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Replacing a 2.5" flattener with a 3" flattener


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I have some problem with my old setup with a fullframe camera and vignetting.

My telescope is a TS130 f/7 APO and the camera is a Canon EOS 6D.

Parts of the vignetting comes from the camera house itself and that is something I can't do anything about for the moment. But my flattener with 2.5" and x0.75 is a little bit narrow and now I replacing it with a 3" x1 flattener. I'm not sure how much DIY this will end up with, but as usual I think it will be a lot :-)

My earlier flattener was a high quality Riccardi M68, the new one is an Altair Planostar 3", not very much written and tested about this one but I think it's good.


As usual I have tried to document what I do on my homepage if you find it interesting to follow:


Now I must decide if I shall build it with an off-axis guding or a guide telescope, or maybe no guiding at all, instead a high precision mount.


Edited by Astrofriend
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  • 1 year later...


After one year delay I started up my telescope and mount to do some testing with the new 3" field flatter system. I have not done very deep test yet but already now see it looks promissing with very low vignetting. But the distance between the field flatter and sensor must be wrong.


You can read more here with photos:



I have ordered a low profile adapter and then save 10 mm, I hope this will be enough to do some test.



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  • 1 month later...

It was a long time ago since I wrote something about my 3" field flatter project.

I have now done some tests and the results are wonderful, almost no vignetting and I can use the fullframe sensor to the last pixel except where the camera mirror is.

I have rewritten parts of my project so you can start reading from the beginning or here:

Only one drawback, the f/7 telescope setup is slower than f/5.3, in practice not that big difference because now I can use bigger part of the sensor when I don't have to crop away the vignetted parts.


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