SaratogaSkies Jim Solomon's Astropics


Latest news

December: Test shots with new scopes/mounts

Dec 21: TMB 80/480 Arrives!

Dec 3: AP1200 Arrives!

Nov 30: TMB 152/1200 Arrives!


M31 (Andromeda Galaxy)

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: Mofidied Canon Rebel XT (350D): Hutech Type I Filter Replacement
Mount: Celestron AS-GT
Scope: Orion ED80 (80mm f/7.5 APO Refractor)
Configuration: Focal Reduced
Additional Optics: Celestron F/6.3 Reducer/Corrector (0.63x)
Filter: None
Effective Focal Length: 420mm
Effective Focal Ratio: f/5.2
Exposure: 25 x 8min @ ISO 400
Total Exposure: 3hrs, 20min
Date: 10/11/2005 12:42:47 AM PDT (start)
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: None
Guiding: GuideDog via Philips ToUcam Pro II (840k) through Orion ST80 w/ Celestron 2x "Kit" Barlow


  • IRIS: Dark subtraction, registration, gradient removal
  • JimP: Flat field, Kappa-Sigma Stacking, White balance, ASINH stretching
  • Neat Image: Noise removal
  • Photoshop: Levels, cropping, JPG conversion

Image Description:

This is my second attempt at M31, this time with a focal-reduced ED80 and the Modified 350D. This was a test to see if I could run the equipment overnight while I slept. Seems to have worked pretty well, but without dithering (which I still do manually), there was a large amount of residual pattern noise after calibration, registration, and stacking. While Neat Image did a decent job of removing that pattern noise, I really need to look into something like GADfly (see the Files section of Digital_Astro) to automate inter-exposure dithering. This is the full frame, shrunk for display on the web. A higher-resolution version of this image is also available, as is my previous attempt from last year with an unmodified camera. North is right.