Thursday, September 26, 2013

Beginning to learn IRIS (Andromeda and Double Cluster)

Seem like I'm starting to learn stuff about astrophotography since DeepSkyStacker is starting to bug me a lot. It's easy to learn and does something nice, but the results aren't that nice to work with further. Everyone seems to promote AstroSurf IRIS as a free (as in free beer) stacking software. It's not that easy though.

To use IRIS you really need to understand what happens in whole process of stacking. I read some ebook about it (can't find the link) and I thought I understood it but seems I didn't. I think I finally understood it after following this guide: IRIS:tä aloittelijoille (sorry, it's in Finnish).

If I understood correctly, here's how it goes:

  • Make master offset/bias, flat and dark. These are all important so don't forget to take them.
  • Calibrate images ("light frames"). This roughly means subtracting processed flat and dark frames.
  • Transform images into RGB
  • Register, which means aligning images so that stars are exactly the same places in every photo
  • Stacking itself
  • Postprocessing (colour balance, colour profiles...)
I felt enlightened when I realized that. Maybe I should have read the ebook I mentioned with a bit more thought, or perhaps reading IRIS's manual would have been a good idea as well. Anyways this goes perfectly with everything else with my stargazing hobby. I tend to learn everything by doing it wrong first.

Then the photos:

Andromeda Galaxy. M31, M32 and M110 of the Messier objects. I took 31 of 18 second exposures. 20 s made the stars trail a bit but on 18 it was unnoticeable. First one was to check everything is in order and then 30 more. Photos were taken on my front yard. Luckily Andromeda was in such a position that none of the streetlights was in front of the camera. I also looked at it visually and I really have to say it was the most I've seen of that galaxy. Quite beautiful gray spot on ocular.

The Double Cluster: NGC 884 and NGC 869. While shooting Andromeda I looked through my 200 mm Dobson at everything I thought I might see. I realized I've never seen the Double cluster although it should be easy to find. It looked nice so after 31 exposures of M31 I took 30 of this. Same 18 second exposures than before.

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