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Preamble:
The updated path for this event crossed a number of large population centres including Auckland, Coromandel, Tauranga, Whakatane, Hamilton and Rotorua. It was hoped that many observers from the northern North Island would participate to obtain observations, although only two positive reports from this region were eventually received. It is possible that the faintness of the star and its proximity to the 96% sunlit moon contributed to this poor showing. The event "rank" was 73 (where "99" indicates a virtually guaranteed path) suggested that the updated path could still perhaps be in error.
Two lengthy chords were reported from Hamilton (Dave Brock) and Gisborne (John Drummond). A miss event was also reported from Queensland although this was well north of the track. These observations indicate that the actual track shifted southwards by approximately one half a track width compared to the updated prediction. The predicted track is available here.
Analysis:
Bearing in mind the comments of the observers (see below), in the following plot the D and R of Dave Brock have been accorded weights of 5/5, the D of John Drummond 2/5, and his R 4/5.
Observers: 1 D. Brock, Hamilton, NZ 2 J. Drummond, Gisborne, NZ
(Plot generated using WinOCCULT)
Note that the accuracy of observer 2's disappearance (on the right of the plot) may not be high because of the large value of reaction time quoted.
The plot shows a fitted ellipse of 223.2 x 129.8 km, PA -31.4 deg. However, this is only one example of an ellipse which can be fitted to the observations. Other ellipses which fit this data include (159.5 x 104.3; -67.4 deg), (165.5 x 112.1, -58.8 deg) and (186.6 x 122.3; -43.9 deg) from which it may be seen that no definitive information about Agamemnon's size can be obtained.
Conclusions:
It is not possible to determine an unambiguous solution based on the two chords reported as multiple solutions fit the data obtained. At best, we can only say that the planet is unlikely to be circular. However Steve Preston notes that the two observations obtained will still yield very useful data. Given the approx 50mas diameter of the asteroid, these observations will provide a "star-relative" position for the asteroid will an accuracy of better than 20mas. That is much better than any ground based data.
It is unfortunate that only one additional observation, well-separated from the others, would have produced a definitive result.
Agamemnon has once previously been observed at occultation (on 2000 March 21), when two fairly closely spaced chords were obtained by observers in Kansas and Oklahoma. A ellipse measuring 168 x 137.5 km was derived.
Observational Data:
Observer's Name : David Brock
Aperture (cm) : 41cm
Focal length (cm) : 200cm
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : 225x
Observing site name : home
Longitude (DD MM SS ; East +ve) : 175 14 11 E
Latitude (DD MM SS ; South -ve) : 37 44 41 S
Height above Sealevel (metres) : 35
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Sky Transparency (Delete two) : Fair
Star Image Stability (Delete two): Good
Other Conditions:
(Wind, Clouds, Lights, etc.): Moon, city edge location
Time Source (e.g. WWVH, GPS) : WWVH
Recording method (e.g. tape) : tape
Could you see the Asteroid? : no
Approx. Limiting Magnitude : 13
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 11 36
Disappearance At : 11 39 17.8 0.5
Reappearance At : 11 39 24.6 0.5
Stopped Observing : 11 41
Duration including applied PE: 6.8 sec
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? :yes
If YES, state value :0.5sec
ADDITIONAL COMMENTS:
Star was held quite easily with direct vision. Occasional breaks in observing to
reposition Dobsonian but uninterupted observing run at least 30 sec. each side of
occultation.
Observer's Name : John Drummond (Dudley Meadows, John Burt)
Aperture (cm) : 41cm f4.5
Focal length (cm) : 183cm
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : 215
Observing site name : Possum Observatory, Gisborne, NZ
Longitude (DD MM SS ; East +ve) : 178 02 33.84" East
Latitude (DD MM SS ; South -ve) : 38 40 03.72" South
Height above Sealevel (metres) : 12 metres
Geodetic Datum (e.g.WGS84,NZ1949): WGS84?
Sky Transparency (Delete two) : Fair
Star Image Stability (Delete two): Good
Other Conditions:
(Wind, Clouds, Lights, etc.): Thin high cloud at times - okay in event
Time Source (e.g. WWVH, GPS) : digital watch - could not get SW station
Recording method (e.g. tape) : tape
Could you see the Asteroid? : no
Approx. Limiting Magnitude : 14.5
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 11 35 00
Disappearance At : 11 39 03 See below
Reappearance At : 11 39 11.5
Stopped Observing : 11 43 00
Duration including applied PE: 8.5 sec
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? : yes
If YES, state value : Disappearance time: 2" (11.39.05 became 03")
ADDITIONAL COMMENTS:
Took me a second or so to realise that star was occulted, I thought my 'blind spot'
had hidden the star. My slow reaction time is accounted for in timing info above.
Had a few problems during the night, the primary one is timing. We just could not
get a time pip on the SW - thank goodness I had set my watch to it a few hours earlier
(when I did have a pip). In addition, my telescope drive gives of massive radio
interference which affects the SW radio big time - so it cannot be used... I did use
the time pips on the phone, but it hung up after one minute!
Observer's Name : John Broughton
Aperture (cm) : 50.1
Focal length (cm) : 185
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : CCD drift-scan, 3.9 pixels per second
Observing site name : Reedy Creek, Gold Coast
Longitude (East +ve) : +153.397
Latitude (South -ve) : -28.110
Height above Sealevel (metres) : 66
Sky Transparency (Delete two) : Fair
Star Image Stability (Delete two): Fair
Other Conditions:
(Wind, Clouds, Lights, etc.): Full moon 24 degrees away.
Time Source (e.g. WWV, VNG) : WWVH.
Recording method (e.g. tape) : Tape.
Could you see the Asteroid? : Only the combined light was monitored.
Approx. Limiting Magnitude : 12.5
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 11:40:00.2 0 0.2
Stopped Observing : 11:42:41.4 0 0.2
ADDITIONAL COMMENTS: CCD drift scan observation. Several overlapping star
trails and an almost full moon made this a challenging occultation to record
however the image indicates with reasonable probability that no occultation
occurred at this location.
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