SaratogaSkies Jim Solomon's Astropics

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Jupiter and Moons   [obsolete]

Image Details:

Camera: Canon Digital Rebel (300D)
Mount: Celestron AS-GT
Scope: Celestron C8-N (8" f/5 Newtonian)
Configuration: Negative Projection (Barlowed)
Additional Optics: TeleVue 2x Barlow
Filter: None
Effective Focal Length: 2844mm
Effective Focal Ratio: f/54.2
Exposure: 9 x 1/2 second @ ISO 800
Date: 6/22/2004, 9:28pm PDT
Location: Saratoga, CA, USA
Acquisition: Manual
Focus: Manual
Dithering: None
Guiding: None

Processing:

  • IRIS: Dark subtraction, flat field, registration, stacking
  • Photoshop: Compositing of IRIS moons and Jupiter images, sharpening, saturation, scale, JPG conversion

Image Description:

An interesting shot of Jupiter and the four Galilean moons. The f/ratio is so high because I put the aperture mask on the end of the telescope, effectively turning the 200mm obstructed Newtonian into a 52.5mm unobstructed offset-Newtonian. For those familiar with telescope optics, the Newtonian design has a secondary mirror in the path of the light that hits the primary mirror, and this so-called "obstruction" can cause a loss of contrast, especially on objects like planets that have low contrast to begin with. By putting the aperture mask on, the secondary is out of the path of the light hitting the primary (now effectively only 52.5mm instead of 200mm), preserving all of the contrast. However, the lower effective aperture could conceivably cause a loss of resolution, but since this is a relatively low effective focal length (2844mm), that loss of resolution isn't evident, and is overwhelmed by the seeing conditions in any case. [In retrospect — what was I thinking!?!? <grin>]

 
NGC 6820 & NGC 6823 (Emission Nebula & Open Cluster)
SaratogaSkies Jim Solomon's Astropics

Search

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!

Links:

NGC 6820 & NGC 6823 (Emission Nebula & Open Cluster)

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: 40 x 4min @ ISO 800
Total Exposure: 2hrs, 40min
Date: 8/30/2005 9:41:31 PM PDT (start)
Location: Saratoga, CA, USA
Acquisition: DSLRfocus
Focus: DSLRFocus
Dithering: Manual
Guiding: GuideDog via Philips ToUcam Pro II (840k) through Orion ST80 w/ Celestron 2x "Kit" Barlow

Processing:

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

Image Description:

This is a "do over" of NGC 6820, an Emission Nebula in the constellation of Vulpecula. In my previous attempt with an unmodified camera, I was unable to capture the faint Hα emission nebula, and was only able to capture the open cluster NGC 6823. The modified camera excels in shots like this. A high-resolution image is also availble. North is up.