Astro 28E: High Sierra Adventure - Lunar Grazing Occultation and the Fall Milky Way


Sept 27-29, 2002



General Information

     We're going to the High Sierras! This will be a fun and educational course during which you will be positively agog with astronomy. This course is built around a unique astronomical event; The northern limb of the last quarter moon will graze the giant star star SAO 78132 at 3:26am Sunday morning Sept 29. This star is a relatively old star, about 50% more massive than the sun and is finishing it's hydrogen burning, evolving into a giant. It glows at about 4,000 degrees Kelvin, and shines at magnitude 8.1. Its orange color will contrast with the moon in our larger telescopes. We will watch as the star is seen to slowly move along the dark edge of the moon, disappearing and reappearing as it passes behind the mountains and valleys seen in silhouette. Such an event is called a "grazing occultation". Our goal will be to record the exact moments that the star disappears and reappears from several "stations"'. These times provide the most precise way astronomers have of charting the changing orbit of the moon (the moon's orbit slowly changes due to tidal friction and gravitational effects from the other planets). The geometry of these events requires that the observers be within a very narrow band (about a mile wide) which traces across the earth as the earth and moon move. The path for this graze crosses over the crest of the Sierra Nevada mountains near Bear Valley ski area. 

   You'll get maps to our specific site  at the pre-trip meeting. This is a beautiful classic high sierra country, with scenery similar to the Tuolome Meadows area of Yosemite - lots of exposed granite with a sprinkling of tall pines and convoluted lake shores. The elevation is 7000 feet so nights will be cool.


   Of course, we'll also have our our scopes to show you the deep sky wonders - last views of the nebulae and star clusters of the summer Milky Way, and the Andromeda Galaxy... Our site will be far from city lights and very dark all night long.


     The Cabrillo Astronomy Club will be along to help show you the sky, help get you rookies into graze ship-shape, and generally enliven the festivities.



Thursday Sept 26; 5‑~8 pm:  On-campus general orientation, planning food, carpooling. Lecture on grazing occultations, origin of the moon and planets in planetarium (Room 706). Planetarium and slide session.


Friday Sept 27

   The class officially begins Friday evening. However, it is a roughly 4 hour drive, depending on traffic, to our campsite. I and perhaps some of the astronomy club will be caravaning down to the site, leaving from the observatory behind the Horiculture Hill around 2pm Friday. I will make sure you have maps to guide you to our site. Basically, you drive into the south bay, through Livermore, across the Central Valley and up Hwy 4. A mile or two before Bear Valley you will see a small sign on the right for Spicer Resevoir. Take this turn off and follow the maps handed out at the pre-trip meeting to the campsite. Look for a purple Toyota RAV4, or scopes. When you arrive, pick out a spot for your tent and set up. We'll eat around twilight. Because we'll be arriving at various times, this is not an official group meal, although the astronomy club will likely do something along these lines.

   After dinner, we'll break out the scopes for some observing and constellation hopping.


Saturday Sept 28

8:20am   We'll start the day with a group breakfast cooked by your tour guide Rick. French Toast is traditional. Or maybe eggs and crepes; we'll see...  Next we'll turn the 8" scope on the sun and have a short talk on sunspots and solar activity. The rest of the morning and afternoon you're free to explore. There are some interesting locales to visit during the day.


- Calaveras Big Trees State Park: This is a grove of giant sequoia, the largest and among the oldest living things on earth. A 40 minute drive south of camp.


- Mercer Caverns & California Caverns: There is a region of limestone in the foothills which have produced a beautiful complex of underground caverns, these are both back down Hwy 4 not far from Angels Camp.


- The Stanislaus River is within a short hike of our camp. Fishing or general relaxation, your choice.


- Ebbetts Pass area; 30 minutes from camp is Ebbetts Pass, over 8,000 feet. There's the Mokolmne River and numerous alpine lakes accessible only on hiking trails or mountain bike.


- Markleville/Grover Hot Springs. Over Ebbetts pass, about an hour drive from camp is the tiny town of Markleville, with the best ice cream malts in the Sierra, and with the Carson River paralleling the road. Grover Hot Springs (developed, alas) is just outside town.


- For those who don't mind a longer drive, taking a right turn before Markleville onto Hwy 89 will take you to Bridgeport and the classic hot springs of this area (Travertine, Crab Cooker, Fales Hot Creek, which also has an interesting history), and south of this is the best preserved ghost town in the west; Bodie.


5:20pm Be back at camp for dinner preparation. After dinner, in late afternoon/early evening light I'll give a campfire lecture on star formation and the lives of stars, on other solar systems, and on the origin of our Universe. We'll also get logistics set for the graze, which happens early the next morning. As it gets dark I'll point out the structure of our Milky Way Galaxy, as we have a perfect view of the inner regions of our galaxy in September evening skies.


Sunday Morning Graze: The graze will happen at 3:20am. Our campsite will be very close to the graze stations we'll want. No doubt one station will actually be at the camp. Being so close will minimize lost sleep time. See below for more on the graze.


Sunday Morning: 9:00am Another fabulous breakfast cooked up by your instructor with some extra fixings provided by the gang.

- Graze Debriefing: we'll discuss our observations of the graze, do a preliminary tape listening so we can pencil in the contacts and make a rough sketch of the mountains and valley's on the edge of the moon as revealed by our teams timings.

- Another solar viewing session if desired. A brief talk on the geology of the Sierra in general and on the Utica Lake area in particular, viewed from our vantage point over the lake.

   Later, we pack up camp and head back. This might be the best time to ponder stopping at the caverns or Calavera Big Trees. We can talk about this when we're up there.


* Unregistered people: Many people ask whether they can bring along a friend, "significant other", or kids/dogs. The school forbids us from handling people who are not officially registered for the class, or members of the Cabrillo Astronomy Club (who will be along for your astro viewing pleasure), for insurance reasons as well as cost. That means that those staying at our campground will need to register for the class.


* Car Pooling: It's a bit of a drive and carpooling will help save trees and keep you from getting lonely too! We'll organize carpools at the Thursday pre-trip meeting.


The Graze of SAO 78132: What to Expect

   We'll set up about 3 or 4 "graze stations", spaced a few hundred

yards apart. Each station will have a telescope, a designated observer, one or more assistants, a battery operated tape recorder, and a radio. The observer watches the star and each time it blinks out he/she shouts "D!", and when it reappears he shouts "R!", as absolutely instantaneously as possible. Meanwhile, his voice is being recorded on a tape recorder along with time signals from WWV. It is by carefully listening to this tape that the times of the events will be deduced. The whole graze will last only about 3-4 minutes. I will have a TV monitor and video camera set up so students can watch and practice with stopwatches getting timings of the events without having to look through a scope.

     The area of the moon being 'grazed' is never sunlit when seen in silhouette from earth, so it'll be valuable new topographic data that we acquire.


* This trip requires car-camping. So, be prepared to bring or share....


- sleeping bag, pillow

- tent, rainfly

- camp food (keep it in the car unless you're eating it!)

- cooking gear

- warm clothes (might get in the 40's at night!)

- optional camera and tripod, would be fun

- sunscreen, Ray‑bans

- binoculars would be nice

- star chart if you have one

- field notebook, daypack

- lawn chair for relaxing/ listening to the lectures


*  The campsite is accessible by car so you do not need backpacks. We should plan to bring our own water. There will be rustic restrooms and campfire rings, tables.  


* In addition, these items below are necessary for getting good graze data:

-- tape recorder with FRESH batteries. This is necessary in order to make a careful voice record of the D's and R's so the times can be deduced.

-- audio tape for the tape recorder

-- If there aren't enough tape recorders/radios, bring along a stop watch if you have one


* Rain: The trip will go, rain or shine. If its raining (God forbid!) bring rain gear.


Other Particulars


* Your grade will be based on attendence at all sessions, demonstrated curiosity, and especially on a take-home, open book final exam. Blowing your graze occultation observations will NOT hurt your grade (assuming you don't sleep through it, that is!). You can take it credit/no credit too; just tell me.


   There will be more handouts and details on where we will be staying, etc. at the Wednesday in-class session. Please note that the Thursday on-campus session is required attendence! I'm looking forward to a fun weekend with all of you!


Rick Nolthenius, Office 706a 479-6506