Occultation of 16 Piscium by (7) Iris, Fri. am, May 5, 2006
Bruce Thompson, Ithaca, NY, video recorded spectacular step events as the bright star, newly resolved as a close double, was occulted by Iris
The occultation was timed visually through cirrus at Dickinson College, Carlisle, PA; there are 3.5 other positive observations
Updated: 2006 May 31
The information below the "________" below was written on May 5, soon after the occultation. Since then, we have received some more observations: Brad Timerson at Newark, NY video recorded a short occultation apparently of only the secondary component of the double star; it was a relatively shallow drop in brightness. The next three observers below did not notice the stellar duplicity: Marek Kozubal at the Clay Center Obs. in Brookline, MA video recorded the reappearance; the disappearance was clouded out. John Holtz visually timed the occultation from his home north of Pittsburgh, PA. Frank Melillo at Holtsville, Long Island, NY visually timed the occultation. ________ Below are messages describing the two positive observations of this spectacular occultation. If you were not one of those observers and were in southern New Jersey, northern Delaware, most of southern New York, and some other areas where it was clear, you missed a good one, and unfortunately with only two chords the size and shape of Iris is not very well-determined. But we will be able to get some measure of the parameters of the close double star. _________________ Messages to and from Bruce Thompson Bruce, Thanks for this. I inserted the observatory coordinates. The double star event assymetry just indicates a PA effect, the components were neither exactly north-south nor east-west relative to the motion of Iris. Were the steps of nearly equal brightness? If not, you should be able to tell whether the sequence was D1-D2- R1-R2 or D1-D2-R2-R1 (or reverse the 1's and 2's, if they denote primary and secondary star). The nature of the duplicity is important to try to figure out which components were involved in the events that Richard Greenberg observed visually at Carlisle. Now I'm really disappointed that I wasn't a few miles farther south in the clear area in New Jersey where I could have recorded a nice video of this, too, from the south side that would have helped a lot in determining the parameters of the double star. David -----Original Message----- From: Bruce Thompson [mailto:bthompso@ithaca.edu] Sent: Friday, May 05, 2006 1:11 PM To: Dunham, David Cc: Richard Greenberg Subject: Re: Iris occultation David, Our e-mails must have crossed in transit. Here is the text I just sent to the IOTA newsgroup....... Cool but clear weather and a clear enough horizon in Ithaca. The spectacular Iris occultation was recorded near the Cornell Hartung observatory at 169N. Lat. 42 deg. 27' 29." Long. -76 deg. 23' 05." CornellHartungBoothroydObs. h 1900 feet (h is wrong, it's 1755 feet according to www.topozone.com) A definite double star step was noted during the event and confirmed by a preliminary look at the light curve. One curious aspect is a time asymmetry between the D and R steps. Preliminary results are: D1: 9:02:08.6 UT D2: 9:02:08.8 R1: 9:02:12.1 R2: 9:02:12.6 More accurate numbers and lightcurve to follow. I hope others had success! Bruce Thompson Tayza Yeelin Ithaca, NY 10" LX200, Watec 902, Moog FR, Kiwi stamp, .avi, home grown field accurate analysis, W76 23.1 N42 27.5 and From: Dunham, David Sent: Friday, May 05, 2006 3:18 PM To: 'Bruce Thompson'; 'greenber' Cc: 'Dunham, David & Joan, home'; 'Robert Boyle'; 'Richard Greenberg'; 'AU ACT Woden Herald, David'; 'C CZePraha StefanikOb. Jan Manek'; 'MD Sykesville Jarret Dixon' Subject: RE: Iris occultation Bruce, from your plot, it looks clear to me that the secondary star disappeared before the primary star and reappeared after it, that is, the event was more central for the secondary star, and the sequence was D2-D1-R1-R2. At Carlisle, being I think south of center, the sequence was probably reversed, D1-D2-R2-R1, but especially with the cirrus that was present, only the primary star events were probably seen. David -----Original Message----- From: Dunham, David Sent: Friday, May 05, 2006 3:13 PM To: 'Bruce Thompson'; greenber Cc: Dunham, David & Joan, home; Robert Boyle; Richard Greenberg; AU ACT Woden Herald, David; C CZePraha StefanikOb. Jan Manek; MD Sykesville Jarret Dixon Subject: RE: Iris occultation -----Original Message----- From: Bruce Thompson [mailto:bthompso@ithaca.edu] Sent: Friday, May 05, 2006 3:04 PM To: greenber Cc: Dunham, David; Dunham, David & Joan, home; Robert Boyle; Richard Greenberg; AU ACT Woden Herald, David Subject: Re: Iris occultation Here are two brightness pictures for last night's Iris occultation. One is the analysis with fields and the other with two fields combined to produce a frame before analysis. It seems like there is some indication of a step in the disappearance in the field picture that gets washed out in the frame one. The reappearance step lingered for a half second! Plot by fields. Plot by frames. If this is a PA angle effect, it seems that at entry the angle of the edge of the asteroid nearly matched the PA. Then on exit they clearly didn't match. Bruce greenber wrote: > Hi all, > I was wondering what a Pennsylvania effect is, but I guess PA > means position angle. > Note that the lead observer for the Dickinson College > Observatory team was Robert Boyle. (Formal name of the observatory is Michael L. > Britton Observatory at Dickinson College.) Any record of a step in > brightness would be recorded in Robert's memory, if anywhere, but he > did not mention it at the time of the observation. My guess is that > what he timed was the first and last event, especially if the star's > full mag was reduced by cirrus. > Does the timing and duration at Ithaca relative to Carlisle make > sense in terms of trajectory and physical shape of Iris? > --Rick ____________________ To: Richard Greenberg Cc: NYiIthaca Bruce Thompson Subject: RE: Iris occultation Richard, Thanks for this. It looks like your height above sea level was about 500 feet from the topozone site. So far, I haven't heard of any other successes. I tried to observe the event from central New Jersey and have a recording of what may be the star, very faint due to thick cirrus; it turns out I was only 10 miles from a 40-mile- wide clear area farther south. I didn't notice an occultation, but the viewing was so marginal that I might have missed it, and might also have been on the wrong star, since the clouds made it very difficult to "navigate" (not a go-to telescope). The IR satellite image confirms what a few observers in Maryland reported, that it was cloudy across the state. The Boston area, where a few were going to try it, was also clouded out. It looked like it was mostly clear over southern New York; I'm copying this to Bruce Thompson to see if he was successful; there were a couple of other observers who planned to try it in the areas were it looked like it was mostly clear. David -----Original Message----- From: Richard Greenberg [mailto:greenberg@lpl.arizona.edu] Sent: Friday, May 05, 2006 11:59 AM To: Dunham, David Subject: Re: Iris occultation Hi, I am reading 40 deg 12.23'N, 77 deg 11.86W from topozone. i will let you know the nominal coordinates of the observatory when I find out. Who else saw it and got data? --Rick On May 5, 2006, at 10:38 AM, Dunham, David wrote: > Richard, > Thanks for this, glad you were able to get the observation in > spite of the clouds. Could you use either GPS, Google Earth, or > www.topozone.com to determine the coordinates of the observatory? > David > > -----Original Message----- > From: greenber [mailto:greenberg@lpl.arizona.edu] > Sent: Friday, May 05, 2006 6:25 AM > To: dunham@starpower.net; Dunham, David > Cc: Robert Boyle > Subject: Iris occultation > > Hi David, > The occultation by Iris was observed this morning at Dickinson > College Observatory in Carlisle, PA. > We were shooting through clouds, so the planned TV recording > was not possible. Instead it was observed visually by Prof. Robert > Boyle at the eyepiece, calling off the start and finish of the > occultation, recorded on video tape showing a WWV coordinated clock. > Despite the clouds, the occultation event appeared sharp and distinct. > Preliminary results show start at 5:02:03.94 and duration of > occultation of 3.88 seconds. These numbers are preliminary and may be > revised after we time the recording more carefully. > Observers were Robert Boyle, myself (visiting from Arizona), > and several Dickinson College students. This is preliminary. A more > detailed report will follow. > --Richard Greenberg The weather satellite IR image covering much of the path near the time of the occultation is here. Pre-event predictions and plans are here. __________________________________________________ David Dunham, IOTA 2006 May 31 EDT phones home 301-474-4722; office 240-228-5609; cell 301-526-5590 Home (IOTA) e-mail dunham@starpower.net