Rare to get two grazes worth travelling to in one night. Even rarer to get two cresent moon grazes on 6th magnitude or brighter stars in one evening, just a few miles apart. And rarest of all - on opposite dark limbs! This requires the moon's vector and the Earth's rotation vector to be projecting in such a way to insure rapid rotation of the graze point, so that the cusp angle can change rapidly. These conditions all converged on the evening of January 15, 2013. Derek Breit, Walt Morgan, and I all took note. Rick Baldridge was also on board, but his balky car was more seriously ill than he'd thought, and wasn't cleared for launch on graze day. So he reluctantly bailed at the last minute. I had this pair on my Events list for some time, and the skies looked to be clear. I contacted Becky, who was eager to join on her second graze, and this time to be an observer gathering data. I spent two evenings working on planning locations and running OCCULT4 and Google Earth to find the perfect spots for Becky and I. 6.3 magnitude ZC 3444 would graze the southern limb at the end of twilight, 2 degrees from the southern cusp, and then 4.9 magnitude Kappa Piscium would graze the northern limb of the moon 4 degrees from the cusp 2 and a half hours later. The cusp angle would have to rotate fully 6 degrees in that brief period.

As we got close, weather promised to be clear, and Derek Breit and Walt Morgan took note independently and sent out an email. It's always more fun and more valuable when you can get together with friends and do these grazes and asteroid occultations, so I suggested to Becky that we all meet and do these grazes where the paths were relatively close - in the Gilroy/Morgan Hill area. Becky was really excited about observing and getting timing data on her first grazes. She'd accompanied me on the Oct 26 '12 graze in Bonny Doon, but this one she'd be taking her own data by voice/WWV radio/tape recorder method.

First graze, of 6.3 magnitude ZC 3444 through Aromas and Gilroy, CA at 6:30pm. The graze is only 2.2 deg from the southern cusp and the profile has only 2 steep mountains whose right sides near the summits will probably be sunlit. 3 maybe 4 timings.

I rushed around in the afternoon - a 3 mile run on the beach, then packed gear at home, then off to InShape for a short swim, then to the observatory to pack the scopes and rest of the gear, then to Becky's in Aromas, then jump on 101 and up to the meeting site on Frazier Lake Rd and Shore Rd in the ag fields south of Gilroy.

I got onto our dirt road, just 2 miles from the meeting site, and drove down about 300 yards to Becky's station and offloaded the 8" Meade, timing equipment, and suggested she get the station up going and then I'd run down in about 15 minutes after getting my station up. She got the WWV radio working, polar aligned the scope, verified the star and the correct cusp, practiced with my mini-cassette tape recorder, and discovered that there was no power from the 9V battery I gave her for the scope. When I returned after my own initial set up about 100 yards north of her, I brought the VOM tester and sure enough - the battery had only 1.5V, not the 9V advertised;. it was DEAD! So, she'd have to use the slo-mo control to keep the moon and star in view. Meanwhile, at my station I had my own troubles after getting everything up and running. The star was beautifully set off against the cresent and earthlit dark side (see title picture at top)... but with 3 minutes before the onset of the graze, the telescope froze up. No tracking, no response from the hand paddle. Darn Meade electronics! Too late to restart and get in another 2-star alignment, so I flipped the power off/on and it came back up, and I simply used the hand paddle every few seconds to reposition the star, while insuring the bright cresent didn't sit on top of the time stamp. It all worked fine, and I got the whole graze successfully recorded. Becky and I both had 4 events from the two big mountains.

Meeting Site After Each Graze - In Morgan Hill: the Taco Bell at the corner of Condit and E. Dunn, just off the Hwy 101 in Morgan Hill a couple of miles south of the graze sites for the second graze.

Second graze - at 9:06pm; 4.9 magnitude Kappa Piscium grazes the north limb 4 deg from the cusp, but at an altitude of only 10 degrees. Looks like a good profile at 0.9mi south. Here's the predictions. Getting a good horizon is critical.

On playback, I realized I'd forgotten to check/replace the batteries in the tape recorder. It taped fine early on, but by the midway of the second (very cold) graze, the batteries were clearly suffering, as Becky sounded like she was on helium, and the second ticks were racing by. Will take some additional effort to reduce them. My own video recording is beautiful! I should try and download it and make a compressed .avi and post to YouTube. 25 D's and R's in the space of 2 minutes on an Earthlit moon is a visual treat.

The data reductions are here.