----- Original Message ----- From: "Greg D." ko6th_greg@hotmail.com To: amsat-bb@amsat.org Sent: Sunday, April 25, 2010 8:34 PM Subject: [amsat-bb] Hitting a southbound Moon

Hi folks,

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, being 90.

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?

Greg KO6TH

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.

73" de

i8CVS Domenico