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Total observed chords: 2
Observers: 1 Justice, Ivanhoe, Vic, Australia 2(M) Buda, Parer St Obsy, Vic, Australia 3(M) Curcic, Caulfield Obs, Vic, Australia 4 Blanksby, Wandin, Vic, Australia 5(M) Litwiniuk, Pakenham, Vic, Australia
(Plot generated using WinOCCULT)
Event Analysis:
Two clear occultations were seen with three quite close negative observations. The observations of Stefan Buda and Peter Litwiniuk in particular form very good constraints on the location of the southern limb of the asteroid.
With only two chords across the asteroid (and one of those quite short and therefore heavily susceptible to reaction time considerations) the result presented above is likely to have significantly larger errors that the formal errors suggested by the plot. Nevertheless, the separation of the two chords enables a reasonable value for the dimensions of the asteroid to be derived.
The expected diameter of Gudula was about 43 km, and the average of the two dimensions obtained - about 29km x 50km - is about 39.5 km, in good agreement.
Gudula has not previously been observed at occultation.
Observational Data:
Observer's Name : Mark Justice
Aperture (cm) : 10
Focal length (cm) : 50
Type (e.g. SCT; Newtonian) : Refractor
Magnification : 28
Observing site name : Ivanhoe
Longitude (East +ve) : 145 deg 02' 43.3"
Latitude (South -ve) : -37 deg 46' 14.6"
Height above Sealevel (metres) : 40m
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : -
Sky Transparency : Good
Star Image Stability : Good
Time Source (e.g. WWV, GPS) : WWVH
Recording method (e.g. tape) : Camcorder for audio only
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 12:09:00
Disappearance At : 12:09:37.4 | ??? | I think I responded reasonably
Reappearance At : 12:09:38.6 | ??? | Was caught by surprise, suspect slow response
Stopped Observing : 12:10:00
Occultation Duration : 1.2 sec
ADDITIONAL COMMENTS: My first occultation recording.
Observer's Name : Jim Blanksby
Aperture (cm) : 15
Focal length (cm) : -
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : 187
Observing site name : Wandin
Longitude (DD MM SS ; East +ve) : +145 25 26.7
Latitude (DD MM SS ; South -ve) : -37 46 47.6
Height above Sealevel (metres) : 180.8
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : -
Sky Transparency : Good
Star Image Stability : Good
Time Source (e.g. WWVH, GPS) : WWVH 10 MHz
Recording method (e.g. tape) : Tape
Could you see the Asteroid? : Unsure - see below
Approx. Limiting Magnitude : 13
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 11:59
Disappearance At : 12:09:33.5 0.3 - Not applied
Reappearance At : 12:09:36.8 0.3 - Not applied
Stopped Observing : 12:15
Duration : 3.3 sec
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? : No
ADDITIONAL COMMENTS:
While an object was visible during the occultation my estimate was that the magnitude was brighter
than the predicted star value of 13.5 (Goffin) or 13.3 (Update). After watching a mag 7.5 star for
some minutes I feel that I would barely have been able to detect 13.5/13.3.
Yet something was plain to see (at the same place in the field as the target star); perhaps a double?
When not occulted the field of view contained only one other star that I could see - faint, towards
the edge of the field (say 6 to 7 arc min from target star) roughly in the MP direction of travel.
I did not set up early enough to attempt detecting the MP prior to the continuous observing session,
nor did I observe an hour or two later. The next night (26th) I looked, not exhaustively, in the MP's
expected area with a follow-up the subsequent (27th) night without identifying an object of the
brightness that I recall during the occultation.
Observer's Name : Stefan Buda
Aperture (cm) : 20
Focal length (cm) : 120
Type (e.g. SCT; Newtonian) : Dobsonian
Magnification : 40
Observing site name : Parer Street Observatory
Longitude (East +ve) : +145 06 16
Latitude (South -ve) : -37 50 32
Height above Sealevel (metres) : 118
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : ?
Time Source (e.g. WWV, GPS) : wwv (10MHz)
Recording method (e.g. tape) : tape
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 12:07:00
Disappearance At : No disappearance
Reappearance At : No disappearance
Stopped Observing : 12:13:00
Observer's Name : Bratislav Curcic
Aperture (cm) : 41
Focal length (cm) : 650 (f/16)
Type (e.g. SCT; Newtonian) : Cassegrain (Dall Kirkham)
Magnification : N/A (prime focus webcam recording)
Observing site name : Caulfield Obs
Longitude (East +ve) : +145d 01.404m
Latitude (South -ve) : -37d 53.828m
Height above Sealevel (metres) : 150m
Geodetic Datum (e.g.WGS84,NZ1949): ?
Height Datum (if known) : ?
Time Source (e.g. WWV, GPS) : WWV
Recording method (e.g. tape) : webcam recording at 25 frames per second
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 12:03:00 0.04 (webcam at 25 fps)
Disappearance At : none
Reappearance At : none
Stopped Observing : 12:12:00
Observer's Name : Peter Litwiniuk
Aperture (cm) : 20
Focal length (cm) : 203
Type (e.g. SCT; Newtonian) : SCT
Magnification : 81x
Observing site name : Pakenham
Longitude (East +ve) : 145 29 00
Latitude (South -ve) : -38 04 01
Height above Sealevel (metres) : 62
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known) : -
Sky Transparency : Good
Star Image Stability : Fair
Other Conditions : cloud increasing from the west
Time Source (e.g. WWV, GPS) : www.time.gov
Recording method (e.g. tape) : manual
Could you see the Asteroid? : no
Approx. Limiting Magnitude : 12
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
COLUMN FORMAT TO USE---> __:__:__._ _._ _________________)
Started Observing : 11 56 45
Disappearance At : No disappearance
Reappearance At : No disappearance
Stopped Observing : 12 16 50
Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings? : no
ADDITIONAL COMMENTS: No occultation seen.
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