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Batch processing short subs into longer subs?

Mark KnechtMark Knecht
in PixInsight
I'm a casual home astro-photographer using an inexpensive Sky-Watcher AZ-GTI mount and an EvoGuide 50ED scope. In general I find that I can shoot 20 second subs reliably but not longer due to tracking errors. I'll post a link at the end of a simple movie created in PixInsight that shows typical tracking on my stock AZ-GTi.

After shooting many hours of a target over multiple nights I end up with so many subs that PI cannot handle it due to 24GB not being enough memory. 

QUESTION: Is there an automated way to batch process consecutive 20 second subs into what would be the equivalent of a single 5 minute sub? I.e. - just take the subs in order, combine (in the 20 second case) 15 of them and output that as a single new sub? Essentially - run WBPP in small groups outputting the the registered master for each 15 sub group?


Thanks

Comments

  • BlockHeadBlockHead
    The simple answer to your question is... no. 
    It is rare this is a solution... but, in this case you are running into a combination of software and computer hardware limitations. A better mount at the end of day (or night) could actually be the easiest solution- but I understand there is a cost to this.

    Now...let me venture into the unknown... Could you have WBPP output groups of files- that subsequently could be integrated into individual files... which are again combined as you want. Yes..  You would need to generate the files in such a way that a group number is in filename OR you can take your files as they are right now..
    and create folders like M42_Group1 , M42_Group2, ...  You put as many files in each folder as your computer can handle.  You use the keyword "M42" on the post processing. WBPP will output  a single combined image for each group. It will pick a reference for registration from within in each group... so the group combined files you have will not be registered with respect to one another.

    So... THEN you run WBPP again on your grouped/combined files with no preprocessing...just registration and integration.

    So... the answer is... you run WBPP twice. This would not be hard to do...  and I think it does address your question and you will finally have a single integrated image.

    If you are interested... this might make a good example video... but it sounds like I would need to download 1,000 frames to demonstrate. 

    That is a beautiful video showing the issue you are dealing with.

    -the Blockhead
  • Mark KnechtMark Knecht
    Thanks for the answer. I think there's some good potential here. The software I'm using (KStars & Ekos - Open Source stuff) does have the ability to append a time stamp. Possibly a simple Python program that understands the time stamp well enough to constrain a group to a certain delta time between the first and last sub and then renames the subs (or creates folders and moves the subs) so they could be grouped for the first pass through WBPP?

    I'll turn on the time stamp and shoot some subs tonight to play with.

    And I can easily create a few folders by hand and do some experiments on a small scale.

    I don't want to duplicating the files for storage space and run time reasons, and also want to consider how I go backwards from grouped files to ungrouped in case I discover that different time groupings provide better results. Backward may be a non-issue if it just means collecting the files back out of the folders.

    Thanks for the ideas!

    Cheers,
    Mark
  • Mark KnechtMark Knecht
    BTW - I completely agree with the comment as to getting a better mount. However I'm in the learning phase and don't mind the minor frustrations this mount causes me to endure while learning. I suspect when I do buy a new mount I'll be a lot more educated about what questions to ask and what specs to look at. 

    Thanks!
  • BlockHeadBlockHead
    Well... you sir are a glutton for punishment! (this is an extreme case I think) The field rotation is really a killer! I am assuming this is an Alt-Az mount? (otherwise the polar alignment needs to be refined...)
    1. -the Blockhead

  • Mark KnechtMark Knecht
    Old discussion but I did eventually get this SkyWatcher AZ-GTi mount running in equatorial mode with 60 second subs. Stacking is much more efficient and the results are better.
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