SaratogaSkies Jim Solomon's Astropics


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B33 (Horsehead Nebula)   [obsolete]

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: William Optics 2" APO 0.8x Reducer/Field Flattener
Filter: None
Effective Focal Length: 480mm
Effective Focal Ratio: f/6
Exposure: 21 x 8min @ ISO 800
Total Exposure: 2hrs, 48min
Date: 2/21/2006 7:35:35 PM PST (start)
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, ASINH stretching
  • Photoshop: Compositing, Levels, Desumdging, cropping, JPG conversion

Image Description:

This is B33, aka the Horsehead Nebula in the constellation of Orion. Photos of this stunning object captivated me as a kid, and were among the many things that kindled my interest in astronomy. In that sense, capturing this image is satisfying at a number of levels, even though it could probably use another several hours of exposure. There was a nasty internal reflection from Alnitak that I had to de-smudge-i-fy in Photoshop in order to remove. Not sure what caused it, but it most certainly involves interactions among the Hutech Type I UV/IR block filter, the WO reducer, and the ED80 objective. Time for some science to figure out the culprit.

This is my second attempt at the Horsehead. My previous attempt from last year just ain't all that great. This one is much better. Funny what happens when you triple the effective exposure time. <grin> Mouse-over the image above to see the annotations, and see the link to last year's image for more information about this target. A higher-resolution image is also available. North is left.