 All right, another thing I want to show you before we dive into processing here is just what a single sub looks like in each channel and then what it looks like after they're stacked. We'll see this a little bit as we go, but a lot of people just are curious about this upfront. So keep in mind, this is just for this particular object, which is the seagull nebula or sometimes called the parrot nebula, IC 2177, but it's still illustrative, I think, of what you can maybe expect out of an object that emits in hydrogen alpha O3 and S2. So the first thing we're going to look at here is an H-alpha single sub. So this is one five-minute exposure with the ZWO ASI 1600 in H-alpha. Now let's look at after it's been stacked. So this is, I think, like 30 sub exposures stacked together. And so you can see there's a single, there's a stack. So a lot comes out in the stack as you increase the signal-to-noise ratio by stacking many together. Here's a single O3 sub, Oxygen 3. You can see there's just barely something there. This is a little bit hard to make out. Here's after we stack, and then it's a lot more evident where that O3 is. Again, I'll show you a single and after the stack. Okay, and then last, here's the S2 signal, so the sulfur. There's a single, oh, sorry, this is a single, got out of order, and there's the stack of the sulfur. All right, with that said, we can move on. All right, now we're going to start processing, and we're going to start with a program called Deep Sky Stacker. It's a free program. You can download it online, just Google Deep Sky Stacker. It is Windows only, but I know some people use something like Wine to get it on Mac or Linux, but I've only used it on Windows. There are alternative stacking programs, like Seek Quater, I'm not exactly sure how to say it. There's also something called Open Sky Stacker, so if you are looking for something that isn't Windows only, there are alternatives, or you can try to get it working using Wine. Anyways, it's free, it works pretty well for registration and stacking of your images, if you're doing Deep Sky astrophotography. You basically just follow along here on the left-hand side from the top to the bottom, so I'm going to start with Open Picture Files, and this is asking for my light frames. I've already organized everything here, so I have my lights, my flats, my darks, my dark flats. I'm going to go into the lights folder, start with the HA, go ahead and press Control A to select all the files and click Open, and if I scroll down here, you can see it's a bunch of files loaded. If I click Check All, I can see how many, okay, so I have 32 HA light frames loaded. I've already gone through these and thrown out a few that I knew were bad, but I'll show you how you could do that in Deep Sky Stacker as well. What you can do is click on one and then use this little histogram slider guy up here in the upper right, doing it pretty badly here, okay, there we go, and you can zoom in. I'm just using my scroll pad here to zoom in, look at the stars, and then you can move through, and it will keep applying that same histogram stretch, so you can get an idea of what each frame looks like to see if there's any that you want to throw out. Okay, anyways, that's the light frames, I'm going to go ahead and add my dark frames here, then add my flats, and finally my dark flats, okay, so with everything added there, I'm not using bias, I have found with the ASI 1600, I don't like using bias frames, instead I just use these dark flats, which are just like darks, except they are timed so that they are the same exposure length as your flat frames. So I have 32 light frames, 15 darks, 29 flats, 20 dark flats, seems okay, as long as everything is in the double digits, it will probably work pretty well, and, but since we are doing a complete narrow band image with not just the HAA, but also the S2 and the O3, I'm going to load those, but into different tabs down here. One thing that's not entirely intuitive, but it makes sense once you get used to it, is that down here, it says main group, and if we were just doing like a DSLR stack in Deep Sky Stacker, this is all we would have to worry about, but since we're shooting mono and we want to separate out by filter, we're going to use this group one to add the next filter set, so main group, we're going to remember is all HA, I'm going to then click on the group one tab, and go through the same process of adding first my lights, but this time for the O3, then my darks, these are actually the same darks, but it doesn't matter, then my flats for the O3, and finally my dark flats for the O3. Okay, so now this is all O3 stuff, I'm going to go ahead and click check all, okay, so now we have all of that. Deep Sky Stacker is actually smart to recognize that those were the same dark frames I loaded in the HA group, so it still says 15 right there, but you can see both the flat frames count, the dark plate frames count, and the light frames count have all increased. Okay, lastly, I'm going to now click on group two, and add my S2 lights, I know this is all a little bit tedious, but I just want to show every step, so no one loses track of what I'm doing here, again the darks are the same darks that I used before, because you don't need to shoot different darks for different filters, since the camera doesn't know what, you know, if it's completely dark it doesn't matter what filter you're using, but flats you do have to shoot by filter just in case your filters were dirty and they had different dust patterns on them. Okay, so now I have everything loaded, I'm just going to go ahead and click check all again, and just look through this, and normally what I would do now is I go into each individual frame, and check it, and make sure that it looks okay just by going through here, I'm just using my arrow key, my down arrow key, to look through each frame, and really you would want to actually look at the stars, make sure that you don't have any streaky stars in each frame, I'm just sort of abbreviating this process, because I've already actually looked at all of these, but you'd want to look at every light frame, and weed out any that were bad, just delete them from the list. Oh, this is actually a cool frame to show, see these, these are probably satellites or airplanes, don't have to worry about those, if you see some frames that are fine, except they have some of these streaks through them, because of the airplanes or the satellites, just leave those in, because as long as you're using at least 10 subs, that's not going to matter, those are just going to average out. All right, so let's just say I've looked through all the light frames now, I'm going to go back to my main group here. Now at this point, we don't know what is the best reference frame to use. So the cool thing about Deep Sky Stacker is after we register all of these pictures, it will give each picture a score, and we can pick the picture that has the best score to register all the other frames to, meaning that it's going to use that frame to assign any offsets. So if something is a little bit shifted, we know that they will actually, because I used what's called dithering, so it's moving the pictures around purposely, it's going to then take one frame and register all the pictures from all three filters to that frame. So I'm going to go ahead and click register checked pictures. I'll leave all of these settings alone, but I'm going to turn off stack after registering right now, because I just want to register and then look at the score of each sub. Under advanced tab here, I'm going to go ahead and click on this compute the number of detected stars. This gives me an average in the HA tab of 540 stars. That's a perfectly acceptable number. If you have hundreds of stars, that's good. My feeling is if you have like something like 10,000 stars, you probably want to lower the threshold, because then it's going to just be doing too much work trying to find the patterns. If you have like under 100 stars, that's probably, you probably want to raise the threshold a little bit. If you, actually really anything above like probably 50 stars will work, but if you have like under 10 stars, it's probably going to fail. So that's just sort of a ballpark. I'm not exactly sure about those numbers, but you just want to always, I always go in this advanced tab and press that just to sort of make sure that everything is looking fine. But usually with this default 20%, it usually works fine. Okay, I'm going to go ahead and click okay. And then it's immediately going to start calibrating. It's taking all of the dark frames right now creating a master dark frame. We'll just let it do that. And then we'll see what happens next. It's now creating the master dark. It does all kinds of just with the default parameters, it does kind of all kinds of averaging and throwing out outliers. What this median Kappa Sigma means is that it looks at a standard deviation of all the values and throws out outliers that just seem like they're not in every picture. You want this because you want your master dark to be a true standard for what the what the dark current is anger camera. So now it's doing the same thing for the dark flat frames. I'm going to probably go ahead and just fast forward in the video through this because it's a little bit automatic. You don't have to worry about it too much. And I don't have much too much else to say. But basically, what this is doing is it's taking all the individual subs and condensing them down into masters. So you have a master dark, a master dark flat and a master flat for each filter, it then calibrates all the light frames per group or per filter, and then assigns each sub a score based on the signal to noise ratio and the roundness of the stars. So we'll let it do its work here. It's probably going to take like an hour or something. And then we will come back and move on to the next part of this, which is stacking everything based on a single reference frame. All right, it's done registering all of these and has given everything a score. I'm going to go ahead and sort it by score, just by tapping my mouse right here on the word score twice. And so what this does is now I can see that frame 18 has the best score 8679. And if I scroll down here, I can see the worst HA frame has a score of 4110. I don't know exactly what this score means. But in terms of the number, but just higher numbers are better. So I'm going to use the frame that has the highest score to register everything else. If I look at group one, which is the 03. That doesn't have a higher score. Look at the S2. That doesn't have a higher score either. So the HA is going to be the one that I'm going to use. And specifically, this one that has the highest score frame 18. To make it the registration master frame, I'm going to right click on it and sorry, not registration master reference frame. That's for the deep sky stacker terminology. And so I'm going to right click on it and choose use as reference frame. When you do that, you'll notice that over here in score, there's now this little asterisk next to it. So you can remember that that is your reference frame. So now when I register, it's going to use that one. I'm going to go ahead and click uncheck all. Okay, next, I want to just register all of my HA frame. So I'm just going to go ahead and select everything here, right click and check. So I have everything in the main group checked, nothing in group one or group two. Then I'm going to go into stacked check pictures. It lets me know, you know, I have the darks, I have the dark flat, I have the flats. And I can go into recommended settings here and just look through. It's using sigma clipping, it's using blah, blah, blah. Okay, I basically just use the recommended settings automatic alignment. I typically don't mess with things in here, but if you want to mess around, you can there's a lot of different options. But I think that the defaults are usually pretty good. I'm just going to use standard mode for stacking. Okay. And I'm going to click okay again and let this do its thing. So when it says computing offsets, what that means is it's taking all of the different HA lights and using the reference frame to register all of these different light frames. And it's already created master darks, master dark flats and master flats. So you can see that it just used the masters that it already created. And right now it's already going in and stacking all of the lights together. So this actually shouldn't take that long. The, you can see the estimated time remaining here under two minutes. The part that takes longer was that first step where it was actually creating all of the master calibration frames and then calibrating all the lights for each filter. This is actually a pretty quick process by comparison. Just creating your master HA light is what you can think of it as. Notice now it says angle 178 degrees. What happened there was there was a meridian flip, meaning that the frames on the second half of this are almost 180 degrees different than the first one because we changed from the east to the west side of the meridian. Okay, now it's loading our final auto save.tiff. You can see where it's located right up here. Some other videos I've seen on Deep Sky Stacker will suggest you now mess around with this and apply and save off that picture and then go on to Photoshop or GIMP or whatever it is you're using. There's really no reason to do any processing in Deep Sky Stacker. And actually if you read the instruction manual it says this is basically just here as a convenience. So you can sort of see what your data looks like. It's not meant as a thing for actual final processing. But if we now go back into the folder, the HA folder, you can see in addition to all of these pictures we now have auto save.tiff. I'm going to go ahead and pull that out of the folder and rename it here as HA.tiff. Another thing you can do instead of doing it that way is you can choose save picture to file over here and just make sure that embed adjustments in the saved image but do not apply them is the option checked rather than apply adjustments to the saved image. And then you can just call it something HA final.tiff and save it wherever you want. I'll just save it to the desktop. So either way you can just you can choose save picture to file and just make sure that this embed adjustments in the saved image but do not apply them is the option or you can just rename the auto save either way will work but you don't you definitely don't want to make any adjustments in deep sky stacker and apply them before you save the final stack. Okay let's go back here. Okay so next we're going to do the 03 and if we look back at the main group here we can see that everything is unchecked but I still have this little asterisk I'm going to go into that means this is the reference frame that it's going to register everything against. I'm going to go into 03 and if everything isn't already checked I'm going to go ahead and check everything again the way you can do that I'll just do uncheck all click on the first frame shift click on the last frame then right click and choose check. Okay for some reason I don't have the dark frames loaded anymore so I'm going to go back in here into the main group and also check all my darks just click and shift click and check. Okay so I have those 15 dark frames 25 light frames from the 03 30 flat frames 20 dark flat frames. Okay now that I have everything I needed for the 03 stack checked and I am going to be registering against this HA reference frame again that's really important that for each filter you're using offsets against the same reference frame so that when you put all three filters together into a full color image they're all stacked together correctly. I can now go over here to stack checked pictures and there are some things that are not so great about deep sky stack or terminology because when it talks about registering frames to a reference frame it uses the word offsets but then it also uses the word offset for bias so when it says no offset right here it's talking about there's no bias frames loaded but that's fine because we're not using bias frames we do have darks dark flats flats and of course lights 25 03 lights so basically we're just repeating this process now for the 03 I'm going to click okay again it'll go through do its thing and I'll check back in a second here. Okay the 03 is now stacked um you'll notice that up here it saves it to the HA folder the reason is that uh for whatever reason deep sky stacker thinks that the autosave should always go into the the same folder that the reference frame is in any case I'm just going to use the save picture to file command down here under processing make sure that this embed adjustments in the saved image but do not apply them is the option that's checked and call this 03 final and click save okay so now if we look at our progress here we have the HA final the 03 final tiff um you'll notice that the little preview on each of these is black that's perfectly fine do not worry about the fact that you're not seeing anything in these yet other than maybe some really bright stars um because these are not yet stretched um we'll do that in the next step lastly though we have to go back here to register checked images one more time go into or click uncheck all to uncheck all the 03 files go into group two which is the s2 frames click on the first file scroll down shift click on the last file right click choose check go back here to our main group and check all of the darks click shift click right click check so 15 darks I only got 15 lights on s2 that's okay uh normally I try to get 20 but 15 is okay 30 flat frames 20 dark flat frames okay so that's all set again it's still going to register against our reference frame which is here in the main group HA and let's go ahead and click on register checked images no sorry stack checked images okay no bias frames that's fine we're gonna be stacking an hour and 15 minutes of s2 all sounds good let's click okay and it does its thing okay now we have the s2 done again it saves it to the HA folder but we can go ahead and just go to save picture to file make sure that the do not apply the adjustments is checked and save this as s2 final tiff to the desktop we're gonna minimize deep sky stacker and this is what we want to see when we're all done a aj o3 and s2 all 16 bit tiffs all stacked calibrated and registered we're now going to go ahead and move on to the next step okay so we have our stacked master files out of deep sky stacker and now we're going to turn to photoshop i am using adobe photoshop cs6 but really any version of photoshop that you have this kinds of stuff that i'm going to do should work in just fine anywhere from cs3 or 4 on you should be able to follow along just fine including the newest versions um go ahead and open what we got out of dss deep sky stacker so i'm just going to go to file open and select these three files these three tiff files and click open it opens them up each in their own tab and the first thing that we want to do is we want to stretch them here in photoshop if you've seen my um my ryan video we this should be familiar we're going to just use the basic image adjustments levels command to stretch the images um you can get to it from image adjustments levels or you can press command l on mac or control l on windows to get to it we're presented with this and what we see here is a histogram bump that's way over here on the left hand side and what we want to do is we want to stretch this bump out and get it over more over here towards the middle not quite in the middle but like about a quarter to a third of the way over and the way we're going to do this is we're going to take the mid slider here and take it and move it over to the left and click okay and you can see that did something to the image here but we're going to have to do this a number of times it's an iterative process i find works best so i'm just going to press command l again because i'm i'm on a mac or you can press control l on windows and just move that mid slider over and just do this a few times now you'll notice the picture it's very bright you don't have to be too concerned about that because all of the data is right here so we're not we haven't really clipped anything yet there might be a few stars that clip but you don't have to worry too much about it but at this point we don't want to bring this bump any further over so we're going to start readjusting the black point so i'm just going to take this slider all the way over here on the left the black slider and bring that right up to the edge of the histogram bump here and click okay you can see that brought it back down um this is looking pretty good but i think we can do a little bit better so i'm just going to keep pressing command l and just keep stretching a little bit more just repeating this process of bringing the black point over the mid point in a little bit and i'm going to finish up with just a black point adjustment something like that and you notice that the picture is fairly gray even the sky is is pretty gray that's fine for now i'm just trying to basically reveal all the detail in the picture and then we can make global adjustments after we've combined it into a full color image i'm now going to go to the o3 tab here and do the exact same thing i did with the h a stretch it with the levels command again and again iteratively again using this midpoint slider just moving it over to the left and then eventually also taking the black point slider the one on the left there and moving it to the right like so all right that looks pretty good um one thing though that i notice is that this corner seems a little bit artificially bright to me you can see where the o3 signal really is here it's this diagonal right here but this corner just seems a little bit bright compared to this corner and i think that is because this whole side of the picture is actually has a little bit of a sky gradient to it so i'm just going to fix this in sort of a crude way here since this is just a basic processing video there are probably better ways to do it but i'm just going to use a curves adjustment layer and i'm going to just bring this down here on the left hand side until i'm looking in this corner and i'm just trying to just trying to bring that down about i don't want to make it completely dark i i just want to bring it down a bit something like that and then i don't want that to apply to the whole image you can see it made the whole image darker i just want it to apply to this corner so what i'm going to do is with this layer mask selected on the curves adjustment layer i'm going to grab my gradient tool here can press g for gradient to get to it and i'm just going to draw a gradient like that across that corner so you can see what happened in the layer mask here is we just have this sort of gradient effect on this corner and what that's doing is it's gradually darkening this corner so up here it has very little effect but down here it has more of an effect and the effect is we basically just sort of darken this corner a little bit so that it matches the sky better up here because like i said i i have a feeling that this is sort of artificial sky brightness um and not the actual o3 signal since i like how that looks i'm going to go ahead and take these two layers click shift click and combine them using layer merge layers you can also use the keyboard shortcut command e to do the same thing so if i press command e or control e on windows it merges those two layers into one okay and we still have the s2 to do so i'm going to press command l or control l on windows and move this midpoint slider to the left a few times you can see what this is whoops press the wrong key you can see what this is doing is it's spreading out this histogram peak as it's also moving it over from the left hand side but the important thing it's doing is it's spreading it out the information is very compressed when it's in a linear state and then we do this non-linear stretch and add all this contrast to the picture and i'm basically just doing this by eye um both looking at the histogram bump and just remembering how the other pictures looked i've done a lot of narrowband pictures so i've gotten pretty good at this but one thing you'll notice here is that my background sky level is a little bit darker here my o3 and s2 compared to my h a so i'm just going to reset the black point of that one a little bit to match these better okay i think that looks pretty good now next step is you'll notice that on each tab here it says these are gray scale images the mode is gray scale that's what that little gray means the slash 16 the 16 means we're in 16-bit imaging mode um with uh the reason we didn't want to work in jpeg for instance is that jpeg only accepts an eight-bit mode and so then you're not going to have as much accuracy as you're doing those stretches and things like that um let's go ahead and but anyways the the important thing here is right now these are all gray scale so even if we wanted to turn these into color image we couldn't because of the imaging mode so let's go up here to image mode and change this first one from gray scale to rgb color and nothing happens at first um but if we look over here in the channels panel right to the right of the layers panel you notice that now we have our red green blue channels available to us if i look in my o3 we just have one just the gray channel but that's okay what we're going to do is we're going to take the o3 and s2 and combine them with the ha using this channels command so i'm going to first choose the red channel go to my s2 grab the whole thing with select all i'm going to copy it you can go to edit copy or press command c control c on windows and i'm going to go to my ha picture make sure the red channel is selected and i'm going to paste it into that channel command v okay i've now pasted the s2 into the red channel i'm going to continue this but i actually already have my ha paste in the green channel that's how i want it so all i have to do now is paste my o3 into the blue channel here so i'm going to command a to select it command c to copy it and command v to paste it into the blue now we can turn these all back on and we have a nice full color image i'm gonna go back here to my layers panel and that looks pretty cool that's just a straight what we call show image or sh o image meaning that it's just mapped color the sulfur is in the red the hydrogen is in the green and the oxygen is in the blue and we haven't done anything else to the image and that's how it looks i'm going to show you just a few more things though we can do with it first i'm going to deselect and the first thing that i notice is that we have some registration artifacts meaning the three different channels were rotated a little bit differently here so along the edges we have these color artifacts left over so i'm going to get rid of those with a crop so i'm just going to press c for crop and i'm just going to drag this in a little bit on each side and i'll rotate it a little bit so we're getting the most of the image that we can get that looks pretty good maybe get a little bit more here on the bottom no not really okay i think that's as much of the image as we can get so zoom back out i'll cut press enter to accept the crop and that looks pretty cool um next thing i'm going to do is i'm going to use the selective color adjustment layer to just mess around with the colors a little bit if we just wanted to keep it straight show we could and we could maybe just apply for instance just like a curves um to reset the black point and call it a day i think it looks pretty cool but if you did want to do something like Hubble palette where we remove a lot of the green i want to show you how you could do that as well so you'd open up a selective color adjustment layer and i usually start with the neutrals under the colors picker right here so you have red yellow green cyan blue magento whites neutrals and blacks i'm going to choose neutrals and i'm just going to remove some cyan and some yellow to get something like that then i'm going to go now that we have sort of changed the colors a little bit here i'm going to show you what i did as before that's after that's sort of in the right direction but then we're going to go into yellows and remove even more cyan so you can see then what was sort of a yellowish green when you remove cyan from uh the yellow channel you bring in a lot more warmer orange gold tones so i'm actually just going to go all the way over and do negative 100 on the cyan on the yellow i'm also going to increase the black level a little bit just to make those oranges even a little bit more dramatic and if you wanted to go full on a hubble palette and really remove the greens entirely you could go in here into the greens channel and remove all the yellow and cyan from the green and then you get this kind of effect so that's one choice you can make if you want to go with that look i'm going to go ahead and reset those because personally i like a little bit of green left in the image right now i think the greens dominating a little bit too much so i'm going to go into my scions and blues and take out a little bit of yellow from them and increase the cyan maybe a little bit just play around with this and go back into neutrals and bring up the cyan and bring down the yellow just a tiny bit just to make those blues nice and rich okay and so we have a pretty colorful image now i like the color mix if you find this too garishly neon or whatever you can always go now into something like vibrance and desaturated a little bit if you or if you really like extreme color you could you could up these a little bit you could up the vibrance and saturation i really consider all of that kind of thing personal taste personally for me i think maybe just like a negative five or so on each of those let me turn that off and on looks a little bit better but also to me now the whole image is just a little bit too flat and a little bit too um bright so i'm going to then open up a curves and just reset my black point just a little bit bring down the shadows by adding a control point right there but then bring back the highlights like that and really make the stars pop as well yeah i like that a lot better so this is before very flat after but doing that now i think that it's like just a little bit too saturated so i'm going to bring down the saturation just a little bit more okay almost done one thing i noticed is that after we applied all those color changes i notice over here on the left hand side or left hand corner we still have a little bit of an artifact showing one thing i'd recommend you always do when you're doing mono imaging is check your corners because this is pretty common type of thing and it's very easy just to crop it away just check the other corners those look good okay so i'm pretty happy with this there are other things that we could do but i think this looks pretty cool got a nice variety of star colors of course these star colors aren't accurate necessarily because this sho imaging so it's not you're not going for accurate colors this is a color mapping where you're really just trying to see sort of the interaction of the gases out in space that part of it is real all the spatial relationships of the gases is completely real it's just that the colors we are assigning to them here are just arbitrary basically the only thing that has a bit of semblance to reality is the o3 response is this sort of tealy green greenish blue so probably the truest color here is the o3 the ha and s2 response are really not gold like this they're very red so if you did want to take this in a more natural direction um all you'd have to do is just keep playing around so you take the yellows and you add a lot of magenta and remove a lot of the yellow and you can you can start moving it into a more natural looking direction if you want to um okay so probably know about saving but if you do file save as you can save it as a photoshop file and return to this later on that's always a good idea even if you're pretty sure you like it I often find you know it's good to look at it after a good night's sleep and make sure that you still like it in the morning um when you're all happy with it though and you want to save it for the web the photoshop has this really nice file save for web command in older versions um in newer versions I think it might be under export or something like that but it should still be there somewhere so file save for web and this way you can just make sure you're in the srgb color mode which is what you want for uploading things to the web and you can pick jpeg or png you can also resize it here if you need to and I'll just save it off as a jpeg make sure I like how it looks just opening it up in preview I'll just try opening it up with chrome as well just make sure it looks good on the web browser yes okay I think that looks nice let's check out on the details here yeah um one thing you'll notice especially if I zoom in here is there's a fair amount of noise still left in the image at 100 scale um in my opinion the best way to get rid of that noise if I wanted to it would be just to take more sub exposures the more uh integration you have meaning the more total exposure you have the the easier it is to reduce that noise in a very natural looking way for this image I don't really mind the level of noise here um because when I'm looking at it zoomed out it really doesn't affect the image for me and um that's how most people are going to look at the image is not zoomed in pixel peeping but just looking at the whole thing but so when an image for me when an image you know looks okay um full screen like this and the noise isn't noticeable zoomed out then I'm fine with that level of noise um this is just about six hours of exposure all right that's it for this video this again was just a basic overview of narrowband processing in deep sky stacker and photoshop if you have any ideas for future videos please let me know in the comments um or anything else that you want to tell me about just let me know I I do read all the comments and if you want to support me to make more videos check out patreon I'll leave a link under the video and you can also get early releases that way and other perks including the higher levels one-on-one coaching if you want that so thanks so much for watching clear skies have a great one