SaratogaSkies Jim Solomon's Astropics


Latest news

December: Test shots with new scopes/mounts

Dec 21: TMB 80/480 Arrives!

Dec 3: AP1200 Arrives!

Nov 30: TMB 152/1200 Arrives!


NGC 2244 (Rosette Nebula)

Mouse-over to see annotations. (Requires Javascript) Click to see high-res version.

Image Details:

Camera: SBIG ST-2000XM
Mount: Astro-Physics 1200GTO
Scope: TMB 80/480 APO Refractor
Configuration: Prime Focus
Additional Optics: n/a (Prime)
Filter: Astrodon SII, Hα, OIII 6nm Filters
Effective Focal Length: 480mm
Effective Focal Ratio: f/6
Exposure: {2 Hα, 2 OIII, 3 SII} × 32min @ -20°C
Total Exposure: 3hrs, 44min
Date: 2/28/2008 9:11 PM PST
Location: Saratoga, CA, USA
Acquisition: CCD Commander
Focus: Manual
Dithering: CCD Commander
Guiding: Self Guided


  • IRIS: Registration
  • JimP: Dark subtraction, Flat field, Kappa-Sigma Stacking, White balance, ASINH stretching
  • Photoshop: JPG conversion
  • Neat Image: Noise reduction

Image Description:

This is NGC 2244, aka, the “Rosette Nebula”, an emission nebula and open cluster in the constellation of Monoceros. This is First Light, photographically at least, for my new-ish TMB 80/480 SuperAPO Refractor. This fast, f/6 refractor has significant field curvature, as can be seen by the flaring of the stars toward the edges of the image. I have the reasonably well-matched TeleVue TRF-2008 Field Flattener/Focal Reducer on order to improve the edge performance of this scope.

Mousing off the image reveals a “Hubble Palette” narrowband image, with R:G:B = SII:Hα:OIII. Mouse-over the image to see a pseudo-“True Color” image, in which those narrowband emission lines are mapped to their approximate color as seen by human vision. Specifically, the red SII and Hα wavelengths are mapped to red, and the aqua (blue-green) OIII wavelength is mapped to both green and blue. Also, a smidge of Hα is added into blue to simulate the Hβ wavelength.

A higher resolution image is also available. Compare this narrowband image with this “true color” image of the same region, taken with a DSLR and an ED80. North is up.