Re: ATM Aberrations

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

Rich, I'm not too sure what the question here is as generally shortening up
or enlarging the apereture diameter of a design causes the abberations to
continue their erroneous ways.
What this means is that if you get a particular abberation with a design,
shortening the focal length will increase the abberation as it's always
increasing as you go out from the center.
You can use almost any pair of glasses at f20 and get a good design of color
correction but as you get the focal length then the glasses need to be a lot
more specific as to what is needed to do an acceptable design.
If you want to have fun, take a common glass, BK7 for example, and make up a
glass that will give you a good color correction for a F5 design.  Take care
that the spread is a viable one for the glass and, when you are done, you'll
have a better idea of what is needed for a good design.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net