Hi,
>>How did you manage to avoid the star trails then for such long exposures?
> My equipment for astro photos is a telescope on an equatorial mount and
the
> camera with lens mounted in parallel. If placed right, i.e. with good
polar alignment,
> the equatorial mount allow to follow the "motion" of the sky simply
rotating one gear
> only: this is what the motor do (if not placed right... this is another
problem!).
I see. That does explain a lot :)
> An equipment not too expensive is a "blind" motor with camera attachment
> that you can put on a tripod. This combo does not require user
> intervention and if right placed (again...) it allows you to use a 100/200
mm tele and
> use up to 15/20 minutes exposure. Only to mention one, Vixen make one.
That doesn't sound too bad, also, Mike's suggestion for the $5 home made
wooden mount doesn't sound bad.
> The great advantage of using a long exposure is that you can collect more
> photons, thus seeing on the film also very faint stars: with the 135/2.8 I
> was able to record stars that are only a few brighter than ones that I can
> see with a telescope with an aperture of 100 mm (the 135/2.8 has an
> aperture of less than 50 mm).
In your opinion: at what exposure times do such star field pictures become
interesting? Is it necessary to take pictures that last several minutes, or
are the results of pictures with a 10-20 seconds exposure time also
interesting enough already?
> As far I know, pushing the film does not affect the reciprocity defect.
> There are methods used for minimizing the defect but there are not easy
> (very low temperature, or "washing" the film before exposure in a nitrogen
> bath...).
Yowza! Aren't there any more subtle ways to get around this issue? Also,
does anyine know how badly Provia 100F pictures look when they suffer from
reciprocity failure?
Cheers!
Olafo
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