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!


M16 (Pillars of Creation)

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

Image Details:

Camera: SBIG ST-2000XM
Mount: Takahashi NJP
Scope: Takahashi Mewlon 180
Configuration: Prime Focus
Additional Optics: n/a (Prime)
Filter: Astrodon SII, Hα, OIII 6nm Filters
Effective Focal Length: 2160mm
Effective Focal Ratio: f/12
Exposure: {6 Hα, 11 OIII, 13 SII} × 15min @ -20°C
Total Exposure: 7hrs, 30min
Date: 8/16/2007 10:30 PM PDT (Start)
Location: Saratoga, CA, USA
Acquisition: CCDSoft
Focus: Manual
Dithering: Manual
Guiding: Self Guided


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

Image Description:

This is M16, aka, the “Eagle Nebula”, an emission nebula in the constellation of Serpens. This is my first Narrowband (aka “Tricolor”, aka “False Color”, aka “Emission Line”) Image with my new SBIG ST-2000XM camera and Astrodon SII, Hα, and OIII 6nm emission line filters.

These filters pass only an extremely narrow band of wavelengths which, respectively, correspond to the dominant wavelengths emitted by ionized Sulfur, atomic Hydrogen, and doubly ionized Oxygen gas. Images taken in this fashion therefore show the distribution of these gases in the emission nebula cloud.

The emission lines in the image above are mapped to RGB as per the so-called “Hubble Palette”, where red is SII, green is Hα, and blue is OIII. This is the same palette used in the famous Hubble Pillars of Creation photo, so named because this region of the Eagle Nebula is an active region in which star formation is occurring. The Hubble has a slight aperture advantage over me, and a slight altitude advantage as well. <grin> But I'm pretty pleased with this as a “First Light” foray into narrowband imaging.

Note that by mousing over the image, it will change to 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. North is up.