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RE: [APML] IC1396 in Ha /Tech Pan
If my memory serves me (sometimes is doesn't), there was a section in
Wallis and Provin's book that had a 6 hour Tech Pan image taken with a
Celestron 14 and a homemade autoguider. I forget the name of the author,
but the article is in the back of the book. Just look for the section on
autoguiders in the table of contents.
Ken
-----Original Message-----
From: John C. Mirtle [mailto:spampit@shaw.ca]
Sent: Wednesday, September 24, 2003 6:15 PM
To: Discussion of Film Astrophotography
Subject: Re: [APML] IC1396 in Ha /Tech Pan
Jim,
Stacking vs. long exposures I would think would be determined by
background density. I wouldn't try 2-3 hours from in town, but it
shouldn't
be a problem from a dark site. If I can shoot 45 minutes at f1.5, that
works
out to 3 hours at f3 - assuming no reciprocity failure.
I have shot TP in the 2-3 hour range many times. Two examples are
http://members.shaw.ca/jmirtle/pickering.htm and
http://members.shaw.ca/jmirtle/m33-crop.htm . I have compared the 2
hours
on M33 with a 1 hour and a 90 minute exposure and there is no question -
the
2 hour shot recorded more "stuff" and recorded a better limiting
magnitude.
As I recall, Chuck Vaughn shoots his tri-colour blue and green images
for 3
hours. I have heard of people shooting up to 5 hours with tech pan, but
I
cannot remember who/what/where or when.
You should be able to shoot through 90 minutes without any trouble
at
all. Unless you are shooting through filters, it's hard to say if you
really
need to. What would be interesting would be seeing Scott's results
through a
10nm or 3nm H-alpha filter. I don't know if anyone has ever done this
with
film, but it would really reject light pollution! This works for CCD's
but
may not for film. If the passband frequency changes as you get off-axis,
then when you get to the edges of a piece of film, the filter might
actually
reject H-alpha.....
John Mirtle
Calgary, Ab. Canada
----- Original Message -----
From: "Jim Janusz" <jjanusz@dc.rr.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, September 24, 2003 3:46 PM
Subject: Re: [APML] IC1396 in Ha /Tech Pan
Hi John,
Interesting, at 2 to 3 hours don't you think reciprocity will set in?
I've
never shot TP past 90 minutes. Maybe Scott should stack two or three
shots
rather than go that long?
Jim
----- Original Message -----
From: "John C. Mirtle" <spampit@shaw.ca>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, September 24, 2003 2:10 PM
Subject: Re: [APML] IC1396 in Ha /Tech Pan
> Scott,
> Looking pretty good for your second tech pan image! It looks like
your
> lens has a "hot spot", probably exaggerated by the light pollution you
are
> shooting through. The bright patch just to the right of 1396 shouldn't
be
> there. You might have to do some Photoshop jiggery pokery on your
images
> from town to reduce this. For comparison, have a peek at
> http://members.shaw.ca/astrophoto/files/ic1396bw.jpg done with a 180mm
f2.8,
> H-alpha and 60 minutes. It was shot from a mountain top 10 hours west
of
> here back in 1991, it does not have the brightening your image does.
> Exposure time varies so much, depending on sky brightness, how
effective
> the hyper is, development time, etc. I haven't shot through a
> telephoto/H-alpha combo for a while, but have been meaning to. I would
> probably start at 2 hours @f2.8, possibly 3. With my Schmidt @ f1.5
and a
> W92, I usually go for 45 minutes. But this is under good skies, as
long as
> the aurora isn't active. If your scanner can't pull out an image, then
you
> have probably gone too long. :-) It's hard to tell from this end if
you
can
> shoot longer. The background density caused by light pollution will be
your
> limit. If the background is pretty thin, then shoot longer. If you
have to
> hold it up to a mag -26 light source to see anything, then back it off
a
> bit.
>
> John Mirtle
> Calgary, Ab. Canada
> http://members.shaw.ca/jmirtle
>
> ----- Original Message -----
> From: "Scott Hammonds" <shammonds@creatorsview.com>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Wednesday, September 24, 2003 2:20 PM
> Subject: [APML] IC1396 in Ha /Tech Pan
>
>
> Hi List,
> This is my second reasonably successful Tech Pan image. I am still
> experimenting with processing these black and white images and I would
> appreciate comments and criticisms.
> I managed to get 2 shots last night before I needed sleep after
> returning from the Braves game, I'll try and post the other one later.
> http://www.creatorsview.com/pages/techpan.html
>
> Based on what you see from my images, do you think I should expose
> longer than the 50 minutes I have been using so far? Those of you
> shooting tech pan please let me know what you are using for exposure
> lengths.
>
> Thanks,
>
>
>
> Scott Hammonds
>
>
>
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