[ATM] f12 mirror advice requested

[Philip Lardner]

Mitch,

I'm working on a Folded Stevick-Paul, which is an unobstructed TCT system
with 4 mirrors. I'm using a small 5th mirror to bring the focal plane to a
convenient place and control the focal plane tilt at the eyepiece. It's
designed specifically for solar system and double star work, hence the long
f/ratio. I wanted an f/20 system, but that won't fit in my observatory and
my house is only just big enough to test the f/15 primary! All-up, the scope
tube will be about 10 feet long and will be mounted on a heavy duty fork
with my 20" f/4 riding piggyback for wide field work.

It's an on-again / off-again project that I had to put on hold for the last
few months when I dislocated my shoulder (not from polishing!) I hope to get
back to it this month and continue working on the 10" folding flat. If
you're interested in looking at the design and ray-tracing it, then check
out the links below and download WinSpot, which contains many TCT designs
including an f/10 FSP.

Phil.

Dave Stevick's Weird Telescopes Page -
http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/weird.htm
Stevick-Paul design manual -
http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/stevpaul.htm
Bob Novak's folded design -
http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/folded.htm
WinSpot ray tracing software -
http://bhs.broo.k12.wv.us/homepage/alumni/dstevick/spotplot/winspot.htm

-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net]On Behalf Of
Mitch
Sent: 03 February 2007 02:04
Cc: atm at atmlist.net
Subject: Re: [ATM] f12 mirror advice requested


-----Original Message-----
From: atm-bounces at atmlist.net [mailto:atm-bounces at atmlist.net] On Behalf Of
Philip Lardner
Sent: Friday, February 02, 2007 3:37 PM
To: ATM
Subject: Re: [ATM] f12 mirror advice requested

Yes - I recently finished a 14" f/15 (RofC=10,500mm) and found not just the
focal length but the figure to be extremely sensitive to change while
polishing. I ended up with a RofC = 10502mm and decided that was good
enough! Testing a mirror of that length wasn't easy either. The slightest
air currents really screwed things up, and it also showed up the surface
roughness in the video camera (and other lenses I used) as clear as day!

Phil.

***Just curious, are you making a 17.5 foot high telescope, or is this for
some folded or off-axis design?

Mitch

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