Re: [APML] Back in the saddle...

["Stuart Heggie" <stuart.j.heggie@sympatico.ca>]

Dave - very nice indeed! A perfect way to return to the hobby!

Stuart
http://www3.sympatico.ca/stuart.j.heggie/Stuart.J.Heggie/
Flesherton, Ontario, Canada

----- Original Message -----
From: "Dave Cole" <dave@nexstar11.com>
To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
Sent: Wednesday, March 31, 2004 5:59 PM
Subject: [APML] Back in the saddle...


> I finally got my first film shot in 10 years posted...
> http://www.nexstar11.com/naneb1.shtml  Took it last season, and will
be
> doing more film work this season...
>
> Thanks,
> Dave
> For Nexstar GPS tips, tricks, and general information about the
NexstarGPS
> scopes visit http://www.nexstar11.com.
> For free astronomy software visit www.nexstar11.com, select
"Downloads".
> The UNOFFICIAL site for NexstarGPS information.
> All information is "In my opinion" and not to be taken as fact.
> Non illegitimi carborundum est. - Don't let the bastards grind you
down.
>
>
> ----- Original Message -----
> From: "Carlos Milovic F." <cmilovic@yahoo.es>
> To: "Discussion of Film Astrophotography" <astro-photo@seds.org>
> Sent: Wednesday, March 31, 2004 2:25 PM
> Subject: Re: [APML] stacking & adding film images
>
>
> > >      When you say "add" ... are you refering to
> > > actually adding the images
> > > together, as in a true stack, or are you averaging
> > > all the images together,
> > > as in a true average?
> >
> > Hi Tony
> >
> > Adding and averaging are stadistically the same thing
> > in terms of SNR. Averaging just rescales the result
> > and thus the differences in signal or noise values are
> > only a constant.
> >
> >
> > > Adding all the images together
> > > might have a problem
> > > with all the stars becoming completely saturated ...
> >
> > That is a problem with the "space" we are working.
> > Imagine that we have real numbers instead of integers
> > in the 0-255 or 0-2^16 range. Of course, when working
> > with "real" images (normal images) we are limited to
> > the bit deph, and thus averaging is the correct method
> > to combine the images if the sum of the images gives a
> > value grater than the upper limit.
> >
> > BTW, when you average a set of images in some bit
> > deph, you get a rounding error, and thus working in
> > the higher bit deph avalayble is always a good choise
> > to preserve the data.If you have no choise (for
> > example in a Photoshop earlier than CS), there are
> > some ways to avoid a little this problem and is just
> > to distribute the data in the whole dinamical range in
> > a better way before stacking. I think that Chuck has a
> > method that takes that into account (see Jerry's
> > page).
> >
> >
> >
> > =====
> > Regards,
> >
> > Carlos Milovic F.
> > -------------------------
> > Astro & Photo - CMF
> > http://www.astrophoto.vze.com
> > -------------------------
> > Visita "AstroFoto", el foro de astrofotografía en español
> > http://espanol.groups.yahoo.com/group/astrofoto
> >
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