult than others to illustrate this technique I've picked the rose star cluster which has a somewhat more challenging background to clean up for reasons I'll get into in a little bit as you can I'm in pixon site I've just finished stacking data that I've shot of the rosar cluster and I have the Luminosity red green and blue channels all lined up together and presently I'm running blur Exterminator on each of the channels right now in the correct mode to make sure all the stars are nice and rounded out cleaning them up only takes a couple minutes then I'm going to run blur exterminator in default mode to deconvolve the Stars which well also have the unfortunate side effect of further sharpening the undesirable light worms but it's no big deal we're going to clean them up later on a side note you might be wondering why I have not combined the RGB channels together and then just run blur Exterminator on all three of them together though standard practice it's often undesirable to understand why check out the video linked above it only takes blur exterminator a couple minutes to run on all four plates and then the next step is to run star line on the RG andb channels to line them up with the luminance Channel Once star alignment has worked its magic I'm just going to shrink the original RGB images and the registered RGB IM that star alignment produce because we don't need them anymore then open up the channel combination tool and have it combined the red green and blue registered images running a screen transfer function on the outcome RGB Channel shows that the color is imbalance but that was expected even normal so image solver is run to Plate solve the image and then spectrophotometric color calibration is run to get the colors into balance all of that only takes about a minute now all the developing steps up to now have been pretty much standard procedure at least for the way I go about doing things and up until a moment ago we were looking at the core of the star cluster using the screen transfer function the screen transfer function tries to balance out the dimmest areas of a region with the brightest areas of a region and generally it works well but it tends to fail with star clusters by blowing out the cores so star clusters need a manual adjustment with star clusters you have to be more subtle and stretch the histogram to show as much of the star cluster as possible but I stopped at the point that the stretch begins to blow out the core of the star cluster as soon as I can no longer make out individual detail of the Stars at the center of the core I'm done stretching and when stretching is done noise exterminator is run on the histogram stretched image because the next step is a curse adjustment and while a curse adjustment is just another form of Highly specific histogram stretch I find that consistently after the histogram is stretched it's the best time to run the noise exterminator otherwise you just custom stretching noise as well as your desired image and the next major step in the development of a star cluster is a carefully considered curse transformation my goal is going to be to brighten the Stars especially the outer dimmer stars as much as possible but control the curve in the upper right quarter so that the core is not blown out which is very easy to do I almost always start on the luminance Channel get it adjusted and then either adjust the individual color channels if the image looks like it needs it or just adjust the saturation channel in this case I'm going to adjust the luminance Channel first and then saturation this image was shot on a night of about a 70% full moon so there is just a little bit of a gradient in it but I'm going to deal with that last I know some person say deal with gradients first but I have never met a gradient remover tool that I liked to be frank and I almost never adjust gradients first unless they are really severe and even then very hesitantly because every gradient tool I've seen even the very best of them in my opinion they just remov too much information from the image I generally find that in almost every case there are better options to control gradients than a gradient removal tool anyway I'll get the luminance Channel adjusted here then the saturation Channel and then I'm going to rinse and repeat the entire process separately on the luminance Channel though of course I don't have to worry about adjusting saturation on the luminance Channel now it's the luminance Channel that's really going to bring out and display those stars in the outer regions of the star cluster that really did not show up in the RGB adjustment and that's because the luminance Channel gathers light you could say a full f- stop more efficiently than the RGB channels combined the luminance channel on a mono camera is very efficient at gathering information so when I combine the luminance Channel with the RGB Channel we're then going to get a full color image of the Rose star cluster however it's a bit bright toward the core and I want to do a little more to bring out the outer region of the star cluster so I'm going to adjust the curves bit further now I feel we have a well balanced image there's good color in the image and good luminosity and we have the Stars showing very well but if we take a good look at the core of this image now you can see those lightw worms also really well unfortunately now the light worms are the haze of countless stars that could not be resolved and Atmospheric turbulence and due to the fact that they are in part related to the haze of unresolved Stars some might say they belong in the image but I beg to differ I would like my star cluster images to resemble more or those of NASA which are not riddled with light worms I want to capture the special luminous glow that is found within star clusters and light worms really are more like an aberration of that glow also globular star clusters are generally virtually gasf free it's one of the mysteries of star clusters how did they form and because they are gas- free It is believed that they are very old and formed maybe around the time of their host galaxies or the universe itself but they're nearly gas-free so having what appears to be whiffs and trails of a gas-like structure within a star cluster it doesn't belong there and that's one of the reasons that when I develop star clusters I always get rid of the light worms they just really don't belong in an image of a globular star cluster so now that the star cluster is developed let's get around to the business of killing lightw worms to do this you first need to run a tool to remove Stars I use the star [Music] exterminator all right the star exterminator will take a moment to run and then extract the star cluster from the background now you might and very rightly be thinking why on Earth would I run star Exterminator on a star cluster my target is the stars but in this case we're making star exterminator do the opposite job we're not extracting Stars we are extracting light worms and there they are look at those buggers a whole writhing nest of them disgusting so we're going to get rid of them but we can't get rid of all of them and here's why why look at the core of this star cluster right here there does appear to be something of a writhing mass in there but at the very center you can see Tiny dots that represent Stars the core is so bright yet the light so diffuse due to the density the overwhelming density of the stars that the star exterminator gets confused by by the density of the Stars it doesn't know what is star and what is just light or luminous Haze or background to extract so I'm going to have to be careful with what is done with the very core of the star cluster when I get rid of the light worms now to kill the light worms we need to go to work in Affinity photo so I'm going to save both these images as a starless and a star Tiff and then pop over to Affinity photo my favorite photo editor in Affinity photo I've opened the background layer where the light worms are and the star layer the bottom layer is the background layer where the lightw worms are and the above layer is the star layer following standard non-destructive photo editing procedure I'm going to duplicate each of the layers lock them and make them invest they'll serve as proofs in case I make a mistake and need to back up I'll also apply a screen composite to the star layer so the Stars will show on top of the background layer now in the background I could just erase out the light worms but their Luminosity belongs there so I need to preserve the Luminosity the Luminosity is what gives a star cluster its very special glow due to the massive density of stars within one so the way I'm going to get rid of the lightw worms is to add a gaussian blur filter to the background layer the starless layer the gum layer is opened within the starless layer so that the gsum blur only affects the starless layer then with the Stars visible I'm going to drag the slider bar and turn the blur up until the worms have dissolved into a diffuse Halo of brightness but at nearly 9 pixels of blur a problem becomes evident remember I told you there would be an issue with the core earlier on in the video because star exterminator would have a hard time distinguishing between Star structures in that very bright core and what was background light so the core itself cannot just be blurred with the rest of the star cluster we need to bring back the sharpness of the center of the core so that the discrete stars there can once again stand out this is easy to do first I'll select the Gan blur layer and then select the paintbrush tool I then set the paintbrush tool for mask and select the black color which tells it to create an erase mask I will also set the flow of the paint brush for 20% and the hardness to zero this creates a soft paintbrush and I can selectively and progressively erase out the galum blur from the core bringing back the definition in those stars with that transition done I can continue adjusting the gussian blur I want to increase it a little bit more to continue transforming the light worms into a Halo or Haze of Light Within the star cluster and make the star cluster look more natural all the while getting rid of those lightw worm artifacts but diffusing the light so that the star cluster has an overall more natural and appropriate glow in the end 23.7 pixels of gum blur does the trick now within the star cluster thousands of discrete Stars will show and we have good diffusion of the haze of Light Within the cluster there are just a couple last things to deal with there is just a little bit of a red green gradient in the image and I want to get rid of that so I'm going to pop the image over into graps and use the AI to quickly take care of that problem I'm now operating in grap I'm not a fan of the implementation of graur within pix Insight I know it makes it a little bit more convenient to work with it in pix insight but I like the additional control I get by using the gra bird interface now for a proper gradient removal to be done any edges and imbalances have to be cropped out of the image so I'm going to perform a crop first it'll only take a moment and when the crop is done I will use gra bir's excellent AI I know I said I don't like gradient tools and that is true as a rule but this is a simple gradient and gra bird is working with a very bright Target against a very dark background so this is going to really be a piece of cake there that looks great we have good color and the gradient is entirely gone now we'll pop over to my astrobin channel where I've uploaded a version of the star cluster with the light worms now we can see in the uncleaned up version that there is a distant Galaxy IC 4537 on the right of the image and just left of middle Center there is a wisp that may be a bit of perhaps nebulous gas and unfortunately the heavy calcium blur remove these structures from the image let's put them back in this is not at all difficult to do in Affinity photo so I dragged the cleaned up version of the image in and just labeled it says new version and now I'm going to drag in the old uncleaned up version of the star cluster into the image and superimpose the old version over the new version now the new version was cropped in grap so they won't perfectly align anymore however it's very easy to create a perfect manual alignment I'm just going to set the composits or blend mode on the old version for contrast negate and the new version will be able to be seen beneath the old version as if they were negatives in black and white with full contrast difference making each stand out then we can zoom into the pixel right here and align the two images right down to the pixel and in seconds they are perfectly aligned voila we're ready to get to work I'm then going to change the composit or blend mode of the old version the uncorrected version of the image back to normal so that once again the image is opaque then I'm going to zoom in and move to the location of the nebula structure top left Center drag the old version of the image beneath the new version and then make the new version of the image Invisible by clicking the Little Dot on the right then with the invisible layer selected and the erase tool clicked and the hardness of the erase tool set to zero so it makes nice soft edges and the flow set between 20 and about 30 35% I'm just going to erace out the area of the new layer over that nebula structure and now when I make the new layer visible again the nebula structure which was not removed in the old version by a gausssum blur layer can show through the layers now we're going to pop over to the right side of the image and do the same thing to restore the Galaxy back to the image and once the Galaxy is restored I'll just widen the brush up a good bit maybe two or three times the diameter and give a quick brush all around it to create a nice soft transition between the space around the Galaxy and the darker space from the newer image thus the Galaxy from the the old image will show through and the old image will blend naturally into the new image and voila the image is complete let's take a look at the finished version actually let's compare and contrast the old versus the new version here's the old version with light worms and here's the new version without light worms finally here are the two versions side by side and if you would like to compare higher resolutions of the old version with light worms versus the new version without the light worms look in the description of this video for my asro bin link now I know whether or not to allow the lightw worms is something of an aesthetic Choice some of you may feel that you would rather have them there and some I'm sure would rather choose to get rid of them so like every photography technique see this as just another tool in your toolbox if you were building a project you wouldn't use every tool all the time you'll use the tools that you need depending on what you want the project to look like that's all for now if you enjoyed this video or you have thoughts or observations please leave a comment below and I sure wouldn't mind if you took a moment to hit those like And subscribe buttons now have fun doing astrophotography and get out there and shoot the sky [Music]

Channel: SKY STORY

Views: 2,082

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Id: DytWP2P9fx0

Length: 16min 56sec (1016 seconds)

Published: Thu May 30 2024