Re: [APML] AIP4WIN

[Roland Roberts <roland@astrofoto.org>]

>>>>> "ak" == Koebel, Alen <Alen.Koebel@christiedigital.com> writes:

    ak> Roland Roberts wrote: 
    >> AIP4WIN will only work up to 16-bit FITS
    ak> ...
    >> Also, there is/was a hard limit of 4k x 4k on the image size. 

    ak> Aha. Neither fact is mentioned on the Willmann-Bell web-site,
    ak> AFAIK. Actually, there isn't much of a description at all on
    ak> the web site, that I could find. It's a strange way to sell
    ak> software (i.e., with no adequate description of the features).
    ak> Thanks for the heads up.

Well, they are basically selling the book.  It was the book that
really got my attention as a newbie.  The software was a bonus, $80
for a text is a bit high, but not excessively so (I have a whole book
case full of graduate physics texts where the median price was
probably about $50).

    >> For 35mm that's fine; you are unlikely to want to end up with
    >> much more than about 3k x 2k pixels for 35mm. 
    [...]

    ak> Wouldn't TechPan and a really good lens or telescope have the
    ak> potential to resolve better than this?  Regarding
    ak> oversampling, don't you need to sample at 2 or more times your
    ak> minimum feature size to get "all" the information on the film?

You can make several different arguments about what the maximum
oversampling should be.  Roughly 2X your minimum feature is the rule
of thumb, and a 25µm spot size yields about 1440x960 for 35mm film.
When I scan at 2400dpi (the max for my scanner), I'm already
"oversampled" about 2X for the typical lens.  Of course, this is not
really a hard limit.

You are correct that a good lens or scope might do better than this;
but I also have a telescope optics book that uses the 25µm spot as a
photographic criterion.  What TP gets you is reduced grain size.  At
2400dpi I *do* have some grain effects especially with faster films.
For some lunar images I shot last week with Kodak MAX 400, my scans
show color blotches that, while not really grain, are related to
grain.  Stacking 4 images helped reduce this.

    ak> Speaking of spot size, the smallest star images I've been
    ak> achieving on Elite Chrome 200, prime focus through a
    ak> knife-edge focused 6" Meade Schmidt-Newtonian (definitely NOT
    ak> Takashi or A-P quality :-), are a little smaller than
    ak> 0.04mm. Is this about as good as I can reasonably expect or
    ak> should I be doing better?

I can't really comment directly since everything I have done is
piggy-back (except for the lunar images), but I have features on some
of my constellation portraits that I can resolve (*very* faint ones)
that are separated by about 2 arcmin which is pretty much the 25µm
criterion for my 50mm lens.  Your brighter stars are going to be
larger.  These are all the way down at about mag 12, barely above the
noise.  All the ones that can be readily seen are larger.

roland
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