[APML] Supra 400 Reciprocity

["Steve Lindsey" <stevelindsey@earthlink.net>]

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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