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(meteorobs) FWD: Reciprocity failure and meteor photography




While I was away on my "Florida Vacation" (more details in another message!), I 
got the following interesting response to one of my posts to the Astro 
Photography Mailing List (APML), regarding meteor photography... Mike is a 
frequent poster to APML, and generally well-respected in astrophotog circles.

Thoughts?

Lew


------- Forwarded Message

From: Michael Covington <mcovingt@aisun1.ai.ugadot edu>
Subject: Re: [APML]: focusing aids
To: astro-photo@nightskydot com
Date: Thu, 8 Aug 1996 23:17:06 -0400 (EDT)

The Astro-Photography Mailing List
------------------------------------

> o certain highly "pushable" films give best results for longer exposures, eg,
>   Ilford HP5+ and TriX 400. The problem is that long-exposure (15-90 mins)
>   wide-field (5 to 20 degrees) work such as meteor photog often causes rapid
>   "failure" of faster films down to really low ASA ratings after a few secs.
>   Also problems with films "tiring" after a few minutes' wide-angle exposure.

Hmmm... Reciprocity failure is what you *want*, because you want the film to
get "tired" of the sky background but not the meteors.  Meteors are not
affected because they are brief, bright phenomena.

And those films (Tri-X Pan and HP5+) are indeed severely afflicted with
reciprocity failure.  T-Max films are less afflicted and would probably
fog up sooner while catching fewer meteors.


----
Michael A. Covington                http://www.ai.ugadot edu/faculty/covington/
Artificial Intelligence Center                                           <><
The University of Georgia                Unless specifically indicated, I am
Athens, GA 30602-7415 U.S.A.                not speaking for the University.

------- End of Forwarded Message