Narrowband Workflow for CHI-1-CMOS in APP

If you are having problems with PI getting stuck somewhere in WBPP as some people seem to do or you want a quick way to do a nice NB output that can be published with no additional work and it good enough to impress your friends and family, look no further than APP. If you don't have it they do have a free and fully functional trial of it.

To follow along with this you will need the following files. Note that you have to get the one clicks for this. I am using IC4685 with CHI-1-CMOS and am using the raw uncalibrated images. This link will get them for you: https://app.telescope.live/archive/my?showCalibratedImages=false&telescopeIds=59&targetName=4685

You will also need the calibration files, which are the SHO flats, darks, and bias: https://app.telescope.live/archive/calibration?searchRadius=15&imageTypes=4&filters=(HSO),Halpha,SII,OIII&telescopeIds=59  https://app.telescope.live/archive/calibration?totalExposureTime=299&totalExposureTime=301&searchRadius=15&imageTypes=3&telescopeIds=59  https://app.telescope.live/archive/calibration?searchRadius=15&imageTypes=2&telescopeIds=59

The first thing I do is I go into APP and assign the working directory, normally where my lights are, and then I load in my lights. I am going to do this one using the raw uncalibrated files and then add in the calibration files at this step, that way you also have an idea of what to do when using your own equipment.

Now that you have all of your lights and calibration frames loaded, go to tab 2, which is the Calibrate tab, and make sure you leave everything up top at default, but scroll down and make sure to do your settings just like this:

Now go to tab 3, the Star Analysis tab and set things like this to start initially. The reason I keep the cosmic ray/noise reducer set is that keeps it from trying to see noise as a star and will not use it for star analysis. Note that I have my stars set at 500. If you are trying to do a mosaic and it is not picking up enough to do registration bump that to 2,000. It will take a little longer, but it should get things going. Sometimes you may need to take it higher.

After this you will go to tab 4, the Register tab. Leave it at the default quadrilaterals, set your scale stop from 1-10 (if doing a mosaic set it to 1-15), you can check use dynamic distortion, but that isn't required unless there is distortion toward the edges of the frame or when doing a mosaic, and sometimes leaving it checked gives a really weird result and you will need to uncheck and re-register the frames. Check same camera and optics if the frames have not been saved as registered and they are from the same telescope. Make sure to leave this unchecked if stacking from different telescopes. If doing a normal stack, set registration as normal. There are also mosaic and comet registration modes.

Next go to tab 5, Normalize. You can generally leave this as the default "normal" but if there are any weird gradients or you are doing a mosaic then you want this set to advanced. I have it as advanced here because it doesn't hurt to do that, but it will slow it down some. You do not have to change the scale unless you are doing a huge mosaic, and when I say huge I am talking one where you are doing something along the lines of a 24 panels AUS-2-CMOS or something similar.

Next we are at tab 6, Integrate. You can leave everything at default here, though I highly recommend doing LNC and MBB on this. Here are the settings I have for this one. If doing a mosaic LNC will slow you down big time, even if you do like you should and only stack the master lights as lights, but it can give an improvement. MBB is something you absolutely want on a mosaic because it will make the mosaic seams go away. After you have all of this set you will hit the integrate button you will see when scroll all the way down on this tab.

After everything is integrated you are going to have nice calibrated master lights for each channel. Go into the tools tab and click on combine RGB

Leave things as their defaults, but select SHO (Hubble) 2. You will then click the add channel button and go ahead and select your Ha, Oiii, and Sii channels at the same time by doing ctrl + click (you may have a different method on an OS other than windows). It will ask to confirm what each channel is. Note that one of the TL data doesn't pull the hydrogen alpha info in if you don't manually mark it on the first step of loading lights, so you will have to mark that channel here as hydrogen alpha otherwise it will say "custom" for it. All other channels will auto populate what they are no matter what.

It is at this point where I will make custom changes to the mix of channels rather than using the canned mixes. The only reason why I choose the composite formula I do is it is closest to what I need and the output file will be labeled as such. Notice in the image below that I changed the color mix and the channel multipliers on all 3 channels. If you want to swap to another formula or you want to reset it back to the canned one you can. All you need to do is hit "new formula" to reset it back, or click on the dropdown menu and select a different mix, then click new formula. For this since I already now what I want to do I am going to click on "re-calculate" to apply my mix. Normally with an SHO mix I will have the Oiii multiplier at 3.750, but the Oiii signal in this area is so strong it will oversaturate or blow out some of the stars if you do that.



Notice on the right side that I have "saturation" checked. I left the saturation slider at the default 15 for this. I left "neutralize background" unchecked, but normally it is a good idea to leave it checked. I also left it at the default auto stretch of 15% BG, 3 sigma, 2.5% base, and I left "stretch" checked. You are still in a linear state at this point, the stretch is just to give you a preview of what you have if you were to save a stretched image. If you are happy with this hit the "save" button on the upper left, let it do the default 32 bit fits file, and then once that saves hit cancel on the upper left to get out of combine RGB.

Now that you have done that you will want to crop the image, so double click the combined image to put it in the current display window, then hit batch crop. It will ask if you want to crop the current image, so hit yes.

Next click the -crop image to bring it into the viewer and you can save it as a png, jpg, tiff, and fits file. If you want to keep it linear make sure to uncheck the stretch check box on the upper part of the right side. That will give you a dark looking file and will default save as fits, so you could bring that into PI if you want. If you want to do it in Photoshop save it as a 16 bit tiff, and you can work it either as stretched or unstretched depending on how you have the box checked.  If you want to post it as is, then save it as a png or a jpg.

One final thing on this, feel free to mess with the tools on the left side to change how the image looks. APP is meant to be a full processing program, and some of the stuff is good, other stuff needs a little work. I have underlined the most useful to me.

Remove Light Pollution will absolutely get rid of gradients and can even allow you to "fix" bad flats to some degree, but be careful because it can also mess up your nebula if you do it wrong. GX, GraXpert, DBE, and ABE simply can't come close to how good this tool is. You can even use it iteratively if you want and it will readjust parts of the image.

Calibrate Background doesn't really do much for most images, but it will allow you to use the next tool which is amazing, and that is the calibrate star colors tool.

Calibrate Star Colors is nice but you do not want to use it on narrowband images because it changes your color mix. It works best on LRGB/RGB/HaLRGB or variations of those. You will want to mess with the various sliders and methods of calibration inside the tool because it can get your stars exactly how you want them.

HSL Selective Color is one where you can mess with the color balance of all of the channels and it can give some impressive results, but it can also oversaturate and mess things up so if you do that go ahead and cancel the tool.

Star reducer works to some degree, but I have other ways to take care of that which I like better. If you do use it do it with a very light hand. Correct vignetting has been one I've never been satisfied with since the remove light pollution tool can do what it is supposed to do, but way better. Each time you apply a tool it will save a copy of the image with that tool applied too. So there is a good workflow to get an image that many would be happy with, and you will definitely get an image that is going to be easy to work with.

Every image I have here has been through APP, and most of my Astrobin images were done through APP. I do use PI for deconvolution and linear noise reduction, and I always finish in Photoshop because I can make it do things in far fewer steps than I can in PI, and it even does some stuff that PI doesn't due to those things being meant more for regular photography, like selecting my shadows that are truly deep space, desaturating them, and then running a photo filter over the to get it how I want.