ATM Re: atm-digest V1 #1680

[Atmj1@aol.com]

To Aplanatic, Dave, and others interested:


>>>>>Hi Anthony:

>> One concern I have is flexure of the miniscus.  To deal with this the
>>  curves should be shallow and the element thick.  This spelled Rumak to me.
>>  I played around with various self generated designs, optimising in OSLO 
LT,
>>  but at no time did I even come close to the performance of the design
>>  prescribed in "Telescope Optics."   However, if anyone wants to propose a
>>  Mak prescription which beats the performance of the "Telescope Optics"
>>  Rumak, I'll change my plans.  Besides, I'm thinking at least 8 months just
>>  for the corrector.

>The R and vV Rumak designs that I have worked with on TRACE show excellent 
>performance.  As you recall this is an f/15 design which I consider to be 
>just a little too slow for my tastes even in a visual instrument.  I 
>re-optimized the design for f/10 and it still works well, showing that all 
>on-axis rays are within about a five micron circle at the focal plane over 
>420 nm to 700 nm.  At f/10 and 550 nm, the Airy disk is about 13 microns in 
>diameter, so the inherent normalized transverse aberration in this design is 
>less than 0.5, which I consider excellent.

You might want to give Harrie and call or letter before producing this 
instrument. I will leave the particulars to him.

Kindest Regards,

Bill Cook
editor / publisher, Amateur Telescope Making Journal
www.atmjournal.com