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Tropical LMs? (was Re: (meteorobs) Re: Zodiacal light)
Jim Bedient wrote:
>It seems darker on a truly transparent night from the northern latitudes.
>These are just my opinions and impressions.
I've noticed this frequently before, too, Jim: since LMs are not uniformly
better up here (in fact, for me stuck in the Northeast, they are uniformly
WORSE than the darker sites in HI and Southern FL!), I'd always attributed
this to the paradoxic effect of skyglow...
Basically, the more TRANSPARENT the sky - and the better adjusted you can
get your eyes - the more apparent the natural skyglow of the Earth's atmo-
sphere becomes, and so the BRIGHTER the sky appears... Naturally, this is
only when comparing the very, very DARKEST sites with sites which are just
slightly less dark: from most locations within a couple hours drive of any
medium-sized city, "skyglow" is far outweighted by ambient light pollution!
However, I wonder if there may be other effects at work as well? In parti-
cular, I wonder if true Tropical observing (i.e., from Hawai'i but not FL)
may subject the observer to MORE skyglow, or different patterns of airflow,
moisture content, etc., such that contrasts really are worse, on average?
If so, though, you would think this would show up at least to SOME extent
in Limiting Magnitude numbers, too - even if not as noticeably...
Jim, how do your LMs from Haleakala and Mauna Kea compare with those you
were used to recording from the very darkest sites on the mainland before?
Lew Gramer
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