Hi,
Thanks for all the great input so far, here are some more thoughts:
[Ralf Loi]
> taking stars pictures with only a tripod and a B exposure is easy, with
> pretty good results.
Bulb exposures is indeed what I was thinking of, I see no proper way how to
do this in Auto.
> The only problem is that stars apparently move so if you don't want to see
lines insted
> of points you have to limit the duration of exposure: roughly 10 seconds
with a 50mm (or
> 5 seconds with a 100mm, 20 seconds with a 24mm). This time depends also on
the region on
> the sky and will increase moving from the equatorial zone to the polar one
(of the sky),
Excellent, that's certainly very useful information. If I were to use e.g.
the 100/2 and film rated at 400 ASA, I would have to make sure the not
overdo the amount of stopping down so as not to exceed the 5 seconds
border... Interesting... Perhaps the 50/1.8 is the better choice after
all...
> so as Richard mentioned it is better to use a faster film (800/1600 ASA)
in order to
> fully utilize so a short exposure: I must say that with a dark sky, a
135/2.8 (zuiko, of
> course!) with a Scotch 800-3200 developped at 1600 ASA and exposures
ranging in 5-10
> minutes I took several pictures without having a "washed" sky. With a non
very dark sky
> the exposure have to be limited, but you should try.
How did you manage to avoid the star trails then for such long exposures?
> As to use the lens at full aperture or stopped-down, I use them at full
> aperture for sky photos. The lens will perform better stopped down (a
> couple of stops) in terms of sharpness, contrast and vignetting, but for
> every stop you have to double the exposure, not taking in account the
> reciprocity problem.
Hmmmm, given the exposure times, it might be best to use the 100/2 wide open
and the 50/1.8 and the 24/2.8 stopped down 1 stop (at most)...
> Since I have a telescope but not the motor, I take photos moving the
telescope manually,
> so every minute gained is good.
Does that work well? This doesn't sound straightforward to me. Nonetheless,
I guess it takes a really long exposure to capture stars on the frame that
are not very bright. It would seem some experimentating is in place here.
Interesting project.
> According to the published features of ProviaF, it seems me one of the
best
> film in terms of reciprocity defect, since it does not need a compensation
> for exposure up to 2 minutes (if I remember correct): a very long time.
Excellent, that's good news! Perhaps a stupid question, but does pushing the
film two stops affect the reciprocity failure characteristics of the film?
[Rainer Wagner]
>thats right, stars(in contrast to planets of our solar system) cannot be
>enlarged, they are real point sources in any, even very big, conventional
>telescope. So, a starfield picture tells you a lot about the quality of
your
>lens. e.g. the 55/1,2 at full aperture showed all sorts of aberrations like
>coma,low contrast etc and even poor quality in the middle.
How was this test done again, was it a matter of simply shooting the sky
for, say, 5 seconds with a 100/2 wide open?
>it had to be stopped down to at least 2,8 to yield decent results. The
24/2,8 is quite
>good wide open, my experience with the 50/1,8 is limited, i mostly used the
50/1,4 stopped
So it would probably be o.k. to not stop down the 24/2.8.
>As far as films are concerned, i have used kodak gold 1000 (grainy, but
still nice), Kodak
>and fuji 1600 negative with nice results, kodak 1600 slide and fuji
ms100/1000(medium
>format) Scotch crome only once(hard to get) . Ektachrome E200 for slides
and superia
>800 for prints seem to have a very high reputation among astrophotographers
now.
Another alternative for slide film I have is E100VS, but I doubt it would
outperform Provia 100F for this type of shot when pushed two stops. The
tremendous saturation might work out interestingly for the colours,
though...
More food for thought :)
Thanks again!
Olafo
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