Four positive chords were recorded for this event.

View the updated prediction.

Observers:
  1    J Broughton,Pottsville, NSW, AU
  2    P Anderson,THE GAP,Brisbane,QLD,AU
  3    J Bradshaw,Samford Valley,QLD,AU
  4    J Broughton,Reedy Creek, QLD, AU
  5(P) Prediction 24 Feb

        

Discussion:

The ellipse above is plotted at the best fit to the observed data. Peter's visual observation data (chord 2) has had 1 sec subtracted from the times and as you can see is a very good fit to the rest.
This results in an area about 36% greater than the predicted circle of 139 km. This suggests that the albedo estimate may be too high and that Nemesis is darker than predicted.
With 4 chords we can be confident of the path of Nemesis and that it was very close to the predicted line but about 18 seconds late.

The figure below shows John's first Tangra light curve of the occultation.

The figure below shows John's second Tangra light curve of the occultation.

The figure below shows Jonathan's Limovie light curve of the occultation.

Observational Data:

Observation details for MP ( 128 ) Nemesis
By Star              UCAC2 23177086
On 2012-03-30  at 18:36:16.0

_______________________________

Observer   John Broughton
Location   Pottsville, NSW, AU
Longitude  +153:33
Latitude   -28:23
Altitude   7 m
Datum      WGS84
Telescope Newtonian
Aperture   32 cm
Seeing     Steady Clear
Camera Type  WAT120N        PAL/CCIR
Camera Delay 0.09
Timing     GPS - other linking Video with frame analysis
Disappearance  18:36:23.68
Reappearance   18:36:41.12
Comments:

_______________________________

Observer   Peter Anderson
Location   THE GAP,Brisbane,QLD,AU
Longitude  +152:55
Latitude   -27:27
Altitude   170 m
Datum      WGS84
Telescope Newtonian
Aperture   41 cm
Seeing     Steady Clear
Camera Type  Visual
Camera Delay 0
Timing     Tape Recorder + time signal Visual, PE applied
Disappearance  18:36:08.30 [1 sec subtracted from these times for above plot - jt]
Reappearance   18:36:32.00
Comments:  Located at 17hrs 35min.
Asteroid moved closer and well merged by 18hrs 20min.
At disappearance, asteroid was visible.
Drop in brightness probably took a second -or more.
My timing was as soon as I noticed it dimming.
Over the next few seconds  it seemed even fainter - imagination?
Reappearance was much faster, probably a quarter second.
It was 'out' a long time!

_______________________________

Observer   Jonathan Bradshaw
Location   Samford Valley,QLD,AU
Longitude  +152:50
Latitude   -27:22
Altitude   80 m
Datum      WGS84
Telescope Newtonian
Aperture   36 cm
Seeing     Steady Clear
Camera Type  G-Star         PAL/CCIR
Camera Delay 0.02
Timing     GPS - time inserted Video with frame analysis
Disappearance  18:36:06.53
Reappearance   18:36:28.47
Comments: Perfect conditions. Unexpectedly long event.

_______________________________

Observer   John Broughton
Location   Reedy Creek, QLD, AU
Longitude  +153:23
Latitude   -28:06
Altitude   66 m
Datum      WGS84
Telescope SCT including Cass and Mak
Aperture   25 cm
Seeing     Steady Clear
Camera Type  WAT120N        PAL/CCIR
Camera Delay 0.09
Timing     GPS - time inserted Video with frame analysis
Disappearance  18:36:17.21
Reappearance   18:36:40.41
Comments: