Re: [APML] tech pan revisited

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

Scott,

Looking at you picture of the CA nebula with the vertical lines in it shows
that the spacing between lines is variable.  So here are a couple questions
and comments.

1. Did the lines also show up on the rest of the leader rolled up in your
camera?
2. Does your camera reverse roll the leader (with the emulsion facing out)
or roll the film the same direction as in the cassette?
3. How old is the film and how was it stored before and after hypering?

What I'm guessing here is that the film emulsion is cracking by becoming
brittle when flexed during roll up on the camera spool.  I've never seen
this happen, so it's only a wild guess.  If this is the case, then it's
probably from aging of the film (another wild guess), and the solution would
be to try absolutly fresh film.  Maybe even try developing some unhypered
tech pan run through your camera to see if it's somehow the hypering
process.

I don't have the same cameras you do, but my Nikon F winds the film
reversed.  I have used hypered tech pan, hypered at 50°C for 96 hours after
vacuum at 28 in. Hg without this effect.  If Jim is using a hard (mili-torr)
vacumm, maybe the extreme drying out is causing brittleness.  It can't be
the temperature, since people all over the world are hypering it at 50°C.

I hope the cause can be found.  I'm really curious about what is going on.

Don


_______________________________________________
Astro-Photo mailing list
Astro-Photo@seds.org
http://seds.org/mailman/listinfo/astro-photo