Hi, all. Sorry for replying so late to this thread -- I had a bunch
of digests pending to read...
><<
>With the availability of the observatory at my university, I've decided
>to try my hand at astrophotography. I understand that the old tech pan
>film was some of the most desireable, but with it having been
>discontinued, what are some other good choices for both monochrome and
>color? Something without major reciprocity failure in long exposures. . .
> >>
The reciprocity failure is not _always_ a bad thing; in fact, it's
desirable sometimes, e.g. meteor showers. Anyway, you might
compensate it with a longer exposure time, provided the tracking
device is accurate -- i.e, well aligned.
>Generally speaking, most of the bw film are not too sensitive to the red,
>where is the peak brightness of nebulae.
Yes, the 656nm wavelenght, a.k.a. the Hydrogen-alpha line. A film
range to avoid is Agfacolor Vista, designed to match closely the
spectral response of the human eye -- that is, almost blind to that
wavelength :-( Anyway, I won't recommend any colour negative film,
unless you have a good film scanner...
>One notable exception is TP 2415, both red sensitive and of low reciprocity
>defect.
Oh, my beloved TP2415 ;-) It's indeed _very_ sensitive to red (esp.
656nm), but AFAIK it shows notable reciprocity failure (typical of
classic BW films, like Tri-X etc) _unless_ hypered (when performs
great). I have never used hypered film, though.
Another method to improve film response with long exposures is
something called (IIRC) 'Nitrogen purge', which needs a modified
camera body (!) and sealed optics, but this should be just for
'hardcore' astrophotography, I believe.
>Delta 400 might work pretty well as it is a bit more sensitive
>to red and near IR.
I have no experience with this film, but it should be fine. I
remember some other film from MACO with good sensitivity at 656nm,
but I'm not sure of the exact name...
>For galaxies and star clusters you could also use Tri-X pushed to 1600 asa.
I have used this film (and Ilford Delta 3200) for meteor showers,
with very good results. I took this pic of M31 (Andromeda galaxy)
<http://cjss.sytes.net/etc/m31.jpeg> on Delta 3200, about 10 min
exposure (_manually_ tracked -- my kidneys still hurt! :-) thru a
Zuiko 300/4.5. Sorry for the poor quality of my old scanner (directly
from film)
>For color film one good choice is Ektachrome 200 Professional
>wich I used in the near past (I don't know if it has the same name now).
>It can be pushed 1 or 2 stop with very good results.
Very nice, one of my favourites (now called E200). Great sensitivity
at 656nm and beautiful colours. When pushed +2 (I do E6 myself) it's
rated 640, instead of the expected 800, but with minimal reciprocity
failure. Also Ektachome P1600-X (really a 400 film designed for
pushing) shows bright reds, but more grain too.
>One film that can also be good reading the specs is Provia 100F, but I
>don't have used it.
Fuji Sensia 400 works great, even pushed +2, with _no_ reciprocity
failure and nice colours (the red is not _that_ bright, but it's OK).
I used Provia 400F, but Sensia works equally good and it's less
expensive. Sensia 200 is a strange thing, though. Sensia 100 won't
push as good as the Provia 100F.
>I have an older silver nose 200/4 which I have always been very happy
>with.
[snip]
>If you peruse the archives you'll see
>that the biggest enemy of the 200/4 is vibration, something that is
>mitigated in hand held shooting or if you dampen the vibration with your
>hands pressing down on the camera/tripod as Olympus suggests.
[snip]
>Vibration will never be a problem with long exposure astrophotograpy so
>you can let the 200/4 off the hook on that point. The only other
>question is whether the B/B- grades that Gary assigned to the 200/4 when
>wide open is good enough for the the demands of star images.
Everything's said already... I find the 200/4 optics _superb_, even
wide open; for 'normal' pics, the problem is vibration dampening
(sp?), but this is not an issue for astrophotos. See some of my pics
with the Zuiko 200/4 (mine is an MC) at
<http://cjss.galeon.com/zuiko/astro/index.html>. Again, sorry for the
poor quality of the scans...
When taking these pictures, I noticed that there was almost _no_ need
for tracking corrections -- much better than my previous setup
(Yash*ca FX3 + Zeiss 135/2.8) on the same mount. I haven't got too
much knowledge on physics, but somehow the OM+200 combo is 'easier to
move' than the FX3+135 combo, although they weight _exactly_ the same
-- this seems bad for 'normal' pics, but great for tracked exposures!
>I'm sure someone
>here will have some advice on a low cost lens that will do the job.
>Probably one of the Tamrons.
The old Tamron 200/3.5 (model 04B) is a good performer, but I haven't
tried it in tracked astropics. I know also of a Russian (M42) lens,
the Jupiter-21M (also a 200/4) which is _incredibly_ sharp wide open,
but it won't fit an OM body... and weights a ton!!! :-)
Hope this helps,
--
Carlos J. Santisteban
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