RING OF FIRE EXPEDITION TO MEASURE THE DIAMETER OF THE MOON

Paul D. Maley, NASA Johnson Space Center Astronomical Society, Houston TX USA

The November 29, 1993 total lunar eclipse was more than just an eclipse. The 6th magnitude double star ZC 646 was to undergo a series of eclipses by both the north pole of the moon (as seen from Canada) and the south pole of the moon as seen from Baja California, Mexico. This was the third attempt since 1982 that I have made to coordinate observations of the same occultation from both limits during a total lunar eclipse on behalf of the JSCAS and the International Occultation Timing Association. Why? The benefit of timing this phenomenon, where the same star is observed at both edges of the moon by expeditions separated by over 2000 miles, should result in a better understanding of the absolute diameter of the lunar globe.

The first attempt was made by myself and Chuck Herold from the north limit of a grazing occultation of a bright star in the Philippines in January 1982. The southern limit was attempted unsuccessfully by Australian amateurs. Our expedition brought back the first and only photograph of a complete grazing occultation every taken as of this date (1998). The second attempt was made also from the northern limit by myself, Gary Nealis, Chuck Herold, David Dunham and others from Sudan in May 1985; teams observed from the southern limit in South Africa. Not enough data was obtained at the north edge due to a sandstorm. Neither the 1982 or 1985 expeditions produced enough data at both edges to provide a decent update to the moon's diameter.

Now comes this eclipse. Three of us (myself, Richard Nugent, and Chuck Herold) met in Tucson, Arizona on November 26 where we ordered the traditional Domino's Pizza delivered fresh to the Aeromexico terminal. Then we traveled 2.5 hours by air to La Paz, Mexico and set up camp at the La Concha Beach Resort just north of the city center. This was the nicest hotel (more like Motel 6) in the area and featured such amenities as shampoo that looked like Milk of Magnesia and signs warning against poisoned water on the grounds of the property. It had a nice beach, but was too cold to swim in. We arrived two days early in order to get acclimatized, perform a site survey and take care of last minute logistical problems.

The first thing we did was to find a store that sold motorcycle batteries; we negotiated with the owner Sr. Luis Garcia to borrow a used 12-volt battery which he delivered to our hotel that night. At first he said he would charge it for two hours and to come back to his shop. We ate lunch, returned and Richard hooked up his hair dryer for a few seconds to see if the battery would power it. After the test the voltage had dropped below the minimum of 12 volts. Luis offered to charge it up for six more hours and we left.

Using a rented Hertz Dodge Shadow with 36,000 miles on it, we sputtered our way on to a site north of the village of Santa Rita (which in Spanish may mean 'death to all amateur astronomers'). It was Saturday, November 27. We were headed 178 km from La Paz. But we were not even 5km outside La Paz when Richard observed an attractive monument that looked like a whale tail (or dove, depending upon your view point), and we stopped to take a photo. I reluctantly pulled the car over, he got the photo and then I tried to restart the motor. Nothing happened! The battery was completely dead.

We lifted the hood and began amateur astronomical male troubleshooting, which is like having a debate between the virtues of a Schmidt-Cassegrain and a Newtonian telescope as a tornado is bearing down. We tried to loosen the battery terminals but that did not work. I poured orange soda on the terminals that created a lot of visual chemical reactions yet had no effect on our ability to start the car. Ten minutes passed and two men in an old car stopped and asked if they could assist. While one crawled under the hood, the other offered to go to his shop and get jumper cables. We did not object to that and twenty minutes later he returned with cables and a new battery. We tried to jump start the car and it failed. They then swapped the old battery with the new one and it started right up. At that moment one of the men announced that he worked for Hertz, the same agency we rented the Dodge from. He gave us his card; why he never told us he worked for Hertz at first I will never understand. He had stopped only because he had noticed the Hertz sticker on the back of our car. The new battery worked, it cost us nothing, and we continued our expedition.

At 127km into the journey we encountered a dead horse and contemplated using our Global Positioning System satellite receiver to get its actual coordinates---it is amazing how long one can stoop on an astronomical venture such as this! Passing through Wyoming-like terrain, we finally found our sites. We surveyed them carefully and set up a plan to observe the eclipse there on the following night. We then drove back to La Paz and enjoyed a spaghetti dinner at El Moro restaurant. The weather had been great that day and almost completely clear that evening. Upon arrival at our hotel Richard checked out the motorcycle battery and found it to be working.

Sunday morning (*eclipse day*) dawned crystal clear. We spent two hours catching some sun on the Baja beach, taking photos and preparing equipment. At 7pm we borrowed a bed sheet, chair and towels from the hotel and began our return trip 178 km north to the site area. The sky continued to be clear, a picture perfect prelude to the lunar eclipse. Arriving at 9pm, I deployed Chuck and Richard to a station 0.8km north of me. We had to abandon one site because Chuck had an equipment problem. Both my site and Richard's were situated 20 feet from the highway; trucks kept driving past at the rate of one per minute all night long. The occultation was scheduled to begin about 11:28pm local time (06:28UT). By 11pm, both sites were operational. I found the target star very easily in my Celestron 5 telescope positioned on a portable mount. The moon was already inside the umbra. The ground, which had been clearly illuminated earlier by the full moon, became harder to see. One thing that became apparent immediately was that the area of the moon that was supposed to be dark during the central occultation was actually illuminated. The estimated brightness of that part of the limb was about +8.5 while the star to be occulted had a magnitude of +6. During totality the Milky Way jumped out and stars to magnitude +6 could be seen with the unaided eye.

The short-wave radio time signals were received well on 5MHz and we began recording. I videotaped a total of 4 disappearances and 4 reappearances at my station. Richard had a more difficult time as the star's brightness dimmed as it approached the limb. He only was able to record the initial disappearance during the grazing occultation using a Bausch and Lomb 6-inch telescope mounted on a Meade tripod and with a Palmcorder. for the five minutes of the occultation, I could hear a cow walking through the grass across the highway; I wondered if it would make an attempt to cross near my site. Fortunately it did not. We had passed numerous cows grazing at night on both sides of the roadway which had no fencing. By 12:15am we were packed up and on our way, flush with success, and three hours from the nearest bathroom.

About 45 minutes into the return journey, I slammed on the brakes when I observed that cows were standing in the middle of the darkened highway. How I saw them was unclear since they were black in color. I stopped the car barely six feet from a cow and my two passengers, who had been dozing, were startled enough to remain awake for the rest of the trip. As we sped down the road at only 90km/ hour, we encountered a dead cow blocking the road with another standing over it---another screeching halt! Fortunately we avoided any accident and arrived at our hotel about 3:00am.

By 6:30am we got a wakeup call and headed for the airport. We left La Paz and finally arrived in Tucson, Arizona at 11:10am. Just south of the Tucson we saw the domes of the Multi-Mirror Telescope complex from the aircraft. In Tucson, we met fellow amateur astronomer Derald Nye whom we had lunch with and then traveled to his house to see his observatory and 16-inch telescope. Due to poor airline connections we were forced to spend the night in Tucson and returned to Houston the following day (November 30). A three hour layover ensued and we attempted to invoke the traditional ordering of the Domino's Pizza but found that the city of Houston forbids deliveries to the airport in order to protect the Bambolino's pizza franchise.

On December 1 I received word from Doug Hube in Canada that the expedition in British Columbia to observe the northern limit occultation was also a success, with six observers having obtained data, and three GPS receivers used to plot their site locations.

We would like to thank Steve Davis of Trimble Navigation in Austin, TX for loan of the GPS Flightmate Pro receiver which was vital to establishing our science team coordinates in Mexico.

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