Grazing Eclipse of ZC 798 in Richmond area tonight - New 2013 Aug. 1
Clear sky predicted for graze of 6.2-mag. ZC 798 over parts of Richmond, VA tonight
This is a grazing eclipse of the star ZC 798 by the northern edge of the Moon. In a narrow zone only 400m wide, the star will flash on and off as it is covered and uncovered by small mountains and craters along the northern edge of the Moon. I am undertaking an expedition to observe the event from sites near US 301 in Hanover, VA, with backup sites along US 60 west of Richmond if the clouds clear out of the area more slowly than now predicted.
For non-astronomers, "occultation" is a term that astronomers use for an eclipse of a star by an asteroid or by the Moon. I use the word "eclipse" a few times here since it's possible that police or other non-astronomers might visit this Web page. The graze in the Richmond area will last from 4:52 to 4:55 am EDT; at that time, the 17% sunlit waning crescent Moon will be 25 deg. above the eastern horizon. The star will appear to approach the Moon from the bright side, and around 4:50am, it may be too close to the bright part of the sunlit northern cusp to see. But by 4:52am, the star should have moved to the thinner end of the cusp where it should be visible among small sunlit peaks at the very end of the cusp, and it will become easy to observe as it moves just past the last sunlit peak of the cusp onto the lunar dark side. The current weather forecasts still show that the current clouds should move east out of our area and away from Richmond, but they are expected to linger over the Delmarva Peninsula. Consequently, I've decided to observe the graze from sites along US 301 in Hanover, VA, about 10 miles northeast of Richmond. If you want to join my expedition, meet me at the intersection of Beatty Farm Dr. and US 301, on the west side of US 301, near a place called "Through the Garden Gate", at 4:00 am; if you arrive at another time, call my cell phone, 301-526-5590. The meeting place is 0.1 mile south of Pine Ridge Rd (Rd 1930) and 0.1 mile north of the northern entrance from US 301 to Hanover High School; it is about 4 miles north of the US 301 - I-295 interchange. This aerial view shows the graze path in detail around US 301. Open fields to the east should give a good view of the Moon over the whole "best" graze zone, which is 400m wide, extending south from the predicted northern limit line. The graze path also passes over western and northern suburbs of Richmond, including Henrico; it is between the dark green and gray lines on this map of the northern Richmond area (if you live within the path, I encourage you to observe, but some multiple events will be visible for 3 or more miles farther south). Note that during the 3 hours before the graze, there are two asteroidal occultations, by asteroids Austria and Bilkis, which I will try to observe in the area; click here for details of those events. Also, several minutes after the graze, at about 5:04am, the 6.7-mag. star ZC 796 will reappear just north of the center of the dark limb (cusp angle 80N) with only a little twilight (Sun altitude -12 deg.). That is the information for Washington, DC; the ZC 796 reappearance will occur at 5:02:21 am in Hanover (US 301) and at 5:01:53 west of Midlothian (US 60) in the Richmond area. There's some chance that the clouds won't clear away from the Hanover, VA area as quickly as predicted, so I might switch to some sites farther west. A possibility is to observe from sites along the south side of US 60 in the graze zone; there is a church and commercial establishments with large parking lots there. If that is used, I propose meeting in the parking lot of Central Virginia Bank on the southwest corner of US 60 and New Dorset Rd; it is 0.2 miles west of the US 60 intersection with Route 613 (Jude's Ferry Rd) and about 6 miles west of Route 288 (World War II Veterans Memorial Hwy, the west side of the "beltway" around Richmond. Here is a map showing a general view from Hwy 288 to the graze area where it crosses US 60, and here is a detailed aerial view of where the graze path crosses US 60. SEE THE VIDEO OF ANOTHER grazing eclipse (grazing occultation) that I recorded last year. Brad Timerson has placed on YouTube the video that I obtained of the omega2 Tauri graze on 2012 August 11th with the northern remote 80mm refractor "midi" system that shows 6 disappearances and 6 reappearances of the star. You can see it here. More information about that graze is here. THE PREDICTED PROFILE OF THE GRAZING OCCULTATION This graze has a good profile, but with a narrow multiple events zone that promises a lot of events. The profile plots the distance of an observer north and south of the predicted "spherical Moon" northern limit line in km on the left and right side, and time in minutes relative to the time of closest approach of the star to the Moon's center in the horizontal direction. For each observer, the star appears to move on a horizontal line across the diagram, intersecting the jagged outline of the actual Moon (mapped by the Japanese Kaguya space mission). Each time it intersects the jagged outline, the star will disappear or reappear. Of course, it's the Moon that's moving, not the star, but it's easier to portray the geometry on the diagram relative to the moving Moon. The vertical scale is exaggerated by a factor of about 40 relative to the horizontal scale, in order to show the situation on one page, so the real Moon is much smoother than the jagged profile shown. You can zoom in on the path using Brad Timerson's interactive Google maps Web site. Scoll down to Aug. 2 and click on "ZC 798" for the Google map. In the boxes at the top, specify 0.4 and 0.0, and click on the tabs to their right; that will define the narrow graze zone between a dark green and a gray line. The path extends westward into Texas with Universal times of central graze (note that the graze events will start about 1.5 minutes earlier) listed as a function of longitude in the times item. Note that the graze takes place several minutes EARLIER for areas west of Virginia. ________________________________________________________ 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. Techniques for timing occultations using whatever resources that you may have are described here. Much information about observing occultations of all types is in "Chasing the Shadow: The IOTA Occultation Observer's Manual" available for free download here. _____________________________ David Dunham, 2012 August 1 Phones home 301-220-0415; cell 301-526-5590 office e-mail david.dunham@kinetx.com home e-mail: dunham@starpower.net . Click here for information about other occultations in the Mid- Atlantic region through mid-September. The events tonight are some of the best until after then; the information there will be updated to mid October near the end of August.