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Re: [OM] Astrofest

Subject: Re: [OM] Astrofest
From: "John Petrush" <petrush@xxxxxxxxxxxxx>
Date: Thu, 11 Nov 1999 22:43:16 -0500
Foxy <foxcroft@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> ....
> astro stuff, so delete as appropriate.

More astro stuff.....so delete as you are so moved......

> Some of you may have seen the excellent deep sky photos made by David
Malin.
> He takes 3 photos for each one, using 10" or 14" square glass plates,
> depending upon the telescope.

David Malin is the King of all astro shooters; his work is the yardstick
against which all others measure.  He refined the tri-color technique used
by many amateurs around the world.  He also uses smaller formats of film,
again depending on the scope.

> Unfortunately, Kodak will no longer make the photo plates he needs. He is
> the only person on earth using this type of plate, and Kodak have kept the
> stuff availalbe as a support to the scientific community. But it's time is
> up. So he is going to CCD. I asked him if the quality was as good, he said
> nearly.
>
> But lets put this in perspective. He uses a 5" square CCD array with 64
> million pixels. And 320 Mb per exposure. A different league to us I think.
> He showed some results, but they weren't as good as the film. He said he
was
> not yet happy with them, and will work at them some more. Still, the
> available image is smaller by 1/4 at least.

For wide field imaging, film still reigns supreme but the margin of victory
gets thinner every year.  Astronomy enjoys the distinction of being the
first truly digital science.  All sorts of imagery, spectra, analysis and so
on are possible with first generation digital image capture.  Astronomers
have been using these detectors for years.  They have the advantage of being
much faster, thereby recording more detail in less time, and have a linear
response to light, something no emulsion I'm aware of can claim.  For pure
resolution over the same area, film still wins - I think - and film, so far,
can image larger areas than the largest CCD's.

Each medium has its place and neither is "better" than the other.  They have
different strengths and weaknesses.  Both will continue to be used for a
long time.  For pure scientific measurement however, CCD's have already
taken over.  A human staring at a blink comparator is no match for a digital
subtraction of one image from another to see "what's different between these
two pictures".

> ..... I can't shut him up now. We need a new scope. Maybe I can sell some
children.....

Keep the kid, shoot weddings to finance the new scope!  There are a couple
of excellent mailing lists dedicated to astro photography.  Email me
privately for details.  If you're open to "free advice" gained from hard
experience, just ask.  I'll share what I learned so you hopefully can avoid
a few of the holes I've stumbled into.......

John P
South Carolina, USA





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