A 2.6 second occultation was recorded using the CCD drift-scan technique by John Broughton in Reedy Creek, Queensland. Not far away, Peter Anderson in Brisbane saw no occultation.

View the Updated Prediction

Observers:
  1    J.Broughton, Reedy Creek, Australia  
  2(M) P.Anderson, Brisbane, Australia      

M = Miss

The circle represents the expected 59 km diameter of Rockefellia.

Drift-scan trace:

Discussion:

Another good CCD result from John in spite of the very difficult observing conditions. (See comments below).

Observational Data:

Observer's Name                  : John Broughton
Aperture (cm)                    : 50.1
Focal length (cm)                : 140
Type (e.g. SCT; Newtonian)       : Newtonian 
Magnification                    : CCD drift-scan at 4.2 pixels per second 
Observing site name              : Reedy Creek, Gold Coast
Longitude (East +ve)             : +153 23' 49"
Latitude (South -ve)             : -28 06' 36"
Height above Sealevel (metres)   : 66
Geodetic Datum (e.g.WDD84,NZ1949): AGD66
Sky Transparency (Delete two)    : Good in gaps between clouds
Star Image Stability (Delete two): Fair
Other Conditions:                
     (Wind, Clouds, Lights, etc.): Interference by cloud in a twilight sky.
Time Source (e.g. WWV, VNG)      : WWVH.
Recording method (e.g. tape)     : Drift-scan. Taped shutter and time signal.  
Could you see the Asteroid?      : No
Approx. Limiting Magnitude       : 11-13 (variable during observation)
                                          | Estimated  |
                           Universal Time | Reaction   | Accuracy, Remarks
                              h  m  s     | Time (sec) | 
Started Observing          : 19:40:44.0        n.a       
Disappearance At           : 19:40:56.1        n.a       0.5
Reappearance At            : 19:40:58.7        n.a       0.5
Stopped Observing          : 19:41:14.3        n.a       
Duration                   :        2.6   

ADDITIONAL COMMENTS: With event time occurring while the sun was only 9 degrees below the horizon, 
exposure length was restricted to 30 seconds to attain a strong signal-to-noise ratio in such 
twilight sky conditions. Operating at F/2.7 I also had to avoid saturation of the image which
I estimated would occur after 80 seconds through a clear sky but with altocumulus clouds threatening, 
I elected to interpose the dome shutter across the southern half of the aperture for some extra 
margin of safety. 

During the the middle part of the 30 second exposure where an occultation was possible, cloud 
attenuated the trail by a couple of magnitudes, putting it near but not beyond the level of 
detection as evidenced by a trail of equal magnitude 1' to the north and others nearby. 

The trail in question does show a gap near the level of detection that is consistent with 
prediction for an off-centre chord. If real, the event was 1.5 seconds early and lasted 60% 
of the maximum predicted duration. Though not a certainty, I think this gap more likely 
represents a positive event rather than just natural variations in the background level.

This observation is another example of the power of CCD drift-imaging where a result is 
possible under seemingly hopeless circumstances. An explanation of methodology and relevant 
software is available at: http://www.users.bigpond.com/reedycrk/driftscantiming.htm.

Observational Data - Occultation Not Seen:

Observer's Name                  : Peter Anderson
Negative, I'm afraid.  I monitored betwen 19hrs 38min and 19hrs 45min. ID was positive, 
though the Astro Atlas chart is really substandard for field identification.
There were certainly no events as the image was constantly 'held'.  At the beginning limiting 
mv was say 14.5 and at the end say 12.5 in the dawn, so there was no problem 'holding' the image 
of a 10.8 star.

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