Hi Chuck, Moose, Ralf and all,
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
>My personal opinion is that the poster was wrong. The length of the
>star trail on film or sensor is only influenced by focal length. But,
>like CoC, the final effect is controlled by total magnification.
Like depth of field, what is considered "acceptable" blurring is highly
subjective -- so is the Coc. But as a rule of thumb, "for the usual
sharpness requisites", I find it OK.
However, the real reason behind is... there's no point of using a
larger-than-35mm format for untracked, unguided, "tripod" astrophotography
-- there are no F1.4 lenses in medium format, and very, very few F2. Plus,
it's hard to get very fast films, since the roll format is much more
sensitive to stray light than the 35mm cassette.
From: Moose <olymoose@xxxxxxxxx>
>I know the pros with the big observatories use any and all tricks
>available to increase their images.
Sure! But "real" astrophotography, tracked _and_ well guided on an
equatorial mount, is adifferent matter.
>My own credentials expired decades ago when I
>wasn't much satisfied with pics of the moon taken with a Kodak 6x9
>folder hanging on my home made reflector.
I managed to get a few "barely acceptable" pics of Mars and Saturn, poking a
videocamera thru the eyepiece of the telescope!
<http://cjss.sytes.net/etc/saturno.jpeg>
<http://cjss.sytes.net/etc/marte.jpeg>
>It does seem to me that this image can be significantly enhanced for
>viewing by folks like me.
><http://www.moosemystic.net/Gallery/Others/Santisteban/sagitario.htm>
>I like the dark background and increased detail in the clouds.
Thanks for the work. Since I'm currently using a "krappy kolor laptop" at
the verandah (sp?) facing the beach, I can't judge accurately, but your
image is stronger and nebulae look much better.
However, it _seems_ (here and now) that the brightest stars are now almost
fully white, clipped without the slightly coloured halo, this information
would be sometimes very useful for identification. And I feel safer leaving
the black level (that is, the "brightness" of the sky) higher than usual
because I'm afraid of losing detail on the faintest, darkest objects --
despite the lower contrast.
But, again, I may get a surprise when I return home and re-check your
picture ;^)
From: Ralf Loi <ralf_loi@xxxxxxxxxx>
>In general, every astropic has to be enhanced in some way,
>particularly if it is a digitized film based photo.
Sure, but read previous paragraph about my "reasons" to keep contrast
somewhat low.
>My humble selection is on (already posted here):
>http://outdoors.webshots.com/album/453120252zQWYwx
Thanks for sharing, good work there. I hope I get time to re-digitize many
of the astro-slides I took in the past, and put them in the web.
Cheers,
--
Carlos J. Santisteban Salinas
IES Turaniana (Roquetas de Mar, Almeria)
<http://cjss.sytes.net/>
--
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