RE: [APML] IC 410 uploaded and IC 405 adjusted

["Greg Hartke" <ghartke@adelphia.net>]

Hi, Alan,

I'm sure a lot of people will notice this eventually: Nothing you do will
change the focal length of your refractor. It's not like an SCT where you
actually change the focal ratio when you change the primary-to-secondary
spacing. That's one of the (many) nice things about a refractor! So the
focal ratio may remain, though the T-stop may change depending on what might
be happening with vignetting. It's also worth mentioning that in essence the
T-stop might be considered to vary across the focal plane if there's
vignetting. Yuck!

Regards,

Greg

-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Alan Voetsch
Sent: Monday, November 01, 2004 9:44 PM
To: Discussion of Film Astrophotography
Subject: RE: [APML] IC 410 uploaded and IC 405 adjusted

(snip)

I did check today and there were no spiders, or beehives. I even pulled
my camera off and checked to see if the shutter was staying open. I did
a 5 second check, and it was. If it was partially closing during an
exposure, then that would show. So, that leaves the Taurus Tracker. It
may add to the focal length enough to slow me down to f/9. I have been
trying to look into another option that would allow me to reduce the
focal length, but so far no luck. My work schedule lately has been busy
enough to slow me down when it comes to things like that.

Again, thanks for your insights,
Alan

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