 Happy Halloween everyone today. I have a special spooky video for you I just finished capturing data on the ghost nebula so I carved my pumpkin back here to match and I thought this would be a Really nice opportunity for a special treat in the form of a data giveaway and a basic processing video with free software I do want to thank you green for sponsoring this video And I'll say more about their awesome 100 watt power station halfway through So all you have to do to get my ghost nebula data is Just join my email list and if you already have you can still get it You'll get sent a download link and once there you can just click up here on the folder name and choose download to get all Four fits files and you are of course welcome to share your results on social media if you do try out processing it My goal with this video is to show something that I don't think I've ever shown before on the channel Which is my basic workflow for LRGB processing So this is what I do if I'm working with mono data and I'm shooting through luminance red green and blue filters And what will be a little unique about this video is I'm going to show this process with completely free open-source cross-platform Software so anyone with a computer and an internet connection can follow along with this I have also purposefully tried to keep this straightforward So I'm not going to be doing anything super fancy or complex in this video I'll put the links for downloading the software which are Cyril and GNU image manipulation program in the description for this video and We can go ahead and jump in I'll start by opening Cyril You can see I'm on version 1.0 point six. I should also mention that I am on a Mac This is Mac OS Monterey Don't update to Ventura if you haven't already because I think Cyril does not neither Cyril nor the GNU image manipulation program are working currently Properly on Ventura. So stay with Monterey for now until they can work out those new issues Okay, so here in Cyril the first thing we're going to do is click on the home Directory button or the current working directory button whatever you want to call it is this little blue icon up here with the home symbol and You're going to set it to wherever you downloaded the data So find this folder sh2 136 ghost nebula and click open Then if you click open here, it will go right to that folder and the first thing I'm going to do is work on the luminance File and really by work on it. I mean just stretch it So I've already done the pre-processing on these using the scripts here So that just means calibration registration stacking all that so we end up with these four files and so this is a Fully stacked luminance file, but nothing else has been done to it And when you open it up, it's a little bit underwhelming That's because we're right now in the linear space So there's different visualization modes. This linear mode is just showing you what the computer sees Which is is not much, but we can auto-stretch it so we can see what it looks like And it looks like that so it already looks pretty good This is plenty of of data from a dark site. So you could expect that it will it will look pretty good I'm going to go ahead and turn that back off because I want to show you that is just a preview, right? So if you hover over it, it very clearly says Warning, this is only a visualization Because it's not actually stretching it by clicking auto-stretch there It's just for working on it if you want to do some image processing while the data is still linear But if you just wanted to apply that auto-stretch to the data What you can do is go to the image processing menu go down to histogram transformation and click this little gear icon, this is like the auto stretch icon and There it is now for me the auto-stretch is just a little bit aggressive so what I'm going to do is maybe just back off ever so Slightly and this is sort of hard to do. I think that looks pretty good I'm going to click apply and then from here. I'm just going to stretch it just a little bit More like that Okay, so that looks good to me I'll go ahead and I've applied that so I'm going to go ahead and close it and That's all that I'm going to do with this Luminance image. We're now Ready to work on the RGB but first I have to save off this luminance image So I'm going to go up here and right next to the save icon is a little Save the current image in a different name button. I'm going to click on that I'm going to go down here towards a supported image files and change it to TIFF files and I'll save it as loom.tif that's fine And we can leave all of these options alone We're going to next go into the good new image manipulation program and that can handle 32-bit floating point fine So we'll leave it like that and click save Okay, next we're going to Combine the red green and blue images So I mean if I just wanted to open one just to take a look at it I could so I'll just open the blue image and Again, we don't see anything here because it's set to linear But if I choose auto stretch it looks like that and so you can see it looks fairly similar to the luminance image But a lot noisier because I didn't get as much of each color channel But still pretty good and to do the RGB compositing We go up to the image processing menu and go down Near the bottom of this menu one up from the bottom is RGB compositing and This is pretty easy. All you have to do is just click on This little button where it says none next to each color and put it in the appropriate file So I'll click none there and choose red dot fit I'll click on the green one and choose green dot fit and I'll click on the blue one and choose blue dot fit Okay, and then over here we're still seeing a black and white image That's just because if you look up here, there's these tabs and we're in the red tab But if we click on the RGB tab, we get a visualization of what the full RGB color image looks like and I think it looks pretty good the the one thing I notice is that there's maybe a blue bias in the shadows and There is also some green noise. It looks like So there are ways to sort of adjust that here But I rarely use that because I'm going to apply something called a photometric color calibration anyways So that's really not necessary We can now just close this and we have the RGB composite open So Next we're just going to do a couple little things here before we stretch it I'm going to try to remove some of that green noise. So if you go up to image processing go down to remove green noise Um For some reason this is grayed out, so I'm just going to change it to something else and then reduce the amount Let's do 35% and then I'm going to change it back to average neutral and apply Okay, and so that was a subtle change I don't know if you're going to be able to see it on YouTube If you do that on your own machine, hopefully you'll see that in some of this dust it neutralized some of that green noise So I can go ahead and close that And now I'm going to go back to the image processing menu go down to color calibration click and then click on photometric color calibration and The first thing here is it doesn't know Where this is in the sky so we have to tell it so Again, this is sharpness 136 so we can just type in here sh2-136 and click find and you have to be connected to the internet But it pulls down from simbad, which is a object catalog online Run out of Strasburg. It finds where that object is and it puts in the coordinates right here now in this case it looks like serial maybe found the Correct focal distance and pixel size from the image directly But in case it doesn't you can just enter 1,000 there and 3.7 6 for the pixel size and it will be the correct resolution And that's it now. We can just click ok and it goes out to the star catalogs and Tries to find stars that match in this field and then it does a color correction Based on the actual color of the stars and you can see it's already done and it did a really nice job That looks much better. It removed all of that blue bias automatically So I can click ok Or I can just close it now actually We already applied it and again. This is just a visualization just because it's just the auto stretch so now Let's go ahead and stretch it and With really good data sometimes I'll use this arc sign stretch or this generalized hyperbolic I've tried it on this data and I wasn't happy with what it did to the stars So I don't know if it's something I'm doing wrong, but I'm just going to use the histogram transformation and again and This time instead of applying this auto stretch. I'm just going to do it completely manually So I'm just going to take this middle slider and bring it over here to the left and apply and Then do that same thing again and apply and do it a third time and apply and I'll do it a fourth time Apply I'll bring up something like that. I don't want to do a super aggressive stretch at this point. So This kind of histogram peak like this just over from the left looks pretty good to me Don't worry about darkening the shadows at this point because when we do the LRGB combination We don't actually want the shadow information to be too dark because it's extracting the color from that so this looks fine, I mean ahead and close that and That's all we have to do in zero. So let's go ahead and save this as RG B I'll just call it RG B And I'm going to save it as a TIF file and once again I got to that from this little button right to the right of the save button So I'm going to save it as RGB.tif Back to that same folder 32 bit is fine and click save I should say if you're using Photoshop instead of the GNU image manipulation program You might want to save in 16 bit because a lot of processes in Photoshop are not 32 bit compatible Okay, so now let's go ahead and open up GNU image manipulation program This video is sponsored by Ugreen as an astrophotographer I find there are tons of things that need charging before I go out for the night everything from star trackers to smartphones to Camera batteries, but keeping track of all their chargers is annoying and it takes up a lot of space So I really appreciate Ugreen's 100 watt power strip because this really simplifies my charging needs It can sit right on my desk and it provides plenty of power for me to fast charge my phone my laptop my star tracker My camera battery all at once it has three usb-c one usb-a and three ac outlets So you can charge seven devices at once and it does support fast charging on both my Android and Apple devices so check the link in the description to buy one today and Go to file open and we'll open our RGB tiff file It will say something about the color profile. It doesn't really matter what you do here. I'm just gonna click convert okay, and This looks good. I'm gonna now add our luminance as it's on layer. So I'll go to file open as layers and Choose loom tiff and click open Okay, that looks good, too So we have RGB tiff and then we have loom dot tiff on top and on this loom dot tiff on top We're gonna change the blending mode, which is right up here at the top of the layers panel from normal To luminance and luminance is all the way at the bottom of this menu Okay, so I hope hopefully that came across what just happened here was before completely black and white and Here is luminance and that started bringing in a little bit of color now. It's still very desaturated So there's a couple things that we can do to this RGB tiff layer to make it Less saturated to make to bring out the color So I'm gonna go ahead and turn off the visibility of loom dot tiff so you can just see what we're doing here And I'm gonna go up to colors And go down to shadows dash highlights And with this I'm going to Bring up the shadows so you can see the shadows is set to zero And I'm just going to raise them up like that to let's say We'll start it 60 Around 60 is fine and so you can see this is a very flat look It's not the look that we want to end up with But what we're telling this is that in this color information. We want to grab color from this background to You know back off just a little bit. Okay That all looks fine. So I'm going to go ahead and click okay And then the next thing that I mean so if we just look at it now not a huge change yet But the next thing that I'm going to do is I'm going to add saturation to this layer And actually when I'm doing this I like to have the loom layer turned on So then you can get a preview of the final image So go ahead and turn the loom layer on but make sure that you have the rgb layer selected We'll go back to the colors menu and choose saturation And This is where it gets really cool because the image will come alive with color So you just grab this little scale slider and move it up And you can see At 1.6. I can see a little bit of the color coming into the stars, especially into those orange stars But if I keep moving it up I'm going I'm going to go way up here. I'm over two now. Let's see 2.1 Okay, that is looking a lot better You can see some of the blue in the blue halos you can see a lot more color in the nebula And if I want to see exactly what this is doing I can turn it off and on the effect of this saturation by Checking or unchecking the preview button. So I'm going to uncheck it. That was before barely any saturation in the image Turn it back on And you can see all of the natural colors of the stars and the nebula Are coming out really well Okay, you can always zoom in as well. Just click on the main window and then on a mac just hit shift plus And so you can see I mean it turned the preview back on and off that's before That's after and you can see this is a really cool yellow reflection nebula, which we rarely ever see Another one I can think of is um around ontaries in scorpius But uh, that's really neat. I really love that Ghost reflection nebula getting the yellow color of it And then these little things I mean those are mostly gray, but they're they're still interesting looking We're also getting a little bit of color here. This is a herbig hero object And I mean the the star field this is how I like my stars to look You know, there's I like the little stars to be basically filled in with color but these big bright blue stars to not be Super saturated in the core because I just think it looks a little bit artificial But other people do like the more filled in look in that case you could go back to zero and use arc sign stretch rather than Histogram transformation, but I'm really liking how this looks so I'm going to go ahead and click okay to accept it And I'll just take a final Look here. Let me zoom back out with the minus key I don't really see much I would change Maybe I'd do a final crop You know, I could consider Going starless with star net plus plus and we could bring out more of the background dust That might be something I would do I'm not going to show that in this video because I really just wanted to show the basic process of combining luminance with rgb and sort of give you an idea of Um How much Saturation you really have to add to get a look like this. Let me go ahead and turn off the luminance So this is what the rgb looks like so really pretty weird looking and that is completely normal I want to emphasize that when you combine rgb with luminance Your straight rgb is going to look very flat and very saturated and that is just completely normal Processing for this kind of thing once you add the luminance it completely changes the the nature of the image So, um That's really it if I wanted if I thought I might continue processing in The GNU image manipulation program. I could just do file save and save as an xcf file I'll go ahead and do that But when you're all done and happy with it you can do file export And from here you can save it as any type of file Just type in a different file name if you want jpeg or png or tiff or whatever you want and click export Well, that's it for this one Hopefully you learned something about lrgb processing and I look forward to seeing some of your takes on this data on social media Feel free to tag me if you want me to see it And you're now seeing all of my current members on my patreon campaign If you want to see your name in the credits you can sign up over on patreon.com slash nebula photos it Has a bunch of benefits outside of your name in the credits of long videos I have made some exclusive videos just for patreon. There's monthly zoom chats There's a discord community where you can ask questions. There's monthly imaging challenges. There's Imaging projects with a group And of course there's direct way to message me with all of your comments and questions So if you like these videos you want to learn More and learn faster consider joining over there on patreon for as little as one dollar a month Again, the link is patreon.com slash nebula photos until next time. This has been nico carver clear skies