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6 inch APO killer Sold!

Price - $75.00

Ad Number: 183423

Posted: 14 Sep 2019

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This is an old mirror sold by Harry Ross many years ago. It bench tested as a good sphere. In this aperture and focal ratio (about f/12) a sphere is a good optic and you do not need to parabolize the mirror. The focal length as marked on the back is 75 inches as you can see in the picture but as I recorded it was about 69 inches. I am sure that is about right but you will want to measure it for yourself to be sure. Because of the tiny secondary obstruction these long focal ratio Newtonians can deliver a superb color-free image that is quite comparable to an expensive APO refractor. I am adding a 1 inch 1/10 wave circular mirror which by my calculations could serve as the secondary for your scope. It would certainly work for testing purposes before you obtain an elliptical flat. The coatings on the primary mirror are good but it has suffered from some clumsy cleaning attempts during its long history and there are many small sleeks on the surface. In my opinion this is still very usable as is without recoating. If you can come up with a 75 inch tube for these optics you should have a very fine scope for a lot less money than a six inch APO! US sale only. Paypal only and I handle the fee. Free CONUS shipping.


  • Condition Fair
  • Location CO

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