(IAAC) 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?
Lew Gramer (GRALE)
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