Re: [APML] Speeding up film with cold weather

["westergren" <westergren@netzero.net>]

Alan and Jerry,

Supra400 unhypered keeps going and going and ...

My film tests of Supra400 show that most of the reciprocity loss occurs in
the first 17 minutes to 1 hour.  After that, the film has little more
reciprocity loss out to 2 hours-16 minutes tested unhypered, and out to 4
hours-33 minutes tested hypered.  My tests of unhypered were done before I
got the last ND filter that allow me to test to 273 minutes.

Here are some numbers.  I measured the Schwarzchild Exponents for red, green
and blue.  They all follow the same pattern.
Exposure           Schwarzchild Exponent
1 sec                   1.00      1.00       1.00   RGB
256 sec(4.3 min)   .91       .95          .84
1024 sec(17min)   .84       .87          .79
4096 sec(68min)   .78       .78          .79
8192 sec(136min)  .76      .74          .74

Descriptions of the equations for Schwarzchild Exponent are in both Robert
Reese's and Michael Covington's books.

Don

----- Original Message -----
From: "Alan Voetsch" <critter12952@yahoo.com>



> Hi Jerry,
>
> --- Jerry Lodriguss <jml@astropix.com> wrote:
>
> > >My results so far show that Supra recorded well
> > over
> > >twice as much light in a 330 minute exposure as it
> > did
> > >in a 140 minute exposure. This film is a slow, but
> > >steady collector of light.
> >
> >
> > How did you measure twice as much light?
>
> I don't have a way to measure it. The prints show it
> and after looking at the negatives just now, they not
> only show more nebulosity, but many more stars as
> well.
>
> > >That really surprised me, as I assumed 150-180
> > minutes
> > >would be my upper limit. I can occaisonally see 5.6
> > >magnitude stars here, but I'm 50 years old. I'd
> > guess
> > >6.0+ would not be out of the question for younger
> > >eyes.
> >
> >  From the darkest site, 60 to 90 minutes at f/8
> > would be about max, and
> > that's only 120 to 180 minutes minutes at f/11, and
> > you are at f/10.
>
> I can't explain it, I ain't a genious. :-) The facts
> show that I can keep soaking up light for at least 5
> 1/2 hours.
>
>  > Perhaps the T/stop of your scope is much slower
> than
> > the f/stop. Maybe you
> > are closer to T/16.
>
> Would you have any idea how I could figure that out?
>
> > Of course, you can also go past the skyfog limit and
> > keep building density
> > in the film, but loosing faint stuff also.
>
> That doesn't appear to be the case.
>
> > Five and a half hours and 400 ISO film with good
> > reciprocity failure at
> > f/10 is just causing a mental disconnect on my part.
>
> Sorry, but maybe it's the film. I've been using it for
> 3 years now. It starts out more slowly than other
> films I compared it to (Fuji 800 and LE400). Way
> slower. But it never slows down, You keep getting
> these incremental increases in light gathering that
> match the exposure time. I expected it to drop off
> after a couple of hours, but it doesn't.
>
> Sorry I was slow responding, but it took me all day to
> get around to going through my negative box.
>
> Alan
>
> __________________________________________________
> Do you Yahoo!?
> HotJobs - Search new jobs daily now
> http://hotjobs.yahoo.com/
>
> --  APML Archives at <http://astro.umsystem.edu/apml/>  ---
>              Unsubscribe at <majordomo@seds.org>
>
>



--  APML Archives at <http://astro.umsystem.edu/apml/>  ---
             Unsubscribe at <majordomo@seds.org>