SaratogaSkies Jim Solomon's Astropics


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NGC 2359 (Thor's Helmet)

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: None
Effective Focal Length: 1000mm
Effective Focal Ratio: f/5
Exposure: 34 x 8min @ ISO 400
Total Exposure: 4hrs, 32min
Date: 3/21/2007, 3/22/2007
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: Sharpening, levels, cropping, JPG conversion

Image Description:

This is NGC 2359, aka Thor's Helmet, in the constellation of Canis Major. NGC 2359 glows from the energetic winds from a so-called Wolf-Rayet Star, HD 56925 (see label in the mouse-over feature). As described in this APOD, “Wolf-Rayet stars are rare massive blue giants which develop stellar winds with speeds of millions of kilometers per hour.” The blue-green color is mostly [OIII] emission. Pretty cool. The RGB data was collected over two fairly horrible nights. This image could definitely use some Hα exposures to improve the contrast, but that will probably need to wait until next year. A higher resolution image is also available. North is left.