Re: [ATM] Front aperature size on 20" RC

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

My method is more to look back at the angles generated by looking
at something off of the axis.  For a strict Newtonian telescope,
it is easy as the EP on a large scope should be at least 2" which
has a radius of one inch.  This means that the end of the tube
should be at least that much bigger in radius to keep from
vignetting.  Other designs such as always barlowed Newtonians and
Cassegrains will, of course, end up with other values for the
spacew needed for the far end of the scope but the strict
Newtonian value should always work out just fine.  If you know
the magnification ratio of the secondary, you can always use that
to divide into the aperture of the EP to figure out what needs to
be on the front of the scope.
Shdn you bo gfz ing the scope design, all that you need to use is
the chief ray, the one going through the center of the scope.
Ignore the presence of any secondary or other obstruction as you
proceed through the design until the surface is needed.  In other
words, don't use an obstruction to stop the ray.
Bob May
Due to the large volume of SPAM thaat I'm getting, add an open
square bracket to the subject line or my spam filter will reject
your post~
rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
Replace the obvious words with the proper character.

_______________________________________________
ATM mailing list http://www.atmlist.net/