 Hello and welcome this is Nico Carver from Nebula Photos. This is part 2a in a series on capturing and processing the dumbbell nebula. If you haven't watched part 1 what you can do is watch the first 22 and a half minutes of part 1 and then if you're interested in processing with SIRL and the GNU image manipulation program then you can switch over to this video after the first 22 and a half minutes of part 1 and the big advantage to processing with SIRL and the GNU image manipulation program is that they are both free and they are both completely cross platforms so they're available on Windows, Linux and Mac OS. I'm going to be showing this tonight on a Mac. I'm using Mac OS Monterey which I believe is the current stable release of Mac OS and I'm on an M1 MacBook Pro. So to download these programs you're going to go to their respective websites and just download the software. So I'll do that here and just so you're aware these are the current releases as of the time of recording. So for SIRL it's 1.0.3 and for the GNU image manipulation program it's 2.10.32. They are both easy installs. You just drag and drop into the applications folder. The one thing that can be a little bit tricky in new versions of Mac OS is if I just double click the application SIRL to open it right now it might say this is from an unidentified developer can't open it sorry blah blah blah so all you have to do is right click or control click and choose open from the right click menu and then it will instead say it's downloaded from the internet but are you sure you want to open it and you can just say yes open and then it will remember that choice and won't throw any security warnings after that. Okay so here is SIRL and this is a full-featured astronomical imaging program. We're going to use it for calibration and stacking and registration and all of these kinds of tasks that are normal with deep sky images. The first thing that you want you're going to want to do is we've already gone over in part one how to organize your data but just to re-emphasize because this is very important with SIRL you want everything in one folder so I have one folder here called M27 and then inside that folder I have four subfolders biases darks flats and lights just like that all lowercase that's exactly how we want it and you it might throw an error if you don't have it exactly like this so that's why I'm really re-emphasizing that because that's the most common error that people run into. Oh and the other common error is just not having enough room on your hard drive so I've put these on an external drive and you can see that external drive has plenty of space two terabytes but you know you just want to drive with plenty of extra space for this stacking process because it does use a fair amount of temporary storage. Okay so let's get going here the first thing we're going to do is up here in the upper left we're going to change the current working directory you can see right now it shows it right here in the center it's nico slash desktop and we want to change it to M27 on my external drive so I'm just going to go into volumes pick my external drive here and choose M27 okay you can see I just changed the working directory you can see it right up here at the top volumes 2022 number three M27 and then we are basically ready to go we can just click here into scripts and choose osc preprocessing it will say you're about to use scripts running automatic scripts is easy blah blah blah but it you know you can tweak these things with the manual commands I understand all that I take the risks and I think the script will work fine for our purposes so I'm going to click run script and off we go now this is what you should see it should give you a console and it should immediately start working creating you know bias master frame and all of this if you instead just immediately get some kind of error read the error message try to understand it it will be in English it will it will make some sense but don't just you know close the program and give up if you run into some error message just read it and it will usually tell you what to do so you know like I said the most common thing is is the directory is not being right the I mean the folders if the next most common thing is just not having enough space for it to complete everything it needs to do so anyways this is now a fairly automatic process you can occasionally check in on it to make sure it's still going but it's going to take quite a bit of time because it's doing a bunch of different things it's going to create our calibration files it's going to calibrate all the lights it's going to register all the lights and stack them and so when it's all done it will say you know process complete and we can open up our finished stacked and calibrated file so I'm going to jump ahead to that it'll probably on a laptop take a few hours so I'm just going to leave this alone and I'll catch up with you when it's all done okay it's finished the whole process of calibrating registration and stacking we can see it says done here total execution time six hours 17 minutes again I was doing this on a laptop it would be faster you know on a machine with a better processor or more RAM and that kind of thing but it will still probably take you know hours to do it when once it's finished it doesn't you know it tells you it's finished successfully but there's no image here yet you do have to open it so we just go over here to open in the upper left and click on result dot fit which should now be in your main folder okay and you open it and you don't see anything it's it looks black and that is completely normal this is not stretched if we look down here at the bottom of the interface in the middle we can see we're in the linear display mode that means it's sort of how the computer sees the file but it's not that useful as a preview so what we can do is we can change it to auto stretch and now we can see there's m27 right here now it's still black and white what is going on there well this is just the red channel if i switch to the green channel you can see it looks like that there's the blue channel and there's the rgb preview again now why is it so green this is a very normal thing with dslr's when you're working you know with an astro specific uh processing software like zero or dss or pix insight it's it's nothing to be worried about it just means that the the color channels are a little bit off and there's you know two green pixels for every one red and one blue and a dslr camera so green can often dominate like this so that's completely normal don't worry about it okay and the first thing that i'm going to do under the image processing menu is a background extraction the way this works is you can either let it set samples using the generate button or you can set samples yourself which are just going to it's going to use to make a model for the background um and then it's going to either divide or subtract that background that's the correction i usually start with the vision uh and since there might be some nastiness right on the edge of this i'm going to go in a little bit from the edge but i'm going to try to get sort of one sample without too many stars in each corner you know one up here one over there and definitely one in the center okay and then i'll click compute background one nice thing with serial is you can always see what it's doing over here in the console so i can see it's now it extracted this background model from the red channel now it's now it's done it from the green channel and then it'll do it from the blue channel okay and then next let's do a color calibration and specifically i'm going to try a photometric color calibration first um i find that this usually works better if you can get it to work so i'm going to type in m27 and let it find you know this object which it did and it put in the coordinates okay then let's try get metadata from image for the pixel size and the focal distance and it got those exactly right just from reading you know the metadata from the image you do want to double check this i know for fact these are right uh but you know double check make sure that it got them right don't just assume but again this is to know how big a field to plate solve so it has the coordinates it has our metadata from the image okay let's go ahead and try it click okay okay and i can see it did work you can see the over here the green channel got a lot more normal looking not so bright and down here on the console it says photometric color calibration applied so i can close this process now and let's look at our rgb image again and now it looks a lot better right um you know we still have the nice green uh dumbbell nebula but the background and the star color all looks a lot more normal now so uh next thing that we can do is stretch the image because what we're seeing now again is the auto stretch but if i go back to linear it's actually still like this so let's now apply a permanent stretch through the image processing menu we'll go down to histogram transformation and if we want to try just applying the auto stretch you can click that um and apply it or if you'd rather uh you know reset it you can do the stretching manually so i'll just show stretching manually because i can find it sort of fun to see the image come alive so each time i click apply i am applying a little stretch and it can be fun just to sort of watch it uh get brighter and decide at what point uh it's bright enough for you now i'm just taking this middle slider and have been moving it over to the left now eventually when you keep doing that you'll see that the background the the dark part of the image becomes more sort of gray um so to change the shadows we can take uh this shadow slider the one on the left and move that into the right and basically this process of taking the mid tones or highlight slider moving those to the left taking the shadow slider moving it to the right is going to stretch out the histogram it's going to make this wider um as we as we stretch out those those mid tones to zoom in in uh zero you hold down the command key or i guess it would be the control key on windows um and just scroll uh and then you can scroll back out so i'm just going to scroll in a little bit here you can see there is a little bit of trailing on the stars uh we can try to fix that in the GNU image manipulation program but otherwise i think this looks really good you definitely get the nice dumbbell uh shape to the nebula and i really like all of the the colors we're seeing so far starfield looks good um so i mean if i was just going for a you know a fairly conservative edit uh that's just really naturalistic i could just stop right here maybe i would crop to taste but otherwise i think this looks really nice if you do want to crop in zero i'll just show that uh all you do is just click on one of the color channels doesn't matter which one and then just click and drag out how you want to crop and you can change this crop box you can you know grab an edge or if your mouse is in the center you can move the whole crop box around it does give a nice little center spot there so if i wanted to center i'm 27 i could okay once you've drawn out a crop box that you like and you've adjusted it just right click anywhere on the screen and you'll get a nice right click menu um there's other cool things in here but i'll just mention crops since that's what we're talking about and if you choose crop here it will crop to whatever that selection you just drew out is there's of course a lot of other things we can do in here so if you just wanted to finish in zero um you know and wanted to apply a little bit of color saturation you can do that here and you know it it makes the colors a little bit more saturated which can often look good when you are ready to save this either for display on the web or bringing it into another program like i'm going to instead of clicking save there that just saves the current fits file click on this next button over where it says save the current image in a different name and when you do that you can then save in different formats so you can save as a jpeg if you're or a png if you're putting it on the web or you could save as a tiff file for bringing it into photoshop or or affinity or a new image manipulation program or whatever whatever else you'd like so i'm going to save it as a tiff file i'll call it m 27 zero dot tiff and click save and then it gives you some different options here um you can leave it in 32 bit uh especially if you're bringing it into a new image manipulation program which supports 32 bit it or you can also uh put it down into 16 bit at this point you know because we've already done the stretching i think it's fine to go down to 16 bit i wouldn't go down to 8 bit um and definitely leave compression on none okay let's go ahead and save and then i'm just gonna open good new image manipulation program again i'm on version uh 2.10 here we'll go file open and open that m 27 zero dot tiff file there we go and you know this already looks really good um so there's not that much i really want to do in here the one thing i do want to show though is how to get rid of this little bit of star trailing that we're seeing so the way to do that is we're gonna first duplicate this layer so you can just right click on it and choose duplicate layer and then we want to make what's called a star mask so the way to do that is go to the select menu go to select by color and then click in the center of a few stars holding down shift and you can see as i'm doing this we see the selection outline so we can see it's selecting lots of stars i want to go after a few of the fainter stars here too okay that looks pretty good um however uh it's not a perfect selection yet we want to modify it a little bit so let's go back to the select menu and let's grow this selection by let's say two pixels uh okay so now you can see it's circling the stars quite a bit better maybe a little bit too much so now let's feather it so let's go to select feather and feather by one pixel okay i'm going to switch to what's called a quick mask um in the new image manipulation program you can get to that mode of working by pressing shift q and so and it's it's a toggle so if i press shift q again it goes back to the marching ants mode uh but shift q and then what you'll see is everything you know that isn't red is what you have selected right now and the one thing that i want to fix is it's selected a bit of our dumbbell nebula in addition to the stars so i'm going to just grab a uh brush and let's change the size of that brush just a little bit make it a little smaller perfect and i'm just going to paint with black where i don't want it to select which is the nebula because right what we're trying to do is just make a star mask where it only is selecting the stars okay good enough let's go back to marching ants mode shift q okay and then i want to turn this selection into a layer mask so i'll right click on the layer choose add layer mask and choose selection and you can see then what we had selected the stars are what it turned into the layer mask okay so we can now deselect so i'm just going to go to select none okay we're almost done i know this is a little bit uh complicated but it is worth it i think uh to get rounder stars and again i did this purposefully if you didn't watch part one yet because i wanted to show this method so i exposed a little bit too long to get these trailed stars because i wanted to show how to fix them uh with this method okay so anyways we have the layer mask again this is the star mask let's click back on to the normal image and we're going to change the blending mode here to darken only darken only okay and it says darken only nothing seems to have happened but now what we're going to do is we're going to nudge this layer to make the stars round i'm going to click onto the canvas here and then i'm going to use my arrow keys i'm going to press down a couple key a couple strokes and to the right uh just one stroke okay and that's it let me show you before after before after and this is a and you know you know zoomed in like this and maybe doesn't look perfect but if i zoom out a little bit that's much better it's it's not only making the stars um less prominent because they're not as trailed but it's also literally sort of making them rounder um and the way that this works is we're basically just taking the stars and we're darkening the part that is trailed with this blending mode so it's a very nice technique if you have slightly trailed stars you could have slightly trailed stars for a number of reasons even if you're tracking maybe something went wrong um and so this is a really nice way to fix that i think really the only thing i do at this point is it just looks a little bit uh low contrast so maybe i just go layer new from visible adds a new visible layer there and on that new visible layer i'll go into color and curves and i'm just going to reset my black point here by just dragging over the shadow slider okay save in GNU image manipulation program if you want to come back to this just do file save and you can save it as an xcf file or if you want to save it for the web do file export as and you can then just type in the format you want so i'll do m27.jpeg export i'll do full quality so um this again is a completely untracked no no star tracker just a fixed tripod showing you what you can do on a planetary nebula in this case the dumbbell nebula using free software i think it looks really excellent really nice star color nice even background the nebula pops we fixed the star trailing so that's it for this one hope you enjoyed uh till next time this has been Nico Carver Clear Skies