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Re: [OM] Which OM is best for astrophotography

Subject: Re: [OM] Which OM is best for astrophotography
From: Chi-hung Yeung <bcchye@xxxxxxxxxxxx>
Date: Wed, 16 Jul 2003 14:51:19 +0800
Hi,

I have been using the OM-1 for astrophotography for more than 30 years. Yes, I bought my OM-1 at around 1972. I have a little trick to share with you. If you cannot find the 1-8 screen, you can "polish" out a small portion of the standard screen with tooth paste so that it is somewhat translucent. This will make focusing through the telescope especially when doing eye-piece projection photography much easier. The down side is that the meter reading will be a bit wrong.

Moose asked about mirror lock and vibration. Yes, Moose is right that the vibration will not affect long exposures. However, another branch of astrophotography requires short exposures. This includes shooting the Moon, the Sun and the planets. For this subjects, we commonly use telescopes and shoots at extremely long effective focal length (e.g. 10,000 mm) and shutter speeds shorter than a second. In these cases, vibrations from the mirror and shutter are intolerable. The mirror lock helps to remove most of the vibration and the shutter is replaced by a black card in front of the telescope in cases.

C. H. Yeung


At 05:10 AM 16/07/2003 +0000, you wrote:

olympus-digest         Tuesday, July 15 2003         Volume 02 : Number 4180
==============
Date: Tue, 15 Jul 2003 14:27:43 -0400
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Subject: [OM] Which OM is best for astrophotography

Presumably you will use the OM-1 with a 1-8 screen which is designed for
very long lenses and astrophotography.  If you elect to go this route
first see if you can find a 1-8 screen.  Since the OM system has been
discontinued certain low volume accessories (like 1-8 screens) are
becoming harder to find.  On the other hand, OM-1's in all states of
repair are plentiful. If you only intend to use this for astro work you
do not need a working light meter and none of the shutter speeds except
"B" need to work unless you intend to do some lunar and planetary stuff.



Date: Tue, 15 Jul 2003 14:20:34 -0700
From: Moose <olymoose@xxxxxxxxxxxxx>
Subject: Re: [OM] Which OM is best for astrophotography

OK, I 've had a question for some time for you astrophotogs. In
exposures measuring from 10s of minutes to hours, what difference does
mirror lock-up make? Mirror, aperture and shutter crash-bang all damp
down in maybe a second or 2. So out of all the light that makes up even
a 2 min. exposure, less than 1 0s disturbed. How can that affect the
image? None of that light which is in the wrong place, and a moving
wrong place at that, will even register on the film.

Moose


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