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Path: utzoo!watmath!clyde!cbosgd!ihnp4!alberta!cadomin!andrew
From: andrew@cadomin.UUCP (Andrew Folkins)
Newsgroups: net.astro
Subject: Re: Photographing Halley's Comet
Message-ID: <648@cadomin.UUCP>
Date: Mon, 16-Dec-85 13:26:22 EST
Article-I.D.: cadomin.648
Posted: Mon Dec 16 13:26:22 1985
Date-Received: Tue, 17-Dec-85 04:45:44 EST
References: <1970@watdcsu.UUCP>
Reply-To: andrew@cadomin.UUCP (Andrew Folkins)
Organization: U. of Alberta, Edmonton, AB
Lines: 46

In article <1970@watdcsu.UUCP> haapanen@watdcsu.UUCP (Tom Haapanen) writes:
>
>
>So, what kind of film should I use (I'd prefer slides, but...)?
>What about exposure times and apertures?  The lenses I either own or
>can borrow include a Canon 100-300/5.6, Tamron 70-200/3.5 and a
>Vivitar 75-205/3.8.  I also can use a Vivitar 3x multiplier and a
>Makinon (el cheapo) 2x multiplier.  What kind of combination should I
>be using to avoid huge grain and massive lack of sharpness?
>
>Thanks for any help.
>
>				   \tom haapanen
>				   watmath!watdcsu!haapanen
 
I would recommend digging up the last few issues of Sky & Telescope or
Astronomy magazine. They have a regular column on photography, but lately, 
due to Halley's, they have been keeping the material on an introductory level.

I've done a bit of astrophotography, all unguided (you point your camera at
the sky and open the shutter).  Ektachrome 400 slide film gives fairly
good results, with exposures of ~30 seconds using a 50mm lens at f2.4.
Keeping the exposures short will minimize star trailing, a faster film
will record fainter objects before the images start to trail.
With a film this fast though, the longer exposures tend to fog the film
due to skyglow and light pollution.  Also, the larger your lens, the smaller
an area of sky you will photograph (the 50mm will easily get all of the
Big Dipper), but the faster the stars will move through the camera's field
of view.

If you want to go for longer exposures, in the 10 - 60 minute range, the
solution is to guide your camera.  One of the magazines mentioned above 
had an article (sorry, I don't have the reference, but I can dig it up)
describing a simple Poncet mount, which you can use to guide a camera for 
several hours.  It is very simple and cheap to construct (~$50, if I remember 
correctly).
 
Two important thing to remember : 1) a dark sky will greatly improve the
quality of your pictures, and 2) you will have to experiment with combinations 
of exposure times, f/ratios and lenses. Have fun!
 
-- 
Andrew Folkins        ...ihnp4!alberta!andrew    
 
All ideas in this message are fictional.  Any resemblance, to any idea,
living or dead, is purely coincidental.