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Re: (IAAC) Re: (meteorobs) LM Star Count vs Milky Way Perception



>>Anyone else with stories to tell (or maybe actual science to relate)
>about this
>>effect - either naked eye or at the eyepiece?
I am always wondering of where the LM estimates are coming from. For
myself, I used to estimate it with the classical S&T (and maybe IMO?) Ursa
Minor chart but I have recently updated this chart using Hipparchos data
(newer and better): this update is changing some magnitudes around Polaris
(between 0 and 0.3 mags).
I believe the discrepancies reported are (at least partly) explainable with
the various ways of estimating the LM; if a standard way of estimating it
was found, maybe it would reduce the data scattering which nevertheless
would still exist.
In fact, I agree with all, the phenomena has to be related to the point
source vs extended object opposition; it is logical to think that as the
night sky grows clearer, it is because of the atmosphere becoming heavier
(more oxygen and nitrogen molecules, more water and dust particules) and
thus reflecting more "pollution lights" and transmitting less "astronomical
lights". When the background sky grows brighter in this way, a comparison
star will keep a higher contrast (beeing stellar) than a nebulous object as
the Milky Way (beeing extended): the latter will mix up with the background
more "efficiently". Our brain will confuse more easily two nebulous
structures (fuzzy object in fuzzy background) than a star embedded in
nebulosity (crisp star in fuzzy background).
clear skies, Yann.
Yann Pothier	tel: 01 43 41 43 29
11 impasse Canart, 75012 PARIS, FRANCE
Email: ypothier@abi.snv.jussieu.fr
Site : http://pegase.unice.fr/~skylink/publi/cielextreme

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