Grazing occultation

by Rich Neuschaefer

In Union City we were looking at the moon through low clouds (fog). Some of the time we couldn't see the moon. Alan and Albert were using 8" and 6" reflectors respectively. They could at times see the star. I couldn't see it in my TV 76 (3") refractor. The clouds thickened enough to block the view of the star for Alan and Albert at graze time. The star was near the terminator at the northern ("smooth") end of the moon. The star "moved" from the shadowed side of the moon toward the sunlit side. The graze was very close to the terminator.

A member of the graze team, Ed, went to a spot along the graze line south of Los Banos. He was able to record the graze on video tape through his 10" SCT . Ed said the sky was clear, the seeeing was poor, and "the mosquitos were out for blood".

What's so interesting about lunar grazings?

  1. You get to see a star wink in and out from behind mountains on the Moon. It is one of the few astro events that is "active". You see something change over a short period of time.

  2. It is fun getting out to a site along a thin line where you are most likely to see the graze. Sometimes you wind up in odd places. You could be on a country road. Or, in my case three of us were in the parking lot of a city park at 10 o'clock in the evening in Union City. We got to see and hear BART a few hundred yards away while we were setting up our scopes.

  3. You can record the event with a video camera.

  4. Grazings don't happen often, at least where you can easily get to a graze site.

I hope more of the people involved in this last graze will post to TAC. It was interesting reading how they tried to get in just the right spot. Sometimes they found the maps they were using didn't show gates that kept them a little off the graze line.

Getting information from several people in different locations along the graze line does help collect useful information.