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NG Field Notes: Final Pluto “Eclipse” Tonight

The following is a roundup of updates from astronomers in the field, partly funded by National Geographic, who are attempting to catch an occultation of Pluto and its small moon Hydra. If you live in Southeast Asia and own a telescope, there’s still time for you to get involved in the project and collect data...

The following is a roundup of updates from astronomers in the field, partly funded by National Geographic, who are attempting to catch an occultation of Pluto and its small moon Hydra. If you live in Southeast Asia and own a telescope, there’s still time for you to get involved in the project and collect data for the team!  -V

6/29 Update From Katherine Lonergan, Wellesley College

The Pluto and Hydra occultations had us all on the edges of our seats. Last-minute heroics enabled our team members on Nauru (by means of a new telescope gear on the one flight a week from Australia to Nauru), as well as a group of new volunteers across five nations, to join in the observations. The latter group helped to expand our range of observers in the new predicted Pluto and Hydra shadows within 12 hours of the event.

None of our sites have returned certain reports of occultations observed yet, although most were able to collect at least some data. Some mysteries of data remain to be analyzed more thoroughly once our team members return from their outposts in the Pacific. We’ll also be waiting to hear from the amateur astronomers who teamed up with us about their own results.

6/28 Update on the Update, From Leslie Young

It’s the day after the second occultation. What happened? Where was Pluto’s shadow? That might need to wait for one more post.

We had clear skies at Cebu City, and excellent image quality from Christopher Go’s 14-inch telescope.  Clear skies and good data were also reported from Kauai, Faukes in Maui, Singapore, and—for the Pluto portion of the night—from Majuro. From other places, we’re mostly getting the weather report.  Mixed or heavy clouds at Hale A’a, Waikoloa, Java, Oahu, Lahaina, Kuriwa (Blue Mountains, Australia), Kwajalein. No report yet from Japan, our northernmost sites.

Nobody’s reported a positive occultation yet. We expect Pluto to be north of most of our sites, and Hydra is a tough target, so perhaps this is not surprising. Also, conditions were cloudy most places, which makes pulling out the signature of the occultation more difficult. We see something mysterious in the Cebu data though. We’re asking the rest of the team if they see anything, too.

6/27 Update From Leslie Young in Cebu, the Philippines

The story so far: Compared to our predictions from March, new star position measurements in early June moved the predicted June 23 shadows south and the June 27 shadows north, and then the June 23 occultation showed the shadow path close to the March prediction.

What do *you* believe? Do you think that this means that the new star positions are not as good as the old ones? In this case, the June 27 shadow prediction is near where is was in March, and we’d expect Hydra’s shadow to cross the middle of Australia and Pluto’s shadow to cross Hawaii, the Marshall Islands, Nauru, the southern Philippines, and Indonesia.

Or, do you think the new star positions are good? In this case, the June 27 shadow prediction is north because the star changed, and north again because of the update from June 23. We’d expect Hydra’s shadow to cross near Hawaii, the Marshall Islands, Borneo, Malaysia, and Sumatra, with Pluto’s shadow crossing the northern Philippines and many areas of Asia (Japan, China, Taiwan, northern Thailand).

In any case, here’s the rundown as of about 4:00 UT, or ten hours before event time.

Hawaii: Three telescopes on the Big Island, at two sites (a 24-inch at Hale A’a, and a 16-inch and a 24-inch at Waikoloa). Prospects: near new predicted Hydra shadow, in old predicted Pluto shadow.

Maui: Faukes 2-meter and 14-inch in Lahaina. Prospects: near new predicted Hydra shadow, in old predicted Pluto shadow.

Kauai: Two 14-inch telescopes in Barking Sands, one mobile. Prospects: near new predicted Hydra shadow, in old predicted Pluto shadow.

NEW Marshall Islands: Using a third telescope on Kwajalein atoll, even though you need to take a boat or helicopter to get there. This was made possible by the New Horizons mission to Pluto … Thank you, Alan Stern! Weather looks dire. Prospects: near new predicted Hydra shadow, in old predicted Pluto shadow.

NEW Nauru: We managed to get replacement gear shipped to Nauru in time for this event. Not easy, as flights only arrive from Australia once a week. Prospects: in old predicted Pluto shadow.

NEW Japan: Added 1.6-meter Nayoro/U. Hokkaido telescope 44°21′ N  142°28′ E and 1.88 m OAO/Okayama telescope of NOAJ, 34° 34′ 37.47 N 133° 35’38.24″ E, alt. 372m. These are the two largest telescopes in continental Japan. There are rainy season conditions though. Prospects: in new predicted Pluto shadow.

NEW Philippines: Looking at adding new sites in Manila. The weather is great in Cebu, lousy in Manila. Prospects: southern edge of new Pluto shadow, north of new Hydra shadow, in old predicted Pluto shadow.

NEW Indonesia: Bossca Observatory observers (Mark Bullock, John Stansberry) have arrived and all looks good except the weather.  Students of the Department of Astronomy are going to make observations of Pluto from the campus, which is around 15 kilometers away from Bosscha, to try to get a pair of chords on Hydra. The weather does not look good. Prospects: south of new Hydra shadow, in old predicted Pluto shadow.

NEW Malaysia: Whew! This is crazy! So far, for certain, the Langkawi Observatory, Malaysia, but Christopher Go’s been finding many amateurs. We’ll see how many we get tonight. Prospects: in new Hydra shadow, in old predicted Pluto shadow.

Thailand: Tracking down some possibilities, nothing definite. Prospects: in new Hydra shadow, in old predicted Pluto shadow.

From Peter Tamblyn in Nauru

First event night was very frustrating … mostly usable skies, but a mostly unusable telescope. A stripped gear was interfering with our ability to track stars as they moved across the sky with the Earth’s rotation and was making pointing at faint targets nearly impossible.

We used up all the time prior to the event coaxing the telescope into tracking the moving sky well enough, and didn’t have time to find the target field. One opportunity lost.

We knew what part we needed to fix the telescope, but could we get it to this remote island in time for the second occultation opportunity? With very limited Internet access, we mostly sat and watched, feeling helpless, while possibility after possibility
was ruled out. The team in Majuro has this spare part with them! But there’s no way to get it from them to us in these few days. Another spare was thought to be in Boulder … but couldn’t be found. Finally, Jeff from the Kwajalein team locates a dealer near Sydney with the upgrade kit for this drive … three hours before the receiving cutoff in Brisbane. Hopeless.

But not quite! The dealer (Michael Chaytor at Bintel) persuades the aircraft loaders in Brisbane to accept a weekend delivery! Michael arranges an urgent courier of the part from his shop to the aircraft loaders in Brisbane, and it makes it onto the Nauru flight!

This morning we went to airport desperately hoping the part had been accepted, loaded, and unloaded. Success! Six hours of repair work—mostly as expected, but with some frightening hiccups—leads to a working, upgraded gear and a fully functional telescope!

—Picture courtesy Peter Tamblyn

Tonight we lined up the telescope and verified it could track the spinning sky well, just in time for a major rain storm. We pack up, cover up, and haul our soaked bodies back under cover to wait it out. Fortunately, it’s only about a half hour long. Shortly thereafter, we have the science camera on the field. We take test and calibration data and just wait. Clouds come and go, but none look as threatening as the one that dumped rain on us. Just one more hour to wait!

FYI, we did have one scheme to get around our broken telescope: If we could mount it _sideways_ on a rigid vertical surface, we could use only the good gear for the essential sky tracking. This is a fluke of the fact that we’re basically on the Equator. In astronomer-speak, a sideways [polar aligned] alt-az telescope here is an equatorial telescope. We couldn’t find any appropriate structures on site, so we scouted the island for alternate sites.

—Picture courtesy Peter Tamblyn

From Cathy Olkin in Majuro, the Marshall Islands

Last night [June 23] we decided to get a quick dinner before heading out to our observing site at the Weather Service Office. We went to the one fast food restaurant on the island: KLG, the local equivalent of KFC. It looks a lot like KFC, and the food tastes a lot like KFC, but it is not KFC.

We got set up on the sky and ready to go more than an hour before we could start taking our data of the sky at twilight for calibration purposes (because the sky was still too bright). Fortunately, we had plenty of time because it started raining. We had learned from a previous night to set all the electrical equipment close together and off the ground so if (or should I say, when) it starts to rain we can continue running power to the equipment and drape a tarp over the telescope. We covered the telescope with tarps again and waited out the rain. The rain was brief and we waited for the right light levels to get our calibration data. We realized that the best time for our twilight calibration data is precisely when the bugs come out and start biting. Fortunately, we were prepared with bug spray.

—Picture courtesy Cathy Olkin

After our calibration data, we got a good alignment of the telescope allowing us to point the telescope to our targets accurately. Then it rained again! We threw tarps over the telescope to wait it out. We commanded the telescope to ‘sleep’ while the tarps were over it so the alignment wouldn’t be lost.

Now we just needed to wait until 11 p.m., when we would start recording data for the occultations (Pluto and Charon). We watched the clouds come and go, then more clouds coming. Since we were at the Weather Service Office, we checked the time-lapse movies of the radar images. It didn’t look good. There was a storm forming and it was going to be hit-or-miss on whether we would have clear skies.  We had the telescope pointed at the star field for the occultation and the stars would disappear and reappear as the clouds moved by.  At 11 p.m. there were no thick clouds, and instead a thinner haze was overhead. Our system could handle that as long as the clouds didn’t get too thick. We started recording data and stared intently at the computer screen looking for any indication of the star dimming which would indicate we observed an occultation.

Finally Harold and I both saw it, the star was fainter than it had been and only that star was fainter (meaning that it wasn’t clouds).  We watched and it was faint for a long time, around 90 seconds—not what we were expecting. The most recent prediction had us outside the shadow path to the north, so we were expecting at most a graze from Pluto, but with a more than 90 second chord, we were near the center of the shadow! We were excited and astonished that we were near the center of the shadow and that the clouds stayed away long enough for us to record the data.

—Picture courtesy Cathy Olkin

The next hour was spent intensely reducing the data to share with our colleagues, who were also observing these occultations from all across the Pacific. We monitored e-mail to hear how the other teams were doing. It was great hearing the reports from all the other teams. The June 23 occultation observation was a success. Now on to the 27th!

(The Pluto occultation research is supported by NASA’s Planetary Astronomy program, NASA’s New Horizons Mission, the National Geographic Society’s Committee for Research and Exploration, and the Southwest Research Institute.)

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