[guide-user] Interesting lunar eclipse simulation
James Ellis Jan 21, 2000
Hello all,
Given that there are two lunar eclipses visible this year, I decided to
have a look at the visibility situations of both of them.
Not from Earth, though, but from the far side of the moon looking back at
the point of maximum eclipse.
It is an interesting, illustrative simulation to help in describing
eclipses to non astronomers or beginners.
I set my altitude at 1450000km for both eclipses, which is just about the
place where the Earth's shadows cone comes to a point and creates a nice
annular eclipse.
For the 21/1/2000 eclipse I set the lat to N20.055 and long to W70.978 and
the time to 04:55UT (mid eclipse).
For the 16/7/2000 eclipse I set the lat to S21.25 and long to E152.775 and
the time to 13:55UT (again mid-eclipse).
Then GOTO Earth..
Notice a couple things : 1. the July eclipse has the moon near the central
part of the shadow - actually very very close and 2. the ring of sunlight
around the Earth is about 30"wide.
The January eclipse has the moon off centre towards the south and the ring
of sunlight around the earth is about 60" wide (the difference being
because the earth is farther from the sun in July).
Turn your monitor brightness up if the disks are dark.
Bill : this might be an interesting pic for an ad??
I found this an interesting exercise to do and only wish I could have done
it in my high school science class 10 years ago!
Hope everybody had a good eclipse last night and I'm looking forward to
ours in July...
Cheers
James
PS Two problems I had with this, though - when I was refining my lat and
long the altitude kept resetting itself to 0AU or 1500km instead of
1500000km and my graphics prog couldn't open the bmp files I created.
"An elephant : a mouse built to government specifications"