SaratogaSkies Jim Solomon's Astropics


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M109 (Barred Spiral Galaxy)

[Hα+R G B]

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: Celestron C8-N (8" f/5 Newtonian)
Configuration: Prime Focus
Additional Optics: Celestron/Baader Multi Purpose Coma Corrector (MPCC)
Filter: Hutech Hα Front Filter (HA-FF)
Effective Focal Length: 1000mm
Effective Focal Ratio: f/5
Exposure: 42 x 4min @ ISO 400 (RGB), 24 x 16min @ ISO 1600 (Hα)
Total Exposure: 9hrs, 12min
Date: 5/16/2006 and 5/17/2006
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: GADFly 1.0.5
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, Hα Combination, White balance, ASINH stretching
  • Photoshop: Sharpening, Levels, cropping, JPG conversion
  • Neat Image: Noise reduction

Image Description:

This is M109, a Barred Spiral Galaxy in the constellation of Ursa Major. This is also First Light for my new Hutech Hα Front Filter (HA-FF). For this image, I captured 6.4 hours of Hα over two nights, and 2.8 hours of RGB data on a third night. Not sure it was worth it. .

The Hα regions, such that they are, appear as the small, cherry-red regions in the spiral arms of the galaxy (see the full-resolution image). M109 turned out to be a poor choice of target for testing the Hα filter. This is because the Hα regions in M109 are very small; i.e., not easily resolved, even at the reasonably long focal length of my Newtonian (1000mm). Of course, using a DSLR doesn't help, since the Bayer matrix permits only one in every four sensor locations to record the Hα wavelength. M101 and M51 are in my cross-hairs while I wait for the summer Milky Way objects to be well placed at my site (namely, West of the Meridian early at night).

The image above is a slight crop of the full field. A full-resolution image is also available. North is up.