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Smaller (M63) Riccardi 0.75x - enough for Full Frame?

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I was wondering if the smaller, M63 thread Riccardi reducer is enough to light up a full-frame sensor?

I have a 90/600 apo and intend to use the reducer with all kind of cameras I encounter, Sony A7, monochrome CCD, etc. I expect this piece of glassware to be a (very?) long-term tenant in my gearbox:).

According to specs (42mm field diameter), it should cover the frame. Does anyone using this reducer?

Edited by GTom
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It's not the reducer alone that is responsible for the image circle - the reducer is just going to be a limiting factor. So that means it can provide a maximum circle of 42mm - but the circle you actually get depends on the main optics and what that is able to provide. You need to determine the image circle size provided by your refractor, if that can be reduced by 0.7x (or whatever the reduction ratio is...) and still produce 42mm then you will get the maximum size quoted. 42mm is marginal for a full-frame sensor, there will be darkening in the corners but you should be able to correct with flats.


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Thanks Chris. I found a few examples, that it should be doable (for one, a sample shot on TS' own site of my APO, but I also found one with a bigger photoline APO). Full frame is rather a future plan for me, but I want to build up my gear in a way, that it's completely FF ready. If a nice camera comes in my way in the classifieds, i don't want to be held back by small filters, adapters, especially not by the 2nd most expensive part of the optical train after the main lens...

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  • 3 weeks later...

Takahashi claim 44mm for the FSQ85 but I know from two examples that it will not get anywhere near to covering the full frame Kodak CCD chips. It's not so much vignetting as stellar distortion which is the problem. By my calculation you need 45mm for the big Kodak sensors. I think only sample images will tell the truth. Another issue with reducers can be severe internal reflections. Again only sample images will tell.


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