(90) Antiope is a binary asteroid, with equal components about 90 km across
orbiting each other in a circular orbit 170 km apart. The pair is predicted to
occult a 14.2-mag. star near the sickle of Leo, 7 deg. northwest of Regulus,
just before 1:11am MST tonight (or early Sunday morning, March 15) in a path
that moves from southeast to northwest, crossing both the Tucson and Phoenix
greater metropolitan areas. An occultation of a bright star by the pair
observed from California and Oregon in 2011 generated the iconic outline of the
two objects that is shown on the left side of IOTAâs main Web page at
http://occultations.org/ . With the fainter star that we have tonight, we ;
wonât be able to do as well, but those with large-enough telescopes (and/or
integrating cameras) are encouraged to try to observe the event, to obtain some
more lines across the object at a different orientation than has been recorded
before.
The star is UCAC4 534-049318 at J2000 RA 9h 43m 43.4s, Dec +16 deg. 41â
38â. Antiope, at mag. 13.7, is brighter than the star, so it will appear to
merge with the star to form a combined object of about mag. 13.2 that will drop
0.5 mag. if one of the Antiope components covers the star, for up to 8s. Two
dips are possible if both components cover the star at your location, or
neither if you have a âHercules chordâ that passes between the two
components, without occultations by either. There is a pair of stars only 2 arc
minutes west of the target star; they are about 1 arc minute apart, with
magnitudes of 9.3 and 10.2, with the brighter star farther from the
considerably fainter target, so they will appear as a convenient arrow pointing
to the target. Finder charts of different scales, and other event details, are
at Steve Prestonâs page for the event at
http://www.asteroidoccultation.com/2020_03/0315_90_68214.htm . I have prepared, ;
but can't attach, 3 finder charts with zenith up for the Phoenix region, one a
finder-scope field showing stars to mag. 9.7 (the rectangular âmighty miniâ
field shown is about 3 deg. wide, a little less than standard 5-deg. finder
scope fields), and the other are telescopic fields (similar to the video FOV
for an 8in SCT with focal reducer) showing the two stars near the target (at
the center), and other stars nearby. If you send me an email request, I can
send those charts directly to you. The target star will be 52 deg. above the
western horizon, azimuth 253 deg. The 61% waning Moon will be 6 deg. above the
s.e. horizon, azimuth 119 deg. and 109 deg. from the target star, so it should
pose no problems for the occultation.
Skies cleared well across the Phoenix area this afternoon and so far this
evening, so we hope that will remain for the occultation. But the IR satellite
loop shows patches of clouds moving across northern Baja Calif. towards the
Tucson and Phoenix areas, with the NWS forecasting about half-cloudy skies at
the time, but better than the cloud cover estimates on Occult Watcher.
Unfortunately, itâs already very cloudy over most of California, so itâs
unlikely that weâll obtain any observations of this occultation from there.
On Tuesday night/Wed. morning, Mar. 17/18, thereâs another occultation, of a
13.3-mag. star by the asteroid (456) Abnoba expected to occur over Tucson,
important since the orbit of the asteroid was updated specially by the JPL
Horizons team (for an occultation of a bright star successfully observed from
Colo. and Okla. On March 5 UT) and it would be useful to obtain another
occultation astrometric fix from the Tues. night event, to better verify the
accuracy of the new orbit. However, it looks like the next low pressure area
will be over Arizona bringing us even more rain and clouds. If there is any
hope, Iâll send another message about it. Keep in mind the next bright
occultation over both the Phoenix and Tucson regions, at 1:25 am Sat. morning,
March 28 th , when (479) Caprera will occult a 10.4-mag. star.
With the cancellation of the physical NEAF meeting in New York, we will be
staying in Arizona during much of April.
David
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