Quote:
Originally Posted by Stevec35
I'm a bit late with this one Rick. A spectacular image to be sure and one of the best images of this galaxy I've seen.
Cheers
Steve
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Thanks, Steve!
Quote:
Originally Posted by alpal
Yes Rick,
I noticed that when I went to the website.
It all seems quite confusing but your image is so sharp
that I start to wonder about the worth of spot diagrams.
cheers
Allan
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Allan, I've been reading the Telescopes, Eyepieces, Astrographs book by Smith, Ceragioli and Berry. They analyze a lot of designs in detail including Ritchey-Chrétien and Dall-Kirkham. Both need a corrector to cover a wide image circle (RC has field curvature and DK has coma) but with a corrector both designs are capable of very good performance.
The book shows spot diagrams for all the designs they analyse and ray-fan plots are provided as well. These are really useful - you can actually "read" the aberrations from a ray-fan plot and get a much better feel for the (theoretical) performance of a design.
Cheers,
Rick.