Last night's (304) Olga Occultation Timed at 2 stations in Virginia
I video recorded a 2-second occultation south of Ashland
David DuPuy and students timed it visually at the Virginia Military Institute's observatory in Lexington
Updated: 2006 April 25
Last tonight, I video recorded the occultation of TYC 0777- 00134-1 by (304) Olga with an 8-inch SCT from a location about a km north of the Hanover County Airport south of Ashland, VA and about 4 km south of Steve Preston's central line. The occultation lasted about two seconds around 1:17:37 UT. I'll get the coordinates and accurate times later; this was the first occultation that I recorded using my new Collins image intensifier (nice to see the 10.4-mag. star appear relatively bright, surrounded by 13th-mag. stars, making it easy to find the target star). Below is my answer, then David DuPuy's report, of the observations at VMI. David, Many thanks for your observation. This was the occultation of the Davids, since as far as I know, only you and I observed it. Your estimated duration is probably most useful. Combining with my observation, it should be possible to get an approximate size of Olga [unfortunately, I think that's not likely since they were nearly on the same line as me; again, it would help to know observer's plans to deploy mobile stations like mine more effectively]. Next time, you could time the occultation more accurately either using a tape recorder (to directly record voiced calls of the events) or, with that large a telescope, you should use an electronic eyepiece or the $120 security camera (PC164C) available from Supercircuits to video record the occultation. See http://iota.jhuapl.edu/timng920.htm for more about timing occultations. David At 08:49 AM 4/25/2006, you wrote: David, I got a timing on the Olga event last night, and presume I send the details to you at this address?? I'm in Lexington, Virginia (at Virginia Military Institute). The telescope is a 20-inch DFM, so finding the star was no problem. The procedure was that I was at the telescope, and I had two cadets with me who each wrote down the seconds number from their wrist watches, which we had previously synchronized with the NavObs. I'm confident the times are good to the nearest second. Start: 9 : 17 : 30 End: 9 : 17 : 32 Long/Lat 79 deg 23' 39" +37 deg 45' 30" (coord of observatory) Elevation = 1080 ft. The event was considerably shorter than the predicted 3 seconds. My sense at the telescope was that it was no longer than 1.5 - 1.7 sec. I do not know how to estimate the drop in magnitude, but it was considerable and the star practically dropped out of sight. Start/End was very abrupt (very short fall/rise time). Can you shoot me a one-line email, so I know you got this okay. Do you need any other details? Thanks, David ------------------------------------------------------------ Dr. David L. DuPuy dupuy@vmi.edu 540-464-7504 Department Head Physics & Astronomy Department Virginia Military Institute Lexington, VA 24450 Elizabeth Warner and students watched the star from a couple of telescopes at the University of Maryland's observatory in College Park, MD, but as expected, no occultation occurred at that location 140 km north of center. An approximately 2.5-sigma north shift would have been needed to reach them. However, the actual shift was much smaller. Unfortunately, a few other observers in and near the path had equipment and/or schedule problems and so were unable to acquire the target star in time. One observer was ready at a mobile site just south of the predicted northern limit, but he brought the charts for tonight's occultation by Euterpe rather than the ones for Olga and wondered why the star was so low, not realizing his error until he got home. As noted before, there just wasn't enough dark time after sunset to set up and pre-point a remote telescope. Steve Preston's prediction must have had an error smaller than half a sigma or so for me to have had an occultation near the center. I think the relatively low number for Olga gave it a better observational history so we didn't get a surprise like the 1.5+ sigma south shift we had for (1315) Bronislawa last week. We were also lucky with the weather, with nice clear skies for both Bronislawa and Olga, but heavy rain over the weekend between them. But our luck will run out for the 27 Euterpe occultation tonight (Wed. 1:26 am EST, 5:26 UT) - Astro Meteo is forecasting essentially overcast skies across Virginia, Maryland, and most of W. Virginia. They are forecasting clear skies in most of Ohio for that event, and also from s.e. Alberta to southern Wisconsin, so hopefully some observers in those areas (such as Milwaukee & Madison, WI; Minneapolis; & N. Dakota) will observe that 0.4-mag. drop event (for details, see Steve Preston's page for it here). For the Olga occultation, predictions, links to charts, and pre-event plans are here. _____________________________________________________________________ David Dunham, 2006 April 25 phones home 301-474-4722; office 240-228-5609; cell 301-526-5590 Home (IOTA) e-mail dunham@starpower.net