Good grazing "eclipse" of ZC 2702 Wed. evening, Oct. 17 - Updated 2007 Oct. 17, 4 pm EDT
Weather permitting, the crescent Moon graze can be seen easily with any small telescope from a rather wide path extending from southern Alabama to Maine
We need MORE help to time the multiple occultations of the star from locations in the graze zone, to map the polar lunar mountains and craters
Skies are still mostly clear from central Virginia to just north of Trenton, NJ; proceeding with expedition to s. Columbia, MD as planned
The path passes over populous areas, including Atlanta, Washington, and Baltimore, plus Philadelphia suburbs
In the DC region, Manassas, Fairfax & McLean, VA; and Bethesda, n. Silver Spring, the Applied Physics Laboratory, and Columbia, MD are in the path
My effort will concentrate on Atholton High School and vicinity in southern Columbia, MD
The visible satellite loop shows lots of clouds in West Virginia, but they are mostly dissipating as they move eastward, and it's still clear along the path across most of Virginia to just north of Trenton, N.J. So in spite of the last Astro Meteo forecast, copied below, I think we have a good chance for clear skies for this good event across the Washington, DC region, and I am proceeding with my plans, described below, to set up multiple telescopes at and near Atholton High School in southern Columbia, MD. If you can come join us there, to help me run the 6 stations that I plan to set up, I'd appreciate it. And if you have your own equipment, there are many places in the area to set up. If you live elsewhere in the path, please try to observe the graze from home, or from the location most convenient to you; best will be in locations outside of the range from 0.5 km north to 1.2 km south that we plan to cover in Columbia, MD. ___________________________________________________ At noon, I wrote (but superseded by the above: The fourth Canadian Astro Meteo forecast (Clear Sky Clock uses it) is now available; it's the last one before the event, with a 12h prognosis. It's not good, showing mostly cloudy from Manassas, VA to n.w. of Philadelphia. But it might not happen; the forecast for the current time is much more pessimistic in the Maryland/W. Va./northern Va. area than the actual visual satellite image shows. So we'll go more with what actually develops during the afternoon, deciding about 4 pm what to do (which I've done; see above). The Astro Meteo forecast is best for the area from Perkasie, PA to the Hudson River, and central VA, around Charlottesville, and maybe in the Conn. River valley of Mass., and poor, overcast to mostly cloudy, along most other parts of the path. ___________________ And I wrote last night: Expedition to southern Columbia, Maryland Those working at Applied Physics Laboratory (APL) who have telescopes and/or timing equipment and who live outside the graze path, are encouraged to pack their equipment in their cars to have it with them during the day tomorrow. Others who can travel to the graze path are also encouraged to have their equipment with them to be ready for the event in case the forecast clear skies do happen. If it is clear enough, you can be ready to either observe from APL, or join my effort near Atholton High School described below. I plan to concentrate my effort, with most of the 6 telescopes and video recording systems that I have, at and near Atholton High School, 6520 Freetown Rd, Columbia, MD 21044, since the grounds, playing field, and nearby fields and parking lots provide places that woill have good views of the Moon from one of the most interesting parts of the lunar profile. I've scouted out the area, and have found several safe locations that will have good views from 0.5 km north to 1.2 km south of the smooth-Moon southern limit line (the green line on the maps). I've added maps showing the area around Atholton High School to this Power Point file. Those interested in joining this effort can meet me at the first (northern) parking lot just south of the athletic fields at either 5:30 pm or 7:00 pm EDT; if you can come to the earlier meeting time, that will help (if the weather looks like it will be good enough to warrant the effort). To get there, take the Cedar Lane (north) exit from Route 32 (it's the first exit west of the interchange with US 29) and travel north on Cedar to Freetown Rd. Turn right (east) onto Freetown Rd. and go 0.6 mile to just past Fair Oaks (on your left) to the north entrance to the Atholton High School parking lot on the right, just south of the athletic fields (which you will pass on your right). My mentor student Jennifer Cheng is a student at Atholton H.S. and may be able to get others there to help with the effort. The green limit line passes through the High School track field, while the school buildings are south of it. If you have trouble reading the Power Point files, the .jpg map files are here for the general area, the detailed view on the south side of the school showing the meeting place, and the detailed view on the north side of the school, but these are not labelled showing the meeting place and high school like the Power Point file. In addition, APL is in the graze path, and some members of the APL Astronomy Club will probably try to observe the graze from the north ball field near the pavillion at the north end of campus, where the star party was held last month, if the weather warrants the effort. If it looks reasonably clear, it would be useful to get observations from other parts of APL, such as from the parking lot at the corner of Sanner and Johns Hopkins Roads, and from just south of the intersection of Montpelier with Johns Hopkins Rd. We'll talk about this during the Astronomy Club meeting at noon in classrooms 5-6 of the Kosiakoff Center. Good luck with your observations. David Dunham, 2007 October 17, 3 am EDT Phones home 301-474-4722; office 240-228-5609; cell 301-526-5590 office e-mail david.dunham@jhuapl.edu home e-mail: dunham@starpower.net _______________________________ Below is part of the message that I sent to amateur astronomers near the whole path from Virginia to Maine Monday night (Oct. 15/16). ________________ A Rare Opportunity to see Celestial Motion If you live in the 5-mile-wide ZC 2702 graze zone, extending across Manassas, Fairfax, & McLean, VA; and Bethesda, n. Silver Spring, Columbia, n. Baltimore, and Bel Air, MD, you have a rare chance to observe the sky's dynamic motion, higher than any Earth- orbiting artificial satellite, as the 6.8-mag. star flashes on and off among craters and mountains along the rugged south pole region of the Moon for a few minutes just before 8 pm Wed. evening, Oct. 17. The last time we had such a good event in the Washington, DC region was when the Maia graze occurred over the northern and eastern Maryland suburbs in April 2006. You don't need a large telescope to observe this event, and you might not want to take the time to set up your biggest instrument (unless it's ready to go in an observatory) for a show that lasts only a few minutes. Any small telescope, with lens or mirror 2 inches or larger, can see this event, and might be easier to transport and set up. _______________ Timing the graze to determine the lunar profile Besides watching such an interesting event, even more rewarding would be to also time the series of disappearances and reappearances of the star. This way, you can add to the efforts of other observers to build up details of the lunar topography, to see how the mountains & valleys that caused your events line up with those of observers nearby on the profile. If all amateur astronomers who live within, or could travel into, the graze zone could time this graze, we could obtain an extremely detailed profile of the Moon's mountains and possibly even set a record for such an event (although the over 300 timings and 55+ stations deployed near Houston for a graze in 1985 will be hard to beat). You can just call the events "off" and "on" or "D" and "R". Sometimes, a mountain top will occult the star so briefly, maybe just a few tenths of a second, that you can't call "off" and then "on"; we call such an event a "blink". Similarly, the star may "flash" briefly in a deep but narrow lunar valley, and even partial or gradual events, caused by Fresnel diffraction of the star's light at the Moon's edge, might be seen. Much more on timing the grazing occultation is given in a section near the bottom of this page; we plan to time-calibrate WTOP at 103.5 FM so that station, which can be heard on any car radio in the northern Virginia/central Maryland area, can be used as a time base. _______________ The Star, ZC 2702 The star, ZC 2702 = BD -28 deg. 14765 (actually, that's a Cordoba Durchmusterung #, since the actual Bonner Durchmusterung only extends to about dec. -22 deg.) and its SAO number is 187048; the star is at J2000 RA 18h 37m 03.4s, Dec. -28 deg. 30' 47". On Wed. evening, one won't need a star chart to find the star; it will be the only relatively bright star close to the southern edge of the Moon, and observers can just use my view of the Moon to follow the star in. But some have telescopes with Go To features that work best for finding stars using either the SAO number or the J2000 coordinates. You can get the ZC catalog here. _______________ Coordinating observations, especially in n. Virginia and Maryland Please help us coordinate observations of this good grazing occultation by letting me know if you're in the path and will be trying to observe it. [Note: With the current worse weather forecast, not knowing which locations might be clouded out, there is less incentive to do the work to figure out coverage; in general, we'll take what we can get with the least effort]. If you reported your coordinates or address to me before January 2007, I probably included you in the 2007 graze predictions and you are likely to be in the "observer scan" list for this graze below, which includes all stations I have within 4 miles of the smooth-Moon southern limit line as defined by the "Grazereg" program. A longer "observer scan" list including some observers with large travel radii even more than 100 miles away are included in this full list. In the observer list, the observers are listed from west to east, but their coordinates are not given here. They will be included in the longer list at the above link, but the coordinates are given there only to the nearest 0.1 deg. The list only tells the distance, but not whether you are north or south of the line. I know for some of the stations which direction it will be, but it would help my planning if you could go to Brad Timerson's Google Maps Web site and zoom in on your location; if you double click on your location, it will center the map there and display the map center long., lat., and distance in km north or south of the limit line. The Grazereg line below is 0.4 mile (or 0.6 km) north of the "Occult" program limit line, which is what I've used for all of the maps I've made of this event and also which Brad Timerson used for his interactive Google Maps Web site. EVENT: OCT. 17, 2007 STAR: ZC 2702 SAO 187048 HIP 91273, MAG. 6.8, SPEC. K0 MOON: 36% SUNLIT, WAXING SOUTHERN LIMIT GRAZE EAST LONG. NORTH LAT. UNIV.TIME MOON MOON SUN POS.ANGLE CUSP DEG. ' " DEG. ' " H M S ALT. AZI. ALT. OF GRAZE ANGLE - 77 30 0 38 43 24 23 58 8 17.6 206.3 -18.1 163.63 14.1S - 77 15 0 38 54 36 23 58 27 17.3 206.6 -18.3 163.61 14.1S - 77 0 0 39 5 48 23 58 46 17.0 206.8 -18.6 163.61 14.1S - 76 45 0 39 17 2 23 59 4 16.8 207.1 -18.0 163.60 14.1S - 76 30 0 39 28 18 23 59 22 16.5 207.3 -18.3 163.60 14.1S GEODETIC DATUM USED: WGS 84 (GLOBAL) STAR CATALOG: XZ80P PREDICTION GRAZEREG-VER. 2007 BY IOTA/ES, E RIEDEL & D Dunham, IOTA OBSERVER SCAN CITY STATE OBSERVER/STATION DISTANCE, UT CLOSEST Fan Mtn Obs VA Univ.ofVA 32in. 1.9 MI. UT 23.9432 CharlottesvillVA Univ.ofVA McCormick Ob 3.4 MI. UT 23.9475 Crockett VA NOVAC via Stewart A 2.8 MI. UT 23.9650 Nokesville VA Sam Somers 1.4 MI. UT 23.9677 Vienna VA Jeff Guerber A 1.3 MI. UT 23.9740 FALLS CHURCH VA FIALA~ALAN A 2.4 MI. UT 23.9746 Rockville MD Steven Miller 3.0 MI. UT 23.9772 BETHESDA MD MILLER~JAY H. A 0.1 MI. UT 23.9767 Bethesda MD Vince Sempronio mapson 0.9 MI. UT 23.9771 Bethesda MD John Wetmore A 1.9 MI. UT 23.9766 Bethesda MD Mikael Reardon A 0.6 MI. UT 23.9772 Silver Spring MD Ed Abel 20cm? 0.3 MI. UT 23.9790 Ashton MD Greg Mort 3.0 MI. UT 23.9801 Fulton MD John Carrico 1.0 MI. UT 23.9810 A P L MD N. field AC site A 0.2 MI. UT 23.9813 Columbia MD Don Gardner A 1.8 MI. UT 23.9821 Columbia MD Peter Chen 0.1 MI. UT 23.9827 Towson MD A.Storrs, Bates, WHW A 0.1 MI. UT 23.9868 Baltimore MD BlmbObs Tolea/STScI A 2.3 MI. UT 23.9863 Bel Air MD HCAS L. Hubble 2.6 MI. UT 23.9918 Garrison NY Frank Suits 2.1 MI. UT 0.0351 Williamsburg MA Bryce Babcock A 2.4 MI. UT 0.0543 in NH CARACAPPA~LON A 0.9 MI. UT 0.0620 _______________ Other events For information about other occultations and expeditions planned in the Mid-Atlantic region, click here. The rest of this page mainly has the same information that was posted last week; a few new maps, including Astro Meteo forecasts, have been added. _______________________________ _______________________________ Help us observe the spectacular rare grazing eclipse of a relatively bright star by the dark southern edge of the crescent Moon for about 6 minutes shortly before 8 pm EDT Wednesday evening, October 17th. Please pass this on to others in or near the "graze" zone of visibility. The detail of the lunar mountains that we can obtain from this event is proportional to the number of locations across the zone from which the event can be observed, so we need as much help as possible. _______________________________ FOR ANYONE WHO LIVES IN SOUTHERN HOWARD COUNTY, MARYLAND, IN THE VICINITY OF A.P.L., OR POSSIBLY ELSEWHERE IN THE GRAZE PATH ACROSS THE WASHINGTON, DC/BALTIMORE REGION: We need your help to map details of mountains and craters near the South Pole of the Moon. Even if you are not an amateur astronomer but if you live within the nearly 5-mile-wide path, or if you know of someone who does live in the path, we would be interested in setting up one of our telescopes and recording systems on a safe location near your driveway or yard where there's an unobstructed view 17 degrees above the south-southwestern horizon. Please contact me if you might be able to help with this; if you're ambitious, we might even let you try to run the equipment (with a little training), to turn on the recorder at the right time and follow the star using the telescope's slow motion controls and finder scope. _______________________________ FOR ALL AMATEUR ASTRONOMERS WHO LIVE IN OR NEAR THE PATH FROM SOUTHERN ALABAMA TO MAINE, OR NORTH OF THE PATH We need your help to map details of mountains and craters near the South Pole of the Moon. If you have any small telescope and if you either live within the graze path, or can travel to it, and have any way to record the multiple disappearances and reappearances of the star, preferably with a tape recorder or a camcorder that can be used as a tape recorder to record your call-outs of the events, you can help us with this event. We have some extra recording equipment and even small telescopes that we can loan, at least in the central Maryland area, if you don't have these yourself. If you live anywhere north of the path and can't travel to it, you can observe at least the disappearance of the star on the Moon's dark side as a total occultation. _________________________________________ THE PHENOMENON An eclipse, called "occultation" by astronomers, of a star in the constellation Sagittarius will occur over much of the eastern U.S.A. and Canada Wednesday evening, October 17th. Within a zone about 5 miles wide along the southern edge of the region of visibility of the occultation, the path of the star relative to the Moon's disk will be a tangent line. As seen from this "grazing" zone, the star will appear to approach the Moon from the lower left (south) side, drawing slowly closer to the Moon's edge until it appears stuck on the edge, "crawling" along it. For a nearly six- minute period, from 7:55 to 8:01 pm EDT for the Washington, DC region and 10 minutes earlier for Atlanta, the star will disappear and reappear, suddenly flashing off and on, among mountains and craters along the southern edge of the Moon. A view of the Moon showing the grazing geometry is shown here. You can see some video files of a similar grazing occultation here. The star is Zodiacal Catalog (ZC) 2702, a star of magnitude 6.8, meaning that it's too faint to be seen with the naked eye, and also will not be visible with most binoculars due to glare from the Moon. But any telescope with a lens or mirror 2 inches in diameter or larger can be used to have a good view of this event. The Moon will be a waxing crescent, 36% sunlit. The grazing occultation will occur on the dark side of the Moon, which will be faintly illuminated by "Earthshine" (sunlight reflected from the Earth), 14 degrees measured around the Moon's disk from the southern cusp of the crescent. In the DC/Maryland region, the Moon will be 17 deg. above the south-southwestern horizon. ZC 2702 = BD -28 deg. 14765 (actually, that's a Cordoba Durchmusterung #, since the actual Bonner Durchmusterung only extends to about dec. -22 deg.) and its SAO number is 187048; the star is at J2000 RA 18h 37m 03.4s, Dec. -28 deg. 30' 47". On Wed. evening, one won't need a star chart to find the star; it will be the only relatively bright star close to the southern edge of the Moon, and observers can just use my view of the Moon to follow the star in. But some have telescopes with Go To features that work best for finding stars using either the SAO number or the J2000 coordinates. You can get the whole ZC catalog at IOTA's Web site. _____________________________ COORDINATION IN THE DC/NORTHERN VA/CENTRAL MD REGION Please let me know your plans for observing this graze if you plan to observe the event from the greater Washington/Baltimore region. Many will be observing from observatories and other fixed sites near home, but many others will be mobile, travelling into the graze path. We want to suggest locations for the mobile observers that will avoid distances from the predicted limit line that will be covered by the fixed-site observers. This will give the best coverage for the graze, giving the best detail of the lunar mountains. _____________________________ THE PATH (GRAZE ZONE) and event times and circumstances The path passes over populous areas, including Atlanta, Washington, and Baltimore, plus Philadelphia suburbs. In the DC region, Manassas, Fairfax & McLean, VA; and Bethesda, n. Silver Spring, the Applied Physics Laboratory, Columbia, Baltimore, and Bel Air, MD are in the path. Note that the graze will last as much as 5 minutes long; you should observe, and be prepared to time events from, 3 min. before to 3 min. after the time of central graze for your longitude. For example, the central time is 23:58 UT (7:58 pm EDT) in the Washington, DC regionk (longitude -77 deg.) and 10 minutes earlier in Atlanta, GA (longitude -84 deg.). You can see the times and circumstances for other longitudes here. The path passes over many populated areas. It starts in southern Louisiana but in very bright twilight there; it becomes fairly easy to observe in southern Alabama. The path ends in New Brunswick, but the altitude above the horizon becomes too low to observe essentially in northeastern Maine. A small map showing the path from Alabama to Maine is here. The path also passes directly over Atlanta, GA, and over parts of n.w. S. Carolina, western N. Carolina, s.e. Pennsylvania, n. New Jersey, s.e. New York, n.w. Conn., w. Mass., s. New Hampshire, and s. Maine that you can see with maps in more detail at the hot links above, and in this Power Point file. The path across Virginia and Maryland is described below, and several maps showing the path in detail, especially across the Washington-Baltimore greater metro area, are in this Power Point file. Virginia: s.e. of Roanoke and near Lynchburg; Shadwell just e. of Charolottesville; Elk Run, s.e.Manassas, Fairfax, McLean with a more detailed path map over northern Virginia. Maryland: Bethesda, Chevy Chase, n. Silver Spring, Burtonsville, APL, e. Columbia, Catonsville, n. Baltimore, Bel Air A detailed map of the area around the Applied Physics Laboratory (APL) in southern Columbia is here. Links for the maps covering the path in these areas are above. Pennsylvania, n.w. of Philadelphia: Royersford, Harleyville, Perkasie New Jersey (n.w.): Clinton, High Bridge, Dover s. New York: Harriman State Park, Highland Falls You can zoom in on the path using Brad Timerson's interactive Google maps Web site. Scroll down to the map on "Oct. 17" and click on "ZC 2702" for the interactive map. I have done that to create the static maps above; the wide graze zone is between the two gray lines. In Virginia and Maryland, the offsets to define the graze zone are at +2.0 and -6.0 km. In Georgia, the offsets are -0.8 and -5.3 km (including the correction for approximately 1000 feet height above sea level). I've used these values for adjacent areas as well, but other values may be better if you plan to try to observe from locations rather far from either Atlanta, GA or Washington, DC; we can help you determine the offsets for your area, either Brad at btimerson@rochester.rr.com or me. ________________________ Timing the grazing occultation Much information about how to time occultations is here. Basically, use whatever resources you have, such as digital wrist watches, small tape recorders, etc., to try to time the graze events to an accuracy of 0.5s or better. It's necessary to have an accurate time base for the observations. This can be provided by WWV short-wave radio time signals at 5 and 10 megahertz, or by the 1PPS (1 pulse per second) signal that is used by some GPS receivers, such as the Garmin 18 (note that most GPS receivers display time only using the NMEA "sentence"; the procedure can cause errors of several tenths of a second, which we would like to avoid; we prefer to have times that are accurate to 0.5 second or better). Since few observers have accurate time sources, we plan to record at one location WTOP at 103.5 FM along with WWV time signals. That will create a master tape that can be used to determine the time of all syllables in the WTOP broadcast, so observers throughout the greater Washington, DC/Baltimore region can use their car radios (or a transistor radio) to play WTOP and make timings relative to it. Timing equipment and even telescopes can be loaned for most expeditions that we actually undertake; we are always shortest of observers who can fit these events in their schedule, so we hope that you might be able to. Much more information about observing occultations of all types is in "Chasing the Shadow: The IOTA Occultation Observer's Manual" available for free download here. Good luck with your observations. David Dunham, 2007 October 17, 4 pm EDT Phones home 301-474-4722; office 240-228-5609; cell 301-526-5590 e-mail david.dunham@jhuapl.edu home e-mail: dunham@starpower.net .