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RE: [APML]: Tri-Color Update

To: "'astro-photo@nightsky.com'" <astro-photo@nightsky.com>
Subject: RE: [APML]: Tri-Color Update
From: Matthew Considine <mconsidine@wesleyan.edu>
Date: Thu, 12 Feb 1998 15:41:44 -0500
Reply-To: astro-photo@nightsky.com
Sender: owner-astro-photo@nightsky.com


A listing of the filters available from Orion Telescope :

#8, #23A, #38A, #56, #80A, #58, #25, #15, #21, #47, #11, #82A

I have this set as an eyepiece-filter collection.

A while ago I called them and asked if they had an transmission data on
the filters, did they do any QA to figure out how close the filters were to
"spec" and who provided the glass.  The answers I got were respectively :
no, no (they just sorta eyeball 'em), and it depends on which Japanese,
Taiwanese or Korean manufacturer they happened to be contracting with
at the time (and no we won't tell you who they are ...)

Real reassuring, huh?

Regards,
MattC

-----Original Message-----
From:   Wil Milan [SMTP:wmilan@airdigital.com]
Sent:   Thursday, February 12, 1998 10:27 AM
To:     astro-photo@nightsky.com
Subject:        Re: [APML]: Tri-Color Update


Tom Krajci wrote:

> > I have noticed that the traditional green filter (#58) is not sensitive
> > to the OIII emission lines. Has anyone tried other filters to deal with
> > this? I would like to avoid using gels, and prefer glass filters.
>
> I've never done tri-color, but Wallis and Provin's book A Manual of
> Advanced Celestial Photography they discuss this problem and
> recommend some alternate filter combinations.

The problem is that the filter combination Wallis & Provin recommend --
Wratten 23A, 47, and 57B instead of the traditional 25, 47, 58 -- seem to be
no longer available. The 23A is hard to get, and I'm yet to find a source
which even lists the 57B. Anyone know where these can still be purchased,
either in glass or gel form?

Wil M.
--
"When I consider your heavens, the work of your fingers, the moon and the
stars which You have set in place, what is Man that you are mindful of him,
or the son of Man that you care for him?"  -- Psalm 8



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end

Follow-Ups:
- Re: [APML]: Tri-Color Update
  - From: Chuck Vaughn <aa6g@aa6g.org>

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