I was going to say to myself before I reached the end of your response was
"expensive, difficult, and we're not going there."
Thanks Chuck. Reality tends to speak volumes, true?
Allen
----Original Message Follows----
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Reply-To: olympus@xxxxxxxxxx
To: olympus@xxxxxxxxxx
Subject: [OM] Re: astropotography
Date: Fri, 02 Mar 2007 18:26:10 -0500
There are only two things you can do in astrophotography on a tripod.
The first is to take a photo of the moon. Since the moon is a sunlit
object it's bright and you can use a fast shutterspeed. The second is
to take star trails. You point the camera at the sky, open the shutter
at a fairly wide aperture and capture the motion of the stars as they
drift across the sky. This is more difficult because there isn't any
fixed formula as to how to do it. The length of the exposure you can
make is very dependent on focal length of the lens and on how much light
pollution you have in your area. The light pollution causes "sky fog"
and film/sensor fogging which limits the exposure.
Anything beyond these two items requires that the camera be guided,
typically by mounting it on a telescope which is on a clock driven
equatorial mount with some means of overriding the clock frequency to
allow for tracking errors. If exposures are very short (as in a few
minutes) it may be possible to use a simple device called a "barn door
mount" which is just two boards hinged together with one being rotated
with respect to the other by a tangent screw. If you use the telescope
itself as the camera lens it typically requires another telescope
mounted on the first for guiding. Guiding eyepieces are available with
illuminated reticles to assist accurate tracking.
When using film you must also allow for reciprocity failure in long
exposures. In serious, long exposure astrophotograpy the film or sensor
may be cooled with dry ice or liquid nitrogen to avoid reciprocity
failure in the film and noise from heat in the digital sensor.
In short, it's hard stuff to do.
Chuck Norcutt
Allen Coltrin wrote:
> As I'm sure you're aware, I have been looking into astrophotography. If
> someone has experience in this field could you tell me if this is a good
> mount to attach one of my lenses to it on my Manfroto tripod?
>
> Thanks,
> Allen
>
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