20-Inch-Telescope-Mirror: Difference between revisions
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*Since the mirror is an F/5 it probably requires a corrector plate | *Since the mirror is an F/5 it probably requires a corrector plate | ||
*Since it has a hole in the middle the tube length would be on the order of 50 inches or about 4 feet. This is very short for such a large aperture. Very desirable I would guess for this reason. Sub-Reflector will not be a flat. | *Since it has a hole in the middle the tube length would be on the order of 50 inches or about 4 feet. This is very short for such a large aperture. Very desirable I would guess for this reason. Sub-Reflector will not be a flat. | ||
*I will need to get access to a knife edge tester to test this mirror. Without figure data the mirror sell price will be much lower than otherwise possible. | |||
Revision as of 11:40, 5 March 2007
Perkin Elmer/Boller & Chivens 20" F8 primary telescope mirror
Per John Urciolo
Regarding the mirror... It came from a former NASA facility that excessed it along with the Unertyl mount. There are no specific numbers on any part of the mirror or its heavy circular housing. I was able to determine that it was made by Perkin Elmer/Boller & Chivens from the original government sheets. No additional information such as a model or serial number was provided by NASA. The Unertyl mount is intended to allow X-Y positioning of the mirror while holding it securely on an optical bench (for optical calibration??). I am assuming this mirror to be parabolic due to the fact it was intended to the best of my knowledge to ultimately be used in a telescope.
My Deductions
The central hole appears to be about 4 inches in diameter. Boller and Chivens was a telescope company that was bought by Perkin Elmer is my conclusion and they made optical telescopes and some spectrographic instruments. The mirror figure is either suitable for a human viewing telescope or a schmidt camera. The curvature implies human use.
Notes
- www.clausing.com Clausing is very expensive. I have an email in to get a quote on a 20" mirror recoat
- John came back with a figure of 0.25 inches for the sagitta of this mirror
- Online Sagitta Calculator
Inputs Value
- Sagitta ==== 0.25 inches
- Diameter ==== 20 inches
Mirror Parameters
- ROC ==== 200 inches
- Focal Length (F) = R / 2 ==== 100 inches
- Focal Ratio (f) = F / D ==== 5X
Conclusions
- Since the mirror is an F/5 it probably requires a corrector plate
- Since it has a hole in the middle the tube length would be on the order of 50 inches or about 4 feet. This is very short for such a large aperture. Very desirable I would guess for this reason. Sub-Reflector will not be a flat.
- I will need to get access to a knife edge tester to test this mirror. Without figure data the mirror sell price will be much lower than otherwise possible.