Desert Moon Observatory

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Journey to the Antumbra:

The Annular Solar Eclipse of

May 20, 2012

For many years it has been know that on May 20, 2012, an annular solar eclipse would sweep across the Pacific Ocean, ending its journey across the Earth in the panhandle of Texas. While annular eclipses are no where near as interesting as a total solar eclipse, its proximity to Las Cruces meant that we could not ignore this none-the-less rare event. So the co-directors of the Observatory, Berton and Janet Stevens, started planning to observe this event.

Standard procedure for any eclipse is to stay mobile. This would be Bert's ninth attempt to be near the centerline of a solar eclipse and this is one of a number of rules that he developed for successfully observing these events. To become stuck at a fixed location usually brings clouds and a lack of observation.

Map of Path

The eclipse entered the United States in northern California, slid over Nevada, northern Arizona, northern New Mexico, and into Texas. The western end was often cloudy, as was the eastern end. That left the middle, with the Arizona area being the most likely to be clear. While climatic forecasts are interesting, it is the actual weather that is important. Weather Underground provides predictions some eleven days out. If the weather was clear along the entire path, it would be most efficient to observe in Albuquerque, the closest location to Las Cruces that was easiest to reach.

The forecast from weather Underground was mostly for clear skies, but it would occasionally jump to cloudy and then the next day back to clear . Bert contacted the Albuquerque Astronomical Society (TAAS) to see what they had arranged for the event. They had worked with Bernalillo County to arrange a viewing area near the Pavillion for the Hard Rock Casino Presents, just south of the airport. They had set aside an area specifically for astronomers just half a mile from the centerline, and this sounded like a good option.

Even with this good option, we also continued to look at sites further west along the path. Three additional sites were selected in New Mexico and Arizona. These were US 491 near Gallup, Chinle, AZ, and Page, AZ, near Glen Canyon Dam. This last location is where Nils Allen would be observing the eclipse, but was another six hours driving and the outlook that Nils was at was almost five miles from the centerline, which would make the Moon appear slightly off-center. The centerline actually ran through nearby Page, so we looked at that as an option as well.

Selected Sites

As the day of the eclipse got closer, I ran exposure tests to verify the correct exposure time for photographing the eclipse. Using color negative film provided a wider exposure range that would still produce acceptable prints. While the tests were done with the Sun near overhead, the eclipse would be low in the west, so I added two stops to the estimated exposure. The test pictures produced good images with a Meade ETX-125 with a solar filter over the front.

A few days before the eclipse, the forecast seemed to stabilize as clear in Albuquerque. We planned to travel up there the day before to be ready to make the final weather decision, so we would have plenty of time to travel westward, if necessary. The day before the eclipse we packed up the car, the telescopes, and ourselves and headed up north. The trip was uneventful.

We settled into our hotel and connected to the Internet to get the latest weather. While further south and west would be clear, moisture was working into the Albuquerque area from the northeast. This could create clouds and even thunderstorms in Albuquerque and northeast. With the weather being uncertain, we decided not to travel any further west and throw our lot in with the Albuquerque group.

Sunday dawned clear and with our observing site committed, we did a little shopping in a local mall. We then headed back to the hotel and picked up the rest of the equipment and headed out to the observing site. It was rather warm as we arrived at the site. We advised the traffic director that we were amateur astronomers and they directed us into the west end of the parking lot where other amateurs were already starting to set up. We drove around and picked an observing site that had a good view of the west.

We started setting up the equipment. Janet had her six-inch f/8 Edmund Scientific Newtonian with a full-aperture solar filter. She also had a a Coronado PST. I was using her ETX-125, also with a full aperture solar filter. The camera was at the prime focus of the instrument. We also had a camcorder with a solar filter to try to record the eclipse on video. All the equipment was in good shape and working.

Equipment Lineup

As first contact approached, the sky to the west was clear, but there were a few clouds off to the east. They were not coming our way. Our gamble had paid-off and we were ready to observe the eclipse.

The Sun was eighteen degrees up at first contact (6:28:28 p.m. MDT). We watched the Moon slowly creep onto the Sun's disc. The view was excellent with all the instruments, Bert had inadvertently left the cable releases at home, so Bert used the self-timer on the camera to allow the mirror to come up well before the exposure started. This greatly reduced the vibration from mirror-slap, but there was only one delay setting of fifteen seconds available, so exposures needed to be started fifteen seconds early. Catching second or third contact would just be luck.

We had a few visitors as the Moon slid onto the Sun, we gave them views of the eclipse with the six-inch and the PST. We also gave out a few pair of eclipse-glasses that we had brought along, They had run out of them in the public viewing area, where they had a huge tent, food, and most importantly, port-a-potties. It also kept most of the public out of the astronomers' area since they had solar telescopes set up over there for viewing.

Janet was viewing the eclipse through the PST and her six-inch with a solar filter. She remarked about the difference in the two views. Through the 6-inch, in visible light, the sunspots were clearly visible. In the PST, in hydrogen-alpha light, the sunspots almost completely disappeared.

Janet with equipment

The Sun finally started to stretch its arms around the Moon as second contact approached. At 7:33:42 p.m. the end of the cusps came together as the Moon moved completely onto the Sun's surface at an altitude of only 5.5 degrees. Even with most of the Sun blocked, it was still quite bright. Normally, things would seems bit dim with the Sun overhead during an eclipse, but with the Sun this low, it did not seem so unusual, but it still seemed a little murky.

Mid-eclipse came at 7:35:55 p.m. with the Sun and Moon forming a perfect circle in the sky, only 5.1 degrees above the horizon. Switching between photographing, and viewing, I sneaked a peak at the eclipsed Sun without a filter. It was amazing to see this brilliant ring of fire hanging just a above the west-northwestern horizon. I quickly brought the solar filter back in front of my eyes.

After a brief four minutes and twenty-seven seconds, the eastern edge of the Solar ring broke apart as the Moon began to move off the Sun at 7:38:08, a scant 4.7 degrees above the horizon. A giant cheer went up from everyone watching the event. A helicopter flew over taking pictures of the crowd assembled for the event.

Janet and Eclipse

We watched the Moon leave the Sun's disc until the Sun finally set at 8:08 p.m. With the Sun gone, we began the process of taking the equipment apart and packing it for the trip home. People were leaving quickly, depending on how much equipment they had to pack. By the time we were done, it was almost dark. We returned to the hotel to get an night's sleep. The late television news had stories about people observing the eclipse from parks all over Albuquerque.

The trip home was uneventful and we started unpacking the equipment, knowing that we would be using it again in just two weeks to observe the once-in-a-lifetime Transit of Venus. It would be an exciting two weeks of astronomical events in the desert southwest!

Here is a short video sequence of the eclipse:

Eclipse Animation

Last updated 2012-06-26