[Laser] photon flux for magnitude 6 stars

[F1AVYopto at aol.com]

29/03/2006 06:21:33
toasty256 at yahoo.com wrote:

[Since the human eye is close to 1 square centimeter in
area when  dark adapted, these photon counts seem
insanely high. Could this guy be using  the wrong
formula's or constants for this? or my poor math
skills may be  showing up. hi
mag. +6 = 
1.1 x 10E-10 watts/m2
or 
1.1 x 10E-14  watts/cm2 ]


Tim

I had started from this values: 
Sirius magnitude of  -1.4.
“Sirius-like star” shines 1.37 x 10E-7 W/m2 of energy on earth’s  surface.
I found with my calculations something like 9.10E-11 W/m² at  magnitude 6. 
(Very near your 1.1 x 10E-10 watts/m2 = 11 x 10E-11 watts/m2)
If  we assume that star light is monochromatic with a mean wavelength of 500 
nm or a  mean frequency of 6 x 10^14 Hz, at this energy, there are 2.5 x 10^18 
photons  per Joule. (Planck formula)
The average diameter of the pupil of an  acclimatized eye to the darkness is 
6 mm.  The surface of the opening is of  3.10-3 X 3.10-3 X 3,14 = 28.10E-6  m² 
so that gives 10000 photons / second  not so far your 28000 photons / second 
in a 1 cm² pupil. 
You see our results  are very the same.

73 Yves
http://pageperso.aol.fr/YvesF1AVY/UKINDEX.html