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Re: [APML] Gamma-Cygnus Region and Perseid Meteor Fireball
>>>>> "Ray" == Ray Butler <ray.butler@nuigalway.ie> writes:
Ray> Interesting to see Tony Hallas' description of long term
Ray> radiation damage of the emulsion. I'd like to see a graph of
Ray> how fast this kills off a film, and how much it depends on the
Ray> nominal ISO speed. Film manufacturers must have conducted such
Ray> studies.
I've always been pretty skeptical of the cosmic ray theory. Yes, they
are coming in all the time. Most cosmic rays do not, of course, reach
the ground. Secondary products *do*. 22 years ago, as an undergrad at
MIT in physics, one lab exercise was measuring the time of flight of
muons. The muon source was cosmic rays. I doubt I have my lab notebook
anymore and if I do, I certainly have no clue where to find it or I
could tell you what the count rates where. (The point of the exercise
was to measure their speed by varying the separation between two
scintillators and measuring the change in the delay as a function of the
separation. You end up measuring it as a subtantial fraction of the
speed of light which is why the muons can survive the long trip down
from the upper atmosphere where they are produced).
It seems like we had this discussion a year or two ago and I vaguely
recall estimating a hit rate then.
As a quick sanity check, some films *do* store for much longer than
their nominal shelf life. That would indicate at a minimum that there
is more at work than just cosmic ray hits. If not, all films of a
particular speed and grain size should behave pretty much the same; at
least that's how I read the "receptor sites" logic.
regards,
roland
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Roland B. Roberts, PhD RL Enterprises
roland@rlenter.com 6818 Madeline Court
roland@astrofoto.org Brooklyn, NY 11220
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