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Preamble:
Very high hopes were held for this event, the updated path for which crossed a number of large population centres. Tauranga was expected to be close to the northern limit and Hamilton to the southern limit, with the path directly crossing Napier and Auckland. Although the event "rank" was only 71 (where 99 indicates a virtually guaranteed path) considerable effort was nevertheless put into recruiting new observers and providing co-ordination to ensure the best possible coverage. By the night of the event, reasonably good coverage of the predicted path had been obtained.
However, the actual occultation path on the night shifted north by slightly more than one track width, leading to a 2.8 second occultation being observed in Whakatane by Diana Watson. (Predicted maximum duration was 4.1 seconds). The path shift observed at this event was unexpectedly large.
No certain occultation was timed at Whangamata, although the observer (observing under difficult conditions) suspected an extremely brief event. If the chord observed at Whakatane was on the northern side of the asteroid then a significant occultation would also have been visible from Whangamata. This leads to the conclusion that the Whakatane chord sampled the southern side of the asteroid. The Whangamata report can then perhaps be treated as a constraint on the location of the southern limb of the asteroid.
The plot below shows the relative locations of observers. A circle of the expected 53 km diameter of Iolanda has been placed such that Whangamata lies on its southern edge.
Observers: 1 Watson, Whakatane, NZ 2(M) Barker, Royal Oak, Auckland, NZ 3(M) Beal, Hamilton,NZ 4(M) Blow, Waiotapu, NZ 5(C) Boyd, Te Atatu South, NZ 6(M) Brock, Hamilton, NZ 7(M) Cooper, Napier, NZ 8(M) Dippie, Napier, NZ 9(C) Heywood, Awhitu, NZ 10 Ives, Whangamata, NZ 11(M) Munford, Napier, NZ 12(C) Powell, Tauranga, NZ 13(M) Van Ekeren, Te Awamutu, NZ C = Cloud or other factor preventing observation M = Miss
(Plot generated using WinOCCULT)
Conclusions:
With only one chord observed, it is unfortunate that no definitive conclusion can be made about the diameter or shape of (509) Iolanda given the significant effort that was put into the event. If there had not been such a substantial path shift significant data about the planet would have been obtained.
However, observers Kevin Barker in Auckland and Jethro Van Ekeren in Te Awamutu both reported the star appeared to dim for a period of a few seconds about one minute before the event. (See observer's comments below). These dimmings are very roughly in accord with each other, but were not reported by other observers on adjacent paths. So without further confirmation it is not possible to make any further statements about the reality or otherwise of these dimmings.
Iolanda has not previously been observed at occultation.
Observational Data:
Observer's Name : Diana Watson
Aperture (cm) : 20
Focal length (cm) : 200
Type (e.g. SCT; Newtonian) : Celestron 8
Magnification : 80 times
Observing site name : Whakatane
Longitude (East +ve) : 176 51 50
Latitude (South -ve) : 37 55 25
Height above Sealevel (metres) : 2.8 meters.
Datum : NZ1949
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Good
Other Conditions : A little moisture disturbance
Time Source (e.g. WWV, VNG) : WWVH
Recording method (e.g. tape) : tape recorder
Could you see the Asteroid? : No
Approx. Limiting Magnitude : 13
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 08:53:00.0
Disappearance At : 08:59:10.4 a bit slow!
Reappearance At : 08:59:13.2 reasonably quick
Stopped Observing : 09:09:00.0
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? : No
Observer's Name : Kevin Barker(Ian Ritchie Assisting)
Aperture (cm) : 13
Focal length (cm) : 100
Type (e.g. SCT; Newtonian) : Refractor
Magnification : 38
Observing site name : Back yard 37 Turama Road Royal Oak
Longitude (DD MM SS ; East +ve) : ca. 174 46 38
Latitude (DD MM SS ; South -ve) : ca. -36 54 36
Height above Sealevel (metres) : 100 m
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Good
Other Conditions : Southerly dying down, neighbours outside lights on 20 m away
Time Source (e.g. WWVH, GPS) : WWVH 10 MHz
Recording method (e.g. tape) : Tape
Could you see the Asteroid? : No
Approx. Limiting Magnitude : 12
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 08:58:00
Stopped Observing : ?
ADDITIONAL COMMENTS:
I am fairly certain I had the correct star found the star and watched it but
did not see the dramatic off I was expecting. It did appear to dim a little
a wee bit earlier than the time I was expecting it. But not by three
magnitudes.
Later comments:
One thing that I did see about a minute before the event was due was the
star appeared to dim and flicker a little by about 0.5 to 1.0 magnitude.
This occured for about 3 to 5 seconds. I did not mention this on the tape as
it was not the out I was expecting. We started our tape at about 8.58 UT so
this would have been about 20 seconds later.
My magitude estimate is based on the fact the limit was about mag 12 and the
star was still seen o.k. It is probably not precise enough to be useful but
it was what I saw. It did however appear to dim relative to the other stars
in the field.
Observer's Name : Gary Beal
Aperture (cm) : 250mm
Focal length (cm) : 1250
Type (e.g. SCT; Newtonian) : Newtonion
Magnification : 42x
Observing site name : Home
Longitude (DD MM SS ; East +ve) : +175 21 48
Latitude (DD MM SS ; South -ve) : -37 51 09
Height above Sealevel (metres) : 50 approx (160 feet)
Geodetic Datum (e.g.WGS84,NZ1949): Not known
Height Datum (if known) : Not known
Sky Transparency (Delete two) : Fair
Star Image Stability (Delete two): Good
Other Conditions : Intermitent cloud cover at time of event
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 0850
Stopped Observing : 0910
Observer's Name : Graham Blow
Aperture (cm) : 20
Focal length (cm) : 200
Type (e.g. SCT; Newtonian) : SCT
Magnification : ?
Observing site name : Forest Rd, Waiotapu
Longitude (DD MM SS ; East +ve) : +176 22 12
Latitude (DD MM SS ; South -ve) : -38 23 06
Height above Sealevel (metres) : 310
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) : WWV
Recording method (e.g. tape) : Tape
Could you see the Asteroid? : No
Approx. Limiting Magnitude : > 11
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
COLUMN FORMAT TO USE---> __:__:__._ _._ _________________)
Started Observing : 08:58
Stopped Observing : 09:07
Observer's Name : David Brock
Aperture (cm) : 41
Focal length (cm) : 200
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : 125x
Observing site name : Herbert Rd, Mangateparu
Longitude (DD MM SS ; East +ve) : +175 29 33
Latitude (DD MM SS ; South -ve) : -37 35 18
Height above Sealevel (metres) : ~100m
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 : 16
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
COLUMN FORMAT TO USE---> __:__:__._ _._ _________________)
Started Observing : 8hrs 53min UT
Stopped Observing : 9hrs 4min UT
Observer's Name : Ian Cooper
Aperture (cm) : ?
Focal length (cm) : ?
Type (e.g. SCT; Newtonian) : ?
Magnification : ?
Observing site name : Nelson Park, Napier
Longitude (DD MM SS ; East +ve) : ca. +176 53 44?
Latitude (DD MM SS ; South -ve) : ca. -39 29 42?
Height above Sealevel (metres) : 10?
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) : ?
Recording method (e.g. tape) : ?
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : ?
Stopped Observing : ?
Observer's Name : Rhys Dippie
Aperture (cm) : 23 cm
Type (e.g. SCT; Newtonian) : Newt
Observing site name : Westshore, Napier
Longitude (DD MM SS ; East +ve) : E 176 Deg 53.316'
Latitude (DD MM SS ; South -ve) : S 39 Deg 20.677'
Height above Sealevel (metres) : 10 +/ 5m
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) : ?
Recording method (e.g. tape) : ?
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : ~08:58
Stopped Observing : ~09:01
ADDITIONAL COMMENTS:
I had a 100% dark sky with Mag 6 stars clearly visible to the naked eye.
There were localised clouds but none around the area I was observing.
I located the star without difficulty and had time to confirm it thoroughly.
I observed intently for 1 minute either side of the predicted event window
(2 mins 40 total).
Observer's Name : Barbara Ives
Aperture (cm) : 20cm
Focal length (cm) : 200 cm
Type (e.g. SCT; Newtonian) : sct
Magnification : 12.5mm
Observing site name : Whangamata, NZ
Longitude (DD MM SS ; East +ve) : 175 52 31 E
Latitude (DD MM SS ; South -ve) : -37 12 29 S
Height above Sealevel (metres) : 0
Geodetic Datum (e.g.WGS84,NZ1949): NZ 1949
Height Datum (if known) : -
Sky Transparency (Delete two) : Fair to Poor
Star Image Stability (Delete two): Fair
Other Conditions : clouds coming and going
Time Source (e.g. WWVH, GPS) : wwvh - good signal
Recording method (e.g. tape) : tape and/or stopwatch
Could you see the Asteroid? : no
Approx. Limiting Magnitude : +11
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
COLUMN FORMAT TO USE---> _ :_ :__._ _.6_ _________________)
Started Observing : 08:57
Stopped Observing : 09:03
ADDITIONAL COMMENTS:
There's no way I'd put my life on it - but - slightly before time -
after 8:59 but before 9 -closer to 8:59 - I didn't actually time it more
accurately, because the whole sky in the eyepiece was coming and going - it
MIGHT have disappeared fractionally. Eyeblink stuff, not even a second.
Except for that millisecond, the star was there, although wavering in
brightness.
Observer's Name : Noel Munford
Aperture (cm) : ?
Focal length (cm) : ?
Type (e.g. SCT; Newtonian) : ?
Magnification : ?
Observing site name : ?
Longitude (DD MM SS ; East +ve) : ca. +176 55 15
Latitude (DD MM SS ; South -ve) : ca. -39 28 53
Height above Sealevel (metres) : 10
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) : ?
Recording method (e.g. tape) : ?
Could you see the Asteroid? : ?
Approx. Limiting Magnitude : ?
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : ?
Stopped Observing : ?
Observer's Name :Jethro van Ekeren
Aperture (cm) :20 cm
Focal length (cm) :126.5 cm
Type (e.g. SCT; Newtonian) :Newtonian
Magnification :50X
Observing site name :(?) my backyard
Longitude (DD MM SS ; East +ve) :+175 18 59
Latitude (DD MM SS ; South -ve) :-38 01 06
Height above Sealevel (metres) : 100?
Geodetic Datum (e.g.WGS84,NZ1949):(?)
Height Datum (if known) :(?)
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Fair
Time Source (e.g. WWVH, GPS) :(I was not timing)
Recording method (e.g. tape) :NA
Could you see the Asteroid? :No
Approx. Limiting Magnitude :11.5-12
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
COLUMN FORMAT TO USE--- __:__:__._ _._ _________________)
Started Observing :approx' 8h 54m 00s
Disappearance At :approx' 8h 57m 45s (plus or minus 10-20 seconds)
* SEE NOTES
Reappearance At :approx' 8h 57m 46s (one second after disappearance)
Stopped Observing :9h 02m 00s
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? :NA
ADDITIONAL COMMENTS:
I am a little in doubt of this observation since my observation can't really be
trusted I think (and I didn't time it anyway). I didn't see any dip in brightness
at the predicted time, I was quite tired so I could have missed a short dimming
but I don't think there can have been a drop for longer than half a second for
me not to have noticed it.
One thing which worries me though is that the star seemed to drop quite dramatically
in brightness for a short time about a minute or two before the predicted time
(sorry for the inaccurate time). Although quite sudden, the dip seemed too gradual
for an occultation so I am quite dubious about this. It could have been a random
fluctuation in my eye or something.
Later Notes:
I did notice a marked drop in brightness at the time noted above, it seems unlikely
to me that it could have been illusory. The reappearance seemed less sudden than I
had anticipated. I noticed no drop in star brightness at the predicted time.
Later Still Notes:
I said in my last email that I observed the dimming 1 to 2 minute prior to the
predicted time. I can actually give it a little more accurately. I was counting
off the seconds in my head and I am fairly sure it occured within ten to twenty
seconds of the time I give above.
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
Other Conditions : some wind shake
Time Source (e.g. WWVH, GPS) : GPS/KIWI
Recording method (e.g. tape) : Video
Could you see the Asteroid? : no
Approx. Limiting Magnitude : 11.5
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 08:52
Stopped Observing : 09:05
ADDITIONAL COMMENTS:
No event, although any blink less than about 1 second would have been very uncertain.
The magnitude 10.4 star was quite bright on the video, but seeing and windshake made it
briefly disappear at times. In particular on reviewing the video there appeared to be a
disappearance from ca 10:58:26.5 to ca 10:58:27.0. However examining on a frame by frame
basis there were other "disappearances" a few frames long near the time, and in fact
careful examination did suggest a slight image on some frames in the 26.5 to 27.0 interval.
So, I feel quite certain there was no event, only seeing and shake effects.
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