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A 3 second occultation was recorded by John Broughton at Reedy Creek, Qld, Australia, by recording separate CCD images measured photometrically in MaxIm DL.
Observers: 1 J. Broughton, Reedy Crk, Australia
Discussion:
The circle above is plotted at the expected 103km diameter of Iphigenia. With only one chord it is not possible to determine whether John was north or south of the central line of the event. However, assuming the updated prediction was approximately correct would suggest that the chord might lie across the northern portion of the asteroid.
The figures below show the drift-scan image of the occultation and the data as analysed by John's Scanalyser software.
Observational Data:
Observer's Name : John Broughton
Aperture (cm) : 50.1
Focal length (cm) : efl 1750 cm - eyepiece projection at f/35
Type (e.g. SCT; Newtonian) : Newtonian
Magnification : CCD imaging at 2 arc-seconds per pixel, 4'FOV
Observing site name : Reedy Creek, Gold Coast
Longitude (East +ve) : +153 23' 49"
Latitude (South -ve) : -28 06' 36"
Height above Sealevel (metres) : 66
Geodetic Datum (e.g.WDD84,NZ1949): AGD66
Sky Transparency (Delete two) : Good
Star Image Stability (Delete two): Good
Other Conditions:
Time Source (e.g. WWV, VNG) : WWVH.
Recording method (e.g. tape) : Tape.
Could you see the Asteroid? : Yes
Approx. Limiting Magnitude : 17
| Estimated |
Universal Time | Reaction | Accuracy, Remarks
h m s | Time (sec) |
Started Observing : 11:57:01
Disappearance At : 11:59:01.2 n/a 0.4
Reappearance At : 11:59:04.2 n/a 0.4
Stopped Observing : 12:00:31
Duration : 3.0 0.8
ADDITIONAL COMMENTS:
The telescope was adapted to operate with eyepiece projection at f/35
so that a relatively quick image tranfer rate with maximum 8x8 binning
could be achieved at an appropriate 2-arc-second pixel scale.
A sequence of 70 CCD exposures was acquired to more than cover the
uncertainty ellipse. Each exposure of 2.2 seconds duration was followed
by 0.8 of dead time, producing a 3-second cadence. Shutter events and a
clock tick reference were recorded on tape, as I do for drift-scan timing.
Every half minute, the bench was tapped and the time called out.
The audio was later digitized and analyzed in GoldWave software.
Photometric measurements revealed a clear decline of 0.20 magnitude
in image 41, matching within 0.01 of the asteroid magnitude when
it was alone and separated from the star 17 minutes earlier.
This indicates the star was occulted for that entire exposure.
Frames 40 and 42 showed no decline whatsoever so obviously disappearance
and reappearance occurred within the 0.8-second gaps bounding frame 41.
The reported times refer to the middle of those gaps.