SaratogaSkies Jim Solomon's Astropics


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M101 (Pinwheel 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: 88 x 4min @ ISO 400 (RGB), 30 x 8min @ ISO 1600 (Hα)
Total Exposure: 9hrs, 52min
Date: 5/25/2006 and 5/29/2006 (RGB); 6/15/2006 (Hα)
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, White balance, HαRGB combination, ASINH stretching
  • Photoshop: Sharpening, Levels, cropping, JPG conversion
  • Neat Image: Noise reduction

Image Description:

This is M101, aka, the Pinwheel Galaxy, a stunning spiral galaxy in the constellation of Ursa Major. Adding 4hrs of Hα to this recent RGB image really brought out the emission nebulae in M101. Note that mousing-over the above image, in addition to displaying the object labels, will switch back-n-forth between the HαRGB image and the standard RGB image, very clearly showing the effect of the additional Hα data. See that RGB image for more details about M101. A higher-resolution image is also available. North is up.