Re: ATM 16" F/33 valid design?

["Frank Ward" <thewards@mindspring.com>]

Joe,

Nick Loveday designed a system in the early 80's that
accomplished what you want to do with a second convex
parabolic mirror replacing the diagonal. S&T June 1981
page 545 Gleanings for ATM's A "Folded Newtonian" with
Dual Focal Lengths

The center of the primary hidden by the diagonal shadow
was used a second time for the reflection from the secondary.
The rays  then returned thru the secondary to a diagonal and on to
the focuser.(600X with a 12.5" and a 10mm WA eyepiece)

In a conversation with him last year he admitted that no one had
constructed a working model of his design. (I have made the optics
and they are aluminized, but I too have not constructed the upper
cage necessary to install them with the precision necessary to get
the possible f/18 the design allows.) He attributes the lack of interest
to the comment Andy made in a post earlier today or yesterday.

In today's world the quality eyepieces and barlows available and the price
charged so "low" compared to a full scope fabrication that the same
wonderful results can be obtained without resort to multiple surface
reflections.In your very innovative design I count five reflections, for me
an "unacceptable" light loss on objects viewed at f/70, where there
will be next to no light as it is. In your design a 32mm eyepiece would
be your lowest useable eyepiece considering a 50X useful limit on mag.

I am not trying to disuade you. Far from it. Your thinking "outside the box"
by including two focusing mechanisms is quite elegant and cries out to be
used in >some< fashion.  I hope you get back many replies from designers
far better than I with far better and more constructive comments.

Oh, and thank you for taking the trouble to present your ideas and drawings
in such a clear fashion. If you lived in Atlanta I'd like to be a neighbor
of yours.
A few Friday nights with feet up on a sofa bouncing around ideas like that
would do me a world of good.

Best wishes,

Frank Ward
Atlanta, GA




----- Original Message -----
From: "Joe Mayenschein" <mayen1@mwt.net>
To: "Andy Saulietis" <iss@pvtnetworks.net>
Cc: <atm@shore.net>
Sent: Tuesday, January 15, 2002 7:03 PM
Subject: Re: ATM 16" F/33 valid design?


>
>
>
> Andy Saulietis wrote:
>
> > At 08:12 PM 1/15/02 +0100, you wrote:
> > >
> > >
> > >Attention focal length extremists...
> > >
> > >This matter of sanity in focal length choice comes up
> > >periodically. I recall The Simak paper in Astronomy
> > >magazine in April 1984 mentioning that focal length
> > >of 120"
>
> {snip}
> Please check out the below page of a project of a EXTREME long F-Ratio
> scope I was thinking of trying.  what's everyone think?
>
> http://www.qsl.net/wb9sbd/path.html
>
> Joe
>
>