# Visible Tethers Question

Dave English (prospector@sd.znet.com)
Fri, 23 Oct 1998 08:24:04 -0700

```Thank you fellow members for your thoughts about why we can see a -3mm
thether at 120 miles (apx. 200 km).  I was surprised at the positive
responce so I calculated the area of a 12 mile long tether (apx 19 km)
at 2.6 mm (.10236 inch) tether.  It was a surprising 540.47 sq feet
or 50.2 sq. meters and though 12 miles long the eye would receive
low levels of light radiating from the white surface making it visible
at long distances that a short tether (10 feet) could never duplicate.

Following the discussion about area of light sources and reflectance
I will add this, the area of light received by the Earth from the
surface of the giant variable Betegeuse at maximum is 17 square feet
or 1.6 square meters.  This happens to be the same size of an Iridium
panel which is highly reflective and can achieve -8 magnitude but the
visual magnitude of Betegeuse is +.41, the ninth brightest star. The
absolute visual magnitude is -5.5   I used 750 diameters of the sun
for diameter of Betegeuse at maximum and 489 light years distance (it
varies from book to book). I included this information to illustrate
the problems we face in trying to determine brightness of objects
which can be influenced by numerous factors, but it's fun.

One reason I'm a member is so I can ask a question from time to time
about what I observe.  The other night there appeared to be a light
source turning an arc of about 320 degrees.  All I saw was the light
beam at right angles to me, that is, off in space.  Has anybody seen
something similar where a beam of light seems to be radiating from
satellites into space near the satellite?  I saw this once with an
Iridium satellite on a night where it was a lower magnitude, about a
-2, after it had passed by. The beam radiated out from the satellite