Our Astro 28M Weekend Grazes

Upsilon Geminorum Graze - Friday evening April 15

First, on Friday night April 15 we are treated to a spectacular graze of the 4.1 magnitude star Upsilon Geminorum. This is a bright star visible to the naked eye when not in the glare of the moon. The graze occurs 13 degrees from the northern cusp of the 45% waxing cresent moon high in the sky. The profile of the moon (vertical is exagerated by a factor of 20) is shown here. The star will be seen to move from left to right. Our goal will be to choose observing sites which maximize the probability that the star disappears and reappears many times among the hills on the dark side of the moon. The prediction sheet is here.

The graze occurs at 9:48pm. Our graze site will be north of Mojave, about 15 miles south of our campground. If you're coming directly to the graze site and not driving on to the campground first, then look for Randsburg Cutoff. The Mapquest.com map suggests that Randsburg Cutoff now does not connect to the interstate coming down from Tehachapi. If you don't see an offramp, then go a couple miles further to "Business Hwy 58" and get off, heading north. A mile further will bring you to Randsburg Cutoff and you turn left. Use the mapquest map here, and the zoom feature to look at the dirt roads. The north end of our grazers will be 0.5mi north of the limit line. The "x" on the topographic map here is 0.5mi N, where the Los Angeles aqueduct crosses Randsburg Cutoff road

Because it's a long 6 hour drive from Santa Cruz, you'll have to decide carefully whether to have dinner in camp and head to the graze site, or instead to plan to have dinner on the road intercepting arriving students before they reach Red Rock Canyon, perhaps in Mojave itself, and then go straight to the graze site. I will get to the campground ASAP in order to secure spots during this popular time of the year for the desert. Dave McKulle plans to leave around 10am and should get there by 3:30-4pm. I hope to get there a bit earlier. We'll have to leave the campground by 7:50pm sharp in order to get to the graze site and set up our scopes.

ZC 1263 Graze - Saturday Evening

Even more interesting is the graze of the triple star ZC 1263. The brightest star of the system is magnitude 6.9. There is a second star at magnitude 7.7 whose graze path is 6 miles further south. This 7.7 star is actually a close spectroscopic binary of ~8.5 + 8.5 stars separated by 0.155" (about 0.2 miles - easily resolvable for our observers) along a roughly north/south direction. The 6.9 star will disappear and reappear all at once, but the 7.7 star will disappear and reappear in steps, first fading roughly at half brightness. The profile for these grazes is much more favorable than for the previous night's Upsilon Geminorum graze, promising many timings. Our data should help refine the position and orientation of this multiple star system, and be quite spectacular to watch. The 6.9 and 7.7 components are separated by 5.4 arc seconds, easily resolved by our telescope equipment and will be visible as a close binary pair. We'll have to plan out where to put observers, but it already seems that the 7.7 star should be more of the attention, and should be where the video camera gear should go. Hopefully we'll have astronomy club people along with their scopes and visual observers can concentrate on the brighter 6.9 star graze. The other nice thing about watching the 6.9 graze is that the fainter 7.7 graze will happen as well, but just deep enough into the lunar profile so that we should not expect multiple mountains to cause occultations. The prediction sheet is here.

The site for these events is further south; north of Lancaster and west of Edwards Air Force Base - site of the shuttle landings. The graze is at 8:52pm, time enough for us to have dinner and then caravan from camp.