Re: End of an era?


Roland Christen
 

Questars are unique telescopes in that they incorporate a fine optical system along with a fork mount in a very portable package. The design uses an aspheric primary with a secondary spot on the corrector that never needs collimation. The optics are produced by Cumberland Optics in Silver Springs, Maryland. https://www.cumberlandoptical.com/

Although a lot of Questars achieve and exceed 1/10 wave optical correction, the performance is limited by the inherent large central obstruction which is similar to the fast food SCTs and Maks that are sold by the foreign makers. Making a Mak scope with small secondary obstruction is more difficult in production due to the higher order aberrations that must be removed via hand figuring.


Can a 10" Mak-Cass equal or exceed the planetary performance of a near-perfect 8" Apo triplet refractor? Many years ago when Mars was at favorable opposition here at my observatory I had a very still night of almost perfect seeing. I had two scopes set up side by side on a 1200 mount - one of our 8" F8 EDF refractors and one of the AP 10" Mak-Cassegrains. Both scopes were running on the order of 600x on Mars and both showed a wealth of detail. The refractor showed slightly more saturation of the colors and what looked like at first, slightly higher contrast. I was interested to see which one would resolve tiny detail better.

I looked at the polar cap and with the 205mm refractor could see the ragged edges and a thin dark division that seemed to be fairly straight from the edge to almost the center of the polar cap. I switched over to the 10" Mak and saw immediately that the line was even thinner and not straight, but had small kinks and wiggles in it. The polar cap itself had more detail, but again the contrast was very slightly less than in the refractor.

It could be that a 10" APO refractor could outperform the Mak, but it would be a beast. Whereas I can pick up the 10" Mack easily and place it on a small mount and be observing without having to drag out a massive mounting. And no 8" scope of any kind will out-resolve it.

Rolando


-----Original Message-----
To: main@ap-ug.groups.io
Sent: Tue, Aug 4, 2020 1:17 pm
Subject: Re: [ap-ug] End of an era?

Maks are unique in the telescope world. I owned a Questar in the late 90s early 2000s and purchased it new from Questar. About the same time Meade released the 90ETX. I remember people saying it was just like a Questar but so much cheaper. In reality that wasn't the case. I compared many examples to my Questar and never found a meade that could match the contrast, clarity and overall performance. I'm not sure if Questar hand figures the optics like Roland does but the overall quality is top notch. 

I sold the Questar in 2010 in favor of a faster refractor, the Takahashi Sky 90II and now have the Stowaway and sold the Sky90II. I do some astro photography but still enjoy the thrill of the visual chase. Even though the detail isn't same as photos, I still love it. Maybe I'm the odd ball at 41 years old, loving visual astronomy. The quality of the instrument matters greatly to me having owned Celestron, Meade, etc. While I understand the market need for mass produced telescopes, I hope AP and other continue to produce the high quality instruments for years to come.

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