Re: [APML] Supra 400 Reciprocity

[Mr chris schur <comets133@yahoo.com>]

Steve, your asking alot of any film to keep responding
past 90 minutes!  my experience is you should go about
an hour with any color film including Supra which I
shoot all the time.  The general rule is 2x the f
ratio squared for exposure time with a 400 speed film.
 Youll need to get that slow f ratio of yours down a
bit to more like f/8 or prefferably faster.

Chris
--- Steve Lindsey <stevelindsey@earthlink.net> wrote:
> I have been attempting some long focal length shots
> (f11 with my 10" SCT) on
> Supra 400 (old formula) for some smaller faint
> galaxies to get tighter stars
> than on slide film.  My goal has been to do 1 to 2
> 180 min shots on each
> object (preferrably 2 and stack).  The last couple
> of times out I keep
> getting cut off by wind, clouds or the mount running
> out of travel at about
> 100 to 120 minutes.  For object like M101 or M106 or
> M65/66 I don't pick up
> anywhere near enough detail to use for a decent
> image.  Is this just not
> long enough exposure at that FL or does Supra 400
> just run out of gas past
> about 60 to 90 min and maybe is better suited of
> shorter FL scopes?  I don't
> recall seeing really long exposures images on this
> film for comparison.
> 
> Steve
> 
> 
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