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Astropixel Processer users - how to register images taken through different filters so stars line up, yet stacking the images from the 2 different

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#1 dclt


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Posted 21 October 2021 - 12:54 PM

I have dug through the various forums looking for the answer that will tell me how to do what I want to do here & I cannot find the specific answer I need. I have been using APP for a while & am pretty well-versed on the basics.

I know how to do exactly what I'm trying to do in deep sky stacker already, but since I'd rather do it in APP I'm looking for clarity on how to accomplish it there.


Here is specifically what I'm trying to do:
I have imaged the same object with OSC camera using two separate filters on different nights--the astronomik UHC filter & also the Optolong L-Extreme filter. I have multiple nights imaging with each of those filters, so this will need to be a multi-session integration of EACH of those filters.

I want to register ALL the lights from both filters to the same reference frame but to create 2 totally separate stacked images, one for the astronomik UHC only & another for the Optolong L-Extreme only. I need for all the stars & image scale for both stacks to align to each other, because I will later take each stacked image into photoshop and blend together using a method I like that gives me the most control. I do not intend to blend the two together in APP in this case.


I can always stack the astronomik UHC lights & the L-extreme lights completely independently & then take those into photoshop to do what I intend, but this has the potential problem of creating 2 stacked images with stars that are not aligned. Aligning these two in photoshop after the fact is possible, but a lot more tedious.

I can do what I need to in deepsky stacker by manually selecting one sub-frame from the lights to use as the reference frame by which all stars in all the different images will be aligned to & still produce two separate stacked imaged for the Astronomik UHC & L-Extreme, respectively.
I feel sure that many others here have done exactly what I'm describing above in APP. I would appreciate detail on how specifically to go about doing this. Thanks.

#2 jl09


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Posted 21 October 2021 - 02:02 PM

Hi, Not sure that this exactly answers your question, but in APP if you load in your lights (whether they are subs or integrated frames), run through all processes up to and including step 4 registration, then at this stage the lights will be registered. Next, still under tab 4, scroll to the bottom and click save registered frames. Those saved frames will all be registered with one another. 


#3 Kevin Ross

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Posted 22 October 2021 - 03:13 PM

I believe this should be pretty easy. It's exactly the same workflow when doing narrowband imaging.


In APP, on the first page, make sure "Multi channel/filter processing" is checked. If you have different sets of flats for each night, you can check the "Multi-session processing" checkbox. If you just have a single set of flats for each filter, you can uncheck that box.


Click the Lights button, select your UHC images, it will ask you what filter, select "UHC". If you're doing multi-session, choose a session (one for each night with different flats).


Do the same, but for L-Extreme. Type in a custom filter name (there isn't a predefined L-Extreme).


Load your flats. If doing multi-session, you'll load each night separately.


Then when you click Integrate, it will register all of the frames to a common reference frame, but create two stacked files, one for each filter.

#4 ngatel


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Posted 26 October 2021 - 02:30 AM

Load into APP whatever stacks you are going to bring over to PS.

Run Analyze Stars.

Run Register Stars

Run the Normalize Module.

Click Save Normalized Frames (or whatever it says)

Each stack you loaded will be saved as a separate file, only each will “reg-norm” in the file name such as . . .


Now all your stacks have been registered, normalized, and saved as separate files.

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