 Hey everyone, this is Nico Carver from Nebula Photos. This is part two in a new series, I guess, about processing the comet that's in the sky right now, but this will also work for any comet. And in the first part, I showed the process in DeepSkyStacker and Photoshop. DeepSkyStacker is Windows only and Photoshop is paid software. So in this tutorial, part two, I'm going to be showing software that is free and cross-platform, meaning it works on Linux and Mac computers. And I'm going to be using three different software packages in this tutorial, but hopefully it'll be pretty easy to follow along. The first one is Serial, S-I-R-I-L, and you can get it at serial.org. And I just want to mention in the Serial part, I'm going to be basing it off of this written tutorial, which is great on working with comets that's in their tutorial section. I'm not going to be doing all the steps that they show because they also show how to do animations and some other things, but I'll be using most of the things in here. And then I am going to be using StarNet++, which is this program to make your images starless. And I'm going to be using this just to help clean up our comet image when we want to combine the stars in the comet. And this is available at starnetastro.com, and you can just click on download here. And there's a command line tool for all of the operating systems. Okay, and then lastly, I'll be using the GNU image manipulation program. And again, this is cross-platform. You can get it for Linux, Mac OS, Microsoft Windows. I'm going to be using this one right here, 2.10 on Apple Silicon directly. Okay, so that's all of the preamble. You need to download all of those programs. And then you also need your photos of the comet and your calibration frames. So here are my photos of the comet. I've already picked out about, I don't know, 40 or 50 here. I got a question about why I don't just use all of my comet pictures. From my understanding, that often actually degrades your final picture because the comet moves so much over multiple hours. So I usually just sort of constrain it to about an hour or less. And then I have some flats, darks, and bias frames. And the way that Ciro works with the automatic scripts is you want to put all of these into their own folders like this, and then all into one folder. So I have this main folder here called comet photos. And then inside that folder, I have biases, darks, flats, and lights, each with those kinds of frames. Okay, so now we can go ahead and open up Ciro. There we go. You can see I'm on version 1.0.6, which at time of recording is the latest version. And if you look up here at the top in the middle, it tells you your current home directory, which on Mac by default is your pictures folder. We want to change that to our comet photos folder. And the way to do that is just go over here on the upper left hand corner, and you'll see a blue button with this home symbol. And if you hover over it, it says change current working directory. So go ahead and click on that and then navigate to where you have your comet photos. So for me, it's desktop comet photos. I'll click open. And then you can see right up here at the top. That's my current working directory. And then all I have to do is go up here to this blue button that says scripts and choose OSC pre processing. OSC stands for one shot color. And because I took this with a color camera, the ASI 2600 MC, this is the one that will apply. We don't want to do any of these other ones. This is the one for comet pre processing. So I'll just go ahead and click that. And it starts going. So it first makes calibration master files out of your flats and your bias and all of that. And then it will calibrate your lights, register your lights and stack your lights. We're going to have to do some re registration and restacking since this is a comet photo, but this is a good first step to just get everything calibrated. So we'll let that go. So we'll let that go. It should just take a few minutes and then I'll catch back up with you. Okay, that finished. It just took one and a half minutes, very quick. And if we look at the result, what I expect to see is clear stars, but a blurred comet. Well, I mean, first, when you open it, it's just black because that's because we're in the linear visualization space. But if we change this to, for instance, auto stretch and go to RGB, okay, well, it's green. Okay, let's just go into a color channel here. Yes, okay. So the reason you're seeing two comet trails here and two nuclei with a little gap in between them is because I actually picked a group of lights from early in a little bit earlier in the night and then a little bit later in the night because there were some passing clouds. So that's why you're seeing it like that. But yeah, you see that it's a smeared comet image, but the stars look good because, of course, it registered on the stars. Okay, but what we're going to do is now go through the whole comet process, which is a little bit of back and forth through these different tabs up here. So you'll get comfortable with these. So the first tab you're going to have to click on is this one that says sequence. And if I just click search sequences right now, nothing comes up. So that's a little confusing. The reason for that is the sequences are actually not stored in this directory comet photos. They are actually in the process folder. So what you have to do is click on this little blue home symbol again and click into the process folder. And in here, you can see that there's a bunch of sequence files, as well as all of these calibrated files that it used to make this picture. So anyways, click into the process folder, click open. And now when you click search sequences, you should see all of these different sequence files. And the one that we want is this one, pp underscore light, not this one, we don't want the registered because we're going to re-register. You'll now see that there's all of these different sequences. And the one that we want to click on is this one, pp light dot s e q. Don't click on this last one, the registered, just click on the pp underscore light. pp stands for pre-processed. And when you click on it, you'll see here that the view changes. What it changed to was the file that it picked as the reference frame. And we can double check this by going into open frame list. And looking through here and see, yes, it picked number 10 as the reference frame. And the reason it picked this one is just because it had the lowest full width half maximum, meaning the smallest stars. Now in my case, it happened to pick one right in the middle of my frame list, which is exactly what we want for comets. But if it didn't do that for you, you might want to pick a different reference image, one with a good full width half maximum score, but that also puts the comet sort of where you want it in the frame, because it's going to register everything to this file. And so for me, number 10 is exactly perfect because the comet's right in the middle. This is exactly sort of the framing that I wanted. But if not, pick one for you where the framing is good and mark it as the reference image. Then what you have to do is open that reference image by clicking up here into the upper left, click open. And in your process folder, find that file. So PP light underscore 10 dot fit and click open. Okay, now it's open. And the way that I can tell is down here in the lower left, it says image PP light 10 dot fit. So it's actually opened. It's not just showing me it. And what I want to do with the file is color calibrate it. And the reason for this is it'll allow us to apply this color calibration to all of the comet pictures, which will be important later on. So I'm going to click into the RGB tab so I can see what's going on here. I'm going to go to image processing, go down to color calibration. And I'm going to pick photometric color calibration. Okay, and then we want to find hold on. Okay, no, sorry. Instead of clicking find, go down here to say where it says get metadata from image, click on that. And if you used a dedicated astronomy camera with software, it probably will have your coordinates in the metadata, like it did for mine. If that didn't work for you because you used a DSLR or something like that, you'll just have to type these in manually. You probably have them already noted down somewhere. If not, I guess you'll just have to work backwards using like a planetarium tool or something like that to figure out the right ascension and declination. For this field. Okay, then again, it probably auto filled the focal distance and pixel size, but if not, you can type these in manually for your telescope and camera. And then just click, okay. Okay, and it's done. So I'm going to click close. And you can see now it looks a lot better. This looks really good in terms of the color calibration. But it did flip the image around. And I'm not sure if or if flipped it like horizontally. So I'm not sure if that's going to mess things up for registration. So I'm just going to flip it back. I don't know if this is necessary, but I'm just going to do it. So I'm going to click on horizontal mirror to flip it back how it was. Okay, and then there's a very important thing you have to do that is pretty easy to miss. You have to save this reference image, which will override it. If you just go up here and click on the save button where it says save the current fits image, just click that button down here in the console, you'll see it says saving fits. Okay, and then you can click back to the sequence tab and click search sequence again and open up this PP light sequence again. And if everything worked correctly, it should the picture shouldn't change over here. It should stay on your color calibrated number 10. If you switch to this sequence and this goes green or weirdly colored again, then you haven't correctly saved the reference image. Okay, so definitely do all this before you go any further. You need to color calibrate the reference image. If for some reason, photometric color calibration didn't work for you, you can use the normal color calibration where you define the background, you define white, you can use the comments nucleus and then do a black reference a white reference and color calibrate that way. Okay, so now with this sequence open again, we're going to go to registration and go into registration method and choose global star alignment deep sky. And you can leave that alone register on the green all of these other settings should be fine. Definitely don't drizzle and then just click go register. I should say is this is finishing up that in my case, I probably didn't even have to do this because the reference image that it auto picked in pre processing was the same one that I wanted to use, but I'm showing this and you should just do it anyways because your reference image that you pick for the comment might be different than the one that it picked earlier. So just do this anyways. It's a good idea. When that's done, click into stacking. And you want to pick average stacking with rejection for normalization, leave it on additive with scaling and for rejection. You can pick any of these but I'm going to pick Windsor eyes Sigma clipping as long as you have at least like 15 or 20 images that one should work well. The defaults on the Sigma low and high are three and three. For a comment stacking, we usually turn them lower. I've experimented a little bit with different values here and it doesn't seem to really matter, but you know, one or below. So I'm just going to leave them on one. You can try even lower values. It might help reject the comment more, but in my case, it didn't. So I'm just going to leave it on one and then we can give this file a name. I'm going to call it stars stack dot fit and click start stacking. Okay, that's done. Here's the stacked image and you can see it left a pretty big mess with the comments. That's fine though because what we're going to do is we're going to use star net plus plus to just extract the stars from this image. So I'm not going to worry about the comment mess. I'm not going to worry about the gradient. I'm just going to leave this image as is for now and it's already saved. So we can just move on. So we're going to go back to sequence. It's you can see that it switched it to registered PP light dot sequence. That's actually exactly what we wanted it to do. So we can just leave it like that. We can then go back to registration and change it to comet slash asteroid registration. And the way that this works is we pick the object in the first frame in the list and then pick the object in the last frame in the list and it determines the path of that object. So we have to go back to sequence, click open frame list and click on number one. Okay, you can close that now. I'm going to click into the blue channel and then just make a little box around the comet's nucleus, the brightest part here in the core. Go back to registration and click pick object in number one. You can see it picked the pixel values right here of the center of that box. Then I'll go back to sequence, open the frame list again, scroll down, click on the last picture in the frame list. Okay, it's this one. You can close that. And again, I'm going to make a little box around the comet's nucleus. Go back to registration, click pick object in number two. And if this worked out correctly, you should now see that it filled in the velocity measurements in X and Y. If it's done that, you're all ready to go and you can click go register. Okay, that did that in one and a half seconds really fast. Barely enough time for me to take a drink here. So now we'll go to stacking and I'm going to leave all of these alone. So we want average stacking with rejection again, additive with scaling, Windsor Eye Sigma clipping, Sigma low and Sigma high. I'm going to leave on one and one. Again, you can play around with these values, but in my experience, it doesn't matter too much going below one. I am going to change the name of this from stars stack to comet stack. And that's important because if we called it the same thing, it would overwrite that file, but we need two different files. So I'm going to call it comet stack and click start stacking. Okay, that's done. And let's look at the RGB by up here in the upper left click on RGB. And that looks really cool. I think the tail is very distinct. We got the green color. You know, we do have some star trails in the background, but not too bad. You know, maybe there's a way to get those rejected even more, but this looks okay. We can fix that a little bit in the GNU image manipulation program, maybe. Okay, so I'm going to go ahead and process this picture a little bit in serial here. So I'm going to go up to image processing. I'm going to go down to background extraction. And I'll click generate to generate some of these little sample boxes. And then I'll click on the blue channel. And I'm just going to right click on the samples that are too close or right on the tail of the comet. So I don't want it to accidentally subtract out the tail or something when we're doing the background extraction. I'm also going to do get rid of the ones that are too close to the dust tail here. And I'll also get rid of the ones that are right on the star trails. Okay, good enough. Let's click compute background. Okay, that's done. Let's click on the RGB tab to see if we like what it did. I do. So I'm going to click apply a little bit more even. And now let's go ahead and stretch this. It looks stretched already, but this is just the auto stretch. So I'm going to switch it back to linear. Go to image processing, histogram transformation. And we can just click this apply auto stretch if we like what it did there, which I guess I do. So I'm going to click apply, click close, and we'll save this. So I'm going to go up here to the save as which is right next to the save button to the right of it. Down here where it says supported image files, I'm going to switch it to TIFF. I'll leave the name comet stack, but I'm going to go back one directory and save it in my comet photos folder. Since this has already been stretched, we don't need 32 bit anymore. I'm going to switch it down to 16 bit and click save. Okay, then we can go ahead and click open. And I'm going to open up the stars stack, which should be at the bottom of this process folder. Again, since we have it in the linear space, it's all black. But that's exactly what we want. Because what I want to do with this is stretch it. For this one, I'm not going to use the auto stretch because it's going to be too aggressive for what I want with this file. So I'm just going to stretch it manually by taking this mid tone slider, moving it towards the data, click apply, and do that a couple more times. Okay, and then once the data is like this, like about a third of the way out, I'm going to also each time move my shadows slider towards the data. So you can see what I'm doing here. I'm taking the shadow slider, moving it to the right, taking the mid tone slider and moving it to the left, and then clicking apply, which is stretching out the data here. Okay, and then once it looks like this, like maybe I'll make it just a little bit darker. Yeah, like that. Once it looks like that where you can see all the stars, but you don't really see the comet trails yet. That's where we want it. So I'm going to stop right there. I'll click close and I'll save off this file. And again, I'm going to save it as a TIFF file in my comet photos folder stars. This one I'm just going to call stars.tiff. And it's important with this one that we actually do save it as 16 bit. I know some people like to save in 32 bit, but for the next thing we're going to do star net plus plus to work, it has to be a 16 bit TIFF file. So make sure to do that, click save. And now we are done with zero. So I'm going to go ahead and close out. Just click up here and click quit exit. And the next thing I'm going to do is move that stars.tiff file into my star net folder. And look at this file right here, run star net.sh. I'll just open it up with text edit just to show it to you. And let me make that bigger. Okay, so the way that this works is this is the command it runs star net plus plus. This is the input file stars.tiff. That's exactly what we called it. And this is the output file starless.tiff. If yours doesn't look like this, just change it to look like this. Okay, then we're going to run the star net plus plus. Now on Mac, especially if you have a newer version of Mac OS, this will not work by default. You have to give it permission. And I'll just in the editing put that up on screen, but I'll also put it in the video description what you have to do to get this to work. But once you have it working, the way it works is you open up terminal on the Mac. I assume this would be very similar on Linux. I'm going to make this bigger. Okay, and then I need to change to that directory. So I'm just going to do cd space and drag the folder into here, click enter. Now I'm inside that directory and then to run this shell file, I'll just do period slash and then the name of the file run underscore star net dot sh and enter. Okay, and you can see it started working. It says reading input image done bits per sample 16. It found the height and width and it's starting going. If this fails for some reason, then you don't have star net plus plus set up, you know, correctly, or you didn't get the file naming correct or the file isn't a 16 bit tiff. One of these things could be the issue. The speed of this, you know, depends on your computer. If you have, you know, really powerful graphics cards in your computer, it'll go faster. Okay, it's done. I know because it says done exclamation point, I can now close out of terminal. And if we look at the starless image, it looks like this, it seemed to work really well, because all we have here is just the comet traces. And so what we can do now is we can remove those comet traces from this stars image to get us like a stars only image. So that's going to work really well. We're going to do all of that in the GNU image manipulation program. So just to put everything in the same place, I'm going to take my stars and starless image and move them back here to my comet photos folder. And then I'll open up the GNU image manipulation program and open those files. So we want stars, we want starless, and we want comet stack. If it asks about changing the colors, you can just click convert. That's fine. Okay, so there's our comet stack. There's our stars image and there's our starless image. First thing we want to do is select all on our stars image. So you just can go to the select menu and choose all and then edit copy. Go to the starless image and edit paste into selection in place. And it will make a floating selection. Just click on this little new layer icon on the left here. And now you have a pasted layer. Okay, and with this pasted layer, we want to change the mode from normal to difference. And what we're left with is just the stars. And it's also gotten rid of the background, but that is fine and you'll see why in a moment. What I want to do now is make a new layer from visible. So I'll go to layer new from visible. And I'm going to take this visible layer and again, select all, copy, go to my comet stack and paste that in. Again, I'll make that floating selection into a new layer by clicking this new layer button down here on the left at the bottom of the layers panel comes in as a pasted layer. And we're going to change this mode of this layer from normal to screen. And just like that, we now have a comet image with the stars pasted in. Now, it's not perfect yet, obviously, but it's looking pretty good already. The main issue is if I turn off the visibility of our stars only layer is these stars star trails, right? And so there's different ways to go about getting rid of those. One thing we could do is, you know, mask in some of this, except for where the comet is. Another thing we could try is just, you know, smoothing them out. So basically, I could select everything but the comet and apply like a blur to smooth them out. And yet another thing we could try is manually going in and clone stamping. So I'm not going to show all of these methods. I just wanted to sort of present them. But let's just get rid of some of the more big star trails with the clone stamp just to show you that it is possible. So I'm going to increase the size of this. There we go. And I'll pick an area of the sky where there aren't any trails. I'll click on my comet stack layer. I'll press this would be the command key on Mac. I'm not sure what it is on Linux or Windows, maybe control. And that sets a source for my clone stamp. And then you can see I can get rid of some of these star trails by painting in with this area of the sky. Now this is definitely laborious work. So I'm not sure if this is going to be the best strategy, but I just want to show you how this works. Then when we turn back on the stars layer, you can see that section now looks a lot cleaner. The other thing that I would suggest to do is let's make a new from visible where this is all put together like this layer new from visible. And let's hit it with some curves. So we'll go to colors, curves, and let's darken up the background quite a bit. And also do a curve in this part of the data here. And you can see a lot of that star trail stuff sort of disappears anyways when we really darken up the background, but we still get the nice tail of the comet. So I'm actually fine with it like that. I'm not going to do any more cleanup, at least for this tutorial. If you want to spend some time doing it, go ahead. But I think it'd be pretty boring to show that in a video tutorial. But hopefully you get the idea of how you could clean up the comet stack if you wanted to. If you didn't feel like it, you could just darken the background. And I think this looks really good on its own. So hopefully this was helpful and made sense. I know it was a lot of steps, but we went from Cirol to star net to the new image manipulation program. And in the end, we have this clear comet with the stars. So you're now seeing the names of everyone who supports this YouTube channel over on patreon.com slash nebula photos. It's an excellent community of dedicated amateur astrophotographers, just people who want to learn and are very willing to share their own expertise. We have over 800 members now. There's an active discord that you can get involved in. And I can't thank my patreon members enough because I'm now doing this full time thanks to all of you. And it is what has allowed me to make these videos and to really pursue this as my own business. So thank you so much to all my current patreon members. And if you enjoy this channel, I think you will get a lot of benefit out of joining my patreon community. It starts at just $1 a month. And for that you get a bunch of perks, including direct messaging support with me, a monthly zoom chat with the whole community, a monthly imaging challenge organized on discord, where we pick different targets every month, and a whole lot more. So if interested, head over to patreon.com slash nebula photos. Till next time, this has been Niko Carver, Clear Skies.