[APML]: Visual magnitude

[Alfredo Zanazzo <alferd@mbox.lol.it>]

I read often on this list reports of succesful (or unsuccessful) nights
with indication of what the visual magnitude was.
Personally I think that is rather difficult to establish exactely this
value as everybody has a different capacity of detecting faint stars.
I was considering the lower part of Cepheus rhombus as a test, asking
the visitors of my observatory to count the stars in it. as I had read
in an article that 14-15 stars mean a magnitude superior to 6th.
Well, once one of these friends who does not know anything about 
astronomy, replied to me surprised: "how could I count all those dozens
of stars that I see?".
I got a low power binocular and made a control: incredibly he was able
to see exactely the same as me using a 2,5X galileian!
Another article on Astronomy magazine mentioned that with magnitude 6
you can not spot clouds.
I hardly believe it as I was seeing the clouds during nights in which
you could count 9 Pleiads stars.
In 1987 I spent a week at Mira Observatory in Carmel Valley,famous for
a beautiful dark sky.
With no hints of human sign at 360 degrees of horizon I could see a lot
of stars and a heart-breaking Sagittarius but the sky was not very dark!
With my surprise my host Mike Simmons told me that above 6 magnitude
the sky becomes brighter due to the stars light!!
The result is that I dont' know yet after years the maximum visual 
magnitude
of my site (600 meter only above sea level)!
I would like to know some opinions about the subject.
Alfredo
-- 

--
Regards, Alfredo Zanazzo ( alferd@mbox.lol.it )

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