Has anyone considered the fact that from the Antenna site or any site to the west will now have the glow from Phoenix to the east now instead of north ? The early object risers may be in the glow and may not be able to be seen. Since the surface brightness is measured in mag/sq arc sec will there still be enough darkness for these objects to rise above the glow ? Since this is in Tom's expertise maybe he can figure out what we should expect. Ken Sikes ----- Original Message ----- From: "Tom Polakis" <tpolakis@xxxxxxx> To: <sac-board@xxxxxxxxxxxxx> Sent: Tuesday, August 24, 2010 11:17 AM Subject: [sac-board] Messier Marathon Site Before we give up on the Antenna site in favor of a site with lower horizons, I wondered if anybody has measured the altitude and azimuth of the obstructing mountains, and compared this to where the low setters and risers are. Seems like the only directions that really matter are due west (M74 and M77) and east-southeast (M30). Perhaps to a lesser extent, it's nice to have a low northwest horizon to be able to pick up such objects as M33 and M31's satellites in the evening rather than the morning. By the way, on the morning of April 3, M30 will be pretty easy. So maybe all that matters is a low west horizon, which Antennas has. One illusion that is at least as strong as the "moon illusion" is that of mountains seeming to loom higher in altitude during the day than they really are. I have found that you can set up right next to a mountain -- as is the case at Antennas -- and it turns out to be only 5 degrees high. If I can show that the obstruction from the terrain around the Antennas site is being overestimated, would it still be under consideration as a Messier Marathon site? Before heading out to the site, I think I can take a shot at this with Google Earth and simple trigonometry. If it's out of the question for some other reason, however, I won't make any more effort. Thanks. Tom