Re: Optical COmms experiment

From: Tony Beresford (
Date: Sat Apr 28 2001 - 23:02:11 PDT

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    The following reply has been sent to regarding the brightness of a 3 watt lamp
    Bob, your query about the apparent magnitude of a 3 watt
    lamp was reposted on the Seesat mailing list by one of the
    subscribers. As a Life member of Amsat I feel I should have
    a try, particularly as I dont contribute much these days.
    The illumination of your "radiator" is crudely about
    5E-11 Lux, at a range of 800Km(500 miles). This assumes that the
    efficiency is 5 percent in converting to light. So one ends up with
    0.15 watts of light which is about 100 lumens. I also
    assume this energy is spread out over a quarter of the
    possible solid angle of a sphere radius 800Km
    Since a magnitude zero star provided an illumination
    of 2.5E-6 Lux, The lamp would be 5E+4 fainter , or at about
    mag 12.8
    Tony Beresford  FRAS, FBIS
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