View the updated prediction.

Discussion:

From: Thomas Widemann 
Sent: Wednesday, May 06, 2009 10:44 AM
Subject: Quaoar occultation report

Dear all,

We report an attempted observation of an occultation of UCAC star
26252549 by trans-Neptunian object Quaoar on May 1 2009. 16
observations were performed in 15 stations (see attached map), with
telescope diameters ranging between 1 m and 25 cm. 4 were clouded
out, 2 were lost to pointing/timing, 10 acquisitions were negative. A
brief summary of observing reports is attached.

The shadow was predicted to pass slightly outside the Earth, although
given the uncertainties involved, it could have been potentially
visible from Australia and New Zealand. Recently updated prediction
was derived from a reanalysis of the star position by the Rio group
of its 2008 observations, with an applied ephemeris offset for Quaoar
of 0.015 arcsec in RA and -0.175 arcsec in DEC. A stellar occultation
by Quaoar's satellite (distance of about 0.35 arcsec, with an
estimated diameter of 100 km) or any additional orbiting material,
was not reported.

We would like to take advantage of this report to invite all
observers involved to acquire post-event images of Quaoar along with
nearby UCAC stars and send them to our group, to improve offset
determination for future event predictions.

We thank you again for your help and response.
Thomas Widemann
Bruno Sicardy
Paris-Meudon Observatory

Observational Data:

Observation details for MP (50000) Quaoar
By Star              2UCAC 26252549
On 2009-05-01  at about 13:45

-41 -29 -36.2 S Vintage Lane, New Zealand, Bill Allen, T60cm, 1-sec exp + T40cm, 2-sec exp.
-173 -50 -20.72 E
37.5 m
00 00 00. no event
00 00 00.
---------------------------
-33 -39 -52.0 S Hawkesbury Heights, Blue Mountains, NSW, Dave Gault, 25 cm Newt.
-150 -38 -28.0 E
286. m
00 00 00. no event between 13:28 and 14:05
00 00 00. GPS - time inserted
---------------------------
-32 -27 -21.3 S Mudgee, NSW, Steve and Jan Quirk, 31.5 cm Newt., 0.25-0.5 s
-149 -39 -45.6 E
508. m
00 00 00. no event between 13:42:01 and 13:55:50
00 00 00. hazy cloud during obs
---------------------------
-40 -51 -20.21 S Waikanae Beach, NZ, John Talbot, 25 cm, 0.25-0.5 s
-175 -01 -57.31 E
5 m
00 00 00. missed target zone by 1 screen 20 arcmin
00 00 00. 13:30-13:50 deteriorating transparency
---------------------------
-33 -55 -33.47 S Bankstown, Sydney, NSW, Ted Dobosz, 28 cm, 5 s
-151 -01 -26.93 E
25 m
00 00 00. SBIG ST10XE 3x3 binning
00 00 00. no event between 13:30 and 14:00
---------------------------
-35 -25 -00 S Canberra, ACT, Dave Herald
-149 -05 -00 E
500 m
00 00 00. no event between 13:35 and 14:05
00 00 00.
---------------------------
-42 -50 -49.4 S Hobart Canopus obs.1-m telescope, Tasmania, John Greenhill
-147 -25 -52.6 E
1000 m
00 00 00. no event between 13:10 and 13:50
00 00 00.
---------------------------
-34 -19 -55.2 S Stockport, South Aust., Blair Lade, Tony Virgo, clouded out
-138 -44 -4.0 E
200 m
00 00 00. clouded out till 15:00
00 00 00.
---------------------------
-27 -28 -00. S Jonathan Bradshaw, Brisbane, QLD
-153 -01 -30. E
100 m
00 00 00. no event
00 00 00.
---------------------------
-27 -59 -25. S John Broughton, Gold Coast, Australia
-153 -22 -7. E
200 m
00 00 00. (delayed) no event between 14:02:11 and 14:30:38
00 00 00.
---------------------------
-17 -37 -00. Tahiti, Southern Stars Observatory, Roland Santallo, clouded out
+149 +29 +00.
100 m
00 00 00. clouded out
00 00 00.
---------------------------
-23 -22 -40 Rockampton, Queensland, Steve Kerr
-150 -30 -50. E
100 m
00 00 00. negative
00 00 00.
---------------------------
-20 -34 -21. Mount Isa Astronomy Group, Marc Katona, Len Fulham, 28 cm
-139 -34 -01. E
370 m
00 00 00. Mallincam Hyper Plus CCD cam at prime focus
00 00 00. seeing Antoniadi II, transp. 9/10, no event 13:25-14:10
---------------------------
-43 -59 -5.1 S Mount John NZ 1-m telescope, Brian Loader, Alan Gilmore
-170 -28 -49. E
720 m
00 00 00. Variable clouds thickened 25 min before time of event
00 00 00. clouded out
---------------------------
-30 26 53.4 Armidale, NSW, Chris Wyatt, 35cm
-151 37 16.3 E
1090 m
00 00 00. clouded out
00 00 00.
---------------------------
-45 52 34.8  Beverly Begg Observatory, Dunedin,NZ,  Ashley Pennell, 35 cm
170 29 49.5	E
63	m
00 00 00. negative
00 00 00.
---------------------------
-23 16 09.6  Glenlee, Queensland, Australia, Stephen Kerr, 30 cm
150 30 00.8 E
50	m
00 00 00. negative
00 00 00.
---------------------------
-33 26 01.0 E Kariong,NSW,Australia , Hristo Pavlov, 20 cm
151 17 37.0
180 m
00 00 00. negative
00 00 00.
---------------------------