[Laser] Re: Lunar Eclipse

[James Whitfield]

It has been interesting trying to follow the discussion.  There is a lot of
thought going into the synchronicity of the the power grid and delay time of
light from the limb of the Earth ( as seen from the Moon ) versus the point
on the Earth's surface along the line from the centers of the Earth and
Moon.

It seems to me that no one has considered the "wave shape" of the light
source.  There is talk of the 60 cycle power grid and three phases, which
results in a 360 Hertz pulse rate of the light.  Assume for the moment that
we only had to deal with Sodium Vapor lamps and only one time frame, that is
all of the lamps are equal distant from the Moon, which acts like a mirror
that returns all of the light pulses to the test sensor at the same time.

The Sodium Vapor Lamp, being a gas discharge type, will fire when the line
voltage reaches the trigger point ( Does anyone know what "angle" that is
from zero crossing of the power line? ) and will have its current limited by
a ballast of some sort.  Is the light output more or less constant until the
line voltage drops to the point that the gas discharge is quenched?  What is
the "angle of the quench?

I know that the assumption of constant light output for the duty cycle is
shakey at best, but if it were true and if we can assume the start angle is
about 75 degrees and further if the quench angle is about 60 degrees, then
what does that leave for the composite waveform of the light emitted from a
bank of lamps balanced on each of the three phases?    If I got my figures
right, the pulse starts at 75 and goes to 120, then the next starts at 135.
I think that gives 45 to 15 duty cycle or 75 percent on, 25 percent off.

I am not suggesting that this guess is valid.  But if it is "in the ball
park" ( to use the American idom from baseball ) it may be the effects are
as important as synchronicity and travel times from curved sources and
curved reflectors.  If you overlap the effects, it may be more difficult
than was prevously assumed.


James
 n5gui