Re: [APML]: Star Trails

[Wil Milan <wmilan@airdigital.com>]

Chris J Serio wrote:

>         The other night I set up my Canon SLR with a 35mm wide angle lens
> and 200 speed film set on f/8. I pointed it toward the milkyway and left
> it open for about 30 minutes. When i had the film developed it looked
> like the picture was taken during the day. The picture was sky blue with
> about 4-8 star trails. There was very little light pollution because i
> live in the woods. Why did it do that. Do i have to develop it any
> special way? I would like to thank Rod Mollise for his answer to my last
> question. He helped me very much. Thanx

I'm not sure what you mean by "living in the woods." Living outside a city is
no guarantee of not having light pollution because the light pollution from
an urban area affects the sky for many miles around. Around here the sky glow
from the city of Phoenix, for instance, is easily visible from 50 miiles
away. Bear in mind that film can "see" light pollution much too faint for
your eye to detect.

You might try shooting a few test shots of different exposure times. Try
taking exposures of 2 minutes, 5 minutes, 10 minutes, and 20 minutes. Take
such a series of shots with the camera pointing straight up and another with
the camera pointing closer to the horizon. If the background sky is dark and
many stars are visible in the shorter exposures but the sky is fogged in the
longer exposures, that is due to light pollution, whatever the source. That
"light pollution" source can be the moon or illuminated clouds, so make sure
there is no moon and no clouds in the sky when you do the test shots.

Also, what kind of film were you using? If you were using print film you
might take a look at the negatives and compare them with what you see on the
prints. A lot of film-lab technicians don't know what to do with astro shots
and they may have overexposed the print to get something out of it, the
result being that the dark sky shows up as blue-grey. If you see a lot more
star trails on the negatives than on the prints then the problem is how the
prints were done.

If you used slide film be aware that most slide films (and most print films,
for that matter) are not suitable for astrophotography. Most slide films take
on a color cast on long exposures. I don't think that's the problem in this
case, but if you want to shoot slide film I'd recommend Kodak Ektachrome
Elite II 100 slide film. For star trails Fujichrome Velvia also works well.

I hope that helps.

Wil Milan
--
"When I consider your heavens, the work of your fingers, the moon and the
stars which You have set in place, what is Man that you are
mindful of him, or the son of Man that you care for him?"  -- Psalm 8