SaratogaSkies Jim Solomon's Astropics


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B86 (Ink Spot Nebula)

Click to see high-res version.

Image Details:

Camera: Canon Digital Rebel (300D)
Mount: Celestron AS-GT
Scope: Celestron C8-N (8" f/5 Newtonian)
Configuration: Prime Focus
Additional Optics: n/a (Prime)
Filter: None
Effective Focal Length: 1000mm
Effective Focal Ratio: f/5
Exposure: 8 x 4min @ ISO 200
Total Exposure: 0hrs, 32min
Date: 8/4/2004, ~10pm PDT
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: None
Guiding: Manual through Orion ST80 w/ Celestron 2x "Kit" Barlow


  • IRIS: Dark subtraction, flat field, registration, Kappa-Sigma stacking
  • Photoshop: Cropping, image scale, JPG conversion

Image Description:

This is B86, the Ink Spot Nebula, in the constellation of Sagittarius. A dark nebula is a cloud of dust and gas that obscures light coming from stars and other objects "behind" it. In this case, the dark nebula obscures the massive number of stars in the Great Sagittarius Star Cloud of the Milky Way. The small grouping of blue-white stars just East (left) and South of B86 is the open cluster NGC 6520. This is a slight crop of the full-size frame. A higher-resolution image is also available. North is up.

This is my first guided image. Thanks much to Jim Shuder for bringing his guiding apparatus over to my house for a fun evening of imaging. Jim brought his 60mm guide scope with all of the associated hardware, a Philips ToUcam 740k, and his laptop computer running GuideDog software. Analysis of the GuideDog data showed RMS guiding errors to be on the order of 1.4 arc-seconds, which is excellent for a mount that has over 60 arc-seconds of peak-to-peak Periodic Error. This allowed all of our 4-minute exposures to have crisp stars, though I had to toss the one in which an airplane trespassed into our imaging field.