 Okay, in this video I'm going to be using two free open source programs for processing astrophotography. First one is called CRL, and the second one is the GNU image manipulation program which a lot of people have already used probably. But CRL is really cool, it's at CRL.org, and if you haven't used it before you can download it right from this site using the download link. I'm going to be using the beta version, which is available right here on the homepage. If you just click on this and then scroll down a little bit, you can see there are pre-packaged versions for different operating systems. Since I'm on Mac OS, I'm going to use that one. So I'm just going to click it, say allow, and then it will start downloading. If you're on Windows or a Linux system, you could use one of those. Once you've downloaded and installed CRL, go ahead and open it. And because I'm using the beta version, it does say unstable development version right here. If you do find any bugs, what you can do is over here, the very far right is the console. And this is keeping track of everything that's going on while you're processing your photos. And what you can do is click on this little button down here. If you hover over it, it says export the log. And this will create a log of everything that went wrong so they could track down those bugs and fix them. So if you do run into any bugs, please report it to the CRL developers by exporting your log. So far, though, I haven't run into anything. But I've just been using mostly some of the basic things like stacking and calibration and things like that. So there is a lot you can do manually by running through these different tabs up here at the top. But one thing I really like about CRL is that it actually can be very simple to just do all of your pre-processing using a script that's built into the program. So what pre-processing means is your calibration. So it takes all of those bias, darks, and flats files that you created, turns them into a master bias, a master, dark, and a master flat, and uses those files to calibrate your lights, meaning taking out all of these deficiencies like hot pixels and vignetting and things like that using these different calibration files. And it can do all of that automatically. It also will automatically register all of your lights, meaning look at the star patterns and put them all in the same place, which it has to do before it can stack all of your lights together, meaning averaging them and throwing out random noise. And so we're going to do all of that in one go using a script. The only thing that is required to use this script, I'm just going to hide CRL here for a second, is you have already had to have organized your files into these four folders. And the folders have to be named exactly like this. All lowercase, biases, darks, flats, lights. And then of course, in your biases folder, you're going to put all of your bias frames and your darks folder, all of your dark frames, flats and lights, so on. So it's a good thing to keep track of which files are which while you're shooting them. But if you haven't done that, you could just use the file system here to figure it out and organize them appropriately. So you can click on one here and see what kind of file it is. So this is obviously a flat. This is a light. You can see the stars and there's Andromeda. Now the darks and bias are a little bit harder to keep apart. But if you are on a Mac, what you could do is press Command I or get info and it will give you info about that file. So I can see that the exposure time on this one was one eight thousandths of a second. But if I'm looking through my files and I don't know where the darks start, I would just have to find the file that has an exposure time of one second because that would mean it was my dark. Anyways, enough about that. You're just going to organize your files into these four folders and put them all into a folder called M31. Then with Cyril, you're just going to go up here to this blue button up here at the top called scripts and choose OSC pre-processing. And what OSC stands for is one shot color. And so that describes DSLRs, but it also describes any color camera, including dedicated astronomy cameras that are one shot color. Meaning that you capture all of the colors in one shot with a Bayer matrix. Okay, it says you're about to use scripts. Running automatic scripts is easy. However, you have to keep in mind scripts are not magic. Automatic choices are made, blah, blah, blah. Make sure you still want to continue. Yes, okay. And it fails. And the reason that it failed, so I just wanted to show you this, is that it didn't find the biases folder. And you're like, hmm, why didn't it find the biases folder? I made all those folders correctly. What's going on here? And the reason is, is because we haven't set up a home directory. We haven't told it where to look. And so we can do this by just clicking this little home icon right up here. Going to my desktop and clicking on M31. And now it knows where to look for these folders when I run the script. So now if I run the script again, this time it goes right into converting 73 files. So that means it's taking the bias files and turning them into fits files or whatever it does, it goes right ahead. And we don't have to do anything from this point out. It will do everything for us and it will take a very long time. Because I am doing this on a laptop and we're stacking close to 1,000 lights, so something like 990 something. So it's gonna take a very long time to calibrate, register, and stack that many lights. So I'm just gonna leave this overnight going and we'll pick back up in the morning. Okay, I had to quit out of Cyril to do some other things, but I've opened it back up here and we have our resulting stacked file. It's a fits file ending in .fit and it's called result.fit. If I open it up here, at first it won't look like much because we're still in our linear state. But if we go down here to where it says linear down here in the middle bottom of the screen, this is our display mode option. And I'm gonna change it from linear to auto stretch. Now with auto stretch on, I can see the image. Right now we're looking at the red channel, but I can also look at the green, the blue, and an RGB preview. What we can see from the RGB preview is that one, we have sort of an interesting stacking artifact here. And two, there is a sort of a green dominant feel to it. The green channel seems a little brighter than the other two. We can fix this with color calibration. But before we jump into color calibration, let's go ahead and first crop the image. So to crop in serial, you're just going to make sure that you're on either the red, green, or blue channel, not the RGB preview. So I'm gonna switch over to blue and then just click and drag to make a box like that and then right click on that box and choose crop. There we go. And now I can apply some color calibration. So if we go up to image processing and go down to color calibration, there's two options here. They both can work well. Photometric color calibration, which I've showed in past videos, you would just type in the name of the object. So in this case it's M31 and select it and it will fill in these details for you. You can click get metadata from image and it will fill in those details for you and then you just click OK. And it will do all of the color calibration tasks automatically based on star patterns in the image. Now, for some people, this has maybe not been working very well or failed, so I just want to show you the other method, which I think is a little bit more foolproof. So I'm just gonna close out of this one and show you the other color calibration method, which is more manual. It's just color calibration. The way this one works is you find an area in the image that represents the background, so an area that doesn't have too many bright stars. Something like that will work for this image. And then I click use current selection over here. And it pulls from my selection and fills in these fields. And then I can click background neutralization. And we can see it neutralized the background a little bit. But the galaxy itself is still pretty green. And so that's the white reference. And so let's go ahead and also fix that. I'm just gonna draw a box over the galaxy here to use as the white reference and click use current selection for the white reference and then click apply. Okay, and hopefully you can see that it did work pretty well. We now see that there's a fair amount of gradient in the background, but we're not gonna be able to fix that with this tool because this tool only applies global adjustments. And so to fix the weird color gradient in the background now, we're going to use background extraction. So I'll close out of that, go up here to image processing and go down to background extraction. And I'm going to turn down the samples per line option a little bit because 20 samples per line is a lot of samples. I'll click generate. That's still a lot of samples, but I think that Pix Insight likes fewer samples for its background modeling or it works better with fewer samples. And I've noticed that I think Cyril likes a few more than I'm used to. So I'm just going to leave it with more samples, but I'm going to right click on all of these samples that are either right on or a little bit too close to the galaxy. Because what you're trying to do with these samples and just right click delete samples, what you're trying to do with these samples is model the background. So if you have a sample on your deep sky object, like the galaxy here, that wouldn't be a good representation of the background gradient. And it would throw off whatever this is doing. So I'm just going to do something like this. And that looks good. I'm going to go ahead and click apply. Switch over to RGB tab. Let's close out of this so we get these samples off the image. And that worked really well, I think. Let's just do an undo, redo to see what it did. So this is before you can see there's a really hot green patch here in the middle and then really hot magenta all along the edges. And then with the background extraction, it looks a lot better. Still not perfect, but a lot better. So last thing I'm going to do here in Cyril is I'm going to go up to image processing and go down to remove green noise. I'll click on the green tab here and click apply. And that's probably a fairly subtle difference. But I did notice some green chromatic noise, especially in this area right here. And that helped just remove it. And now we're ready to, I'm just going to save this one more time as a fits file. And now we're ready to bring it into the new image manipulation program. So I'm going to switch it back to the linear mode here and switch it to 16 bits precision. Let's go ahead and save it. So to save it as a TIFF file, I'm going to use this little save as option here right next to the save button. I'll click on my desktop. And I'll save it instead of as a fits file as a TIFF file. So the ending changed to .TIFF. And then I click save. I do want it to be in 16 bit. No compression. Click save again. OK, I'll go ahead and hide Cyril. And there's our resulting TIFF file. Great. So let's go ahead and now open that up in the GNU image manipulation program. I'm using 2.10. I would recommend whatever is the latest version. And I'll go to the file menu and choose Open. And I'll choose this result.tiff. We'll go ahead and choose Rotate. OK. And then right now, this is still linear, of course. So we're going to go ahead and do our stretching of it first. To stretch, we're going to right click on this result.tiff layer and duplicate it. And I'll call the duplicated layer first stretch. And on that first stretch layer, I'm going to go up to Colors, Levels. And in this Levels command, what we want to do is take the mid-tone slider, which is this middle triangle right here, and drag it over to the left. And you can see when we do that, the image preview changes. And we can now see some detail in here. I'll click OK. And here, I have the histogram window open. If you don't have this window open, it's under Windows Dockable Dialogs. And go ahead and open it up. And I also want us to switch from Value to RGB. And that's a little bit more useful because it shows you all three color channels. But we should have pretty good color balance because we used Cyril's color calibration. So we're just going to keep stretching here. And this time, now that we have the histogram mountain out a bit, we can also use the shadow slider. So I'm going to take the shadow slider and drag that well over to the right here, right up to the edge of the histogram mountain. And then take the mid-tone slider and drag that this way. And by doing this, by dragging the shadow slider this way, the mid-tone slider to the left, the shadow slider to the right, we're adding contrast to the image. We're stretching the image out. And you'll see that this histogram peak or mountain gets wider and wider. And basically what we're trying to do is we want to keep it over here on the left-hand side of the image because there's so much sky information that it's never going to get over here. But we want to stretch it out around this quarter mark. And this will take a few stretches. So I'm going to open up levels once again from the colors menu and do the exact same thing. I'm going to take the shadow slider, move it over, take the mid-tone slider, and move that over, moving both of them in towards the information. OK, that looks pretty good. I'm going to go ahead and try adding some saturation to this now. So I'm going to go to Colors, Saturation. And I'm just going to take the scale way up. So I added 1.7. If we zoom in here, we can see we do have a little bit of blue in the galaxy arms. But it's a little bit hard to see. The sky color and the star color both look great at this point. And so at this point, I don't want to stretch that sky color or star color anymore or really add any more saturation to it. So at this point, I want to separate those things out so I can work on the galaxy alone. And to do that, I want to remove all the stars from the image. And I'm going to do that with a program called StarNet++. It's a free program you can download. I'll show you how. And to work with this image in StarNet, I first have to flatten it. So I'm going to go to Image, Flatten Image. That removes any alpha channel. So there's just three channels, the red, green, and blue. And then I'm just going to export this as a TIFF file called stars.tiff to the desktop. Then what I'm going to do is I'm going to Google StarNet++. This is a standalone program that's useful for removing stars from astrophotography. And I'm going to download it from this source forage page. And if you go to files up here at the top and then go into version 1.1, they have a nice zip file for each main type of operating system. So since I'm on a Mac, I'm going to download the Mac version. Okay, once that's downloaded, I'm just going to move the entire StarNet Mac OS folder onto my desktop here and open it up. And then I'm just going to open up this runRGBStarNet.sh file with a text editor. I'm just going to change these two file names. The first one being the input file. So we called that stars.tiff. And then I'm going to change the output file to m31starless.tiff. This number is the stride. And typically I use a lower stride when I'm at a lower focal length and a higher stride when I'm at a higher focal length. It starts at 128, but you can go down to 16. I'm going to change it to 64 for this image. And typically the lower the stride number, the longer the process takes. So if you wanted to see what will happen, if you run it quicker, you can leave it on the default 128. Okay, then I just have to move this stars.tiff into the same directory. Okay, with that shell file edited like this and the stars.tiff file in the same directory, we now just have to run this file from a terminal command. So I'm just going to open up terminal. And we have to get into this folder. So the command for that is cd for change directory space. And then I'm just going to drag this folder over and hit enter. And then we just want to run this command or this, sorry, this shell script, which calls on the actual program. So to run it, all I have to do is just drag it over and hit enter. And it starts running. It gives us a little information about the file. It tells us how many different tiles that's going to break it the image up into to analyze. That's what the stride number is. So the slower the stride number, the more tiles it will break the image up into and then the longer it'll take. And then it gives us a percentage finished. So this will take some time, probably 20, 30 minutes on my laptop with an image this size. Okay, now that we're done with StarNet, we're going to go ahead and open up the result back up here into GNU image manipulation program. It's this m31starlist.tif file. Okay, and the first thing I'm going to do is I'm going to increase the saturation just with this saturation slider here. Okay, and then I'm going to stretch the image a little bit with curves. I'm just going to go to colors, curves and do something like that. And now the problem is the galaxy looks quite good, but the background is now just as saturated as the galaxy. And so I want to de-saturate the background. And to do that, I need a mask. To create a mask, I'm going to first duplicate this layer. I'm then going to take out, I'll go ahead and name it so I don't get confused. I'll just call this loom mask for luminance mask. I'm going to take my luminance mask layer and I'm going to actually make it black and white by going to colors, saturation and take all saturation out, bringing the scale down to zero. This makes it black and white or gray scale more accurately. And then I'm going to take a curves and just make this mask a lot more dramatic. Basically what I'm trying to do is just make the background completely dark but keep the galaxy white. And so I'll do this through a combination of levels and curves. And now that we have it in this form, just to protect this galaxy a little bit more, I'm going to fill in the outer arms with just a paint brush here. And again, we're not painting the data, we're painting the mask and this mask is just so we can desaturate the background, which has a lot of chrominance noise in it. And we want to desaturate the background without desaturating the galaxy. All right, that's good. Let's go ahead and now apply that mask to this layer. We're going to do that by choosing add layer mask, click add. We're then going to select this luminance mask. So I'll just do select all, edit copy. We can then turn off the visibility of that one, turn on the visibility of this layer mask by right click and do show layer mask. And then we'll do edit paste and we'll anchor this floating selection down into the layer mask by hitting the anchor button. Okay, now we can turn off the visibility of the layer mask just by right clicking and choosing show layer mask again. Just realized I need to, there we go, keep a solid layer below because we just want this to apply to the background. So let me show that layer mask again. And I want to invert this layer mask because I actually want to select the background with white and deselect the galaxy, which should be black. So I'm going to go ahead and choose colors invert like that, that's good. And now I can turn the visibility of this layer mask back off and I should be able to now desaturate and darken the background. So I'm going to choose colors, huge slash saturation, and I'm going to take down the saturation and the lightness of the background. Now let's go ahead and add our stars back in. So here's our stars layer and we'll just do edit copy and edit paste. We'll go ahead and make a new layer from that. And on this stars layer, I'm just going to change the mode from normal to screen. Here we go, and we're almost done. You can see this is looking pretty cool. Only last things I'm going to do is I'm going to rotate this image around just because I like seeing Andromeda in the other orientation, even though it isn't really how it appears in our night sky, I just like it the other way. So we're going to do, and so we'll just do image transform rotate 180. There we go. And then let's go ahead and fix the black point. And I think maybe remove a little bit of saturation because I think it got a little bit too saturated. So let's go ahead and make a new from visible layer. So we've got a layer new from visible. And on this new visible layer, let's go ahead and open up hues less saturation again, take down a little bit of the lightness and the saturation. And then I'm going to open up a curves layer and fix the black point, okay? And then last, I'm just going to work on the background once again. So it's just a little bit too noisy still. So I'm going to go ahead and make a new duplicate of this. So I'm going to right click and duplicate this visible layer and call this new loom mask. And take out the color again. So just go to saturation, bring this down to zero. We'll go ahead and invert it, beef it up a little bit, just with curves. Okay, and then I'm going to make yet another duplicate of this visible layer and call this dsat bg for desaturate the background. On the dsat bg layer, we want to add a new layer mask and bring this layer down into this one. So we'll just do edit copy visible. We will turn off this one, click into this one and click show layer mask and paste it in. We'll anchor that down and then we can turn the layer mask visibility back off by right clicking and choosing show layer mask. And then we can finally take down the saturation. So I'm going to do colors, hues less saturation again and I'm just going to take down the saturation of the background and take down its brightness a little bit to the other thing I'm noticing about it is that it's just like a bit too red and red and blue. So maybe we need to add a little bit of green. So I'm just going to go and go to color balance and so let's click on the shadows here and add a little bit of too much green. Yes, there we go. So yeah, there was just way too much magenta noise in the background. So I'm just going to add a little bit of green and yellow to balance it out a bit here. Okay, but I don't quite like this now because yeah, the background looks a lot better but now the galaxy looks so different than the background that it's standing out too much. So let's go ahead and delete this layer and try again. So on this visible layer, I'm going to first remove some of this blue with the color balance. Actually that's looking pretty good. So I just added a little bit of green and removed a little bit of blue. And that's looking really nice I think. The only problem is still just this a little bit of color noise in the background. I'm going to do a new from visible. So layer new from visible and let's try taking this out with a filter. So let's go to filter enhance noise reduction. Ooh, look at that. So that's a pretty heavy job but I actually like it, that's at four. Let's try taking it down to two. Let's try taking it up to three, back up to four, let me zoom in. Okay, this is at three, that's at four, that's at two, that's at one, that's nothing. So I think I'm actually going to use four. It's interesting because when we were doing this without the serial workflow with the Deep Sky Stacker, I think I found I could only apply one to the noise reduction and now I'm trying four. So we'll see, let's go ahead and try it. You know what, I'm pretty happy with this image. I'm going to stop here. I know it's not perfect, I can still see some like weird banding stuff. Okay, so here's basically just what we got out of zero with a stretch applied, very neutral. And if you want to do a more crazy processing like I did here, we used star net plus plus to separate things out and then use some masking and other saturation and other things, curves to really bring out the image a little bit more, a little bit more artistic look to it. Okay, so let's go ahead and finish off by saving this. I'll save it as an XCF file. That's for if you want to return to it in GNU image manipulation program and keep working on it. And then if I want to save it for sending by email or uploading to a social media, then I would do file export as and just put in whatever file ending you want to use. So I'll just do JPG for JPEG and click export. And it lets me choose the quality, I'll do 100%. It still gives you an idea of the process of using zero and the GNU image manipulation program even though it's not perfect. With these videos, I'm really never going for a perfect image. I'm just sort of trying to show you what can be done with minimal equipment and free processing software to capture something like the Andromeda Galaxy with just gear you already have and free software. So hopefully it's helpful in that respect and you learn some techniques that you can carry forward and try out on your own astro images or you can use my data and try them out too. Everything is available on my website. Anyways, till next time, this has been Nico Carver from nebulaphotos.com. Clear skies.