I found the article, "Sensitivity of the Eye to Spectral Radiation at
Scotopic and Mesopic Intensity Levels," (1955) by Jo Ann Smith Kinney
in my files. Kinney measured spectral sensitivity curves for five test
subjects under a range of mesopic ligthing conditions; from 1.9 to 3.4
log units above the threshold for scotopic vision. reports that the
peak sensitivity of her subjects under mesopic conditions (up to 3.5
log units above scotopic light levels) is nearly identical to their
peak sensitivity under scotopic conditions: 510 nm.

As conditions brightened, test subjects first demonstrated improved
sensitivity in longer wavelengths while still exhibiting a peak
sensitivity to light at 510 nm. At 3.4 log units above scotopic
threshold level, test subjects reported seeing colors such as "pale
blue" and "greenish." Four of the five subjects were between the ages
of 26 and 30. The fifth was a 60 year-old male. He demonstrated less
sensitivity to short wavelengths, which Kinney characterized as,
"consistent with the evidence on the increasing yellow pigmentation of
the lens of the lens of the eye with increasing age."

Bill in Flag

--- In amastro@yahoogroups.com, "Nils Olof Carlin"
<nilsolof.carlin@...> wrote:
>
> Bill in Flag wrote:
>
> >
> > Since naked eye observing is mesopic rather than scotopic, wouldn't
> > that tend to negate the need to determine scotopic mags...at least, in
> > the context of this discussion?
>
> As long as we consider averted vision (which we use under dark skies,
> particularly when trying to detect the faint objects of this
discussion -
> the Blackwell paper comes up with a breakpoint at some 19.2
magnitudes per
> square arcsecond), detection (if any) depends essentially only on
the light
> sensitivity of the rods, so scotopic magnitudes should come into it
(can
> mesopic magnitudes even be defined?).
>
> As for conversions from known standard measured magnitudes to
photopic or
> scotopic magnitudes, this website by Arne Henden might give good help:
>
> http://www.tass-survey.org/richmond/answers/eye.html
>
> Nils Olof
>