Re: stalks vs spiders for secondary mirrors

Clay Spence x3039 (cds@peanut.sarnoff.com)
Thu, 20 Jul 1995 15:02:22 +0500

rhill@LPL.Arizona.EDU (Rik Hill) wrote: > > >rhill@LPL.Arizona.EDU (Rik Hill) wrote:
> > >
> > > If you decide to go this route, keep the Cass central obstruction
> > > small <=15% and you will get good results.
> >
> > Doesn't the magnification factor of the secondary have to be pretty
> > high to achieve this, like roughly six or greater?
> >
> > Clay
> >
> Either that or live with a smaller field.

I'll try again, but I got a magnification factor of 5 2/3 for a secondary that is .15 the diameter of the primary and has a point unvignetted field, i.e., the diameter of the unvignetted field is zero. This is with a focal point at the surface of the primary. Putting it behind the primary takes more magnification. This is also independent of the radius of curvature of the primary.

Clay