DetailsFully multi-coated optics, the Third Planet Optics 2" focal reducer will reduce your focal length by 0.75x shortening exposure times while still retaining a crisp image with excellent color and contrast. Extra long focal length to be perfectly compatible with the TPO RC telescopes, off-axis guiders and filter wheels and is best for CCD sensors with up to a 15mm diagonal. Two element design effectively reduces focal ratios of the Third Planet Optics Ritchie Chretien from f/9 to f/6.75 and from f/8 to f/6.
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SKU OS-FRRC-75 Manufacturer TPO Barrel Size 2" Warranty 1 Year Warranty
- Questions & Answers
Product QuestionsI have an Orion 8 f/8 Ritchey-Chretien Astrograph Telescope and currently using Atik filterwheel + atik 383L+ camera with a sensor size of 17.6mm x 13.52mm: Will it work properly ? How much will it increase the speed of my scope ?
Thank you in advanceQuestion by: Lauric Dubesset on May 15, 2016 5:31:00 PMUnfortunately, this reducer is only a reducer, not a reducer/flattener, and so it will only cover a 15mm diameter FOV (equivalent to a 12mm x 9mm CCD). Your camera has a sensor diagonal of 22.5mm, so the outer 30-35% will show distorted stars with this reducer. At proper spacing, this will deliver on its promise to get you down to f/6.0, but your corrected field of view will shrink to no larger than the FOV you already have at f/8. This reducer is only really recommended for smaller sensor cameras.
There are other options that will work better with your camera like the AP-CCDT67 https://www.optcorp.com/astro-physics-ccd-telecompressor-for-f9-f18-telescopes.html. With this, you can vary the focal ratio from ~f/6.0 to f/5.4 depending on spacing and still cover your 8300 based camera. Our customers report this to work very well with the f/8 RC scopes - especially in the f/6 configuration. Please call us if you have questions.Answer by: Chris Hendren on May 16, 2016 10:59:00 AMQuestion by: Jerome on Jul 23, 2014 8:35:52 AMWhat is the correct spacing for this focal reducer? I just bought one and I have no idea how to configure my CCD camera and accessories.I have an 8 inch RC and a SBIG8300 that is 22.5mm diagonal measure. Also a CFW and OAG. Beyond 15 mm is the problem vignetting or are there significant aberrations too? How bad are the aberrations if any?Question by: Scott dixon on Apr 1, 2015 5:15:00 PMThe problem with this reducer is field curvature. The image will not be focused properly outside the 15mm image circle. For a larger CCD like yours, the AP CCDT67 may be a better choice, though with only a ~29mm image circle you may still have issues illuminating the guide CCD unless the prism is far enough inward. The OAG will not work with the TPO reducer.Answer by: Chris Hendren (Admin) on Apr 1, 2015 6:04:00 PM
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