Re: [APML]: High res monochromatic lens

[epabcc@epa.ericsson.se (Bratislav Curcic)]

Peter wrote :

> designing a super high res monochromatic
> (ie filtered) lens of about 100mm fl at f2.8 to cover a 30 deg circular
> field on medium format.

> Question:
> Is it worth it?

Peter,

In my opinion, no. I don't know how many elements we're talking about 
(I'm guessing at least 4 or 5), but a small Schmidt will be doing the 
same thing even without the filter, and it will have just one element
(I'm not counting spherical primary, it's trivial). Yes, it has curved 
plane, yes it is hard to access and focus, but once you've done with
it you have really useful toy that you can use with any film (color!) 
and any/no filtration.

> Can the 100mm fl TP neg be blown up so much that
> you can really resolve the same sorta detail as an inferior longer fl lens
> but with a much smaller field?

I don't think so. Especially considering that you can use same Tech Pan on
the longer f.l. scope as well ! 

Besides, just count how many objects sized 20 degrees (or more), and strong 
in H-alpha region are in the sky ? Is it worth it making a highly specialized
lens that more or less finishes its useful life after only a few nights of 
astrophotography ? You can't even shoot large comets with it (unless we
get a REALLY weird one !!!).

Bratislav