Two asteroidal occultations across N. America tomorrow night (Fri. am)
I sent the message below to observers in the Mid-Atlantic region, but both occultations will be visible across N. America. The broad Josephina path, improved by a special orbit update, passes over Newfoundland, in morning twilight and low altitude, at 5:48 UT of July 10. A minute later, in a darker sky and higher altitude, the n. limit crosses Nova Scotia. Just before 5:50 UT, the n. limit hits the Massachusetts shore just s. of Boston, then passes just north of Providence, over New Haven, and the Tappen Zee Bridge. After crossing the Mid-Atlantic, at 5:51 UT the wide path passes over Kentucky & n. Tenn., at 5:52 over s. MO, n. AR, s. KS, & n. OK; at 5:53, over most of Colorado; and at 5:54 UT, it’s over Utah, parts of Nev. & sw ID, and most of Oregon. Although the path should be accurate, the actual limit locations are more uncertain than the formal errors imply due to Josephina’s unknown shape and size (perhaps a little larger than predicted from past occ’n obs.).
The Lipperta event will be tough, due to bright twilight, at and just before 7:02 UT in PEI and the Bay of Fundy, but better (higher altitude, dark sky) over s. New England. At 7:03, it crosses s. PA, w. MD, WV, & e. KY. At 7:04, it’s over nw Tenn. & e. AR. At 7:05, sw OK & n. Texas. At 7:06, w. Texas (El Paso, but Las Cruces, NM could have an event). At 7:07 UT, over n.w. Mexico (n. Sonora and San Pedro Martir), but an occ’n is possible over s.e. Arizona.
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Two Mid-Atlantic asteroidal occultations Tomorrow night (Fri. am)
The first will be the best for most, occurring at 1:50am EDT July 10 with a 12th-mag. star about 7 deg. s. of Saturn that will be occulted by the 100-km asteroid (303) Josephina for up to 8 seconds. The wide (due to projection) occultation path includes all of Maryland except the extreme s.e. corner, DC, Delaware, and most of Virginia, as well as most of New Jersey and much of southeastern Penn. The star is almost 2 magnitudes brighter than Josephina, which will be 23 deg. high in the south (azimuth 174 deg.). The prediction is expected to be quite accurate since the JPL Horizons team has updated the orbit using past observed occultations that provided astrometric fixes to a few km with the help of the very accurate Gaia DR2 data for the stars. However, there’s no light-curve shape model for Josephina and past occultations have indicated a somewhat elongated body a little larger than the diameter inferred from standard infrared observations. The cloud cover forecast is poor for s.e. VA and Maryland s.e. of DC, but better towards the northwest, over n. VA, and central & w. MD. The predicted time of the occultation is 5:50:23 UT in DC, about 5s earlier in Baltimore and about 10s later at the Blue Ridge in n. VA; the 1-sigma time accuracy is only 2s. The predicted n. limit passes over the n.e. corner of NJ; Allentown, PA; just s. of Harrisburg (which could have an occultation); and near Frostburg, MD, while the s. limit is over Ocean City, MD; just n. of Richmond (could have an event there); & s. of Roanoke and Blacksburg, VA. The star, UCAC4 314-243004, is at J2000 RA 20h 15m 24.2s, Dec -27 deg. 23’ 42”, in Capricornus near the Sagittarius border and 0.4 deg. south of 5.2-mag. SAO 189065 (itself at J2000 RA 20h 15.3m, Dec -27 deg. 02’; labeled “A” on my charts). See a page for the occultation at http://iota.jhuapl.edu/mp303710.htm for good annotated finder charts centered on the target star; it also has a link to another page for the occultation, at http://www.occultationpages.com/events/20200710_303_Josaphina.html which has three Occult Watcher maps showing the path from Nova Scotia to Oregon, and the latest cloud cover forecast maps, as well as a link to a document describing how to time and report occultations. According to AAVSO’s APASS catalog, the star’s V-mag. is 12.6, but a reddish star so that the Sloan R mag. is 12.1, which may be more appropriate for common red-sensitive cameras. Please let me or Occult Watcher know if you can try to observe this; several mobile stations will be trying the occultation and we don’t want to duplicate your line. Please try this event if you can; more observers give more detailed information about the asteroid.
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The second path is farther north, with the event occurring at 3:03am EDT with another 12th-mag. star about 2 deg. to the right of (west of) Saturn that will be occulted by the 50-km asteroid (846) Lipperta for up to 4 seconds. The path is almost coincident with the n. limit of the Josephina occultation described above (n. NJ to w. MD) but the path is more than a path-width uncertain (1-sigma), so an occultation is possible across central MD, DC, and n. VA. The star is over 2 magnitudes brighter than Lipperta, which will be 28 deg. high in the south (azimuth 198 deg.). In DC, the occultation should occur at 7:03:12 UT +/-5s 1-sigma, about 16s earlier in NJ and 8s later at the Blue Ridge in VA. The star, UCAC4 348-185551, is at J2000 RA 19h 56m 09.9s, Dec -20 deg. 32’ 30”, in eastern Sagittarius about halfway between Saturn and 4.3-mag. 56 Sagittarii, and 9 deg. above and left of Jupiter. The target star is only 0.4 arc minute southeast of a 10.4-mag. star and 3.5’ southeast of 9.1-mag. SAO 188726, labeled “B” on my most detailed chart). Good annotated finder charts centered on the target for this event are also at http://iota.jhuapl.edu/mp303710.htm; it also has a link to the main prediction page for the occultation, at http://www.harvestmoonorchard.com/astro/occultations/LowMagEvents/20200710_185551_summary.html. According to AAVSO’s APASS catalog, the star’s V-mag. is 12.4, a slightly reddish star with Sloan R mag. 12.2.
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After the Lipperta occultation, if it’s clear and you have a low northeastern horizon, you might try to observe Comet NEOwise. Also, visit the updated Mid-Atlantic occultations page at http://iota.jhuapl.edu/exped.htm ; several asteroidal occultations during August have been added.