Telescope Reviews: 20 inch RC Robitic Build...a TEAM Effort....

Hey Preston!
Yep, I be out here, enjoying your posts. The scope sure looks good - first time I've seen all your CAD work as well. I've only seen the detail on the back end until now.

Whether to go reducer or flattener is up to your team's desires regarding FOV. A focal reducer is the more difficult of the two designs, as it tends to aggravate the field curvature and introduce aberrations, requiring S-FPL53 or similar glasses to keep the aberrations under control. The baffle design I did for you is optimized for the basic RC mirrors and field coverage you wanted. The wider field of the focal reducer renders these baffle designs inadequate and allows stray light paths to focus out in the corners.

If you really wanted a wider field for the same camera, I'd personally prefer to investigate a faster, lower amplification secondary/baffle option and clean up the imagery with a 2-element field flattener/corrector rather than try to use a focal reducer on the existing secondary. But that's a lot of extra unplanned optical and mechanical work you and the team probably don't want to get into.

I do feel that flattening the RC field and sharpening up the edge and corner imagery is a valuable corrector option. Your RC field curves toward the secondary, and the 2-element and 3-element correctors I did for it make a nice flat field with 10-15um images over the 0.38-0.95um spectral band. The only noticeable difference between the 2 and 3 element correctors is distortion. The 2-element design has about 0.5% positive distortion, while the 3-element design has <0.001% distortion. The 2-element design obviously costs less to have manufactured, so the trade is cost vs. distortion. The distortion vs. field angle curve can be curve-fitted with a polynomial, so the distortion can be compensated for in post processing with minimal image degradation in the edges and corners.

If you want, I can post up the 2 and 3 element flattener designs, but you get all your pictures up first. I'm like everyone else, waiting to see what you've actually gotten built so far.

S'gonna be a good scope for sure.
Mike

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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and others.