Re: [APML] New North American Nebula

["aljordan@gwi.net" <aljordan@gwi.net>]

Hi Alan,

>From what most people who use the IDAS filter have said, an exposure
increase of 1.6 times the original exposure is a pretty useful number for
emission nebula.  I took a sixty minute shot of the Pelican nebula with the
filter and 400 speed negative film at F6.  The shot was a bit under
exposed.  However, a 90 minute shot really brought out the nebulousity well
without bringing any sky fog.  A 60 minute shot on 400 speed film without
the filter would have lost the nebulousity in sky fog at my location, and
would have been very difficult to process.

Note that number is for emmision nebula.  I tried shooting galaxies with
the filter and found that I would need to go for two or three times the
exposure length so I am not sure if the filter would benefit galaxies
without more experimentation.

Alan

Original Message:
-----------------
From: Alan Voetsch critter12952@yahoo.com
Date: Sat, 7 Sep 2002 16:01:13 -0700 (PDT)
To: astro-photo@seds.org
Subject: Re: [APML] New North American Nebula


--- Alan Brent Jordan <aljordan@gwi.net> wrote:
>This is the first
> nebula shot I have
> taken using a Hutech IDAS LPS filter. 

Hey Alan,

Great shot of the NA Nebula.
I've been considering adding a light pollution filter
to the optical train on my TV-85. I'm wondering though
how much light fall off is there due to the filter,
or, in other words, how much did you increase the
exposure time? 

Alan

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