Saturday, December 05, 2020

Orion: M42, M43, Horsehead and Flame Nebulae

M42, M43, Horsehead and Flame Nebulae in Orion

This is the same data I've been working with for a few weeks now. The two bright stars on the left are two-thirds of Orion's belt, and the bright nebula on the right is the main part of his sword hanging down.  (The image is rotated 90 degrees from what we usually think of as "up" with Orion.) Specs:

  • Camera: EOS 7D
  • Lens: Canon EF 70-200mm f/2.8
  • focal length: 145mm
  • f/2.8
  • ISO 1600
  • Mount: Kenko SkyMemo S equatorial tracker
  • Exposure:
    • lights: 47 frames, 30 seconds each
    • darks: 13 frames, 30 seconds each
    • flats: 10 frames using above setup, but I don't really trust them
    • bias: none (should I? given how much noise is the problem here...)
    • First aligned with rotation (two-star alignment), then stacked using std. dev. 1.5 filter, throwing out extreme points
  • Field of view: approx. 5x3 degrees as cropped
  • Image size: 3338x2225 as cropped
  • Resolution: very roughly, 6 arcseconds per pixel, smallest stars are about 4x4 pixels, so 25-30 arcseconds resolution, I guess, but the brighter stars are about 20x20 pixels
  • Faintest stars in the image: good question! I wish I knew.
  • Software: Nebulosity 4.4.3, GIMP 2.10
  • Date/time: 2020/11/22, about 2:00 a.m. local time
  • Location: Arakine Dam, Chiba, Japan
I have learned a ton about CCDs and image processing, but I have probably learned more about this specific camera/sensor and this specific piece of software than about the principles. Because I had so much learning to do, this photo is probably about 20 hours worth of sitting in front of the computer working.
I'm also sitting on 100 frames at 10 seconds, which might add some detail in the middle of M42. I don't know if it's possible to combine them effectively with this or not. I would still like to make the Horsehead more vibrant, but M42 is so bright, that everything I've done to try to brighten the Horsehead turns M42 into just a wash of white. More to learn, yet, but I think this is pretty close to all that this data has to give.
I'm having fun...

2 comments:

Min Yun said...

Do you remove cosmic ray hits as part of your processing? I don't know if the detectors in the camera are sensitive enough to pick them up. Since you have a lot of frames, your outlier removal probably does that effectively. Have you also played with median instead of mean when you combine the frames? Sounds like you have some stat tools to try different things. Just curious. You begin to see some nice nebulosity in the HII regions, so it is tempting to see how far you can push this. This is far ahead of the first version you show. Very cool!

rdv said...

See my additional comments on the processing adventure at
https://rdvlivefromtokyo.blogspot.com/2020/12/nebulosity-processing-few-comments-on.html.