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NUMBER OF CHORDS : 4
Observers:
1 Blow, Featherston, NZ 2 Picking, Kaituna, NZ 3 Dippie, Wairarapa, NZ (Event duration too indeterminate to be used) 4 Dodd, Martinborough, NZ (Duration uncertain owing to equipment failure) 5(M) Loader, Darfield, NZ (Not shown on plot) 6(M) Rowe, Korokoro, NZ 7(M) Kissling/McGavin, Seatoun, NZ 8(M) Porritt, Whitby, NZ 9(C) Watson, Whakatane, NZ 10(C) Forbes, Philips Line, NZ 11(C) Head/Field, Carter Observatory, NZ 12(C) Hudson, Pukerua Bay, NZ 13(C) Munford, Palmerston North, NZ 14(C) Smith, Phoenix Observatory, NZ M = Miss C = Cloud or no observation for other reason
Comments:
High hopes were held for this event, which ran the length of the North Island. It was hoped that Whakatane observers would be able to cover most of the track width, Palmerston North observers would cover the western part, and Wairarapa and some Wellington observers would cover the eastern track. In the event, both Whakatane and Palmerston North were clouded out.
In the Wairarapa, although the event was seen at four sites, because of equipment difficulties only two sites were able to provide reliable data to of order 0.1 second timing precision.
At site 4 the observer reported times as D at ~13:53:47 +/- 1 and R at 13:53:50 +/- 1 while at site 3 an occultation duration of between 1 and 2.5 seconds was reported. These durations appear inconsistent with each other unless site 3's duration was nearer 2.5 sec and site 4's duration nearer 1 sec.
Using the data as supplied (and excluding data from site 3 which is too indeterminate) the above ellipse of 32.0 x 24.2 km was derived. (Using data from sites 1 and 2 alone produces an ambiguous solution because of the proximity of the chords to each other). Assuming a duration of only 1 sec for site 4 produces an ellipse of 28.0 x 22.6 km, while a duration of maximum 5 seconds at this site gives an ellipse of 47.0 x 26.8 km which includes Palmerston North.
Summary:
The data gathered is insufficient to make any definite conclusions about the shape of Thusnelda.
OBSERVATIONS AS REPORTED BY THE OBSERVERS:
Observer's Name : Graham Blow
Aperture (cm) : 20
Focal length (cm) : 203
Type (e.g. SCT; Newtonian) : SCT
Observing site name : Boundary Road, Featherston
Longitude (East +ve) : 175:20:29.3
Latitude (South -ve) : -41:06:34.5
Height above Sealevel (metres) : 40
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : -
Sky Transparency (Delete two) : Fair
Star Image Stability (Delete two): Fair
Time Source (e.g. WWV, GPS) : WWVH
Recording method (e.g. tape) : Tape
Could you see the Asteroid? : No
Approx. Limiting Magnitude : -
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 13:53:04
Disappearance At : 13:53:46.70 0.7 (not applied)
Reappearance At : 13:53:50.85 0.5 (not applied)
Stopped Observing : 13:55:00
Duration : 4.15 sec
Observer's Name : Richard Dodd
Aperture (cm) : 28
Focal length (cm) : 280
Type (e.g. SCT; Newtonian) : SCT
Magnification : 56x
Observing site name : Matariki Observatory, Martinborough
Longitude (East +ve) : 175d 28' 18.49"
Latitude (South -ve) : -41d 13' 21.69"
Height above Sealevel (metres) : 56.304
Geodetic Datum (e.g.WGS84,NZ1949): NZ1949?
Height Datum (if known) : -
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Good
Time Source (e.g. WWV, GPS) : WWVH
Recording method (e.g. tape) : Tape (Tape recorder failed)
Could you see the Asteroid? : No
Approx. Limiting Magnitude : 12
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 13:00:00
Disappearance At : ~13:53:47 +/- 1 sec
Reappearance At : 13:53:50 +/- 1 sec
Stopped Observing : 14:00:00
Duration : 3 sec +/- ?
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? : No
ADDITIONAL COMMENTS:
Problems with dewing of eyepiece on main telescope, and objective and eyepiece on finder.
Observer's Name : Chris Picking
Aperture (cm) : 20cm
Focal length (cm) : 80cm
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : 123
Observing site name : Kaituna
Longitude (DD MM SS ; East +ve) : 175 31 47.5
Latitude (DD MM SS ; South -ve) : -40 53 18.8
Height above Sealevel (metres) : 250
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : -
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Good
Time Source (e.g. WWVH, GPS) : WWVH
Recording method (e.g. tape) : tape
Could you see the Asteroid? : No
Approx. Limiting Magnitude :
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 13:50:00
Disappearance At : 13:53:43.9 0.5
Reappearance At : 13:53:48.3 0.0
Stopped Observing : 13:55:00
Duration : 4.4 sec
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? : No
COMMENTS FROM OTHER OBSERVERS:
Rhys Dippie:
I began observing intently at 2:52am and between 1 and 2 mins later I observed the target star blink out for a period of between 1 and 2.5 seconds. I was surprised to see it re-appear so soon. However the last person who had used my camera had set the audio input levels right down low, so I have not got audio loud enough to be usable for timing purposes!!
Brian Loader
Viewed on the video monitor the 11 magnitude star was quite faint (the star is F2, hence the camera is less sensitive to it than it would be for a redder star). Seeing was mostly fair but sometimes poorer, so much so that once or twice the image virtually blurred out of view. In particular this happened at about 13:54:05 when the star image disappeared from the screen. It reappeared as a reasonable image with almost occultation like suddeness at about 13:54:13, so much so that I said at the time that the possibility of an event had to be considered. However, the reports from the Wairarapa look to confirm my impression it was the seeing. Subsequent, careful viewing of the tape does show a very faint, very blurred out, image most of the time.... A problem was that there was no other star in the camera field of view. This event does show that even with a video, it would be possible to mistake a seeing problem with an event, for a faint star. However, assuming I would have had the same problem if I had been viewing by eye, it also shows the value of video in being able to rerun the event as many times as one wants.
Gavin Smith
I lost sight of the star about the predicted time, but cannot be sure if I had observed the occultation or not. Antony Gomez
was also at the site with a 12" 'scope, and couldn't be sure if he had seen the occultation either. Earlier he had seen the star and the asteroid through the 20". The view got distinctly hazy about the predicted time.
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