Re: ATM Aberrations

["Richard F.L.R. Snashall" <rflrs@rcn.com>]

Bob May wrote:

>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.
>
This is not the effect I'm experiencing here.  At f/12, one glass is
significantly better than the other.  At f/8, the second glass is
better (though not as significantly).

>
>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.
>
When you say "make up a glass", do you mean choose the dispersion
coefficients?

                        Rick S.

>
>Bob May
>http://nav.to/bobmay
>bobmay@nethere.com
>NEW! http://bobmay.astronomy.net
>
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