Re: Re: Best Film/Shutter/f-stop combination for satellite photography?

Bjorn Gimle (bjorn.gimle@online.dextel.se)
18 Aug 1995 07:24:02 GMT

seesat-l@iris01.plasma.mpe-garching.mpg.de,Internet

Greg Mortensen (GMORTENSEN@delphi.com) asked:

> Quick question:  What's the best film speed/shutter speed/and f-stop
> combination to take pictures of satellites?  It should be noted that I'm
> currently using a 35mm, with 1000 speed film, and a shutter speed of
> 20 seconds.  I use a 58mm lens, at an f-stop of 1.2.

> Unfortunately, I live in an area that can only be described as
> "light-polluted", so these shots generally come out with a bluish sky,
> rather than a black background.

I generally agree with Tristan Cools' (tcools@nic.INbe.net) 
and Nick Quinn's (nick@nquinn.demon.co.uk) answers, but I
have some more comments.

I normally use color print film at 400-1000 ASA, and a 50 mm f/1.4
lens, but I have used b/w and color slide films up to 3200/1600, and
85/2, 135/1.5 (!), 135/2.8 and 250/5.6 lenses. 
My best shots so far where made on 1600 ASA color slides, 
with the 135/1.5 I borrowed for a few days.

Generally, satellites move so fast, that track exposure is not 
affected by general astrophotography concerns about reciprocity
effects, and fine grain for high resolution.

The satellite exposure is proportional to f/F/F, 
where f is focal length, and F is F-stop number.
So your lens is 40.277, which is hard to beat, but for
each doubling of the focal length, you can go down one
f-stop, which is desirable in twilight or light pollution,
without losing satellite magnitudes. Also, a longer focal
length makes it easier to shorten the exposure times, which
makes the sky background darker.

You should try to get negatives (or slides) with a little
background light over the entire surface. If your lens has
vignetting, you must accept some more light in the center.
On prints, the same applies - you should not aim for all
black, this may also make the the satellites and stars dimmer,
unless you control the contrast yourself.

If you have a print shop making prints for you, you should be
able to let them borrow a good picture for colour and darkness.
My "1-hour Photo Quick" always make good, dark-blue prints for
me, even if the negative unfiltered would make it light green
or yellow !

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nick@nquinn.demon.co.uk,Internet
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