Used Astro-Tech 2" Newtonian Coma Corrector

2" Coma Corrector for fast Newtonian Telescopes

• 3-piece modular design (i) Optics in 2" nosepiece with 48mm male filter thread (ii) 2" eyepiece barrel that attaches to optical nosepiece, and (iii) M48 - T2 adapter ring
• Design optimized for use at f/4.5 but will work well from f/3 - f/6
• Reduce coma and field curvature
• Designed for visual and photographic use
• Magnification factor of only 1.1x
• Fully multicoated optics (4 elements / 2 lens groups) with a clear aperture of 43.9mm / 1.73"
• 2" nosepiece features smooth barrel and is threaded to accept standard 2" filters
• 2" eyepiece barrel features brass compression ring and dual large thumbscrews
• Back-focus spacing requirement is 75mm with a tolerance of +/- 5mm.
• For visual use, connect the 2" eyepiece barrel to the main optical nosepiece (as shown in photo 1 above). Additional spacers might be required at the bottom of your eyepiece (not included) to place the focal plane of the eyepiece at the required back-focus distance.
• For photo use, unscrew the 2" eyepiece barrel and attach the included M48-T2 ring to the main optical nosepiece (as shown in photo 3 above). Then attach your DSLR camera to the male T2 thread via a camera-specific T-ring (not included). Additional spacers will be required (not included) between the corrector and your camera's T ring depending on the camera's CCD chip location to ensure that your CCD plane is set to the correct back-focus distance from the corrector.
• For Canon/Nikon DSLR cameras (with a 55mm backfocus including a standard thickness T-ring), you will require an approx. 20mm long spacer (not included).

Specifications:

• Weight:
• Lower barrel with lens elements: 7.4 oz
• Upper eyepiece holder: 4.1 oz
• Complete unit for visual use: 11.8 oz
• T thread adapter: 0.3 oz
• Complete unit for photo use: 7.7 oz