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On 2018-06-09 0:45, Peter Monta wrote:
> Was this at visible wavelengths?  Would the astronauts
> have been able to see anything if they were told when to look?  Of course
> they had a lot to do besides gawk, but on the other hand that's an
> opportunity that doesn't come along every day, to see an artificial light
> source from Earth with the naked eye at lunar distance.

Apparently no reflection was truly detected at Lick Observatory until
August 1, though it was announced days earlier as the moonwalk came to a
close. I have a DVD with the whole moonwalk, and the announcement from
the "voice of Mission Control" is on the soundtrack. I don't know why it
was premature.

A 1969 article co-written by the chief scientist for the experiment is
online, but Science Magazine wants $30 to view it. I'm not that
interested! The abstract does have some useful information:

"On 1 August between 10:15 and 12:50 Universal Time, with the Lick
Observatory 120-inch (304-cm) telescope and a laser operating at 6943
angstroms, return signals from an optical retro-reflector array placed
on the moon by the Apollo 11 astronauts were successfully detected.
After the return signal was first detected it continued to appear with
the expected time delay for the remainder of the night. The observed
range is in excellent agreement with the predicted ephemeris.
Transmitting between 7 and 8 joules per pulse, we found that each return
signal averaged more than one photoelectron. This is in good agreement
with calculations of the expected signal strength."

http://science.sciencemag.org/content/166/3901/99

I think the stated wavelength is a deep red color. The spot size on the
Moon has been variously described as about 1 mile or 7 km. The pulses
were on the order of a nanosecond even back in the day, so I doubt they
would have been perceptible.

"Apollo 11 anniversary: Lick Observatory scientists recall landmark
experiment 40 years ago"
https://news.ucsc.edu/2009/07/3111.html

Unfortunately, I have not been able to locate the "first-person account
of the project" mentioned at the bottom of the above article. I did find
a 1971 Bendix Corporation familiarization manual for the laser ranging
retro-reflector. It contains a description and instructions for setup on
the Moon. On the last page is a diagram of the Sun compass and level
that was used to orient the device within 1 degree.


https://www.lpi.usra.edu/lunar/ALSEP/pdf/ALSEP%20%2323%20-%20LRRR%20Familiarization%20Manual_RevA_050171.pdf

This article shows Aldrin standing beside the seismic experiment (the
one with the troublesome ball bearing level). One of the NASA mission
review documents I saw online mentioned an ineffective leveling device
which needed investigation.

https://www.nist.gov/nist-time-capsule/any-object-any-need-call-nist/moon-and-back-25-seconds

   

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