From: Walter Morgan [WVM13@aol.com] Sent: Monday, October 31, 2005 10:44 AM To: Dunham, David Subject: Tercidina Notice 1 Occultation by (345) Tercidina This is a call for observers for Monday evening, November 14, 2005. On that date, at approximately 10:06 p.m. PST (6:06 November 15, Universal Time), northern California will have the opportunity to witness the occultation of the magnitude 8.9 star TYC 5227-00241-1 by asteroid (345) Tercidina. Depending on the position of the observer, the star will be occulted for as long as 7 seconds. Observers with or without experience in occultation timing are encouraged to join this effort. On request, assistance can be provided to help an individual with techniques and equipment that will lead to accurately timed observations. This is a very favorable occultation opportunity, because the star (in Aquarius) is bright and easily located, and, if occulted, its brightness will appear to decrease by 4.3 magnitudes. (During the occultation the asteroid will be visible only for those with very large scopes, or very sensitive cameras. For most, the star will simply seem to disappear.) At the time of the occultation the target will be at an elevation of 25 degrees, at azimuth 240 degrees (southwest). The event will also be visible from Kansas, Nebraska, Colorado, Utah and Nevada, but northern California is favored because the elevation of the target elevation is higher there. The moon will be near full, but being 69 degrees from the target star it will not interfere significantly with finding the star or observing the occultation. In fact, the bright moon will provide welcome illumination for getting mobile equipment ready. Attached to this message is a map showing the nominal limits for the occultation path across northern California. As always, the actual location is uncertain, but with a Rank of 99, the error for this path is unusually small. The solid green lines on the map indicate the predicted limits of the path, and the red lines near the top and bottom of the map are the one-sigma limits. The predicted path width is 128 kilometres (80 miles). While mobile observers will primarily be positioned between the green lines, observers who are not mobile are encouraged to participate even though they are somewhat outside the red lines, because the path location is not known with certainty. The actual path could be somewhat north or south of what is indicated on the attached map. An occultation by this asteroid was well-observed in September 2002, and data from 24 observers indicated that the asteroid shape differed significantly from an ellipsoid. To see the data from 2002, go to www.poyntsource.com/BREIT_IDEAS/index.htm and click on the Tercidina heading. Each straight line segment on that plot represents a time interval during which the star was occulted for a specific observer. (Exception: the lowest line was a miss that established a limit for the asteroid's size.) The rotational orientation of the asteroid will be different for this year's occultation, and a good turnout on November 14 will be necessary to describe it accurately. The distribution of observers for the 2002 event was perhaps better than usual, but notice that in several places the chords are very close together (in several instances separated only about one kilometer), nearly duplicating each other. This year, with the cooperation of the observers, a more uniform distribution, with minimal chord duplication, can be achieved. But getting observers suitably spaced requires good coordination. If you think that there is any chance that you will be available for this event, please respond so that a good spacing plan can be developed. (No demerits will be issued for those who respond, but find later that they cannot observe.) A dozen lines below the plot of the 2002 Tercidina observations (on the BREIT_IDEAS website) is a heading "Tercidina ALT AZ Finder Charts." Clicking on that will take you to a set of four finder charts for the Tercidina target star. (RA: 22 09 58.6241 DE: -04 08 11.968) It is always advisable to locate the target star days or weeks before the actual occultation, so take advantage of the next clear night to do that. Currently the target star is south at an elevation of 48 degrees at 7 p.m. If you live in or near the path, and prefer to observe from, or near, your home, send your coordinates so the appropriate chord can be reserved for you. (If you do not have coordinates for your site, send an address. Mapping software should then be able to establish coordinates that are accurate enough for planning purposes.) All others should indicate any preferences. Most potential observers live south of the path centerline, so if you live in the northern part, or are available to travel to the northern part, please indicate that. If you will travel with a cell phone, please provide that number so that late-time adjustments can be made if necessary. When we have an estimate of the number of possible participants, and the fixed site locations, a data base will be prepared to plan for distribution of mobile observers. Locations close to either I-5 or Hwy 99 should work very well for most mobile observers. If you believe that you will be able to participate, please send the following to Walt Morgan at: wvm13@AOL.com a. your name and email address b. equipment: scope size and recording method (audio or video); time source c. coordinates of observing location (if observing from or near home) d. preference for observing location (if mobile) e. cell phone number (if applicable) Potential observers will be provided update and reminder information. Walt Morgan - Northern California Tercidina Coordinator