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From: bilbo.niket@LOCUS.UCLA.EDU ("Niket K. Patwardhan")
Newsgroups: net.space
Subject: Photographing Halley's
Message-ID: <8601151959.AA11727@s1-b.arpa>
Date: Wed, 15-Jan-86 14:10:34 EST
Article-I.D.: s1-b.8601151959.AA11727
Posted: Wed Jan 15 14:10:34 1986
Date-Received: Fri, 17-Jan-86 03:21:05 EST
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Organization: The ARPA Internet
Lines: 32

There are two problems..... One is to get the brightness of the kids and the
comet comparable in the final picture, and the other is to get the sizes
comparable.

If the AE-1 has aperture control (that is, you select the aperture and the
camera figures out how long to keep the shutter open) then you choose the
largest aperture (smallest number) and the camera should get you a reasonable
picture of the comet. If the time it picks is a few seconds, then you flash
the kids near the end of the time, and get your picture in a single exposure.
You of course need a manual flash. If you are willing to borrow a friend's
camera for this, try using an Olympus OM-1, it has aperture control, with a
very long time limit. One of the biggest problems with using this technique
is making sure that the camera is reacting to the light from the comet, rather
than something else in the picture, and you make sure of this by letting its
image cover enough of the field of view, and that there are no artificial
light sources in the picture (street lights, the moon, etc).

To get the sizes comparable, you need to put the kids far enough away from
the camera, just like when you take a picture of people walking into a sunset,
and blow them up to the right siz with a telephoto (which you need anyway, since
a straight shot of the comet wouldn't be visible). Since I am not quite sure how
much magnification the comet needs for a reasonable picture, I can't even begin
to guess how far this needs to be. (A mile???? 100 yards? You might need a
walkie talkie to work the flash right).

A double exposure could be simpler because of the size problem.... you first
take a picture of the comet (borrowing somebody's telescope if necessary),
and then take a picture of your kids against a dark and even background. The
only problem would be stars in the middle of the kids.

If somebody knows the right telephoto to use to get the comet to occupy a least
5% of the field of view, please let us know.