[APML] Cosmic ray hits on film (was: To freeze, or not)

[Philip Perkins <philip@astrocruise.com>]

Thanks to Joe and Greg for the very interesting links and discussion.  I 
thought it was interesting how some films responded differently to others 
in space, also that Kodak made a film specially to record cosmic rays.

Roland, thanks also for your insight.  So it seems that normal film should 
record cosmic rays, but all I can say is that in more than 4 years of 
astrophotography I have never seen any sign of cosmic ray hits.  And this 
is not the result from any casual check, because over these 4 years I have 
meticulously inspected all of my blank (unexposed) film strips after 
processing.  The reason for this was to check for hyper density, evenness 
of hypering and evenness of development.  If I saw any marks or suspect 
areas I inspected them with a 10x loupe.  I still have most of these strips 
catalogued in an album.

Whereas after starting CCD imaging I recorded two cosmic hits during my 
very first sequence of images.  The marks they leave are very distinct, 
though I did not realise what they were at first.

Does anyone else think they have recorded cosmic hits on film?  I think 
that any such reports would be most convincing if they were on unexposed 
portions of film, for two reasons:
a)  A 'hit' on an unexposed film portion would most likely identify it as a 
true hit, whereas in an exposed frame it could be difficult to distinguish 
it from all the other "stellar anomalies" that we know occur in exposed 
frames.  Even short meteor streaks could look like cosmic hits.
b)  Unexposed film is far more likely to record cosmic hits because (in the 
case of most astrophotgraphy) there is far more of it than exposed 
film!  In my case some 90% of the film is usually unexposed.

It is possible that some film records cosmic ray hits more readily than 
others - Tech Pan for example?

Thanks
--Philip


>Film will record them.  Under normal incidence in an old-style film
>detector, they will leave point-like marks.  Sitting in your fridge in
>the canister in a random orientation....they could leave just about
>any kind of mark at all.
>
>The muon flux at sea-level is remarkably high; it is about 1 muon per
>square centimeter per second.  They are energetic enough to penetrate
>right through the house and into that basement fridge, unless you
>happen to live in a very deep hole (oh, say about 5-10 meters below
>ground with rock fill over the hole).  The amount of energy they
>deposit in the film is small, but over time I can see how it might
>degrade the film.
>
>regards,
>
>roland
>- --
>                        PGP Key ID: 66 BC 3B CD
>Roland B. Roberts, PhD                             RL Enterprises
>roland@rlenter.com                            6818 Madeline Court
>roland@astrofoto.org                           Brooklyn, NY 11220


Philip Perkins - philip@astrocruise.com
Wiltshire UK & Luberon France
Astrocruise - http://www.astrocruise.com

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