RE: [APML] M33 TV-85, ST2000XM

["Paul Hunsberger" <atillahuns@cinci.rr.com>]

The ST2000 is a strange bird compared to the rest of the ST line.  It is
about 1.5 times less sensitive in the red than it is in blue and green.  I
did a little quick and dirty about 3 months ago with overlaying the QE curve
on the filter curves, and found that the ratio is about 1.6:.95:1 in Red,
Green, Blue (I use 1.5:1:1 for simplicity).

Regards,

Paul

-----Original Message-----
From: astro-photo-bounces@seds.org
[mailto:astro-photo-bounces@seds.org]On Behalf Of Bert Katzung
Sent: Monday, September 22, 2003 7:51 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] M33 TV-85, ST2000XM


Hi Dave:
With this ratio of exposures, I would have thought you would need something
like 1:1:1 weighting but not 0.1:1:whatever in blue. At least for my ST-10,
I would probably have to use 0.8:1:1.1 (or something like that). Is it
possible that what you stored as red was actually taken through a clear
filter? Or maybe there is something wrong with your copy of MaxIm. Could you
post your individual R, G, and B frames? Reduce the size/resolution so it
doesn't take forever to download. Maybe e-mail directly to me (or let me
know by direct e-mail when you have posted them) so we don't take up
bandwidth on this film list.
Bert

Bert Katzung
katzung1@comcast.net
www.astronomy-images.com

----- Original Message -----
From: "Dave Manifold" <dave@davidmanifold.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Monday, September 22, 2003 4:03 PM
Subject: Re: [APML] M33 TV-85, ST2000XM


> Hi Bert,
>     On past color combines, I use something very close to what you are
> saying.  But, the images that were stacked were:
> L 180 minutes ( 18 x 10 minutes)
> Red 70 minutes  ( 7 x 10 minutes)
> Green 40 minutes  ( 4 x 10 minutes)
> Blue 60 minutes  ( 6 x 10 minutes)
> Maybe because the red exposure was the longest of the colors is why I had
to
> combine with such a low ratio for red?
>
> Dave...
>
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> Astro-Photo@seds.org
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