----- Original Message -----
From: "Greg D." <ko6th_greg(a)hotmail.com>
Sent: Sunday, April 25, 2010 8:34 PM
Subject: [amsat-bb] Hitting a southbound Moon
Now that the Arecibo event is behind us, there is still one puzzle that
I'd like someone to explain to me. How do I aim at the Moon?
I'm on the US West Coast. Early in the pass on Saturday, both Predict and
Orbitron told me that the Moon's azimuth from here should be slightly
north of east. It was in the 80-ish degree range, with east, of course,
But looking at Orbitron's map display, the Moon was clearly south of my
latitude. As the pass progressed, the >Moon moved westward on the map,
making a sharper angle to the south of east from here. Both Predict and
Orbitron's Az calculation increased too (eventually crossing 90 degrees),
but always seemed to be north of where >the Moon was.
Why would I aim north to hit a southbound Moon?
Hi Greg, KO6TH
It was only the Sub Satellite Point SSP of the Moon south of your latitude
on the earth surface i.e. the map display but the Moon as seen from your
locator was north of your latitude over the celestial sphere up in the sky
and this is why you aim north the antennas to hit the Moon even if her SSP
on the map has a southbound path.