RE: [APML] Tech Pan/Ha filter focusing

["Scott Hammonds" <capella@creatorsview.com>]

John,
Thanks for the updated link. I'm reconsidering now, especially based on
the length of the exposure. I've got to have some clear weather before I
can do anything! Based on the latest sat image it doesn't look like
there are many clear spots.

Scott Hammonds

 

-----Original Message-----
From: astro-photo-bounces@seds.org [mailto:astro-photo-bounces@seds.org]
On Behalf Of John C. Mirtle
Sent: Wednesday, June 04, 2003 8:48 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] Tech Pan/Ha filter focusing

----- Original Message -----
From: "Jim Janusz" <jjanusz@dc.rr.com>


<- snip ->
some type of scale on the instrument.  See John Mirtle's page for a
great
article on this.

http://members.shaw.ca/jmirtle/ha.htm?

Thanks for the plug Jim! Due to deluges of SPAM I am changing url's and
mail
accounts right now. The H-alpha article is now at
http://members.shaw.ca/astrophoto/ha.htm I don't know how much this will
help you Scott, it's a very different animal when you put the filter
INSIDE
the optical path, especially with a refractive system. I would think
that
some kind of graduated scale might do the job, but you will probably
have to
calibrate it against temperature with the longer tube.

John Mirtle
Calgary, Ab. Canada

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