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[Sticky] Newbie....LRGB processing  

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(@b777capt)
Brown Dwarf Customer
Joined: 8 months ago
Posts: 6
September 24, 2019 23:01  

Hi,

I'm a newbie to APP. I'm also a newbie to my ASi 1600 mm. A few nights ago I took my first LRGB image of the NA nebula. I only took ten subs with each filter at 240". The next morning I made darks, flats and dark flats.....no bias frames . I made flats for each filter position.

Here's my question...how do I process these together? I checked the multi channel box. It would make sense to me that I would apply the appropriate calibration frames to each filter's image then combine them using the RGB combination tool. 

Here's a couple of more questions:

1. After all of the calibration frames are applied and a calibrated image is completed, do you save, for example, "blue" to your working directory?

2. In using my ASI 1600, do most use bias frames.....??

Sorry for the elementary questions. I have looked through the forum and didn't find a specific topic as to how to do this.and none of the tutorials seem to be this elementary.

Thank you...

 

 

This topic was modified 2 months ago by Vincent Groenewold - Moderator

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(@wvreeven)
Red Giant Customer
Joined: 1 year ago
Posts: 94
September 25, 2019 09:09  

@b777capt

Welcome to APP. I have an ASI1600MM as well and always use APP for stacking the subs for each channel LRGB and Ha. My workflow looks as follows:

  • Got to tab 1
  • Enable multi-channel processing
  • Load the lights for each filter and use the "Apply FILTER Header Tag" option
  • Load the flats for each filter and again use the "Apply FILTER Header Tag" option
  • Load the darks and select "All Channels"
  • Load the dark flats and select "All Channels"
  • Load the bias and select "All Channels" (yes, I use bias frames)
  • Go to tab 6
  • Set Weights to quality
  • Set Integrate to median (I usually have more than 20 frames for at least one channel)
  • Enable "Enable MBB"
  • Under Filter select "LN MAD winsor clip" (the bottom option)
  • Hit the Integrate button

This always produces one integrated image per filter which I then process further.

One note: since the ASI1600MM has active cooling, I always make sure to shoot all LRGBHa frames at the same gain, offset and temperature. Then I also took LOTS of bias frames (over 200 of them) and created a master bias. I also took around 60 dark frames for various exposure times (30, 60, 90, 120, 150, 180, 300, 600 and 1200 sec) and created master darks for all of these. Finally I took around 60 dark flats and created a master dark flat for those. That way I have a library of calibration frames that I can reuse. Taking the darks took nearly 15 hours but this only needs to be done once a year or so. For creating the masters I used this workflow:

  • Go to tab 1
  • Enable multi-channel processing
  • Load the darks and select "All Channels"
  • Load the dark flats and select "All Channels"
  • Load the bias and select "All Channels"
  • Go to tab 2
  • Hit the "Create Masters And Assign To Lights" button
  • When done hit the "Save Calibrated Frames" button though I don't think this was necessary but I don't remember because I did this a while back

This second workflow needs to be done once for a given set of darks (e.g. those of 30 sec). Then I would repeat for the other exposure times as well but then load the master bias instead of the individual bias frames and not load any dark flats (no frames nor master) since they are not needed for producing the master darks. It takes less than an hour to create all masters like this.

I noticed that when creating the masters, particularly the master darks, I have to enable multi-channel processing and I have to select "All Channels" when loading the frames. If I don't do that, but for instance only select LRGB for a dark and apply the dark to Ha frames, then I get strange stacking artifacts where stars in the corners, where not all stars are covered by all frames due to dithering, come out as little plusses. As soon as I created master darks as described in workflow 2 all stars are nicely round, even in the corners.

I hope this description is useful to you. Please ask any question regarding this if you have any.

EDIT: As soon as workflow 2 has been done and the master library has been created, you don't need to shoot any darks, bias or dark flats anymore after an imaging session. So instead of loading the individual dark, dark flat and bias frames you can load the corresponding masters. Simply use the Master buttons for that in tab 1. I also created a Bad Pixel Map at some point in workflow 2 and I always load that in workflow 1 as well.

 

Clear skies, Wouter

This post was modified 2 months ago by wvreeven

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(@b777capt)
Brown Dwarf Customer
Joined: 8 months ago
Posts: 6
September 25, 2019 14:48  

@wvreeven

Well, I don't know how to thank you enough for the time involved in writing that. I would have never figured all that out. Now I have to make sure that I'm using the correct technique for capturing the calibration frames. I have done quite a bit of reading and i think I have it figured out. I'm using APT and it contains an app for making flats, darks, bias and flat dark frames. Also the Astrophotography Primer has some info concerning calibration. I have found a lot of online info about the subject.

Again....thank you. I look forward to an APP manual that would help with us new folks.

 

Lynn 


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(@b777capt)
Brown Dwarf Customer
Joined: 8 months ago
Posts: 6
September 25, 2019 16:00  

I do have one more question.....

 

After processing each channel, do I simply save the integration to the working directory then when finished with each channel, use the RGB combine tool to construct the LRGB image? Do you usually change the name of the file to something simple to recognize? There seems to be several files in the working directory labeled with all sorts of terms.

Thanks...


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(@wvreeven)
Red Giant Customer
Joined: 1 year ago
Posts: 94
September 25, 2019 16:29  

@b777capt

APP will automagically save the stacked frames per channel in the processing directory that was selected by you. You don't have to do anything additional for that. As soon as you hear the BOIIINGNGNGNG at the end of the stacking process the files will be there for you. So if you process L, R, G and B lights then you will end up with 4 FITS files in that directory, one for each channel.

Yes, the names of the files look confusing at first, because they contain many of the settings used during processing encoded in them, but they also contain the filter name so it will be clear which is which. The stacked files will have names that start with St for Stack. The Master Flats will be saved in the same directory and their file names start with MF for, you guessed it, Master Flat.

So then go to tab 9 and choose the Combine RGB tool. Load the four St files and APP will automagically recognise which is which by the file name (apart from the Luminance file which is a bug that has been reported several times already) and APP will ask you to confirm that it recognised the filter correctly. In case of Luminance simply select Luminance instead of Custom and you're set. And then you can use the tool to create the colour image for you.


(@wvreeven)
Red Giant Customer
Joined: 1 year ago
Posts: 94
September 25, 2019 16:42  

Let me add one more thing: depending on the sky and light pollution conditions at the moment you were shooting the images, it may be useful or even necessary to pre-process the individual stacks before combining them with the Combine RGB tool. If, for instance, one (or more) stack shows a distinct background gradient due to uneven light pollution (large field of view images quickly suffer from that for instance) then you may want to use the Remove Light Pollution and/or the Calibrate Background tools in tab 9 first. However, you may find that those tools are much more useful after doing the RGB combination. Or you may not want or need to use them at all.

This of course very much depends on the conditions at your imaging site but also occasionally on personal taste or your image processing skills (you may want to do this in a different application for instance). The advise on this varies almost as much as there are astro photography amateurs so please do read up on this and try to find your own way in this.

That of course also is true for my workflows. Perhaps you find that my workflow doesn't work for you at all or needs minor tweaks. Please experiment and see what happens when you modify the settings and find a workflow that works for you. APP generally contains extensive albeit somewhat technical help popups for almost any configuration setting so please do read that and try to come to terms with what that all means because that will help you immensely to master APP.

 

Wouter


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(@vincent-mod)
Galaxy Moderator
Joined: 2 years ago
Posts: 928
September 27, 2019 12:59  

Thanks a lot again Wouter!


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(@b777capt)
Brown Dwarf Customer
Joined: 8 months ago
Posts: 6
September 27, 2019 15:54  

Wouter,

Here's a progress report.

I printed your workflow, read it several times to make sure that I understood each step. Then I took the data that I had plus my calibration frames and plugged it all into APP. I ran each step as you suggested and at the end I had a reasonable image....in color no less. It isn't a great image, as I think it's a little out of focus and I didn't have anywhere near enough integration or calibration time. What's important here is, that the process worked and that I somewhat understand what I'm doing. Now for a few clear nights, better data and more practice.

Thank you again for your help, it's really appreciated.

Lynn


(@wvreeven)
Red Giant Customer
Joined: 1 year ago
Posts: 94
September 27, 2019 16:08  

Hi Lynn,

Thanks for reporting back on your processing efforts. I am really pleased to read that I could be of help 🙂

 

Wouter


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(@jen)
Molecular Cloud Customer
Joined: 4 months ago
Posts: 3
October 2, 2019 14:21  

Thank you so much for this work flow, I’ve been watching this thread with interest as I’m also a newbie to this amazing program that has been doing my head in for a few days now hahahaha 

this has been a great help 🤗 🤗 🤗 


(@vincent-mod)
Galaxy Moderator
Joined: 2 years ago
Posts: 928
October 2, 2019 14:52  

I made it a sticky for now until some documentation is out. 🙂


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(@jen)
Molecular Cloud Customer
Joined: 4 months ago
Posts: 3
October 2, 2019 14:59  

😜 😜 😜 😜  thank you I’m trying these steps now 🤗 


(@wvreeven)
Red Giant Customer
Joined: 1 year ago
Posts: 94
October 7, 2019 11:56  
Posted by: @vincent-mod

I made it a sticky for now until some documentation is out. 🙂

Wow, thanks Vincent!


(@wilsmaboy)
Hydrogen Atom Customer
Joined: 8 months ago
Posts: 1
October 13, 2019 17:58  

@jen

New obsy, new cameras, new software....Jen...the ultimate Newbie 🤣 


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(@jen)
Molecular Cloud Customer
Joined: 4 months ago
Posts: 3
October 20, 2019 13:50  
Posted by: @wilsmaboy

@jen

New obsy, new cameras, new software....Jen...the ultimate Newbie 🤣 

🤣🤣🤣🤣


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