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Equipment Discussions >> ATM, Optics and DIY Forum

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professor emeritus

Reged: 05/02/12

Loc: Down Under
Objective diameter
      #5535706 - 11/23/12 03:11 PM

Does anyone know the diameter of a 150mm Synta refractor lens....that is just the glass.
I'm thinking of replacing the lens of my 6" f8 with an Istar f8 R30, that has the diameter of 154mm. A friend has recently done this with a 127mm lens. He replaced the old Saxon lens (think Saxon are made by Synta) with the Istar one. The glass was exactly the same diameter so he didn't need to muck about with fitting the Istar cell to the Saxon tube...just used the saxon cell. If I can use the Synta cell with Istar lens that would be brilliant. So if any body knows I'd love to know. I'm a bit reluctant to pull mine apart just to measure it. Thanks.

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Post Laureate

Reged: 04/01/08

Loc: Lovettsville, VA
Re: Objective diameter new [Re: Messyone]
      #5535958 - 11/23/12 05:59 PM

Although your friend apparently was successful in his lens swap, there are risks in using a cell other than the one supplied by the lens manufacturer. You need the lens elements to be held securely enough to maintain centering, but not so tight as to become pinched by temperature changes. A properly designed cell is an important aspect of ultimate lens performance. Unfortunately, this aspect does not always receive enough attention.

Personally, I think you should try to adapt the cell to your existing tube. Ask Istar to provide the dimensions of their cell and get an adapter ring machined if necessary.


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