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A definite 7.51 sec occultation was recorded on video by Brian Loader at Darfield, NZ. An additional possible event of 0.35 sec duration was also reported.
There was no updated prediction for this event. View the original prediction.
Observers: 1 B. Loader, Darfield, NZ 2 B. Loader, Darfield, NZ
Discussion:
The circle above is plotted at the expected 77km diameter of Palisana.
Brian's main 7.51 sec event is quite certain, although with only one chord observed it is not possible to say where the chord is in relation to the centre of Palisana's shadow. Also of interest is that Brian noted that the during the main event that there was still a very faint image present, whereas with the asteroid at mag. 13.4 the star should have disappeared completely (limiting magnitude ~11). Dave Herald's suggestion is that this observation could be attributed to a faint but close undiscovered companion to the star.
Brian's report of a possible secondary 0.35 sec event 0.78 sec before the main occultation is also intriguing. However there remains the possibility that this was due entirely to seeing variations.
Observational Data:
Observer's Name : Brian Loader
Aperture (cm) : 25.4
Focal length (cm) : 250
Type (e.g. SCT; Newtonian) : SCT
Magnification : n/a
Observing site name : Darfield
Longitude (DD MM SS ; East +ve) : +172° 06' 24.4" E
Latitude (DD MM SS ; South -ve) : -43° 28' 52.9" S
Height above Sealevel (metres) : 210
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : MSL
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Fair
Time Source (e.g. WWVH, GPS) : GPS/KIWI OSD
Recording method (e.g. tape) : Camcorder Video
Could you see the Asteroid? : no
Approx. Limiting Magnitude : 11+
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 11:38
Possible disappearance at : 11:43:09.39 +/-.01 s
reappearance at : 11:43:09.74 +/-.02 s
(This event could be spurious (cert "2") and due to seeing)
Disappearance At : 11:43:10.17 +/-.05 s
Reappearance At : 11:43:17.68 +/-.03 s
(This event looks certain)
Stopped Observing : 11:47
ADDITIONAL COMMENTS:
The "main" event is certain as there was a 9.8 star 36.6" away from the target and this remained unaffected.
I have checked through the video recording field by field from just before 11:43:08 to 11:43:18.5. For each
field I attempted to classify the image of the target star on a 0 to 3 scale.
0 = no image,
1 = extremely faint, often difficult/uncertain to detect.
2 = a definite, but faint image.
3 = more or less normal brightness.
(There is at least one field where I would describe the image as extra bright.)
Obviously the results of such an analysis are somewhat subjective. It is almost certain that if I did it again,
I would give different ratings in a number of cases.
An Excel plot of this shows a preponderance of "1" during the "main" event. Dave Herald has suggested the results
were due to the star being a close double, I feel this looks highly likely in view of the number of "1" ratings.
Variations in seeing could probably account for the other variations.
The longest spell during which no image is visible is 6 consecutive fields, ie 0.1 second. Obviously this could
represent a brief disppearance of both stars, but I feel seeing is quite likely. (There is at another time at least
one field where the 9.8 magnitude "comparison" star is not visible.)
LiMovie analysis gives very similar times for the main event, although the possible brief preliminary event does not show up.