How to edit DEEP SKY images in SIRIL - powerful FREE astrophotography software for Windows Mac Linux

hello in this video i'm going to do an overview of a relatively new and pretty awesome software for astrophotographers called serial this app is capable of both pre-processing your images which means aligning everything together and stacking their images but also post-processing which means things like stretching the image fixing some colors adding the contrast removing noise etc etc and in this video i'm going to show you a couple of different things in serial that you can do including pre-processing and also some post-processing so you can see what it is capable of because in my opinion it's a very cool software even has things like photometric color calibration which in my opinion is pretty awesome so let's get started alright so in order to download this software we have to go to their website which is serial.org and as you can see right on the landing page right here you can see that this app can work with pretty much any operating system which is pretty awesome which includes both windows mac os and also linux and this is pretty awesome because i am a mac os user and previously i was unable to use deep sky stacker or sequator because those programs work only on windows so if you're on mac os and you are struggling with like virtual machines in order to be able to use deep sky stacker or sequel then you are going to be very happy with serial another cool thing is that this app is absolutely free it is completely open source you don't have to pay anything you can donate if you want to but you don't need to and you can use it for completely free so let's jump into the app and see how the interface looks so this is the basic interface of this app and as you can see there are a lot of buttons a lot of tabs and it can be a little bit overwhelming at first but don't worry because this app is pretty straightforward to use so what we are going to do first is we are going to do some pre-processing and you can do it both manually but also fully automatically to do it automatically you can use one of the scripts that are right here which i'm going to talk about in detail in just a second but also you can use these tabs right here to do a manual stack but the very first thing that you have to do is actually set up your home directory so you can do that by clicking on this little home icon i have already set mine and if you want to do an automated pre-processing using a script it is best to set up your home directory and some place that you have sub directories that are called biases darks flats and lights and in these subdirectories you have the respective images so i'm going to hit cancel because i've already set it you can see it right here what is your home directory and then if you want to run a script it is as simple as going to scripts and then go to osc pre-processing so i'm just going to click on that and as you can see on the right hand side you have a console and in this console it is showing you what the software is doing so as you can see it needs four sets of raw images in the working directory within four subdirectories biases flats darks and lights and it starts by stacking the bios files then it's going to stack the flat files then it's going to do some stacking with the darks and then final pre-processing i am going to actually cancel it out because it can take up to a couple of hours depending on what kind of computer do you have and how many images do you have in this stack i actually have mode of 500 frames and my computer is not the fastest so it took a couple of hours in order to finish this process so i'm going to cancel it out by hitting the stop button right here but if you let it through this is the kind of screen that you would be presented with you can read in green font that the total execution time was that many hours or minutes and that everything went successful and just like that you can pre-process your images and stack all of those single frames all of the light frames and the calibration frames into a final stack with which you can then work in the post-production process and i've been using this automated process myself couple of times and the results are pretty amazing but if you want to do it completely manually and have a little bit more control over which frames are actually taken into consideration in the final stack and which frames are discarded because there was some some movement some gusts of wind or whatever you can do it completely manually as well but i'm not gonna present it today because this is a pretty complex process and really for the basic use of cereal you will most likely get a pretty good result with the automated process but there is one problem and that is because the automated process the script that i have just presented to you expects those four subdirectories so if something happened in the field and you couldn't take flats for instance maybe you uh change the zoom position in your lens maybe you change the position of the focus ring and you cannot take the flats or maybe you just forgot about them and you have only lights then if you try to use this script the serial app will complain because it cannot find those files in those calibration subdirectories but what is pretty cool about it is that it is using a script so you can actually go ahead and either modify this script write your own script maybe get some third-party script so let me show you very briefly how those scripts looks like and how you can write your own so right here in the top right side you have this button and if you click on it you can go to preferences and if you open preferences and go to script you can see what are the directories that serial is expecting the script files to be and this one is the directory with the built-in scripts and those two directories are the directories which you can store your own script so right here i have actually opened those two directories so this is the one with the built-in script as you can see it is macintosh hd applications serial contents resources share serial scripts those are the built-in scripts and you can view those scripts you can copy it from there and customize those scripts to create your own and then if you want to create your own and put them somewhere you can use one of the other two directories so as you can see for instance here i have the macintosh hd users camille which is my username then dot serial and then scripts and right here i have three scripts that i have created for myself and those scripts are pretty simple they pretty much look like this this is the osc pre-processing script that i just talked about this is the built-in script created by the serial developers and as you can see it is super simple whatever starts with the hash bank right here it is a comment so it is not being interpreted by the software or executed in any way it is just for informational purposes and right here it starts with some kind of a command that kicks off everything and then you have as you can see the script is kind of going into the biases directory then it's converting the biases into fit files which are the files that serial is working with then it goes back the cd dot dot is like changing the current directory to a parent directory and then it goes inside the process directory which it have just created and then it is stacking the biases then it's going up again there's going into the flat subdirectory converting the flats go up go into the process then it's pre-processing the flats using the biases then it's stacking our flats then it's going to the darks it's converting the darks it's stacking darks it goes into the light subdirectory it's converting our lights into the fit files and then it is finally pre-processing all our light files using the dark stacked file that it has created before and using the flat file that it had created before and using some parameters like cfa equalize cfa and debayer then it is registering our light frames which means aligning them and creating the final stack using this line and for instance if you don't have darks flats or biases and you only have flat frames you can actually skip a lot of this and this is what i have created right here as you can see one of my user scripts it is called osc preprocessing only lights and if i open this actually right here you can see how it compares this is how it looks and as you can see this is the requires line and then i have skipped pretty much everything here i have skipped it and i'm just starting with cd lights which goes into the light sub directory so i have skipped all of that so i have cd lights then i have converting the lights and then i have pre-processing but i also had to modify this pre-processing command because i don't have any darks nor flats so i just basically removed those two parameters this is the kind of a standard syntax and unix system where you have a command then you have some mode of this command and then you have parameters the dash dark is the parameter called dark and the value of it is equals dark stacked so if i just remove this it will just skip this parameter and also i have removed this to skip the flats and then i came up with this command i'm sorry if this concept of scripts and how those scripts actually look like may be a little bit overwhelming for some of you but don't worry i promise you i won't be showing you any more code in this video what i just wanted to demonstrate is that you can easily take the script that someone else has created and modify it to your needs so let's jump back into serial and let's actually open up one of my stacks that i have previously created this will be a stack of the orion nebula and let's see what kind of capabilities does serial have when it comes to post processing all right so in order to open your stacked image so you can work with it you can go to this open button right here and right here you can open it i have created a shortcut here for my test photos and as you can see i have two fit files this is the orion nebula and this is the north american nebula which i'm going to show you in just a second but let's start with the orion nebula and basically the stacked image that serial is spitting out as a result of the script is a single fits file and this is the file that you can work with serial if you want to move it into photoshop or some other software like this you can convert it into a tiff file which i will be showing you in just a second so let's open that and we have the stacked image opened right here and on the left hand side you can see we have four tabs we have the red channel we have the green channel we have the blue channel and then you have the rgb preview and then on the bottom as you can see it says linear here and this is the linear projection which is how your image actually looks like but if you want to preview how this image would look like if you have done some stretching to this image you can pick one of those options so for instance we have an auto stretch right here and this is how our image would look like if we apply the auto stretch algorithm to it and this is a pretty cool way to kind of gauge what kind of material are we actually working with what were you able to capture in the field and how much information in your image is actually stored but this is of course way over done so i'm going to actually switch to linear because at this point we haven't done any adjustments to our image i just have switched the preview projection from linear to other stretch so let's go back to linear and then you can do a couple of things the first thing that i would do and what cyril recommends to do is actually crop in your image because as you can see on the left side and on the top we have those weird black bars and this is the artifact of stacking because the stacking algorithm is aligning your images and if you have some misalignment throughout the night which is perfectly normal you're going to end up with something like this so in order to crop it you actually cannot do it in the rgb which is kind of an inconvenience you have to switch to one of the channels so let's go to red for instance and then you can draw a box just click and drag and as you can see it doesn't keep my aspect ratio so in order to fix that i can right click and go to selection preserve ratio and right now it preserves the aspect ratio which is something that i like to do and i'm just going to reposition this box to create the crop that i like i think this kind of crop looks pretty good for this image so to kind of accept it you can have to right click and then crop and then we can go back to rgb and we can do one of my favorite features in serial which is photometric color calibration so in order to do that we have to go to image processing and then you have the color calibration and let's choose photometric color calibration and what this feature basically does it is analyzing your scene and is analyzing what kind of stars do you have in your shot it is cross-referencing it with the catalog of known stars in terms of what kind of colors those stars should have and it applies some white balance adjustments to your images which are just right in order to make those known stars to look as they should so this is a pretty cool thing to fix your white balance and fix any of the color issues that you might have in your image but it doesn't always work which i will show you in my second example for this one i know that it will work because i have done it before so you can just move it somewhere here out of the way and then you have to search for the object that you have in your shot so in our case this is the m42 orion so i'm going to click find here it is orion nebula and then you have some parameters here you can play with them but honestly i'm just using the default values and it usually works fine so i'm going to hit ok and this is going to do some processing here in the console and when it is done as you can see it removed this blue color cast i'm going to hit close right here and also on the top side as you can see you have the undo and redo so you can compare what the photometric color calibration actually did by going to undo and reader so let's go to undo this is how our image looked like before as you can see it is kind of bluish and then after the color calibration let's go to redo it looks way way nicer and more natural and right now let's actually do some stretching to this image so i have presented you beforehand the auto stretch preview but if you actually want to apply the outer stretch here you have to go to this histogram adjustment that is right here on the bottom right hand side and then right here we have your histogram and you can either manually apply some stretching to this image or you can choose this icon which is apply the auto stretch algorithm to this image so i'm going to hit that but as you can see the stretch is a little bit too extreme for my taste so if you want to dial it down you can move the midpoint here to the right and just dial down this adjustment so what i want to do is i'm going to dial it down maybe a little bit more maybe a little bit more and this is pretty much something that i would like for this image so i'm going to hit apply and then right here you can iteratively stretch your images even more so you can move the midpoint and then apply apply move apply move apply and kind of in this iterative process you can stretch your image but i kind of like how my image looks like already so i'm going to hit close right here and then as you might have noticed there there there's no layer panel in this software like you may be used to with photoshop there's so there's no easy way to kind of toggle between what your image looked like before and how it looks like after the only thing that you can really do is just use the undo and redo button so i'm gonna test this out this is the image before stretching and this is the image after stretching and as you can see it brought out a ton of detail in the orion nebula which i really like but it also made this image a little bit noisy and as you can see there is this tiny tiny kind of a green cast right here so there's actually an option to remove the green noise so you can go to here and then you have the remove green noise i'm gonna hit just apply without modifying any of the parameters apply here and it kind of neutralized a little bit of this green the effect is very subtle but if you go back in this video and compare the effect is definitely there so i'm just going to hit close and then as you can see the stretching algorithm caused a bit of noise to actually show up in my image so what i can do is i can do go to image processing again and then choose a median filter and the medium filter is going to smooth out this noise in the background and also bring a little bit more details in the nebula which is kind of a perfect combination for an adjustment to this kind of an image so i'm going to change it to a 5x5 which is what i used before and maybe two iterations and then let's just click apply and just like that the image is way way more clean and i kind of like the look of it i would probably bring this image over to photoshop right now to kind of clean up this background even more but this image already looks pretty awesome to my taste and now if you want to actually save this image as a tiff file so if you want to work with it further in software like photoshop you can go to this icon right here you can also hit save and this will overwrite your stack fit file but i want to do that i just want to export it as a tiff file so i'm just going to click this one and then you can change here to a tiff and then just give it a name let's say that i want to save it here in the test photos directory save and then you can choose which format do you want to save it then if you want to bring it into photoshop i would highly recommend to save it as a 16-bit unsigned integer you can save it as a 32-bit floating point but photoshop will kind of act weirdly with these images you want to use you can use set it to bit floating part but if you want to use photoshop i would recommend using the 16-bit unsigned integer and then just click save and that will export your tiff file so as you can see this is a basic post production workflow which i would apply to my images right in zero before even moving them for the final touches into adobe photoshop and arguably this image already looks pretty awesome so if you don't have photoshop you can totally settle for an image like this or finish it off in or whatever you want but hopefully this kind of gave you an overview of what cyril is capable of and right now let's take a look at my second stack which is the north america nebula which is going to be a little bit more difficult because i didn't shoot any flats nor biases that night i only had the lights and darks which you will see in my images then i'm gonna have some colors and vignetting issues and also the north american nebula is way more fainter than the orion nebula and both of these images actually were shot from a bortle seven class sky so a pretty light polluted area i was using a light pollution filter but definitely the more faint nebula which is the north american nebula is going to be more difficult to work with to bring out those nebulosities in this image so let's see what you can do with cereal all right so let's open the stack of the north american nebula so again i'm going to go to the open button and then it's in my test photos bookmark and then the result ngc 7000.fit is the file that i want to open so let's open that and right off the bat you can see that this image is very different from the image of the orion that i showed you before you can see some kind of a trace here of the north american nebula but it is very very faint so let's see what the other stretch preview would show us and actually as you can see the other stretch looks horrible right off the bat you can see my problem with vignetting as you can see this these edges of this image look kind of horrendous and this is because i was not using any flats in this sequence so again this is another argument that you should absolutely take those flat files because they can really improve your final stack and actually i have just created a video talking about differences with the stacked file that was created by using calibration frames and only light frames so you can definitely check out this video a link to it will be down below in the description so with this auto stretch preview as you can see we kind of don't really see much but we can choose a different one for instance the histogram projection is going to show us our nebula so as you can see this is the north american nebula right here and we have the pelican nebula here and this preview mode will help us to actually crop our image which is again the first step that i would do here so in order to crop as you can see this is pretty inconvenient i cannot really select anything in the rgb preview it is showing me that rgb tab is only for visualization operation must be down on rg and b channels so i'm gonna switch to red again as you can see uh this is the like the monochrome version of this image which is on the red channel so again i'm gonna draw a box i need to change it to preserve my aspect ratio and then i'm gonna come up with a crop that i kind of like so i'm gonna include both the north american nebula and the pelican nebula uh something like this this kind of the framing that i like so again right click and then crop and then let's go back to linear to kind of see what we have and again in the linear we don't have much it's the red chance so let's go back to rgb again and then what i would want to do is actually fix the colors in this image because as you can see in this image we have a kind of a reddish brownish cast so if i go to image processing and color calibration photometric color calibration i can type in here the north america i'm a recon find it has found it if i click on that and go to ok it is going to try to do it here but unfortunately i get an error that plate solving failed this image could not be aligned with the reference stars and that is something that sometimes might happen so in this image i actually need to fix the colors with different adjustments so i'm just going to click ok to accept that and i'm going to go back to image processing and then color calibration and then let's choose the color calibration the first option here and what you can do right here is you can actually select a part of the background and use the background for neutralizing the color so this is exactly what i want to do here i'm going to go to red because again i cannot select anything in the rgb preview and then i'm going to select part of the background that i know it's something right here i can actually move this uh switch this back to free ratio i'm going to select something like this i know that my nebula are right here so on this patch of the sky i shouldn't have anything interesting so with this selection you can go to use current selection this is going to populate these four values of the of the corners and then background neutralization and maybe actually let's switch back to rgb so we can see what's going on and then i'm going to click that and it is going to kill this red color cast so this is definitely something that i like i can close this right here and let's see what we have again let's see the outer stretch and right now the image looks way way better do you remember what the other stretch showed me beforehand a terrible kind of a really saturated orange and yellow colors but right now you can actually see my nebula right here which is something that i definitely like you can see kind of a big green noise right here so we can try to remove this green again by going to image processing and remove green noise move it out of the way and apply and it killed a lot of this green really really nice for this image which is something i definitely like i'm gonna hit close right here and then as you can see i also have a problem with this kind of a purple background here and this is most likely caused by the gradient of light pollution because i was shooting this from the city and from what i can remember right around this side of my image was a kind of a big source of light the city center of the town that i live in so in order to kind of try to remove this you can go to image processing and go to background extraction which is again one of my cool features here in serial so i'm going to go to background extraction and what it does if you click generate it that's a bunch of these points and those points should be only set in the background so you shouldn't have any points in your nebula and in order to remove this i can actually maybe generate less samples and go with the tolerance a little bit to the left if you lower the tolerance it is less likely to get any points on your nebula so let's regenerate and as you can see we have less points in my nebula right here but i still need to remove some manually and in order to do that you can right click on those points but again you have to switch to one of the channels so i'm gonna go to red and i'm just gonna right click in order to remove these you can also left click in order to add points but for this thing i think i'm good with just removing the ones that appear in my nebula so i'm going to remove these and then let's go back to rgb and let's see what background extraction does to our image so i'm just going to hit apply and then as you can see a lot of this purple weird kind of things are gone from here remember that we are still in the auto stretch projection so we are not actually we haven't stretched our image yet and this is a pretty cool feature here in serial which means that you can actually do a lot of these operations like color calibrations background removal background extraction etc etc you can do that by previewing how your shot how your image would look like using one of those previews but you are not actually working with a stretch image which is what is recommended it's always recommended to do that kind of operations on a linear image and then do the stretching so let's do the stretching so i'm going to close this one and i'm going to switch this to linear again and this is how our image actually looks like which is again our nebula are barely visible and then i'm going to go to the histogram adjustment and then click on the auto stretch which again brings us back to what we have with the auto stretch preview but this time we can actually do the adjustment and kind of commit it to the image so i'm gonna i'm gonna dial it back i'm gonna move the midpoint to kind of darken it a little bit maybe more maybe something like this so i'm going to hit ok at this point to apply it and then i want to show something else because there's actually a second feature that you can use to stretch your image and that is the asynh transformation so i'm gonna hit that and then you can stretch it using these factors so this one if you move it to the right it is going to brighten the image and if you move this one to the right this is the black point this is going to darken the dark parts so let's just move it maybe a little bit more yes something like this something like this uh this is something that i really like for this image um so you can move it you know depending on your situation as you as you like and then just of course hit apply what i want to do at this point is also apply some of the median filters in order to remove a lot of this noise in the background here so again i'm going to go to the median filter and i'm going to choose the kernel size of 5x5 two iterations let's move it out of the way let's apply it and as you can see it removed a lot of this noise so i'm just going to hit close here and then as you can see this image has still a little bit of a purple cast right here on the on the edges of this image so what you can do is go to image processing color saturation and then let's try to desaturate these so i'm going gonna choose the hue to be magenta and pink and try to dial it down maybe a little bit we can see what it does i can change this this is supposed to like um protect the subject so it is going to favor uh only adjustments in the background as you can see it killed off a lot of this saturation here in my background protecting the nebula but i really like what it did here maybe i overdone the amount so maybe dial it down a little bit and there's only so much you can do with those simple sliders so maybe i will just cancel it out and this is what we have straight from zero so with this image as you can see it was a little bit more difficult to pull out that detail so i would definitely bring it over to photoshop and try to fix those colors with things like selective color adjustments etc but this is out of the scope of this tutorial hopefully by now you can see that serial is a very capable software you can use it on mac os which is something that was not possible to be done with equator or deep sky stacker so for mac os users this is pretty awesome i hope you liked this video if you did please make sure to leave it a like i would really appreciate it and also consider subscribing to my channel because i will be posting a lot more videos about astrophotography photography as well so it's definitely worth subscribing and right now check out these two videos i think they might be very interesting to you check out the links in description to download the software and clear skies see you next time hopefully and bye

Channel: Kamil Pekala

Views: 42,689

Keywords: siril, siril astrophotography, free astrophotography image processing software, free astrophotography stacking software for mac, deep sky stacker mac alternative, astrophotography processing tutorial, siril tutorial in english, siril for deep sky astrophotography, siril image processing, how scripts work in siril, siril features overview, siril photometric color calibration, best software for astrophotography, editing software for astrophotography, how to edit deep sky images

Id: Yg5D43Dc7yQ

Length: 27min 32sec (1652 seconds)

Published: Fri Mar 26 2021