Quote:
Originally Posted by JA
Yes R.
I had to reformat it due to size. it's now attached. Over and above any such assessment in choosing the right flange focal distance I would try using something like an adjustable spacer or photographic Canon bellows and fine tune to the exact distance and then get the exact spacer, using 44mm as your starting point. Or simply try the ZWO to EOS adapters if (??) they accommodate FF sensors.
Best
JA
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Thanks, given that there is a piece of glass within the DSLR body between the lens and the sensor, then it is a reasonable conclusion that this will push back the optical path further away from the lens. My other critical assumption is the thickness of this piece of glass which I am currently basing on 1mm. This is a pure guess on my part so I will see if anyone has a better figure.
I am using the
Astro Mechanics adapter to match the EF200 lens to my ASI6200 camera. The Astro Mechanics adapter is adjustable for spacing and tilt which is perfect for the job. I found however that I am having to wind back the spacing quite a lot more than I calculated and was chasing down reasons for this.
One of the reasons was that Astronomik originally had information on their web site which gave an incorrect value for the optical thickness of their filters of 1mm where in fact it is .33mm.
See this post here for a discussion on this. Allowing for the additional effect of the actual set back distance required for the EOS lens helps further.
I'm still fine tuning the lens set back distance and I probably now down to the level of variations due to the manufacturing tolerances of the various components in the image train. At some stage soon I will (must) stop fiddling and leave it alone
