Intro to Narrowband and Hubble Palette, Part 2c - PixInsight

all right so 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 up front so keep in mind this is just for this particular object which is the seagull nebula or sometimes called the parrot nebula I see you to 177 but it’s still illustrative I think of what you can maybe expect out of an object that emits in hydrogen-alpha oh 3 and s 2 so the first thing we’re gonna look at here is an alpha single sub so this is one 5 minute exposure with the ZW o a si 1,600 in H alpha now let’s look at after it’s been stacked so this is I think like 36 pairs 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 oh three sub oxygen three you can see there’s just barely something there it’s a little bit hard to make out here’s after we stack and then it’s a lot more evident where that o three is again I’ll show you a single and after the stack okay and then last here’s the s 2 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 single and stack all right with that said we can move on okay now let’s jump into processing you can see here on my desktop I have a folder called IC to 177 that’s the object that we’ll be processing today this I took narrowband data so I have the H alpha frames the O 3 the s 2 and then the corresponding flats for those lights and then the corresponding dark flats for those flats dark flats are just like darks for your lights they just calibrate the flats just like your darks calibrate your lights so I have that all organized here you can also download these files from my website nebula photos.com ok I’m going to open up pics insight here’s what it looks like when you just open it up fresh and we’re going to calibrate everything manually so we’re going to start by going to process go down to image integration and choose image integration from that submenu click on add files navigate to my desktop here go into my darks folder and just select all of those darks to add them so you can see have 15 darks there in the input images window then down here under image integration I’m gonna change a few of these settings under normalization I’m going to change it to no normalization when you’re calibrating darks or bias frames you don’t want to use normalization you just want to give everything sort of a straight weight so also under weighting I’m going to say don’t care just give everything all the weights equals 1 I do want to generate an integrated image but I don’t need to subtract pedestals or evaluate noise so I’m going to turn those off that scale estimator I’m just going to leave on the default under pixel rejection I’m going to say answer eyes Sigma clipping meaning that if there is anything to Sigma outside of the norm it will probably just ignore those values under normalization I’m going to say no normalization again and for these clipping options I’m going to turn off clip low range but leave on clip low pixels and clip high pixels what that means is that I don’t want it to think that maybe the amp glow is something it wants to reject we want to keep that in the master dark so I’m gonna turn that low range off but keep these ones on just in case there are some stray things that you may reject okay that’s it so again average no normalization don’t care always equal one generate integrated image winds rise Sigma clipping no normalization all looks good I’m gonna hit this little circle to apply global and what pics insight does is if you have more cores in your system it uses those pores to work a little bit faster so this since we’re only integrating 15 frames this won’t take very long it does give you in this process console an idea of what it’s doing which can be handy if there’s any errors it will also report them over here and a lot of times you can use those errors to figure out where you went wrong and how you can correct ok it’s done so this was real time I then speed up the video or anything so you can see this a fairly fast machine this goes pretty fast you can look at these rejection Maps if you want to I’m just going to stretch them so you can see this is what it didn’t include in the master dark meaning these are pixels that sort of they sort of look like hot pixels but they weren’t in each frame so it rejected them here’s the low rejection map and then if I stretch the master dark it looks like this now that looks a little bit scary it looks like there is a lot of noise there but one thing to keep in mind is that when you apply this STF Auto stretch it is stretching the data to the extreme that it can so while the master dark can look a little bit crazy like this don’t worry about it this is the whole point of doing calibration frames is to remove this noise from your finished image so this looks perfectly normal for the ASI 1600 if we zoom in you can see these little white dots are hot pixels and on the sort of larger scale here these things in the on the sides and the corners is amp glow meaning the I don’t know exactly how to explain it but the the amplifier when it amplifies the signal is apply is is leaving some glow in the frame and we want to subtract that out through the calibration process anyways I’m gonna go ahead and save this off so I’m going to do file save as I’m gonna put it back into that same folder that I’ve been working in and I’m gonna call it master dark I don’t want to save it as a tiff file I’m going to use the X is F file format you can also if you’re planning to reuse this in programs outside of pics inside use the fits file format it’s really up to you if you only work in pics in site then there’s no advantage of fits over X is F so I usually just use the default file format that picks in site uses which is X is F and the defaults here are fine we want to use a 32-bit floating point sample format okay now that that’s done I’m just gonna go ahead and close that okay then what I’m gonna do is I’m going to create master darks using that exact same these exact same settings but with my dark flats for each filter so I’m going to go ahead and click the Clear button right here to clear the list of input images and click add files again and this time I’m going to go into my dark flats folder start with H a and grab these 30 files so yeah now I have 30 files these are dark flats that each one is 0.46 seconds and again I’m going to use the same settings but I’m now going to integrate my master H a dark flat so I’m going to hit the little apply global circle down here and it will go through and integrate this again I’m just showing this in real time but for the subsequent filters the O 3 and s2 I might speed up speed this up so it’s doesn’t get too monotonous but basically again I’m just using the same settings that I used for my master darks that are going to calibrate my my darks which are going to calibrate my lights I’m using those same settings for my dark flats okay it’s done just to show you how this compares there’s my rejection for masters get rid of those there is my H a dark flat so you can see it looks a little bit different than my master dark that I was using for my lights for one thing we don’t get these amp glows in the corners we now get a little bit more of a amp glow in the at the bottom this will look a little bit more similar to what you expect from a bias frame but again we’re not going to be using bias because we’re instead using dark flats so I’m just going to save this off I’m going to call this H a master dark flat and save it as an X is F file okay I can close that again I’m going to clear this list of input images and this time I’m going to add my oh three dark flats and again apply global and I am now going to speed this up because we’re going to do this for a three then we’re going to do it for us too so it’s a little bit boring alright here’s my o3 dark flat save that off close it clear the list and finally add my s2 dark flats apply save that this time is as to master dark flat clothes out that I’m going to go ahead and for now close image integration and open up image calibration and what we’re going to do now is use those master dark flats that we just created to calibrate our flat frames so we’re going to start with H a again I’m using the image calibration process I get to that from process image calibration image calibration where up here it says target frames I’m going to click add files and go into my flats folder start with my H a flats select them all so I have 30 flats up there I’m gonna make a new output directory so I’m going to go into my master folder here I see to 177 click new folder and call this each a flats Cal okay I’m gonna turn off master bias turn off master flat under master dark I mean I leave that checked but I’m gonna turn off optimize optimize is scaling option where if you are scaling based on time you could do that I don’t recommend ever using that with CMOS chips you might be able to use it with certain C CDs that have more linear response to dark scaling but I do not recommend it for DSLRs or any CMOS chips calibrate I don’t need that on either so I’m just going to go ahead and click this little folder here to select the master dark flat which is the H a master dark flat okay so we have that set master dark H a master dark it’s calibrating the H a flat’s and it’s going to output them to this folder that I’ve called H a flat’s Cal for calibrated with all of that set I’m gonna go ahead and hit the little apply global button all right you can see image calibration 30 succeeded zero failed zero skipped that sounds good just to see that it worked what I can do is I can open up one of those calibrated flats you can see unstretched it doesn’t look like much but if I stretch it we can now see the flat frame there and you can see that this was yeah this was taken with my Astro graph which is a pretty flat image there’s just a tiny little bit of vignetting on the corners here I think that’s from my filter not really from the telescope and then there’s a little bit of other weirdness I can’t really tell if those are due spots or what’s going on here but you can see it’s a pretty flat file when we take all of them and put them together things will become even a little bit more apparent what’s going on but this looks good and you might also be wondering as we’re doing this isn’t there a more automatic way to do this there is it’s under script batch processing batch pre-processing sometimes I do use that but it works really better if you are you gonna be using bias frames I don’t know if there’s a way to use this automatic feature if you’re using dark flats like I am here so we have to do it the manual way which is a little bit tedious but once you get used to it it’s not too difficult it’s just uh and once you get used to it you can you can also sort of have a more of an assurance that you know what’s happening with each step along the way okay so now I’m just going to repeat that process for that Oh three and s2 so clear the list add my oh three flats make a new folder called oh three flats Cal drop in my oh three master dark flats right there and hit the circle apply global button and do it one more time for the s two flats s to add my s two flats here which by the way for my system the s two flats are always the longest if you remember the the H a flats were just point four six seconds my as two flats are almost triple that one point two six seconds I’ll make a new s two flats Cal folder and drop in my s to master dark flat here under master dark and again apply okay now that we have calibrated flat files we are going to open back up image integration go ahead and clear this list and we’re going to take our calibrated flat files and integrate them into master flats for each filter so again what I am adding here is that my new calibrated flat so I’m going to start with H a use that new H a flat scale folder and you can see that I’m in the right folder because each file name now has this underscore C at the end okay so I have 30 flats in there I’m going to change these settings just a little bit under normalization I’m going to change it from no normalization to multiplicative I’m going to leave the weights on don’t care all weights equals 1 but I’m going to turn on a valley turn back on evaluate noise and under here under normalization I’m going to turn on equalized fluxes and I’m not going to explain right now what each of these options does but if you’re interested you can always hover over things in pix insight and a little tooltip will often come up and it will explain a lot of these oddest terminology for you if you’re interested okay with that done so again multiplicative average don’t care evaluate noise and under pixel rejection I’m going to just keep using winds rise Sigma clipping and equalize flexes I’ll just also make a quick note here that if you are taking certain kinds of flats like Sky flats winds rise Sigma clipping might not be the best option here you might instead want to use percentile clipping or something else that’s a little bit more aggressive to reject stars in your flats if if you were using sky flats I was using a light panel for this data set so Winsor I Sigma clipping will work fine okay and we’re just going to repeat this process again for each a 0 3 s 2 so here we go all right you can look at the rejection maps really when I’m stretching these rejection maps all I’m doing is just making sure that there’s nothing that leaps out is being really odd because then you might want to rerun the process if the rejection maps look very strange but if there’s just sort of a few pixels that are rejected don’t worry about it just close those out here’s our integrated H a flat and you can see now there is more pattern here again everyone’s flats are going to look a little bit different because it’s about the optical system that you’re using so using different filters using different telescopes you’re going to get a different response here but for this particular combination of things I’m using here this is what my H a flat looks like I’m going to go ahead and save it as H a master flat and I can close out of that and again just like what we when we were used doing the dark flats we’re going to repeat this process using the same settings so I’m not going to change anything down here I’m not going to reset the whole process window I’m just going to clear the input list and this time add my oh three calibrated flat frames open and just hit the apply global butter alright that’s done can closed rejection Maps stretch my oh three and yes this does look quite funky I don’t know if it’s something about the ASI 1600 or the Astrid I know three but I often get this sort of weird reverse look with my oh three filter the good news is that it does seem to calibrate nicely and the other thing to remember is that whenever you are stretching using this stf auto stretch it is showing you the absolute extreme stretch so while it does look funky it’s not really this dramatic it’s just that this is an extreme stretch of the data anyways I’m going to save this off as my oh three master flat and last up is the s2 so I’m going to clear the input list add my s2 calibrated flats and apply all right there’s my s2 flat I’ll save it as s2 master flat close that and close image integration for now open backup image calibration so we’re sort of going back and forth here image calibration image calibration I’m going to go ahead and just hit the reset button down here in the lower right I’m going to go ahead and add my first set of lights so we’re finally on to calibrating lights I’m going to go into H a select these 37 H a lights I’m going to go into output files and make a new folder called H a Cal right here under output pedestal I’m going to use an output pedestal of 800 this is in data units and using a 16-bit scale since I was using how do I explain this pedestal of 50 in a 12 bit range I’m gonna multiply that so that’s why I get to 800 this is sort of a more advanced subject I don’t really I’m not really prepared to explain it right now but basically the reason for an output pedestal is that sometimes when you calibrate you can get into negative values where you get black holes in your data and this is to avoid that so with a si 1600 I’d recommend always using somewhat of an output pedestal here usually between 400 and a thousand is sufficient for my particular data here that I’m using 800 I think is the right value I’m using a gain of 200 and an offset of 50 in the driver but you might want to vary that output pedestal you might also want to experiment a little bit with up a pedestal and see what works best but for this camera I would recommend using one okay so we’ve set up our output directory set our output pedestal can turn off master bias turn off optimize under master dark I’m going to add my master dark here this is the master dark that we created first thing we haven’t used yet I’m going to add my master flat for each a which we just made and so this looks good we have each a master flat under master flat we have master dark under master dark you have calibrated optimize turned off under output files we have an 800 under output pedestal and we made a new folder called a che Cal to drop all of the calibrated files into and we’ll hit go which is the little circle okay and if you just want a quick test of how it worked what you could do is I’m going to open up my first H a light here and I’ll also open up my first calibrated H a lights I’ll just put them side-by-side and give each one an auto stretch okay and they look pretty similar to be honest but you can see that this one has a little bit of vignetting where the the center looks a little bit too bright and that’s been corrected over here sometimes if we zoom in we can also see where it has removed hot pixels so I see one right there I’m going to zoom in one more level yeah sorry think yeah okay I can see two hot pixels right here so one handy thing we can do in pix insight is I can drag this sorry screwing up here okay make this a little bit smaller I can drag this tab right on top of this one and it zooms in to show you the same view so what we can see here you can see the same stars this these three stars right here and right here and there’s a hot pixel there’s a hot pixel and you can see in the calibrated result those have been removed so do you have to actually do this every time no but it can be fun just to make sure things are working to open up a light frame open up a calibrated light frame and inspect the differences close those out and we’re gonna repeat this process for our oh three and our s2 so I’m gonna start by going in two lights oh three select all the oh three light frames make a new folder called oh three Cal you know leave in that 800 output pedestal leave the same master dark in but change out the flat to the oh three master flats and hit the apply button okay and do the same thing for us to add the s2 lights change out the master flat and make a new folder called s2 Cal and hit the apply alright so we now have calibrated all of our lights I’m going to close out of that the next thing that we can do here is either use blink or subframe selector to inspect them if you are using blink you just go to all processes blink you open up a one of the calibrated folders and open up those images and then just use your arrow keys to move through the images basically what you’re looking for here is just any frames that really jump out as bad sometimes though when you’re zoomed out like this it can be really hard to tell so you can try zooming in and then moving through them again and again all of these look pretty similar to me you can see that there is drift between the frames that’s because I had dithering setup so it’s moving between every frame you can also see that this is two sessions the early session it’s a lot brighter than the later session so that’s blink it can be useful but what I mostly use is subframe selector so under all processes I’m just going to jump down to the S hears and choose subframe selector add all my H a calibrated frames and I often actually just dump everything in here at once so I’m actually going to dump in my oh three calibrated frames as well and my s two calibrated frames the scale on this was about 1.6 camera gain was 0.5 electrons to data number is 12 bit that’ll looks fine and the subframe selector as a process it started as a script I think you can still get it there but as a process the way that it works is you have to choose the routine up here that you want it to do so I’m gonna start with measure subframes and then I’m going to hit the apply global button and so you can see what it’s doing over here is since I added everything we are measuring 72 subframes meaning all of our lights that we’ve calibrated and what it does is it looks at both noise in the image but more importantly to me something called a centricity which is the roundness of the stars and a FWHM or full width half maximum which is an approximation of the focus so we’ll let it let it do its will let it do its thing here and then we’ll examine the results okay it’s done measuring and what I can do now is I can use this there’s three different windows that it opens up here this first one we are using to put in what we wanted it to measure and give some system parameters there’s this window which is called expressions and then there’s this window which is your measurements window and the first thing that I often do is I put in an approval formula here and I usually base this on what I’m seeing in the data so looking at full width half maximum I can see that there’s just a few frames that are over 0.7 so I’m gonna try just FWHM should be under 0.7 and apply it oh so I usually do this looking at the data you can see over here the left scale is FWHM the median looks to be around three points something three point three the outliers are up here well over four so let’s just try FWHM should be under or less than four point five and apply it and you can see that then took out one two three four five six seven frames out of our 72 and I’m gonna go ahead and sort this table by FWHM descending just to see how many of those rs2 frames 1 2 3 4 5 so it’s taking out five of my 15s two frames that leaves me with only 10 oh it’s a little dicey I wish I had a better data set here but we have what we have so let’s just see they’re really bad offenders here so you can see we do have a number over 5 but this one has a really really bad centricity of 0.

9 for one so that’s oh three number 20 any of 41:12 - the S 2 frames have bad a centricity yes maybe maybe this one or is that another Oh three frame that’s another Oh three frame 19 okay so I think it’s really just these two frames that I’m gonna want to get rid of let me just check the centricity graph here yep so I’m just gonna you can use the output feature of this but since there’s really just two frames in this grouping that I want to get rid of I’m just gonna actually go into my folders go into oh three Cal and just find those two 19 and 20 just double-check that those are the ones 20:19 the end in one five six and seven oh two yep those are them and I’m just going to delete those out of the folder okay we could also apply a weighting here if we want to I usually only do waiting’s when I have a bigger data set than this this is a fairly paltry data set so I don’t think that a weighting is necessarily called for but a common one that I do is just one over fw FWHM full width half maximum and if i apply that you can see then what happens is that frames that are better in focus are going to get a higher weighting and frames that are not as a not good focus get a lower weighting we can use then use that waiting when we integrate these files into a master and that can be pretty useful when you’re going for certain things in your image so if I was going for trying to get a really nice sharp image I might use that weighting expression I’m not going to actually you can do that and just check out your weightings quite easily with this tool again sort by FWHM this time I’ll do ascending so I can see here that my best frame is this one that’s an H a-frame I think let me see yes number 25 in the H a set right there is my sharpest frame in terms of FWHM it also has a good a centricity of 0.46 Oh pretty good maybe this one’s even better you can see the FWHM is about as good but the centricity is even better point three eight six that’s number eighteen in that same data set so maybe I’d go with that one what I’m looking for here is really just what’s going to be the best frame to register against so what am I going to use is my reference frame when I register all these things so I think I’m going to use this one number eighteen so you just would want to take note of this one way to do that if you’re taking breaks and processing is to save this off as a CSV let’s put it back in the same folder because a lot of times I’ve found I’ll just call this subframe selector a lot of times I found that I I think I’ll remember what I’ve learned here but then I forget and I’ve closed pics inside and then all the processing is gone so I have to rerun it so it’s better just to save it off as a CSV at this point so I can always come back to this data because it is really useful data in a number of ways and I’m not I haven’t gone in depth here with subframe selector expressions maybe another video I could talk more about this and how I use this tool but this is just sort of an overview of narrowband processing so we’re done here I’ve thrown out those really bad Oh three frames I’m gonna keep the somewhat pad as two frames just because I don’t have much data and I’m not going to use a weighting formula but I did find my best frame to register everything against so I’m going to close out of this and speaking of registration that’s where we’re headed next so we’re gonna go to process image registration star alignment and up here where it says reference image this is where we’re going to pick that reference out of a che Cal and it was number 18 so that’s the best oh that’s not it now that is it sorry confusing myself well I could always double-check with my CSV thing here number eighty and night let’s see yes that was it that’s the one that had the really low centricity and a good full width half maximum okay so picked that for my reference image I am NOT going to go into drizzling just because it takes a while and even though this dataset might call for it we just didn’t capture enough to really adequately drizzle I find that you need at least twenty-five to thirty subframes in each channel each filter to really adequately drizzle which again I’m not gonna really go into right now but it is a good thing to do when you have under sampled data like this but we’re not going to do it so I’m gonna uncheck generate drizzle data rest of these settings are fine I’m gonna go ahead and click add files select everything here in the H Akal folder I’ll put them to yet another new folder call this one H a reg order registration and hit apply global okay that’s done so now I’m gonna leave in that same reference image this is important you want to just keep registering against the same image but change out what it’s registering so now I’m going to add in all of my oh three Cal lights and make a note a new oh three reg folder and again apply it okay and then I’m going to do it for the stew frames leaving that H a registration frame in there I’m going to go down to us to Cal select all of these make a new folder called s to reg and apply all right all done with image registration so we are on to the last pre-processing step I know it’s been a long journey already which is the final image integration of our now calibrated registered light frames so we’re going to go to process image integration this time what I’m going to have you do is just reset the process so go down to the lower right hand corner and click the reset button and add our H a registered frames and we’re gonna leave all of this stuff alone everything under image integration we’re gonna leave on the defaults under pixel rejection we’re gonna choose winds rides winds Erised Sigma clipping turn on clip high range leave on all the other things here and run it by the way this is what I usually will always run first off is just basically the defaults with winds royce sigma clipping if something seems unusual i might change it or if i’m going for something very particular i might be adding in drizzle data here or weightings or other things but those are more advanced topics for just your average picture I just run the defaults on image integration and they do a pretty good job all right here we go this is a case where I do think it’s a more important to take a look at the rejection maps so you can see it rejected either an airplane or some satellites there some stars that maybe were I don’t know what the deal is there but and then in the low rejection map the main thing you can see is along the edges here because of field rotation or different sessions I the camera being rotated a little bit differently it rejected the edges a bit and then let’s look at our final integration here looks pretty good to me um can zoom in and check it out it’s pretty low noise this is thirty seven five-minute ETA frames yeah I don’t really see anything off-putting about that so I’m gonna go ahead and save that as just a che and I’m actually gonna also use the identifier a che there to change the identifier you just double click on it you can set it to whatever you want and I’m just gonna minimize this but keep my little H a master in my workspace here alright and now we just do the same thing for low 3 and s 2 and then we will be done with processing pre-processing sorry so go to whoo 3 reg select all of those all this stuff can stay the same and apply alright here’s my oh three results you can see the rotation effect and the low rejection thing is even more extreme there and here’s what we got and you can see that we have these black edges the reason for that is because remember we registered this against the H a so that they would match up right so that means we’ll have to do some cropping but that’s okay this looks like a nice result for the O 3 and finally we are going to do this too Oh before I do that let me save this call it Bo 3 and I’ll add my s two frames right here from s to reg alright that’s done there’s my s2 save that call it us to okay first thing I’m gonna do with these three is crop away these black edges and I’m gonna show you how you can do that identically on all three frames so we’re going to open up process geometry dynamic crop push this over to the side a little bit I’m gonna click on s to here and then I’m just going to click the reset what that does is it gives me this crop box around the edge again the way I did that just click on the one you want to crop then click the reset button and it will give you a nice crop box to play around with and what I’m going to do is I’m going to bring in this top edge then I’m going to move my mouse outside of the box and rotate it a little bit what I’m trying to do is I’m trying to get as much of the image as possible while cropping away those black edges alright that looks pretty good now instead of just applying this what I’m going to do is I’m going to use the new instance icon and I’m not going to click it I’m going to actually drag it off onto my workspace and then you can see it NASA as process one if I wanted to I could rename that if I was planning to reuse it a lot but I’m not so I’m just going to go ahead and leave it as process one and close out my dynamic crop process it’ll say d sure you want to cancel an active session say yes and then I’m just going to apply this process to each channel here ok so they’re all now cropped they’re still registered because remember we’ve just done the same thing to each one I can just check that by moving them like that and the only thing I have to still check is that there’s no black edges remaining which I can see on the o3 there is a little bit so I’m gonna get rid of this one I’m gonna reopen up dynamic crop this time click on the oh three reset it and I just have to drag in this left side just a little bit I’m gonna zoom in to make sure I’m not overdoing it just to get rid of that little black side there and again I’m going to do the same thing I’m going to drag off a new instance closed dynamic crop reset the zoom here and apply this to each channel alright so now we have registered crops images we have our s 2 r o3 and our H a next thing I’m going to do I can go ahead and get rid of this is do some background extraction so I’m going to use dynamic background extraction and this nebula fills most of the frame so I miss to be careful here I’m only going to use a few samples I’m just going to put one in this corner put one in this corner put one here at the top one in this corner and one in this corner it is well maybe I’ll yeah there’s really just no good place to put one in the middle maybe I’ll put one right there there might be a little mission there but generally ok and that’s good I’ll go ahead and apply a subtraction apply it let’s look at the background just by stretching it let’s look at the result yeah I think that improved for contrast a little bit looks looks nice so I’m going to keep that I’m gonna push that over there and just to do the same thing sorry for though three in us two so it’s under background model ization dime dynamic background extraction and I’m just going to apply a few samples where there’s not too many stars mostly along the edges here but I also want one sort of in the center and sometimes I’m a little bit more careful about this but I I’m just sort of gonna do it quickly because I don’t want to make this video too long looks good so I’m going to subtract the background let’s check it out yeah that’s one thing I’ve noticed about the o3 is there did seem to be some brightening effect down in that corner so I’m glad picked up on that looks good move that out of my way runner done asked to I’m just picking samples here where it is just the sky background and not the nebula I also don’t want a lot of stars in my sample because I can throw it off as I’m gonna just run a subtraction correction on it check out the background check out the results okay looks good now we are ready to apply actual stretches to these right now they are actually not stretched if I turn off the auto stretch you can see they are still unstretched so I like to just do this manually to taste I’m going to start with the a che open up where is this intensity transformations histogram transformation but it says no view selected down here I’m going to choose H a underscore DB e I’m going to take this middle slider move it over apply do that again do it again once I get a little breathing room over here on the left hand side I’ll bring my shadows over and you can see that when you bring it over too far right there is the number of pixels that you would be clipping to black so I try to keep that as close to zero as possible and basically what I’m doing here is just I’m making the image more contrast II bringing out the signal that looks good I’m going to stop right there for now if I have to go further on it later I can but I don’t I don’t like to go too dramatic a stretch right away move on to the s2 here just do the same thing bring that over as an initial stretch back off a little bit one more time reset the black here so comparing that to my H a you can see we already have an issue where the stews background level is a little bit too bright compared to the H a I’ll deal with that in a second I’m going to go ahead and stretch my oh three first taking this mid slider over run that a few times reset the black okay so now what I’m going to do before I combine is just sort of get the O 3 and the s 2 to this level of contrast that was so easy with the H a so I’m gonna do that with curves I’m gonna go back to intensity transformations curves transformation I’m going to open up a real time preview here and then I can just sort of see what I’m doing as I’m doing it yeah take it down here take this one up reset take it down again apply reset take that sky background down one more time bring the signal up a little bit and apply okay now I’m just going to go ahead and compare the H a and s two they look more similar in their tonal response now so that looks good I’m just gonna do that same thing with the O 3 open up my curves do a real-time preview and just play around in this part of the curves basically okay I like that I’ll just apply it again okay looks good so now we’re ready to combine these into a color image so I’m gonna go to process pixel math pixel math we don’t want to use a single RGB K expressions I’m gonna turn that off I’m gonna open up my expression editor in my our channel I’m gonna drop my s to double-click G channel my H a blue channel my oh three okay so this is what we call a show mapping or a Hubble palette mapping s 2 is mapped to the our H a is mapped to the green and o 3 is mapped to the blue under destination we want to create a new image for a color space we don’t want it the same as target we want an RGB color image and I can never remember if I want to apply or apply global here I think just apply yeah okay can close out of that here’s our first Hubbell paladin imogen evil nebula if you’re a purist you could just go with that it’s very green but we can play around with it one thing that I am a little bit unhappy about it with it is the the sky background is a little bit too colorful for me so I probably desaturate the sky a little bit and make it a little darker but it’s looking pretty good we have a nice separation already between the channels but I think we can improve it a little bit so to do that I’m gonna go ahead and minimize these out of the way we can do that with just curves so if we go to process intensity transformations curves transformation I’m gonna reset this I can open up a real-time preview here and then just with the red green and blue curves we can do a lot of interesting work just playing around with you know how much red is in the image how much green is in the image and so forth something like that might be interesting again this is just really quick you can get much more in-depth like if you want to mask off certain colors there’s a script up here I believe it’s under mm I don’t use it very much so sorry I’m gonna have to find it utilities color mask so this script is pretty cool you can pick a color like let’s say I want to work on the yellows in the image so I’m going to click the word yellow I want a chrominance mask I’m gonna click okay and it finds all of the yellows in the image and creates a mask for you just like that and then I can really target the yellows and change just that part of the image so this is an option again to apply a mask if you’ve never done this before you just apply it like that and then you’re working on the yellows in the image I mean go ahead and get rid of that I’m not gonna do much with that right now but it is an option if you really want more control over the colors in your narrowbanding that’s a good way to do it really the only thing that’s really bothering me about this image right now is how purpley magenta the Stars look so a quick way to fix that is I am going to go to process all processes and find invert and I’m just going to invert the image and you can see when I invert the image all of those magenta halos turn green and then I’m just going to zap them I’m just gonna turn I’m just going to treat them as noise and go to noise reduction SC n R and color to remove green so if I wanted to do a really dramatic removal of all the magenta halos I would just apply this at 100% I’m gonna try it at 75% instead a hundred I just find whenever you’re using any SCN our process is just too dramatic so I’m gonna bring it down a little bit I’ll apply it see how that looks on the inverted image I think that looks pretty good but to really the real test is we’re going to invert this image back yes and I like that a lot so you gonna have to experiment with this for different uses you want a different amount here we probably could have even gotten away with 50% and it still would have taken out the the magenta halos but left some star color in the image the amount of star color you are leaving in a narrowband image is really up to personal taste some people still like the colorful stars with a narrowband image other people just want pure white stars so it’s really up to you I think this looks good and now it’s really just tweaking if you want to play around with saturation levels you can go to intensity transformation color saturation again this has a real-time preview and so you can bring up you know or down the blues and see how that looks I mean I made me bring up the blues a little bit bring down the greens a little bit bring up the reds bring down the magentas okay let’s may be a little too strong let’s try that yeah I like it again though this is really up to you some people like a nice saturated narrowband image other people would find this too garish and want something with a little bit less saturation another thing that I might do with this image is just take a luminance out of it so here’s to get illuminance all I have to do is just click this button right here extract L component and apply that luminance of a mask and then invert the mask under the mask menu I’m also going to turn off show masks here for a second and I’m just going to then open up curves reset it open up my RGB K curve open up a real- time preview and just take down the sky background a little bit and take down the saturation of that sky background a bit something like that okay just to show you before and after on that one here’s before see the sky backgrounds a little lighter you can see a little bit more blue in that corner and after just taking out a little bit of the saturation in a sky background and making a little darker so that the Nebula stands out a little bit more I’m gonna remove that mask and last thing I’m gonna do is I’m just going to go back into curves one more time reset it go to my RGB K curve open up a real-time preview and I’m just gonna do some final tweaks here with the curve so you can see what this does is it but when you use when you do a really dramatic s-curve it adds a lot of local contrast to the image you want your nebula to take on that sort of 3d effect and so this is a way to do it but when you really stretch it like that then it looks terrible of course it looks garish and you lose a lot of detail when you do that so it’s really just about making these fine little adjustments so that you have bright areas of the nebula and dark areas so this is just a very mild mild s-curve and I might even bring it down a little bit on the top end here okay there of course is always more you can do with an image we could do something with the stars we could have deke involved them or shrunk them or whatever but this is really just basic narrowband I wanted to show you how to properly calibrate register put your narrowband image together with pixel math and then tweak it a little bit with mostly curves which is one of the number one processes to master I’d say in pics insight saving it off we can do file save as and all of the options are right in here we can save it as a JPEG or PNG for the web TIFF for bringing it into Photoshop if you wanted to or other tools and an X is F or fits file or continued work inside pix insight one other thing I’d say about saving Tiff’s out of pics insight is for them to work in other programs I find you really want to use 16-bits mode other programs might be able to read 32-bit mode but usually not pretty well so or you’ll have weird display issues so I always use 16-bit Tiff’s out of pics insight to bring them into other software programs alright that’s it for this session I’ll just make this a little bit bigger so you can see my final result here if you process this yourself I’d be interested to see your results you can share them with me just let me know in the comments of my youtube or you can find my contact information on my website thanks for watching and if you have any suggestions for future videos let me know in the comments thanks .