Re: [APML] Two BIG-telephoto-lens-related questions

["S y z y g y" <syzygy@vnet.net>]

Emmanuele,

I don't know about this Pentax lens but I used a Canon 600mm f/4.5
(non-L) lens (now that was big!) for Astrophotography several years
ago.  Even though it was a very good lens for "normal" photography
(low light wildlife, etc.) it was not really any good for color
astrophotography.  The lens had quite a bit of chromatic aberration
wide open and wasn't really all that sharp when you were trying to
capture pinpoint star images.

The Pentax lens is probably similar.

Bill

----- Original Message -----
From: Emmanuele Sordini <vega@ulisse.it>
To: <astro-photo@seds.org>
Sent: Monday, May 13, 2002 5:05 PM
Subject: [APML] Two BIG-telephoto-lens-related questions


| Hi folks,
| I've run into a VERY big telephoto lens, a 500mm-FL (f/4.5) Pentax
SMC.
| It's a little monster (weighs in at 3+ kg), it is about $800 used
but in
| mint condition and comes with its original case; it originally had a
Pentax
| bayonet mount that was subsequently converted to a Nikon one by a
very
| skilled machinist. Now come the questions:
|
| 1) Is this lens any good for AP? I searched the 'Net extensively for
some
| reviews/shots, but I found almost nothing. I understand this lens is
not
| very common, but since it boasts a 11-cm objective lens, I've a
hunch it
| could be profitably used for AP.
|
| 2) This may seem to be a dumb question, but have they ever made
focal
| reducers (or other thingies that could be used as such) for such
long
| telephoto lenses? I know that I could use a shorter FL lens, so it's
not as
| much of an issue as it is with telescopes, where you can't have one
for
| every potential need :-)) but I don't think I was the only one to
ever ask
| this question.
|
| Any thoughts/ideas/experiences to share?
| Thanks in advance and clear skies from boggy Notherrn Italy,
|
| Emmanuele
|
|
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