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M31 (Andromeda Galaxy)
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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
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- 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
Processing:
- 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.