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Proper Comet Imaging?

DAVID HUFF
in PixInsight
Hello,

This question is directed toward Adam B.  I have watched your videos on Youtube and now in  Horizons on how to process the comet C 2022 E3 ZTF and I did manage to image this comet myself but I was wondering if I did it correctly?  My results weren't too bad but I was not sure if I should have been tracking the comet or just tracking the skies as usual.  I may eventually get a chance to image this object again but next time I want to make sure I am doing it correctly.  So do we track the comet or the stars when imaging a comet?

Thanks!
Dave
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Comments

  • BlockHeadBlockHead
    The method I show is to do sidereal tracking (track the stars normally). If you track the comet... the stars in your images will be streaked. Thus a star removal process like SXT will not work as well. 

    -the Blockhead
  • DAVID HUFF
    Thanks for the advice!

    Clear Skies!
    Dave
  • Phil MisiowiecPhil Misiowiec
    Hey Adam!

    Love the amazing videos you've put together, and I'm so glad I joined here. 

    I noticed you are only using RGB filters for comet imaging - why not Luminance? And if I'm using a camera with great sensitivity and bit depth (e.g. IMX455 sensor), does it even matter?

    Thanks,
    Phil
  • BlockHeadBlockHead
    Yeah, I don't think in general Luminance is going to be very helpful. It could if the comet is moving slowly and not changing much. I actually do not have a clear filter with the setup I use- so I have no choice- but in general I think the complexity of LRGB for comets is pretty high to get everything right. 

    -the Blockhead
  • Bruce Donzanti
    edited January 2023
    I tried a L filter with the RGB image using the same sensor, but it did nothing to help.
  • DAVID HUFF
    edited February 2023
    Hey Adam, I tagged you in social media :-)  Here is a link to the result of your teachings.  Thanks!

    https://www.astrobin.com/vm2wxd/
    image
  • BlockHeadBlockHead
    N I C E ! ! 
    Thanks David!
    -the Blockhead
  • BlockHeadBlockHead
    @Philip Misiowiec

    It just so happens... Telescope Live gave me an assignment to process some of their data ..and it was an LRGB set. The good news is... the methods work fine in this situation.
    I do think the luminance helped..but mostly because they did not exposure much in the colors!

    -the Blockhead


  • DAVID HUFF
    Hey Adam,

    I watched your wrap-up for the comet processing and I noticed you did a few more things.  I actually went to a dark site and my background was almost perfect already after taking 180 60 second subs at F2 (400mm)!  I didn't even have to adjust the saturation!  So it proves that more signal the better, in this case 3 hours @ F2 or for slower scopes it would require a lot longer exposures and integration time.  In this case a RASA 8 with a APSC sized OSC worked perfect for this.  Oh and it was really cold so my camera was reading -25C with the cooler turned off LOL so eliminated all of the dark current.  I even got a little galaxy in my frame, middle right hand side.

  • David Randall
    @BlockHead,

    Thanks for the amazing content on comet processing, and your persistence in providing a straightforward processing pipeline.  What would change in that pipeline for OSC subs?  I opted for OSC over my normal RGB capture on the comet assuming (I think incorrectly) that it would be easier to process without having to align color channels too.  WBPP had CFW selected for my lights and flats, so debayering did happen.  But, when I got to the local normalization step, and was looking at the integrated comet photo, I realized it wasn't RGB anymore.  Where do I need to modify my process to account for OSC?

    Thanks!
  • BlockHeadBlockHead
    I am working on this. I just acquired some OSC data from a kind individual.
    So...let me work on this...
    -the Blockhead
  • David Randall
    Sounds good, thanks @BlockHead
  • Phil MisiowiecPhil Misiowiec
    @BlockHead I'm a member there too. :) I downloaded the same data set and am applying what I learned in your 2023-01-27 and Telescope Live lessons.  I captured some data last week using a similar setup that TL used but it wasn't as good quality (Chile skies > Southern California winter skies, hehe) so was happy to see them publish it. Thanks again!
  • Phil MisiowiecPhil Misiowiec
    Also, I discovered that during comet alignment of the registered images (to get the "comet subtracted" files), setting pixel interpolation to Bicubic B-Spline does a better job removing the comet in this particular data set. 

    Note that I actually downloaded the uncalibrated frames and master bias/dark/flats from TLive and went through WBPP.
  • DAVID HUFF
    edited February 2023
    Hi All!

    I created this animation from the comet frames I captured and posted on YouTube.  Using techniques I learned from Adam, it turned out pretty good!  Used the movie button from Blink with the exception of making a MP4 instead of a AVI file.  Enjoy!

    https://www.youtube.com/watch?v=An-vKs8pn1g
  • BlockHeadBlockHead
    You should be cHUFFed about this result.
    HAHA
    Great job!

    -the Blockhead
  • Phil MisiowiecPhil Misiowiec
    Here's the final result of my attempt. I ended up ditching the luminance frames in the TL data, as I felt I could get a slightly better result with RGB only. 

    Besides learning how to process comets in PI (sweet!), a few more things I picked up:

    1. Full frame CMOS camera subs take a long time to process - especially with SXT! An APS-C mono or OSC camera is likely going to be my preferred option for future comet imaging.
    2. How to tweak master flat frames when they overcorrect. https://www.adamblockstudios.com/articles/cmos-darks-and-flat-darks-part-2 was extremely helpful.
    3. That GAME script is very handy when you need to mask a part of an image to apply corrections.

    image

  • BlockHeadBlockHead
    Interestingly... OSC WITH drizzle is really complex and does not shorten any processing time. Don't be fooled...
    I will be showing this very soon.
    -the Blockhead
  • Phil MisiowiecPhil Misiowiec
    Dude - you are on fire with the comet videos! :) About to watch the OSC ones.

    Quick question - for RGB mono captures, is there a rough formula for figuring out how often to cycle through a filter as a function of time, let's say for 60 second subs? In the first Telescope Live video you mentioned that larger gaps in time make the comet rejection process more accurate. At the same time, if you went with longer exposures, is there a risk of missing something interesting? 
  • BlockHeadBlockHead
    Yeah... you need to figure all of that stuff out from the activity of the comet (shorter if you want detail), its motion (longest you can go without streaking), get good separation between stars (cycling filters if mono)...etc. So there is no prescription- but an accounting of all of this information. 

    -the Blockhead

    P.S. Concerning the comet videos...I think this is it... pretty definitive at this point I feel.
    No one to my knowledge.. no YouTuber... no PI developer has done this kind of in depth workflow.
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