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RE: (meteorobs) Scotopic vs. photopic visual magnitudes for star counts?



When you look at the "big pile" of meteor observations, as long as a 
particular observer is consistent in the way that they measure LM, it 
really doesn't make too much difference. Undoubtedly the precision of any 
individual measurement is low (i.e. not consistant within probably as much 
as a third magnitude) as long as an individual observer measures the LM the 
same way each time (let's say repeatabilty within 0.1 Mag), then a 
representative "observer profile" can be created, i.e., a detection rate 
based on an individual's "measured" LM. This is what ultimately allows 
worldwide observations to be combined. Once we've accurately figured out 
the correct standardization factors.
That is, in a nutshell, the art and science of reducing raw meteor 
observations to a standard platform for comination and comparison.

I would suggest that the LM tables are based purely on the most accurately 
measured (and estimated for visual mgnitude...there is always some residual 
error) start magnitudes contained within each LM polygon. It is at least as 
accurate as any other such star magnitude estimation method.

Wayne
----------
From: 	Lew Gramer[SMTP:dedalus@latrade.com]
Sent: 	Sunday, July 11, 1999 5:44 PM
To: 	Meteor Observing Mailing List
Cc: 	International Meteor Organization News; Internet Amateur Astronomers 
Catalog - Discussion
Subject: 	(meteorobs) Scotopic vs. photopic visual magnitudes for star 
counts?


In a thread this afternoon on the professional-amateur 'amastro' mailing
list, Brian Skiff and others discuss the difference in scotopic ("averted
vision") versus photopic ("direct vision") visual magnitudes. He cites a
recent paper which states that "dark adapted averted vision" should 
actually
respond to many stars (e.g., Vega) as though they were 0.15 magnitudes or
more brighter than they appear to dark adapted *direct* vision...

Obviously, visual star-counts are done using averted vision, and therefore
the extra-foveal ("scotopic") regions of the eyes. Have these photometric
studies in the "scotopic pass band" been taken into account in the IMO's
recently updated Limiting Magnitude conversion tables?

Clear skies!
Lew Gramer (GRALE)
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