Satellites eclipsed on 11 Aug

Matson, Robert (
Mon, 2 Aug 1999 15:35:55 -0700

Hi All,

I agree with Rainer that when precious totality lasts just over
2 minutes, satellite-watching is not going to be on my agenda.
However, for those not fortunate enough to be able to travel
to Europe for the eclipse, a few satellites will offer them an
opportunity to indirectly observe the eclipse in a unique
way.  Anyone living in the eastern U.S., from New York City
to northern Florida, and as far west as perhaps Mississippi to
western Pennsylvania will have an opportunity to see as many as
10 or more satellites become more than 90% eclipsed.  The best
eclipse candidates for eastcoasters that I've found so far are:

#01843 Cosmos 100
#10531 Cosmos 970
#11321 Cosmos 1091 R/B
#11601 Cosmos 1143 R/B
#12987 Cosmos 1328
#14208 Cosmos 1484 R/B
#14680 Cosmos 1535 R/B
#18958 Cosmos 1933
#22788 UFO 2 R/B(1)
#24837 Iridium 12
#25530 Iridium 84

Of these, Cosmos 1143 R/B is probably the best performer.  From
Atlanta, for instance, it will get as bright as +5.6 before
entering the penumbra and getting as dim as +7.5.  It will then
brighten again to +5.8.  Cosmos 1535 R/B is dimmer, reaching a
peak brightness of only +7.6; but it enters very deep penumbra
and drops more than 4 visual magnitudes to +11.8 before brightening
again to +9.0 on the other side.

Cosmos 100 has the steepest drop off in brightness that I've
been able to find.  It goes from +6.5 to +14.7 and back to +10.9.

But for some lucky people, Iridium 12 will be the star performer --
its left MMA is going to "beam" the eclipse right down to them!
Atlanta is supposed to have a -8.3 flare from Iridium 12 at
5:28:03 am EDT.  But Iridium 12 will be more than 92% eclipsed
at that time; this greatly complicates the prediction of what
people will see.  Some will be completely robbed of the glint
because the MMA (from their vantage point) will sweep across
a portion of the sun blocked by the moon.  Others will see a
flare, but it will be faster and dimmer than usual.  But some
people will see a double flare (!) -- one for each side of the
crescent sun.

It occurs to me that if ten or more people spaced themselves
out equally along a 10-km east-west line (with its center at
a maximum predicted flare point), and each photographed the
flare at the same magnification (say, with a 200mm lens), if
you then superimposed the images you'd have a raster scan of
the eclipse!  This experiment is possible for anyone along a
line from Atlanta to Tallahassee, Florida (Tallahassee is
also on the flare centerline).

Iridium 84 will also pass through the lunar penumbra, but
because it's a spare, it isn't a reliable glinter.  --Rob