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Re: (meteorobs) More on LM estimates and sources of error in ZHRs
Have you allowed for the Atmospheric extinction ?
I seem to remember that compared to looking vertically from a high mountain
when looking at 60 deg at sea level only about 25 % of the light makes it
through the atmosphere. I don't have tables of atmospheric extinction to
hand - has anone got some more detailed information to confirm or deny this
?
John Murrell
Message text written by INTERNET:meteorobs@jovian.com
>Lew Gramer wrote:
> Second, the old presumption of 6.5 being a hard physical limitation of
the human
> eye has long ago been disproved: there are double-blind trials done in
the past
> 20 years which have convincingly recorded human faint-star perceptions
down to
> *MAGNITUDE 8.9*! (Refer to experiments publicized by Stephen James
O'Meara, Fred
> Schaaf and others in Sky & Telescope.)
I would like to review these experimental results. How can I obtain
these reports? Do you have copies you can forward to me, or direct me to
a website?
The 8.9 seems unreasonable to me. I feel it must be an unusual case, a
"5 standard deviation" of too small a data set?
I recall, from my early biology classes, that the human dark-adapted
retinal rod cells, are extremely efficient in responding to just a few
photons to yield a detectable response. If the average rod cells, at
their limit, respond to a few photons at mag 6.5, how can a rod cell
respond to 1/9 as many photons (which is the luminosity ratio for the
8.9-6.5 = 2.4 mag difference here) , because that many photons just are
not going to be there ?
The only other factor is the diameter of the pupil, but for a factor of
9 increase in light gathering ability, that person would have had to
have a pupil diameter of sqr(9) * 7mm = 21mm! Maybe ET, but not a human!
Mike Linnolt<
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