 Welcome to part 2a of how to capture a galaxy with your DSLR. If you haven't watched the first part, please watch that part first. The link will be in the description. It will go over the entire capture process and then this video, part 2a, is just the editing process where I'll show you how to edit the pictures that we got in Deep Sky Stacker and GIMP. These are both free programs. If you're not already subscribed to this channel, please subscribe and you can also support me on Patreon. The link to that will also be in the description. Without further ado, here is Deep Sky Stacker. I've switched over to my Windows laptop now and the reason is because Deep Sky Stacker is a Windows-only program. If you are interested in free stacking on a Mac or Linux machine, I am going to make a video about Cyril as well, which also does this same kind of stacking process. I do like Deep Sky Stacker if you do have a Windows computer because of how simple it is and it generally gives you also very good results. The first thing that I'm going to do in Deep Sky Stacker, you may not have to do. It depends on how much internal storage your computer has. I know that I'm running a little bit low on local storage or internal storage, so I'm going to go down here to the Settings option under Options and click on Stacking Settings. Then under Stacking Parameters, this little window that opens up right here, I'm going to go on to the tab all the way over to the right called Output and I've already set it here previously, but normally this would say something like C drive and it would put it in a temporary folder on your C drive, which is your local storage drive, your internal hard drive. I'm working on a laptop with a small SSD and I know that this temporary folder often grows to gigabytes and gigabytes while you're working in Deep Sky Stacker. When you close out the program, it does delete it, but while you're working, you need a very big temp folder. What I've done here is I've clicked on this little button with the three dots and I've told it to instead use a temp folder that I just created on my external hard drive, which here is called 2019 backup and it's the D drive on the computer. So whoops, I just accidentally set it to the D drive. I want to set it to the temp folder on the D drive just to keep things a little bit more organized. There we go. And once I've done that, I can go ahead and click OK and it will remember that setting. It will even remember that setting the next time you open Deep Sky Stacker if you were wondering, assuming you have that external hard drive connected. OK, next we're going to, now we're going to actually get onto the main show, which is starting at the top here over on the left and just working down this list of things to do. Starting with open picture files. And the first thing that I'm going to do is I'm going to navigate to my folder, M101 folder, that's on my external hard drive and I've already organized the files into these four folders using Adobe Bridge, but you can also just use your file system to do this because as you can see when I open one of those folders, it does give me a preview so I can see that all of these are lights. If you have to see them even bigger, you can change it to extra large icons and I can see that there are stars in there. OK, but anyways, what we're doing now is we're opening up all of our lights. So instead of just clicking on one and clicking open, I want to first select them all. So I'm going to click on one and then I'm going to press Ctrl A to select all of my lights and then click open. Just to show you that it worked, I can scroll through here and you can see they're all highlighted, meaning they're all selected. And if I click open, you can see that it brings these all into a list right here like that. Now for some reason, Deep Sky Stacker, when you bring in this first batch of lights, it doesn't select them all. The reason it does this, I think, is because what Deep Sky Stacker expects you to do is to go through your lights, one by one perhaps, and check the ones that you want to use. If you've already checked your light frames in a different program like I did in Adobe Bridge, you don't have to do this process and you could just go over here on the left hand side and click check all to check all your light frames. So you can see I now have 392 checked. I did leave in a bad light frame here just to show you what the process might be like if you were manually checking these in Deep Sky Stacker. So this second one I know is a fairly good light frame. And if I just move my mouse over a star, sorry, it's a little bit tricky with the trackpad. Okay, there we go. So if you look over here in the left hand side, this is a 100% zoomed in view. You can see the star is a little bit oveular, a little bit egg-shaped. That's okay. I don't expect this to be perfect. But that's a fairly round star, right? And if I look at a few more stars, trying to find a big one here, yeah, that one is nice and round. So that looks like a good frame. And if I just click on another random frame here and look at that same big star, again, it's a little bit off, but fairly round. That one looks pretty round, right? Okay, so all of these frames are looking pretty good so far, but now let me show you a bad frame to show you what that would look like. And it's this first one here. I left it in purposefully. If I move my mouse over this, you can see that star looks quite weird. It looks sort of doubled up. And then if I look at another one, the same thing. If I look at yet another one, same thing, another one, same thing. They all have this left to right double pattern. And the reason this happens is, well, there's lots of reasons it can happen. The reason I think it happened not here is because I was probably still walking around the mount when I was leaving after I had set it up to take a bunch of exposures. And because the ground was wet, the mount shook a little bit and that gave me these double stars. So I don't want to use this frame in my final result because it might just leave a little trace of that double star. So what I want to do is I want to remove it from the list. The easiest way to do this is just to right click on it and choose remove from list. And you can see our total number of light frames went down from 392 down to 391. And so you could do this just moving through for each frame and examine them all. If you have another program that you prefer, you can do it in there and then just bring in the ones that you know are good. I'll also mention really quickly here that it does also have this thing up here which lets you brighten up the picture just like that. It's marginally useful when you have this much light pollution because we still can't really see any kind of deep sky object, but I just let you know that that's a temporary stretch of your image. So it doesn't do anything to the final image. It's just for you to view right here. Okay that's enough about lights. I'm going to leave all of those checked and then we're going to go over here back to the left hand side and open up our dark files. And we'll go into our M101 folder, click on the first dark, press control A to select them all, open them up. Dark frames, it doesn't, deep sky stacker doesn't think that any of those are going to be bad or that there's any real reason to examine them, so it immediately checks them all. So you can see as soon as I brought those in, it brought in all 30. Same thing with the other calibration frames. So I'll bring in my flats here and I didn't do dark flats because these flat frames if we scroll down to the flats and then scroll over, you can see that there's a lot of cool information here actually. These flat frames are only 1 25th of a second and because they're only 1 25th of a second, that's not much time for dark current to build up, also called thermal noise. And so usually the only reason to do dark flat frames is if you're having a problem with bias calibration or if your flats are particularly long, like 10 or 20 seconds and you're worried about thermal noise in them. But with such short exposures, I'm not too worried about thermal noise and so I'm going to not use dark flats. But we are going to use bias, so I'm going to click on the bias files here. Make sure I'm in my biases folder and click on the first one, press control A to select all and click open. And I shot 50 bias frames, mostly just because they are so short to take. If you are at all unsure about which are your bias frames and which are your dark frames, another thing you could do is you could just open up all of your pictures and then sort of go through here and find, okay, well, here's all my bias frames. They're 1 8000s of a second. There's my flat frames. They're 1 25th of a second. And there's my dark frames because they're 30 seconds to match my lights. So you can use DeepSkyStacker to figure out which files are which and then just reload them in as darks, flats, and bias if you hadn't already organized them as such. Just wanted to show you that exposure column just in case it's useful. The other thing I can check here is that everything is the same ISO. If I scroll up to bottom, bottom to top, yep, everything is ISO 800, which is good. All right. At this point, if I were doing this live with people, I'd probably ask if there are any questions. But if I've missed anything, I always just ask me in the comments because I'm doing this live, but it's hard without an audience. Okay, so we have everything loaded up here. Everything is checked. I know that because it has these numbers right here. So for instance, if I click uncheck all, you can see they all reset to zero. If I click check all, then we have them all, except for the dark flats, which we didn't take. So that's what you want to see before we move on to the next step, which is we want to click on this register checked pictures. Okay, and basically in Deep Sky Stacker, I use the defaults for the most part. I find that the defaults work pretty well for most kinds of pictures and really the only reason to move off of the recommended settings is if you are a more advanced user who knows a bit more about astrophotography and aren't getting the results you want. I'll just show you a couple of things here, though. Some of these things might be if you run into problems. So the first thing is if you are running into problems, a lot of times it's because you're having trouble with registering your pictures together. And a lot of that comes down to this star detection threshold. What this basically means, I think it starts usually at 15% or so, is the detection threshold is how big a star it's going to look at before it counts it as a star. So if we move this to the left and we lower the threshold, then it's going to let in smaller stars. But at a certain point, it might be confusing a star with a hot pixel or other random noise in your picture. And so if we click that, you can see at 7%, it's finding 405 stars. If we bring it up to 65%, now it's only finding 32 stars. So what is the right number of stars to avoid it lashing onto noise? It's hard to say exactly. It really just depends on so many factors. But what I usually do is I try to look for a threshold where it's finding a few hundred stars, a couple hundred, maybe between 200 and 300 stars. Of course, this really depends a lot on focal length. So if you are doing Milky Way shots or something like that, it might find thousands of stars. And that could be perfectly normal. So don't let the exact number of stars be your guide. Really, it's just you might need to change this threshold if you're having problems with registration. Usually, there's no reason to change it off of the default unless you're running into issues. OK. Next thing here is where it says stack after registering. I think that starts off unchecked. But I usually just go ahead and check it. That means that we're just going to get through everything right now. The other option is if you uncheck it, you could just register your pictures. Then Deep Sky Stacker applies a score to every picture. And then you could use the best picture to do, to re-register and stack and everything. I just don't find it particularly necessary with this kind of thing. So I'm going to go ahead and click stack after registering. And where it says select the best percentage of pictures, you can set this to whatever you want. So if you're not sure about the quality of your pictures, you might want to set it lower. I'm fairly sure that these are fairly consistent. So I'm going to set it higher. I'm going to set it to 95%, meaning that the worst 5% in terms of the stars being out of around, it's going to throw out before it stacks them all together. Next thing we can do here is there's two buttons down here. There's recommended settings. And basically all you want to do here is make sure that it's not throwing any big errors at you. If it was throwing any big errors, it would show up in red. And then there's stacking parameters. And this is where it gets a lot more advanced. But the good thing is, again, the defaults in Deep Sky stack are quite good. So there's really no reason to change any of these unless you really want to. Basically, I'll just explain quickly what a stacking mode is. A straight average would mean that it doesn't do any waiting. It just looks at every picture is equal and stacks them all together. A Kappa Sigma clipping does a distribution. And it looks at things that are outliers and it would throw outliers out. And you really want this on, especially if you're imaging from a city, because you're going to get a lot of satellite trails, a lot of plane trails, different things in your pictures. If you just do a straight average, those will show up in the final stack faintly. If you do Kappa Sigma clipping, those will disappear because it will throw out those pixel values and outliers. OK, hope that makes sense. For a result, we just want the standard mode. That's what you want when you're stacking a bunch of pictures together into one master exposure. Mosaic and intersection mode are, if you're trying to make mosaic of the sky. So basically, you're moving your camera all over the sky and trying to make one bigger field of view. That's not what we're doing, so we're going to leave it on standard mode. You can only, these drizzle options are very interesting and they do seem like we would want this, because the galaxy is going to be very small on our sensor. But unfortunately, because we didn't do auto-guiding with dithering, we can't use drizzle. That really only applies if you are dithering, meaning moving the field a little bit between every frame. Otherwise, drizzle doesn't work. OK, I'll click OK. Everything is fine here, so I'm going to click OK again. It gives me a final check here. This is just a screen that explains everything. It does explain down here that this process will temporarily use 53.9 gigabytes on the D drive. So that's what I was concerned about with having that temp folder on the C drive, because I'm not sure if I even have 53 gigabytes available. And if you don't have that amount available, then the process will fail. It tells me that my total exposure in terms of lights is three hours 15 minutes. So with 391 light frames at 30 seconds each, that's our total exposure time. And that's it. We can go ahead and click OK. It now starts off the process. And I will mention here that right now, you can see, the first thing it does is it says adding offset frame. What that means in Deep Sky Stackerspeak is it's putting all of the bias frames together into a master bias. And I'll mention here that right down here, it says estimated time, remaining time, one minute, 52 seconds. That is not the total remaining time. That is just the total remaining time in this step, which is just the first step in many steps it has to do to make our final picture. Because it has to first add together all of the calibration frames to make master calibration frames, and it uses those master calibration frames to calibrate the lights. It then registers all of the lights, and then finally it stacks all the lights. And some of these steps will take a lot longer than others, but I expect this whole process to take hours, considering we're stacking 391 lights. So I'm just going to leave this. What I would suggest is make sure you're plugged into AC power and just leave it overnight. Or if you're going to work, leave it going during the work day, and then you can pick it up in the evening. I'm going to stop the video here and pick it back up when this is all done. OK, it's now finished stacking. And we do get a little preview here. And there is the ability to alter that preview and even save these changes that you make in DeepSky Stacker. I don't recommend actually using these histogram sliders or these different tabs here, because it's pretty coarse and a little bit hard to use these adjustments. And you're going to get much better results in GIMP or Photoshop or any other program that's better for the post-processing. What we can see here, though, I'm just going to use two fingers on my trackpad. There we go. Or if you have a mouse with a wheel, a scroll wheel, you can use that, that we do see the galaxy now. So remember, in our individual lights, we couldn't really see it. Now we can see the spiral arms right there. But we're going to bring it out a lot more when we do post-processing. The one other thing I want to note here before we move on to saving is if we look at this, this is the linear response of the channels. And for some reason, the blue channel looks almost stretched already. I'm not sure why that is. It's probably has something to do with my light pollution here. But it's something to be aware of. This is a very linear response when the spike is very up and down like that. And this is a more non-linear response when it's stretched out like that. So I'm not sure why that happened. But it's something that may impact our processing in Photoshop. So for instance, I might immediately stretch the green and the red to more match the blue before doing more stretching. Hope that makes sense. You will see, if it doesn't make sense, you'll see in the post-processing what I'm talking about. OK, the only thing we have to do now is save. It does create an autosave that is a 32-bit file. Since in previous videos I've uploaded, the 32-bit file has been causing some issues for people. It's really no big deal. I'll show you how to save a 16-bit file that's in this raw state. And it's really easy. You just go over here to the processing window. You just go over here on the left-hand side to where it says processing. There's a little blue box. And the final option is save picture to file. Go ahead and click on that. OK, the default option here is TIFF image 16 bits per channel, which is exactly what we want. It also should be the default option that down here, it says embed adjustments in the saved image, but do not apply them. And you want to leave that checked. We don't want this apply adjustments to the saved image because then anything that we did down here for preview purposes would actually get applied to the image permanently, and you can't reverse it. What we want to do is just get this image in its raw state and bring that into our next program. For compression, I'm just going to leave it on none. I'm going to go ahead and call this M101-DSS. And I'll save it to the desktop. That's fine. OK, it's done saving. And just to check here, I can double click it. And when it pulls up in the default photos viewer, it should look mostly black. That is what we want to see. If you see a very bright image here, something may have gone wrong with your processing. All right, I moved back to my Mac here, and we have the output file from DeepSky Stacker right here on the desktop. This was the 16-bit TIFF file that we saved out of DeepSky Stacker. So now I'm just going to go ahead and open up the GNU image manipulation program, or GIMP. I'm using a pretty recent version here, which is version 2.10. I would recommend updating if you have an older version because only in recent versions did they add full 16-bit support for images, which is what you need for astrophotography. Let's go ahead and open up our TIFF image that's on the desktop here. It opens up in this central window. Just a few tips for navigating. To zoom in, use the plus button. And usually on most keyboards, the plus and equals button shares a button. So you have to hold down the shift key while pressing the equals key to actually use plus. And then the minus key will bring you back out. So that's how we zoom in and out. We can see it's a mostly dark image with just some star cores here. That's what we expect. The first action that I'm going to do is I'm going to go ahead and go over here to the Layers panel. The Layers panel is in the lower right. And I'm going to duplicate this layer. I always like to initially duplicate the layer so I can always go back to the initial one if I need it. The way to duplicate is you can just right click and choose Duplicate Layer from the contextual menu. Or you can go up to the Layer menu at the top of your screen and choose Duplicate Layer from there. Once it's duplicated, I'm going to go ahead and rename the layer by just double clicking and typing in a new name. I'm going to call it First Stretch. With that done and the first stretch layer selected, we're going to work on some levels, meaning stretching the image using the Levels command. But before I open up that, I'm going to first look at my histogram here. And you should, if you are on a recent version, see the histogram up here in the very sort of upper right area. If you don't see it, go to Windows, Docable Dialogues and just choose Histogram and it should pop up over there. And what I want with this histogram is to be able to see the red, green, and blue channels. And so if you go up here to where it says Value and go down to RGB, you should now see red, green, and blue channels appear right here. And one of the issues with this image, probably due to the heavy light pollution, is that the red, green, and blue channels are quite separated. And the blue channel is like way over here, like right along the left edge in the almost being clipped while the green and red channels look a lot more healthy. So we're going to try to correct that a little bit in the Levels command, but it's helpful to see the histogram here as we're working. And I'll also note if your histogram looks like that, because this area of the screen is way pushed over to the right, go ahead and just grab this little three dots right here and stretch this over so that we can really fully see this histogram. Because right now, actually during the stretching, being able to see the histogram is actually more important than being able to see the image. So it's fine to shrink the image down a little bit so we can more clearly see the histogram. Anyways, let's go ahead and open up the Levels command. It's under the colors menu. So we go up to colors and then choose levels. And just like in this histogram panel, under channel, we can use value if we want to just stretch the entire image, but I'm going to be actually working on the red, green, and blue channels separately. And so the first thing that I'm going to do is I'm going to try to stretch out the red and the green and get them fairly evened out and then we'll work on the blue last. So this is going to be an iterative process, meaning that we're going to do it multiple times. It's very difficult, especially with such a crude display to get it right the first time. So we have to do it a few times to stretch out the image. And the way I'm going to do this is I'm going to take the mid-tone slider here and move it into the left and take the shadow slider here and move that to the right. And then hit OK. So each time I bring up the levels command, I have to re-choose the channel that I want to work with. And basically, I'm going to do the same thing that I did before, which is stretch out that red channel a bit. And we'll do this a few more times. Okay, now that the red is sufficiently stretched, I'm going to do the same thing to the green. And it's just, again, just something we are going to keep working on. Remember, each time go up here to channel and select the channel that you want to be stretching. Okay. At this point, I'm going to try to bring the blue a little bit off of this left side to better match the green and the red. So I'm going to go to colors, levels, and this time pick blue. Okay, and at this point, it can be useful to zoom in a little bit. So we can see the galaxy that we're working on. Right now, because there's this heavy light pollution cloak, it's a little bit hard to get an idea of the color balance just from this. But it can still just be fun to sort of see it come out as we're doing this stretching. So I'm going to try to do a little bit more balancing here. Again, just with this color levels command. So I'm going to bring up the blue just a little bit more. So it's now at least overlapping with the red and the green. We can see that the blue is a lot more stretched out, which is why the background is completely blue here. So we want to stretch out the green and the red a little bit more. So let's go to colors, levels again. Bring up the red. Okay, that was obviously too much because it brought that red peak way over to the left side. So that's not what I wanted to do. I'm going to go ahead and undo that. So I'm just going to do edit, undo levels. Let me try that again. I was a little too aggressive there. So let's do colors, levels. Again, choose red and I'm just going to do a smaller move this time. And the reason I'm just doing this very gradually and then waiting is because the histogram display doesn't update immediately because it's basing it on the preview. So basically I make a move here. It has to send that information to the image and then the histogram display over here changes based on what it's seeing in the preview. So basically what I'm doing is I'm just trying to sort of line up the black points of the blue and the red over here. Okay, that's good. I'm going to go ahead and click okay. And now we'll go back into colors, levels and try to deal with this green channel. And basically, whoops. And basically the green channel needs to be stretched out some more. So I'm going to use both of these. I'm going to use both of these sliders, both the shadows and the mid tones and just sort of watch it over here. That's looking better. Maybe just a little bit more of this one now. Okay, that's fine. I'm going to go ahead and hit okay. And now we're really to the point where doing any more stretching at this point might be counterproductive because we can't really see the true color of the image because we've brought out the light pollution gradients so much, both the vignetting of the system but then also this crazy color is just all the local light pollution gradients that we need to subtract that before we can really get a true sense of this histogram. So to subtract it, we first need a version of the image that is free of both the galaxy and all the stars. And this is basically just a model of the background. And to create that model, I'm going to go ahead and duplicate this layer again. So I'm going to duplicate the first stretch layer. Again, the way we can duplicate a layer is by right clicking on it and choosing duplicate layer from the contextual menu or you can go up to the layer menu and choose duplicate layer from there. And I'm going to call this duplicated layer background. And to this background layer, we want to basically do some processing on it to remove all the stars in the galaxy but leave behind this just sort of general gradient of the background. So I'm going to start by going up to the filters menu and under filters, there's different categories here and go ahead and choose the enhance and then choose de-speckel. And what I'm going to do in de-speckel is I'm going to raise the radius to the highest it will go, which is 30 and watch what happens when I do that. I'm actually going to go to an area of the picture with more stars. Okay, so here it is at the default value and then if I raise it to 30, you can see even the bigger star cores all sort of disappear. I'm going to go ahead and hit okay. Okay, and that takes out a lot of the bright stuff in our image to, we might want to just try running it again. Let's see if that works, I'm not sure if it is. We can just try repeat de-speckel from the filters menu. Didn't seem to do much. So we're still going to have to deal with these smudgy little bits here. Go to filters, choose blur and then Gaussian blur. And again, the default size of the blur will be insufficient for this job. So let's go ahead and raise it way up. I'm just going to enter something in here. Let's just try 200. Okay, so I'm just looking at the preview here and with the Gaussian blur set to 200, it seemed to have taken care of all of those smudges left, both the pinwheel galaxy smudge and all the little leftover star halos. So that looks good to me. Again, just play around with this until it looks right for your image. I'm going to go ahead and hit okay. And now we have, if we turn the visibility of the background off and on, what we should see is that we basically just have this blurred background model that perfectly reflects the color and intensities of our actual image, the first stretch image. And so now what I'm going to do is I'm going to duplicate the first stretch again just in case anything goes wrong here. So I'm going to go right click, duplicate layer. I'll call this duplicated layer BG for background removed. Okay, and now what I'm going to do is I'm going to take the background layer here and we're going to apply it down to the BG removed layer using the mode command. So basically every layer in the layers panel has a mode applied to it. And usually we have the normal mode applied, which means we're only seeing the background layer here because it's on top of our layers and the layers panel. But if we want to subtract the background from the layer below, we can choose a different mode here. We want to choose the subtract mode. So we'll just open that up and go down into the list and choose subtract. Okay, and you should immediately see the image instantly sort of looks a lot more like a deep sky image as you'd expect. Let's zoom in here though and just take a look at the pinwheel galaxy. And one thing that we don't want to do is take away too much of the image at this point, meaning clipping to black because you can see that the sky is very dark here when we use the subtract mode. So I'm going to change the opacity a little bit of this background layer. So you can see mode is set to subtract. Opacity right now is set to 100. And I'm just going to go down a one percentage point at a time until I can see that I'm not losing any detail in the galaxy. And so you can see as I'm doing this, a lot of the detail of the spiral arms are coming out. And so I'll just go back up to 100. Okay, and you can see a lot of that faint detail in the arms is just clipped into the black background. But if we go down to, I think we were down to 80. Now a lot of that detail comes back. So at this point, even though we're trying to subtract the background model, we don't want to do so in a way that is destructive to the image. Let me zoom out a little bit here. The only downside to the way that we're working now is that because we're only subtracting the background model at 80%, we're still left with a number of gradients. The truth though is I was never expecting to use the entire field for this image. So I'm going to crop to a much smaller area anyways because I just think that will highlight the pinwheel galaxy. In this larger field, I feel like it gets a little bit lost as our main object. And since I'm into this for mostly artistic reasons and don't really feel the need to preserve the entire field, I'm just going to crop down. And so I'm not going to worry that we still have a bit of a gradient on the edge here. If that is a worry to you though, you could subtract at 100% and then just try to deal with the clipping other ways. But I'm just going to try to get the most out of the galaxy and do that by cropping away a lot of the field. Okay, anyways, so that's now set. This is what the picture looks like now. Just to clean up the layers panel a little bit though, I'm going to merge this layer down into the one below it. And you can do that by right clicking on that layer and choosing merge down. I believe that's also available. Yes, that's also available in the layers menu up here, merge down. And then the BG just becomes a part of the BG removed layer below it. Okay, so now we have first stretch, which looked like that. And we have background removed, which looks like this. The next thing that I'm going to do is I'm going to crop. And so let's zoom in here a little bit with shift plus or shift equals to make the plus sign. And I'm just going to find the parts of the picture that I want to keep. And so there's some cool things in this field. One is there's a little edge on galaxy right there that I definitely want to keep. There's also an irregular galaxy up here in that corner. So I'm going to use those two as my sort of like corners of the image and make sure that I am including those when I crop. Okay, so I'm going to open up the crop tool, which is over here in the tools panel. It's the third row down four over from the left. And I'm just going to do a free crop that includes both of those features that I mentioned. Something like that. And you can see that by cropping down to this, we now have a fairly uniform sort of bluish background. Okay, I'm going to hit return or enter to accept the crop. And we're well on our way. So now the issue, if we look over at the histogram, is that the blue channel is way out here and the green and red are more in line. So we're going to maybe dial back the blue a little bit or stretch the green and the red to even these out a little bit, which will give us more natural color here. So let's open up that colors levels command. Again, and I'll bring up the blue channel here. And I'm just going to bring in the shadow slider a little bit, something like that. And actually, since we're sort of working on all the colors right now, I can actually, I don't have to close, I don't have to hit okay yet. I can make that adjustment to the blue and then switch right over to the red. So I'm going to do that. And I'm going to bring up the red channel a little bit, something like that. And at this point, it actually can be useful to look at our images we're doing this. I'm going to zoom in a little bit or maybe not. Okay, I'll zoom in next time. So this is actually looking really good. The only thing that I might want to do is just bring the level, the red over just a tiny bit more, too much. There we go. Okay, I'm going to hit okay. Now let's go ahead and zoom in. Okay, and we still have just a little bit of an uneven background, but let's see if that matters as much once we do a few more steps here. The next thing I'm going to do is I'm going to make a luminance layer. And basically what I mean by that is a layer that is devoid of all saturation, devoid of all color. And we're going to use that luminance layer as a mask as we get going here. So let's go ahead and create it. The first thing we're going to do is we're going to duplicate the BG removed layer. So I'm going to right click and choose duplicate layer. I'll rename this luminance. I'm going to go to colors, desaturate and choose mono mixer. And basically this lets you change a color image into a mono image or a luminance image. And it lets you change the red, green and blue channel mix if you want to. So I'm just going to play around with this a little bit. That looks fine. And hit okay. And now with this black and white image, I'm going to stretch it in such a way that the stars and the galaxy really stand out, are really white and the background is quite black. We're going to try to make it really dramatic because that's what we want for a mask. So we're going to use the colors option again. This time I'm going to use curves. And we're basically just going to apply what's known as an S curve here, okay? And again, this is an area where I feel that doing it in a few steps is useful. So I always start by putting a point down here in the shadows area and then do something with this one up here. And basically what I'm trying to do is just make the stars and the galaxy quite bright in the image so that eventually we can just knock the background down to black like that. We want more, okay, I'm going to call that good. So basically we've just made a very black and white mask where it's protecting the stars and the galaxy but excluding all of the background information. And what I'm going to do with this now is I'm going to make a new version of the BG removed layer. So I'm going to go ahead and duplicate it again. And I'm going to call this saturate and I'll make another version of that. So duplicate it once again and call that desaturate. And so basically I want to saturate the galaxy and the stars and desaturate the background. And with both of these, we need to apply the luminance mask to them before we do our work on them. Okay, then I'm going to right click on the saturate layer and choose add layer mask. We can just start it with white, that's fine. Then I'm going to go up here to my luminance layer and select it, so do select all, copy it to the clipboard. So you can either just do copy or copy visible, either one will work. Okay, I've added a layer mask here. I'm going to go ahead and choose that we want to edit the layer mask. So make sure that work on the layer mask is X right there. Then go ahead and paste. So you can do edit, paste or command V on Mac, control V on Windows. For whatever reason, this is the way Gimp works instead of just pasting it right into the layer mask. It puts it as a floating selection, which you can then do different things with. But we want to anchor it into the layer below, in this case, into the layer mask because that's what we last selected. So just going to hit the anchor button right there. And now you can see that it's been put into the layer mask. Just to double check that, what we can do is we can right click on it and click show layer mask and we can see, yes indeed, our layer mask is now the same as our luminance layer. Okay, now we're going to do the same thing for the de-saturate layer, except we want a inverted luminance mask. So let's go ahead and turn the luminance mask back on and duplicate it. And I'll just rename this inverted loom. And then let's go ahead and go up to the colors menu and choose invert. It does a straight inversion of the black and white, which is what we want. Since we really want to protect the galaxy here, I'm also going to apply a threshold to this inverted loom, meaning that it's going to become even more black and white, not just this sort of shade of gray here. So I'm going to go up to the colors menu and go down to threshold and then raise the middle slider over here to the right until that galaxy part is completely filled in, hit okay. Okay, now let's go ahead and copy this to the clipboard. So I'll do select all, edit copy. I can go ahead and turn off the inverted loom and the luminance, turn on the de-saturate layer, go ahead and add a layer mask to that layer, control click or right click and choose add layer mask. Doesn't matter what we put in at this point. Go ahead and then select that layer mask. So just make sure that you have edit layer mask clicked there. And then let's go ahead and paste. Okay, let's paste. And then again, just like we did last time, anchor that floating selection down into the mask. And then just if you wanna be sure that it actually is there, just click right click and choose show layer mask and we can see, yes, it is there. Okay, so I'm gonna turn off show layer mask, click on the actual image here, the de-saturate layer and I'm going to go ahead and do what the layer says. We're gonna de-saturate the background and also darken it a little bit. So let's go ahead and go up to the colors menu again. Choose saturation. Nope. Go to the colors menu again, choose hue dash saturation and I'm gonna bring down the saturation and also bring down the lightness, okay. And then on my saturate layer, I'm gonna do the opposite. So I'm gonna go ahead and go up to that colors menu, choose hue dash saturation and bring up the lightness and bring up the saturation. Okay, if we look at our galaxy again, we can see that we're getting some blue color in there. It's a little bit faint still. So one thing we may want to do is actually just duplicate this saturate layer that will bring it up even a little bit more and I can duplicate the de-saturate layer too. And let's just look at our RGB histogram again. It's looking pretty good. One thing I'm noticing is that the picture has a little bit of a green cast to it. So one thing we might wanna do at this point is make a new from visible layer. So under the layer menu, there's an option to make a new layer from what's visible and it just makes a new layer over here that just is called visible. And I'm just going to try to, in this layer, balance the colors a little bit better and zoom in on the galaxy. So you can see that we have some blue and yellow look to it but which is what we want but it's also a little bit too green in general. So I'm going to again go to that colors, open up color balance and let's just try adding a little bit of magenta to the image, a little bit less green. And I think that immediately improves it quite a bit. It's a little too far. You can also play around with the cyan red command here. I think that definitely improved the star color quite a bit by adding a little bit more red and we can do the blue, yellow. So right now we're working on these color levels in the mid tones but we might need a fully different option for the highlights and the shadows. So I'm going to go ahead and click okay on that and go ahead and zoom out back a little bit. This is looking really nice I think in terms of colors but really what I want to do at this point is bring down the background level quite a bit. So I'm going to use that that desaturate layer mask. Let's just go ahead and duplicate this visible layer and I'm just going to call this Black Point Correction. I'll go ahead and add a layer mask to that and I'll turn back on my inverted loom here and let's just copy that, turn it back off, click on my Black Point Correction Mask, press Command V or Control V on Windows and then anchor that down into there. Okay, so we now have the inverted loom as the mask on the Black Point Correction meaning it's not going to bring down the color of the galaxy or the stars. Okay and then I just have to click on away from the mask onto the actual image because now we want to actually make an adjustment to the image but with that mask applied. So we have to click on the image. One little way to know which one you're clicked on I mean, it makes this white box around it but the other thing to keep in mind is that if you're clicked on a mask you'll see that there's a green border around the image and if you're clicked on the actual image then there's a yellow border. So we want the yellow border. Then I'm going to go up to the colors menu and go down to Curves and I'm just going to reset the Black Point just like that by just bringing it over and you don't want to go too far with this. I know that might look better to some but it makes the image look a little bit, I think, fake. So we really want to be careful here with how far we go with this. Something like that is better than just bringing it really into the clipped black area, okay? And there's not too much more I want to do with this. The one thing that is bothering me a little bit is just that if we look up here, I don't know if you can see this because it's pretty subtle but there's this dark area right here that it's a little bit darker than the rest of the sky. What I think happened is there was a dust mode that didn't get corrected by the flats and so I just want to bring up the values in that area a little bit. Okay, so what I'm going to do is I'm going to create a new visible layer. So a new from visible again. So now we have visible number one here. I'm just going to rename this touch up and I'm going to add a layer mask to that. So just right click and add layer mask. I want it to be black. Okay, so now we have a black layer mask on there. The layer mask is selected. Now I'm going to choose a brush, the paint brush tool. I'm going to change the color of that brush to white. I'm going to use a 0% hardness and the rest is fine. I'm just going to adjust the size until it sort of matches that streak I see. And then I'm just going to draw out a line on there. And if we want to look at it, we can show the layer mask, there it is. Turn it back off. And that line just basically matched where I saw that it was a little bit darker in the background because of that artifact. Now I'll click, now actually I'll zoom out so you can see the whole image again basically. And now I'll click back onto the actual image here and go to colors, curves. And I basically just want to brighten up that area of the image just a little bit. So I'm just going to grab the curves. And you can see if I go too far, then it's quite obvious what I'm doing. But if I just brighten it just a little bit like that, then it just sort of evens that area out. And one thing that I'm noticing is that I didn't quite cover the whole streak with my first brush stroke. So I can leave this curves on, but now just click back on the layer mask, bring up the paintbrush again, and just try to paint that in a little bit more until it looks good. All right, that looks good. So I think we are about done here. This is our final image out of the GNU image manipulation program. Hopefully you can see that we do have some star color here. We do have some color in the galaxy. Of course, this is a fairly noisy image, which is to be expected shooting from Portal 9, but I think a lot of people might still be happy with this given the conditions. So final step out of GNU image manipulation program is to save it. And so if you want to return to it and keep editing it here in GIMP, you can do save as and save it in the native format. So I can just call it m101.xcf, click save. And then that will keep all the layers information if I want to come back and try fixing something or changing something, I can come back in and just delete a layer, try again, that kind of thing. Okay, then I'm just gonna do file export. And this is how you save anything other than the GIMP file format. So the default is PNG, but if I want to do JPEG, I can just switch it up there to .jpg and it'll save it as a jakepeg instead. Gives me some options. I'm just gonna do 100% quality, click export. Okay, there's our final image out of GIMP. The one thing I might, I really like how the stars came out in this one. The one thing that I might do a little bit differently is I think the way that I did the layer masks, we got a little bit too much noise in the galaxy. I think when I use that threshold command on the one layer mask, it made this a little bit too standoffish, even though it does really stand out this way. So I might change that a little bit, but overall, pretty happy with it, given just an hour of work in GIMP. If you have any questions or suggestions, please leave them in the comments. And if you stick around here for a second, you'll see all of the people supporting me on Patreon. I've been getting a lot of new people in that community and I really appreciate all the support. Till next time, this is Nico Carver from nebulaphotos.com. Clear skies.