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Re: (meteorobs) Photographic Meteor Rates (Reply)
For amateurs interested in Meteor Photography, let me refer you to the
following:
Meteor Photography - by Peter M. Millman
Amateur Telescope Making - Book Two (1954)
Scientific American
This paper is somewhat dated but it contains alot of useful
information regarding direct, and objective prism spectroscopy of meteors.
Today, objective transmission gratings are much prefered over objective
prisms but the latter should still be used if that is all you have. For
best results the cameras should also be equipped with occultating or
interupting shutters in order to provide velocity info and persistant train
data. Attempts should also be made to do triangulations in order to provide
height data.
Another useful reference is:
Chapter 21 - Titled: METEORS - by P.M. Millman & D.W.R. McKinley
contained in: The MOON METEORITES and COMETS (1963)
edited by: B.M. Middlehurst & G.P. Kuiper
Book 1V in the series - The Solar System
Millman classifies cameras used in meteor programs as follows:
Type A: Conventional lenses - F-4.0 to F-8.0 - focal length 100-500mm
Type B: Conventional lenses - F-l.0 to F-3.5 - focal length 50-200mm
Type C: Baker Super Schmidt Meteor Cameras - F-0.65 focal length 200mm
These cameras have average efficiencies of: A:B:C: - 1:5:200. That is to
say, if camera "A" photographs one meteor, camera "B" should record five,
and camera "C" two hundred. With the camera "A" catagory, Millman reported
securing one photograph per 100 hours of exposure time. This is of course
increased if you photograph during peak shower periods. Professor John A
Russell reported,that the spectrograph that he was using would record a
detectable spectra of a zero magnitude meteor. He was using an F-2.5 - 7
inch fl Kodak Aero Ektar with a 30 degree objective prism on Kodak Royal X
Pan 1250 ASA film. One could expect to go two magnitudes or so fainter with
a direct camera. Spectrographs are less efficient as the light of the
meteor is spread out into a spectrum. Camera efficiency is also dependent
on the velocity of the meteor. You will reach fainter magnitude meteors, if
it's angular velocity is slow rather than swift.
-----------------------------------------------------------------
Edward Majden epmajden@mars.ark.com
1491 Burgess Road Meteor Spectroscopy
Courtenay, B.C. CCD's - P.E.P.
CANADA V9N-5R8 Amateur Astronomy