Quote:
Originally Posted by bojan
Thanks Rob and Rodney for comments :-)
As to distance from flattener... My setup is C11 and FF-FR.
I believe the image Rodney supplied is applicable to refractors only..
After hours spent playing with varying sensor to FF-FR distance by +/- 10mm, and using both Celestron and Meade FR, there was no significant differences in behavior that I could detect. So my conclusion was it was FR thing, and sudden increase in field curvature away from centre (both C and m Meade behave almost the same way), in the area already affected by vignetting (~6mm away from sensor centre).. So I decided to crop out the corners of the frame and keep only central square where those aberrations are not visible.
https://www.iceinspace.com.au/forum/...75#post1558975
Generally there is not much info on the subject out there.. just a lot of confusion..
Funny thing, the best results re filed curvature I obtained with my "own" flattener - 50mm doublet (200mm FL) that came from old russian binoculars, but the coma and CA is slightly increased. (BTW, I have thread on this subject on forum, link is here.
Anyway.. at the moment I put this project (tilter) on hold for a while, but I will revive it when my circumstances allow. |
I’m interested in the observation that the spacing diagram is applicable to refractors only. Ive heard this stated before but have never been able to track down any primary sources that confirm this. Do you have evidence to state that it is applicable only to refractors? If yes, I would very interested to peruse this. Also, it would informative to execute the test with racking the focuser in and out as I mentioned above with your system as I believe that it would give you more clues as to the issue. It could also answer the questions as to whether the diagram is applicable to refractors only.