Occultation by (491) Carina in Calif. & Ariz., July 6
Probable 2.6-sigma prediction error is largest in recent years
Largest deployment for an asteroid occ'n; unattended scope taken & recovered
New: 2004 July 19The attempts to observe the occultation of a 9.9-mag. star in Aquila by (491) Carina on July 6th set a couple of records. First, it had the largest shift from Steve Preston's prediction of any of his predictions where we have some idea of where the path went, in terms of the claimed accuracy. Sam Herchak's single positive observation well north of the path near Payson, Arizona, and Bob Jones' negative observation just inside the northern limit northeast of the Salton Sea, indicated an approximately 2.6-sigma north shift. Steve Preston has examined the DSS image of the star, and found some suspicious "bumps" near it. A 12th-mag. star blended with the target star could easily throw off the astrometric measurements by several times their normal accuracy, and that could happen in this low galactic-latitude star-rich region. But I claim another record for the Carina event - the largest deployment by one observer for any asteroidal occultation. After less than 2 hours of sleep, I spent more than 4 hours setting up 4 stations near Calif. highway 111, a north-south road about 3 miles east of El Centro. As it turned out, even that wasn't enough time. But I did get 4 telescopes set up at approximately five-mile (8 km) intervals over a total distance of 16 miles, each of them with finders collimated and video cameras attached and focused. Half an hour before the event, 3 of the telescopes were correctly pointed, but then, as described below, things started to unravel, and only one of them successfully recorded the target star, for an almost 3- minute interval centered on the predicted occultation time. Like the several other observers (excluding Herchak) of this event, it was a miss (no occultation), as all the other stations would have been. One of the stations failed because it was taken, another dubious "first" for an unattended telescope, but fortunately recovered. It underscores the care that must be taken in setting up and hiding unattended equipment - you do so at your own risk, IOTA does not encourage this and will not be held responsible if a loss occurs. There were signs that it was not a safe location, which I ignored at the time, but won't in the future, and hope you don't, either. Below is an account of the night's activities, but first, a description of the equipment. I flew on Southwest Airlines from Baltimore to Ontario, Calif. with two clamshell suitcases, each containing a 5-inch Celestron and 4-inch Meade and each with simple metal stick mounts. Also in the suitcases were 50-mm finder scopes for each telescope, which had dovetail bases; the plastic screws were all removed from the finders and placed in plastic baggies so they wouldn't be sheared off (as happened for two of them when I made a similar trip with 3 telescopes last October). Batteries for the PC-164C video cameras were also in the suitcases, along with clothes, towels, and a pillow to fill the space to safely transport the suitcases that way. At home before I left, each suitcase weighed 69 pounds, just one pound under Southwest's 70-lb. limit; most of the other major airlines now have 50-lb. suitcase limits. The PC-164C cameras, short-wave radios, 3 camcorders, a Sony Video Walkman, and a few other items were in a hard-sided carry-on case well within the size limits; it weighed 28 lbs. I also had papers for the occultations and the IOTA meeting in a "personal item" laptop bag (along with the laptop) which weighed another 20 lbs. Travel with all of this stuff was tiring, but uneventful (that is, safe; nothing broke). The occultation was predicted to occur at 4:28 am local time (PDT; = 11:28 UT) of July 6. I arrived in El Centro at 10 pm and got a room at the local Motel 6. Then I located a site for the southernmost station, which I was most concerned about because it was only 4.5 miles north of the Mexican border and 3.5 miles north of the downtown part of the sizeable city of Calexico. I found a good site at a turnoff from a frontage road a couple of tenths of a mile south of Heber Road; it was a good dark site with no lights or buildings within half a mile and I could set up a telescope in back of a sign so it couldn't be seen from the frontage road. I'll call this station #1, and number the others consecutively northward. I went back to the motel to get some much-needed sleep. A little after midnight, I set off for station #2, finding a good site between Aten and Cruikshank Rds. about 6 miles north of station #1. Untraveled old hwy. 111 parallels the current Hwy. 111 there, and there was a turnoff into a field where I set up one of the Meades behind some bushes where it was hard to see (the scope's dark blue color helps in that regard). I was able to locate a 9th- mag. star near lambda Ophiuchi in the video field at the right time such that the target star would be there at 4:28 am; I clamped the telescope axes there and left it with the usual "Please do not disturb - precisely pointed telescope to observe the eclipse of . ." . etc. and giving my cell-phone #. Then I skipped station 3 and went to the northernmost station 4, planned for Mead Rd. about 1.5 mile southeast of another sizeable town, Brawley. There was a dirt road paralleling Mead Rd. so I set up a C-5 beside that road near a telephone pole next to a sluice gate in a parallel small irrigation canal. Like most of the Imperial Valley, where only low crops are grown with the little water available, there was no vegetation nearby to hide the telescope. While locating gamma Ophiuchi, a vehicle passed me on the dirt road, which I thought a little strange, it being after 2:30 am. Shortly after it passed, I looked up, expecting to see its tail lights well in the distance, but I didn't see it at all. I clamped the telescope pointed at gamma Ophiuchi at the right time so the target star would be there at 4:28 am, and left to locate station 3. I found a good site for it, in a field about 100 yards south of Harris Rd. and 0.3 mile west of route 111, aligned the 4-inch Meade and focused the camera, but at that time, there were no easily-found stars at the declination and hour angle that the target star would have at 4:28 am. So I left the station, with the intention, if there was time, to return and point the telescope properly before the occultation. I went to station 1 and set up the other C-5 there, and got it pointed in the right direction, now only half an hour before the occultation; time was running out. Now the unravelling began. I went to clamp the C-5's declination, but somehow loosened it instead and the scope swung. I swung it back to approximately where it was, checked the finder field but didn't recognize the stars, but now there was no more time; I had to return to at least stations 2 and 4 to connect and start camcorders to record the event. I started one at station 1 just in case it was pointed all right (inspection after the event showed it wasn't) and went to station 2. I connected a camcorder there and started recording, along with WWV time signals, then left to station 4. I got there about 7 minutes before the occultation, but discovered that the white C-5 was gone! Thinking maybe I had the wrong road, I went up to the next one half a mile farther north, a turn-off with weeds that would have been much better, but that wasn't it. I went back to where the C-5 had been and saw many footprints there, mine from setting it up. But there were a couple of other footprints on top of mine. Now, almost at event time, I knew that the scope had been taken. I looked up, and noticed 200 feet farther west down the road were two parked vehicles, both with farm workers asleep in their cabs. One was a pickup; nothing in its back, and the cab was too small for anything but the driver. The other was a camper with the windows dirty and mostly covered, but I shined my flashlight in a clean hole in the back - there was the C-5! I woke up the worker in the cab and asked him to open the back; at first, he just said "no comprende". I was rather agitated and he soon figured out what I wanted, and opened the back, letting me take the telescope and the video camera battery, which I had disconnected. He meekly indicated that he thought I had just left the scope there like I was dumping a broken appliance; he couldn't read my sign (next time I'm in the southwestern USA, I'll also leave one in Spanish). If he had been more intent on stealing the scope, rather than just picking up a "discarded" item, he could have driven a mile or two away and I would have never seen it again. The telescope was in an exposed location (considerably more so than the others), easily visible with its white barrel. After the vehicle passed me on that lonely dirt road, I should have realized it was no longer safe. Twilight was just beginning, so I hurried to pick up the other scopes (two with camcorders running) before they might be discovered by workers beginning daily activities. That was uneventful; they were in better locations that attracted no attention. I returned to the motel, disassembled and packed everything, and slept another half hour before leaving to catch my flight at Ontario. Inspection of the video obtained at station 2 showed that it did record the target star at the right time. Better than leaving fixed-pointed telescopes unattended is to leave them at a home with the owner's permission (usually easy to get if you set up before 10 pm), or leave a less-skilled observer, or anyone, with the scope. The latter has the advantage that the person with the scope can start the camcorder at the right time so you don't have to do that with a "last-minute" run between the stations, allowing the stations to be placed farther apart. That actually happened, successfully, for the 559 Nanon occultation on July 1, where I set up one C-5 and pointed it about 1.5 hours before the event, at a location a few miles west of 29 Palms, Calif., leaving Don Stockbauer there to turn on the camcorder and plug in the PC-164C and PA3 microphone batteries five minutes before the occultation. He made no adjustments to the telescope pointing, which was fixed, not driven, but he did look at the target star as it drifted across the camcorder field of view and saw the occultation when it occurred. In the meantime, I had driven about 13 miles farther east where I set up one of the Meade 4's to successfully record the occultation at that location. Because my flight to Ontario had been delayed, and the drive from Apple Valley to the sites 100 miles away at 29 Palms was long, there was no time to set up a 3rd telescope for Nanon. The lessons learned are that the equipment can be transported by plane and works for stars of mag. 10.0 and brighter; that even more time needs to be used for such ambitious endeavors, at least 1.25 hours (and preferably 1.5 hours or more) per station, preferably for an early morning event with setup starting even before sunset; and that care needs to be taken in finding attended or well-hidden sites. The temporary loss at station 4 was almost prevented, and another miss chord could have been obtained there, if I had picked up Dan Falla in San Diego on the way to El Centro. He was interested in helping, but I wanted to drive back to Ontario airport by way of Palm Springs rather than the only slightly longer way, but with much more daytime traffic, via San Diego, so I couldn't return him and decided against it. As it turned out, by going by way of Palm Springs, I arrived at Ontario airport about 3 hours before my flight departed; I would have had enough time to drive Dan (who does not own a car) back to San Diego and should have done that. I definitely would have left him at station 4 to give me less distance to travel between the other stations before the occultation. For an occultation that occurs over an observer's home or observatory, they might set up one station there to be run by their spouse or a friend, pointing it in the right direction beforehand, and then travel away to observe with a portable telescope at another location. Roger Venable, Steve Preston, and I have all attempted that for some events, and others who have two telescopes and recording systems might do that as well. David Dunham