Low-cost Celestron C8 to F2.0 conversion

[Dark Raven]

This guy used £215 SharpStar 2" 0.95x MPCC to convert Celestron C8 F10 to F2.0 instead of £1k Starizona Hyperstar 8 V4. 

He also provides CAD files for required adapter in the video descriotion.

Quite cool DIY hack. Obviously, not perfect but certainly interesting. Thought it might be worth sharing here.

 

[michael8554]

If the secondary convex mirror has a non-complex figure, then the CC might work as well as it would at the normal location ?

Michael

[davidc135]

Interesting to see any results but the scheme is very likely nonsense.

The spherical secondary in an 8'' Celestron sct contributes around  6 waves of correction in addition to the 16 waves or so provided by the corrector plate. So the wave front will be already badly under-corrected before it enters the MPCC.

I think the MPCC also contributes under-correction varying inversely as the fourth power of the focal ratio. Looking at some spot diagrams it works well at f4.75 but only barely at f3.8 so at f2 there will be a huge blur due to spherical aberration. If the CC contributed over-correction, that might counter the 6 waves mentioned above but, as the Baader MPCC 3 is under-corrected, I expect this design is the same.

On the plus side I imagine the field would be pretty flat and the coma reduced.

It would be fun to see.

David

Edited August 13, 2023 by davidc135