Re: [ATM] computing Yolo

["Bob May" <rmay@nethere.com>]

Warping a secondary and/or primary is one way to gain an off-axis
figure on a mirror surface.  This can make a huge difference in
the spot diagram!  Look at the various designs of Cassegrains
when they are looking at an off axis object and only look at a
part of the spot diagram and you'll see all kinds of interesting
stuff.
In all, that little warping harness is extremely important to the
performance of the instrument!
If you really want to have fun with figuring, take and find out
how much pressure you need to do the correct warping and put it
on the glass in the oposite direction and get back the spherical
surface with that stress on the glass.  When you release the
stress, you will find that you have put the approximate right
amount of shape onto the glass so that it doesn't need to be
stressed in the telescope.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net

----- Original Message -----
From: Mircea Pteancu <mirceapte@yahoo.com>
To: Bob May <rmay@nethere.com>
Sent: Monday, April 28, 2008 10:25 AM
Subject: Re: [ATM] computing Yolo


> Bob
>
>   Thank you for your points.However I still don't understand
why inserting in ''winspot'' the specs of  Art Leonard's 12''
F/15 Yolo,the output was a F/25 Yolo.Figuring or warping to
strange shapes like thoroids don't change the F ratio of a
system.
>   I was scalling downward because my blanks are 3'' plate glass
,1/2'' thick,once  part of a supermarket  window.
>   Scalling downword,toward a more ''relaxed'' system ,shoud
work ,isn't?
>   My first instrument was a 4x 50mm Galilean refractor,the
second was still a refractor of one metter focal length stopped
down to 23 mm aperture,both with spectacle lenses.I set the F
ratio of the second refractor according to formulla in the
Danjon/Couder book to obtain the so called
''pseudo-achromatism''.Your singlet lens refractor  with an
aperture of 4'' is having a slower F ratio of F/50 (or F/60?)
because aperture is bigger.Do you have a detailed description and
/or observation reports with this instrument,please?.If I would
live in USA I would ask your permission to look through your
refractor;especialy now when I'm reading ''La Dioptrique
Occulaire'' of Cherubin d'Orleans.Regards,Mircea
>
>
>
>
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