(PrisNo6) wrote in message . com...

Good point. I had always assumed that light pollution was bluer. I've
never heard of any studies on whether urban light pollution scatters a
reddened or bluer light. If it is reddened, then that would tend to
wash-out the increased ability of the human eye to see fainter
reddened stars, as compared to Johnson V magnitudes.

Maybe, maybe not. When viewed at moderate exit pupils (3mm and lower)
in a telescope, the light pollution in my area is attenuated well
below the level of color vision. Even naked-eye, I don't see color
in the light pollution anywhere from the zenith down to about altitude
45 degrees on a half-decent night. And skyglow from the Moon seems to
be *just* below the threshhold of color vision except right around
the Moon itself. So it is not obvious that color matters after all.

What you can split depends on aperature, magnification and _the
relative magnitude of the bright and dim star._ I have a citation I'll
dig up on this. The relative magnitude of the stars makes for a really
pronounced effect, angular separation being equal.

There was a fine pair of articles exploring this in the Jan 2002 issue
of Sky&Telescope.

My own experience is that the limiting magnitude
estimation with a hand-held binocular, including a small 8x40 bino, is
pretty much impossible and leads to collection of measurements that
that such a large variance that they are not useable.

You're probably right; binocular shake is just too big a factor, and
too hard to control and/or quantify. Owning a pair of image-stabilized
binoculars really brings that home; it is perpetually amazing to see
how many stars snap into existence when I press the IS button.

However, this raises the question of why you are interested in
limiting-magnitude studies in the first place. Is it to measure
the skies, the instrument, the observer, or all three?

- Tony Flanders