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Re: [APML] 'Astrophoto Program'

Hi Saint:
Your calculation of f50 sounds about right. Do you have Michael Covington's book, Astrophotography for the Amateur? Very good for this sort of question. On the other hand, do you really have 5 inches from eyepiece to film? That's a pretty long projection path! Anyway, (page 77 of the 3rd edition) magnification = (s2 - F2)/F2, where s2 is eyepiece to film distance and F2 is the eyepiece focal length in the same units. So mag is about 5 for your system and on an f10 scope, you end up with f10 x 5 or f50. As you discovered, it's MUCH too slow for anything other than the moon or a bright planet. For the Crab, try prime focus at f10 on fine grain film (eg, E200) for 60 minutes, and enlarge. You may have to take several shots and stack to get rid of the grain if you want to enlarge a lot, but it's a lot more practical than a 60 hour exposure!
Hope this helps...
Bert
 
Bert Katzung
katzung1@home.com
www.astronomy-images.com
 
----- Original Message -----
From: Saint Machiavelli
To: astro-photo@seds.org
Sent: Monday, 19 February, 2001 8:01 AM
Subject: RE: [APML] 'Astrophoto Program'

I sent a copy to you, including the vbrun300.dll that Scott Barbee sent me last night.
I do have one question about it though. This is for anyone who has played with eyepiece projection photography.
According to this program using a Meade 8" SCT in eyepiece projection mode with a TeleVue Plossl 21mm, the film plane 5' I have an f/stop of f/50.5 and an exposure time of 60 hours to photograph the M1 Crab Nebula on Kodak 400 PPF with the milky way slightly visible.

I think I've drastically missed something in my research on eyepiece projection photography, as I have never had any indication that it would require such an f/stop or take so long.

On the other hand the program has already cleared up some of my calculations on Prime Focus, which helps to explain why my first set of deep sky photo's Triangulum galaxy (M33) came out like they did, all faded and dark.