Astro 28Y: Field Astronomy At Mono Lake: Aquarius Meteors and a Lunar Graze

July 25-27, 2008

Post Trip Photo Page

This Astro 28 installment will feature not one but two big events - the Delta Aquariid Meteor Shower, and also a grazing lunar occultation.

The Delta Aquariid Meteor Shower. This shower is caused by debris from an old comet. The parent comet is not known for sure, but Comet Macholz 96P is the leading candidate. Now, the exciting thing is, this comet had a major break-up happen in the mid '90's, freeing up vast amount of cometary dust and pebbles. The orbital period is only a little over 5 years, and so its possible the strength of this shower will be increasing in coming years. In the past, this shower produces about 20 meteors per hour at maximum July 28. The shower is active from mid July to mid August.

There are other meteor showers active in late July - probably the most active meteor shower period of the entire year. We also have the (weak) Capricorniids peaking about July 31, the first of the spectacular Perseid Meteor Shower members will also be arriving, the iota Aquariids, the northern Delta Aquariids (a separate but likely related shower) are also active. We'll have great fun disentangling the meteors from these several showers! All of these showers are made of bits of comet rock no bigger than a grain of sand (usually), or maybe a pebble for the bright ones, burning up and ionizing our atmosphere as they enter at 140,000 feet per second 40 mile above our heads.

How to Observe Meteors? This is the Fun Part...

We'll set up a circle, each of us snug in our sleeping bags, hot chocolate mug nearby. We'll focus on the sky and report each time we see a meteor. I'll help you with identifying the shower that it came from, or if it's instead a rogue "sporadic". Check out the data we gathered and sent off for scientific analysis on last summer's version of this trip - Astro 28V. The radiants come up late, Good counts shouldn't be expected much before midnight.

And - A Lunar Grazing Occultation

As morning dawn begins to brighten the sky on Sunday morning, a bright 7th magnitude star will graze the northern edge of the 30% sunlit cresent moon. These events are spectacular to watch, as the star glides over the ghostly earth-lit polar regions of the moon, blinking on and off as it passes behind silhouetted mountains and canyons on the edge of the moon. I'll have a video recorder setup on our 10" scope and make a movie of the event. Go-getter students will man nearby "stations" (if they can pack one our scopes into their car) and we'll be able to assemble a profile of the mountains and compare to the predicted profile. Our data will then be reported and become part of the data base used to keep accurate and refined measures of the orbit of the moon. It is still the most accurate way we have of determining the exact changes in the orbit of the moon. In order to see this, we must position ourselves carefully. The lunar profile for the graze is here. And the predictions are here.

Our Campsite

We have the good luck to have a campground which is exactly in the right location to observe the Sunday morning graze without having to drive. It's lower Deadman Campground. It's located on Deadman Creek (headwaters of the Owens River), a few miles south of June Lake, and an easy 2 mile drive along forest service roads west of Hwy 395. There's no reservations and it's a summer weekend, so there may be competition for campsites. Hopefully we'll get there early enough on Friday to grab all we need. It's got restrooms, tables, but no spigots. We can use the creek water for cleaning and washup, and plan to bring your own water for drinking. We'll have opportunities during Saturday's excursions to stop and refill water bottles etc. When you arrive, my goal is to camp on the south side of the creek, as shown on the terrain map at right. That location is exactly 0.50 miles south of the graze limit line.

I'll have detailed maps which help you navigate from Santa Cruz over the Sierra to our campsite when I see you on our on-campus meeting. I'll also have fee waivers so you can drive into and through Yosemite without paying the usual $20 fee. Nice!

Planetary Science Adventures During Saturday

We'll have micro-lectures throughout Saturday as we caravan around the area, studying some of the youngest volcanic features in North America, including Pahnum Crater, volcanic faults near Mammoth Lakes, and the Black Point eruption site north of Mono Lake. with it's beautiful tufa formations. Recently, it was discovered that there was a large comet impact hitting North America just 13,000 years ago. This coincides with the date of the Black Point volcano eruption on the north shore of Mono Lake. With new information, I'd like to lead a hike up a nearby creek to search for the tell-tale dark layer of burned material left from the cataclysm. That would be a great find, scientifically, since so far there are no published mention of this layer in mainland California (but also no reason it shouldn't be here! No one has looked - the discovery is quite new).

We'll drive another 30 miles north of Mono Lake to study and enjoy the famous hot springs around Bridgeport, including Buckeye Hot Springs, Travertine Hot Springs, and Fales Hot Creek all just a few miles from each other. See pictures of the Bridgeport area hot springs from last year's Astro 28S class. And the general Mono Lake / Yosemite area was the subject of a recent Image Quest Photo Workshop on which I helped crew.

As a backup in case the regular campgrounds are all full (not likely), we'll head for the camping area along Virginia creek in an open meadow near Virginia Lakes, high above the spectacularly scenic aspen groves of Conway Summit above Mono Lake and just below the Sierra Crest at the boundary of Yosemite National Park. During the day we'll explore Mono Lake (gulls and other birds love this lake for breeding and as a way station during migrations). One advantage of the Virginia Lakes site is that it is higher in elevation and therefore probably cooler

Virginia Lakes (left) are in a picturesque high canyon, and Mono Lake (right) is far below. Our camping area would be just off the lower right side of this photo (click for enlarged version). The canyon sides are steep though, and our view of the sky would not be as good as at Honeymoon Flats. Below Virginia Lakes is Conway Summit, and its beautiful stands of quaking aspen, still green in August, but just beginning to change to yellow in a few higher elevation spots.

(Conway aspen photo: copyright Doug Broussard. All Rights Reserved)

The Plan

Friday July 25

Arrive as soon as you can to the campsite. It's about a 6 hour drive, depending on traffic. I should arrive in the late afternoon. Set up your tents, group kitchen area. We'll cook dinner before dark.

8:30pm - 10:30pm: Lecture around the telescopes. We'll study the star formation regions of the Sagittarius Spiral Arm, the distribution of giant globular clusters, the dark nebulae (including the famous "Dark Horse" nebula), and the planet Jupiter and its moons amid the Milky Way star fields.

10:30-12:30am: We'll set out our sleeping bags and do meteor counts while munching sweets and whatever other nasty stuff you guys bring along. I'll show you how to log your counts.

Saturday July 26

7:30am: I'll get up and begin preparing the batter for our French Crepes breakfast. Figure on eating at 8:30am. Late risers beware. Snooze/lose!

9:30am: We consolidate into a few cars and begin our adventures. First stop will be Mono Lake north shore and the Black Point volcanic formation and Wilson Creek. We'll hunt for the Black Point ash layer and search for the Pleistocene impact layer. Will we find it? Who knows - but we won't find it if we don't look. I'll have specimen bags and labelling. If anyone's got a good microscope that doesn't need power, bring it along to camp so we can take a look later Saturday night.

Noon. Head north to Bridgeport and Buckeye Hot Springs - my favorite hot springs of the Sierra. Enjoy a Native American hot/cold contrast session as the hot springs is right on Buckeye Creek. Then, drive back to Bridgeport and Travertine Hot Springs for lunch. Lecture on planetary science, plate tectonics, the geologic history of California, and ending with the story of hot springs formation and prospects on other planets.

3pm - Stop at Mono Lake (either the north shore county park with nice lawns and shade trees, or the more dramatic but stark South Shore tufa reserve).

5pm - Hike to Pahnum Crater on the south shore and it's amazing black glass formations. You'll swear you're on the moon. Search for artifacts. We found an arrowhead last time. Lecture on Long Valley caldera and its history

7:30pm - Return to camp and fix a dinner of Asian rice and veges. If we're early enough, we (you?) can do a short hike over to a giant BLISTER on our planet - an obsidian dome.

9:30pm - 10:30pm - Telescope session and lecture on cosmology

10:30-Midnight. Meteor counts

Sunday July 27

4am - Up early to observe the graze, (then quickly go back to sleep!)

8:30am - late breakfast of eggs and veges and fruit.

9:30am - pack up camp and drive to June Lake - it's just a couple miles off Hwy 395 on the way back home - and do a swim and final lecture, as well as summarize the lunar graze results. Hand out the final exam, and say our farewell's.

During the day, we'll study the local geology and lecture on the history of the earth and the inner solar system, with special emphasis on the geologic history of the Sierra / Basin & Range boundary region in which we'll be camping. I'll be treating you to my famous French crepes breakfast on our first morning, and cooked eggs and/or veges on the second morning. I'll also be providing dinners of pasta and other delicacies. Maps, academic handouts, and carpooling will be handled on our pre-trip meeting in August just before the weekend trip. Click below for the details. Here is the planetary science hand-out which I'll be distributing once I see you at camp. Check out some of the locations we'll be seeing by viewing my Astro 30 webpage

Google terrain map of Wilson Creek and north Mono Lake

Google terrain map of Bridgeport hot springs area

Google terrain map of Pahnum Crater

Grading

Your grade will be based on two components. (1) A take-home written final exam. You'll have 10 days to complete and mail in or drop off. and (2) your demonstrated curiosity, participation, and helpfulness during the get-togethers during the field trip. Fun is an essential ingredient to any good learning experience! Please take note - your full participation in all group activities (lectures, hikes, excursions) is required in order to receive a passing grade. There have been times in the past when students have wanted to go off and do their own thing. I'm not fond of "herding cats" and so don't make a big deal out there in the field. But you will not pass the class if you don't stay with the group.

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