RE: [APML] Tech Pan shot

[spampit <spampit@shaw.ca>]

George,
	If the technology fails you for guiding, there is always manual
guiding! It builds character. :-) I didn't notice that you were using the
Lumicon filter. That being the case, you can most certainly go longer! Under
a moderately dark sky at f3.5 and the Lumicon filter, you can shoot for at
least an hour with a first/last 1/4 moon up. I have always stayed 30 degrees
away from the moon, it may well be possible to shoot closer than that. I
never really did find the limits to this type of photography with
telephotos. Under a dark sky and a Wratten 92 I know that I can shoot for 45
to 60 minutes at f1.5 and still have a printable negative. (with 5 minute
development) http://www.astrofoto.ca/john/n7822.htm Maximum exposure time
will vary, depending on your type of light pollution, how well the film is
hypered, humidity levels etc. Maybe start with 45 minute shots at f3.5 and
see what happens. You are going to need a very good polar alignment for
these long, wide field, high-rez images! I never did try shooting under full
moon, you might as well try. Push the envelope!

John Mirtle
Calgary, Ab. Canada

-----Original Message-----
From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org] On
Behalf Of George Anderson
Sent: Monday, August 08, 2005 8:59 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Tech Pan shot

Hi John, nice to hear from you again.
I haven't done any vignetting reduction on the photo yet, too busy
debugging other problems with my setup. I am in the process of switching
from my 70mm f/10 guidescope with a 10mm EP containing a homemade
non-illuminated crosshair, to my B&W quickcam on a 500mm f/8 mirror
lens. The sensitivity is ok, just a real pain to align with the mount.
The field of view is so small that I can't even swing polaris in a
circle.
That shot was done with a Lumicon HA filter under moderate light
pollution, at 18 minutes the negative is thin to say the least. I did
two more shots saturday night with the quickcam and laptop for visual
guiding. Much easier on the eyes, but I hadn't aligned the camera and it
was out by a good 5-10 degrees from the mount axis. Very nice trailing
(three star diameters) on the two 30 minute shots...  :^(
Just how much of a moon and at what angular separation from the target
is safe with the HA filter? That will improve my shooting nights by 200%
if I can shoot up to the quarter moon. Our weather always improves
around that time.

George
Clear skies and good health



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