Preamble:

The updated path for this event crossed populated regions of NSW as well as passing close to Adelaide, SA. The star was relatively bright but the event was at an inconvenient time of night. The prediction was of extremely high accuracy. The predicted track is available here.

One video and three visual chords were observed. An additional occultation was seen but the event was not timed accurately.

Note that the chords have been assigned different weights in the fitting process. Please view the plot below in conjunction with the notes provided by the observers and the comments in the Discussion section below.

Observers:

  1    Bosloper/Pickard, Kelso, Australia   (Visual - Weight 0)     
  2    D. Gault, Hawkesbury Hts, Australia  (Video  - Weight 5)  
  3    R. Giller, Barden Ridge, Australia   (Visual - Weight 3)
  4    A. Brakel, Downer, ACT, Australia    (Visual - Weights 4 & 3)
  5    J. Morland, Curtin, ACT, Australia   (Visual - weight 3)

(Plot generated using WinOCCULT - Disappearances on the left; Reappearances on the right)

Discussion:

Note that the above fit is very dependent on the weights assigned to each observation.

• While Case Bosloper and Ray Pickard at Bathurst Observatory did see the event, it is unfortunate that they were unable to time it accurately. Their very approximate times (based on their memory of the events) are clearly offset in relation to the other chords and have therefore been assigned a weight of zero.

• The video chord of Dave Gault has to be assigned the highest weighting (5) as this is the most accurate timing (even though event times were only determined by 'eye-and-ear' from the videotape). Recording the event on video removes the reaction time of the observer normally present when an event is seen at the telescope, while the ability to replay the video and audio together many times should minimise any subsequent reaction time issues.

• Roger Giller's D and R appear to be a little displaced relative to the chords on either side. As Roger notes below he had some difficulty with time signals, eventually having to resort to the Telstra talking clock. (Although a number of Australian observers have noted that on occasions this can be seconds out, Case Bosloper advises that on this occasion the Telstra signal only had a 0.1 sec delay against WWVH 6 hours before the event, and had not moved significantly from that figure at about 18:49 UT). However Roger also notes that because of the timing method he used (see below) his duration would be more accurate than the actual D and R times. He writes that his reaction time could be longer as it did surprise him a bit although he was looking directly at the star. His observation has been assigned weight 3.

• Albert Brakel is a very experienced observer with a number of positive occultations to his credit. His D observation was assigned a weight of 3 and R observation 4, based on his larger quoted reaction time for the disappearance.

• John Morland's reported times were adjusted by minus three minutes for the reasons outlined below. However his chord is still offset from the adjacent chord of Brakel by about 2-3 seconds, although a plausible explanation for this is presented by John in his notes. It is tempting to allow John's chord to slide along its length so that its midpoint is more in accord with the midpoints of the other chords. Doing so certainly alters the fit obtained. However no such adjustment has been made at this point because the exact length of the adjustment to be made is indeterminate. John's observations have been assigned weight 3 in the meantime.

Observational Data:

CHORD 1:
Observer's Name                  : Ray Pickard, Case Bosloper
Aperture (cm)                    : 35 cm
Focal length (cm)                : 391 cm
Type (e.g. SCT; Newtonian)       : SCT Celestron
Magnification                    : 150 X 
Observing site name              : Bathurst Observatory
Longitude (DD MM SS ; East +ve)  : 149 40 03
Latitude (DD MM SS ; South -ve)  : -33 23 44
Height above Sealevel (metres)   : 760 m
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known)          : AHD71
Sky Transparency (Delete two)    : Good  
Star Image Stability (Delete two): Poor
Other Conditions                 : Heat plumes from hazard reduction burn-offs. 
     (Wind, Clouds, Lights, etc.): Wind 2, Cloud 0/8
Time Source (e.g. WWVH, GPS)     : WWVH
Recording method (e.g. tape)     : Tape
Could you see the Asteroid?      : Yes
Approx. Limiting Magnitude       : NELM 5.7-ish
                                          | Estimated  |
                           Universal Time | Reaction   | Accuracy, Remarks
                              h  m  s     | Time (sec) | 
Started Observing          : 18:17
Star and Object Merged     : 18:19:46                   from tape  
Disappearance At           : guessed as 18:23:53 as rough estimate
Reappearance At            : guessed as 18:24:03 as rough estimate
Star and Object Separated  : 18:29:57                    from tape 
Stopped Observing          : 18:30

Was your reaction time (also known as Personal Equation) subtracted from 
any of the above timings?  : no

ADDITIONAL COMMENTS: 

We can't submit a chord as we were fooled by the fading rather than extinguishing. We did record times 
of merge and separation, though, and these could be retrieved from the tape. The star was also followed 
through the Vixen refractor (80 mm, 30 X, 90 cm focal length) and appeared to be affected by heat plumes 
of hazard reduction burn-offs which were going on, on some hills near the line of sight. The star was 
appearing and dissapearing all the time so I (Case) couldn't time a specific disappearance moment. But 
in hindsight, it was gone solidly during the WWVH 10 Mhz voice announcement just before the 4:24 minute 
marker. But the signal was too noisy to pick the moment.

Ray was watching the star "boil" through the C14 at 150 X, of 391 cm focal length. He didn't see the 
moment of disappearance clearly as it only semed to fade a bit. But there was a clear sudden brightening 
about three seconds after the minute marker of 18:24 hrs. Both were not recorded as voice marks on the 
tape, but only from memory. The lesson is that with a 250km asteroid and only a 1.5 magnitude drop, we 
should have been prepared for a fade rather than a total extinguishment. We missed it because of a wrong 
expectation. The star was on the faint side for the conditions, when using the Vixen. The asteroid was too 
bright for the use of the C14 at 150 x. As the star brightness was only temporarily pinched a bit, we saw 
a good illustration of what could be avoided by the use of video gear.


CHORD 2:
Observer's Name                  : David Gault
Aperture (cm)                    : 25
Focal length (cm)                : 122
Type (e.g. SCT; Newtonian)       : EQ Newtonian
Magnification                    : About 80x (PC164C at Newtonian focus)
Observing site name              : Gault's Backyard
Longitude (East +ve)             : 150 38'27.9
Latitude (South -ve)             : -33 39'51.9
Height above Sealevel (metres)   : 286.1
latitude, longitude and altitude : WGS84 and MSL
Sky Transparency                 : Good
Star Image Stability             : Good
Time Source (e.g. WWV, VNG)      : GPS
Recording method (e.g. tape)     : KIWI
Could you see the Asteroid?      : Yes
Approx. Limiting Magnitude       : 12.4 with camera
                                            | Estimated  |
                             Universal Time | Reaction   | Accuracy,
Started Observing                : 18:00
Star and Object Merged           : 18:18:	|  	| 	| 
Disappearance At                 : 18:24:05.50	|  0.xx	| 0.20	| took 2 frames to dim
Reappearance At                  : 18:24:19.20	|  0.xx	| 0.20	| took 2 frames to brighten
Star and Object Separated        : 18:30:	|  	| 	| 
Stopped Observing                : 18:55
Was your PE subtracted from 
any of the above timings?        : See notes  

ADDITIONAL COMMENTS:

The asteroid was seen during the event and both the disappearance and reappearance took two full 
frames to change luminance. Time pips were supplied by GPS/KIWI and video and audio signals were 
recorded. Times were estimated by ear and eye by replaying the video time and time again. A means 
of having visual flashes recorded with the image and stepped through frame by frame would be the 
prefered method.  I am working on developing this method but alas it's the case of too many 
projects and not enough time.

The full resolution .AVI file is 2.4Gb and I'd be happy to burn it to DVD and make it available to 
anyone who can analyse it further.  I am also happy to trim the video to the minimum length and 
compress it into .mpg format hopefully to get the file size to 1Mb so anybody can download it 
(possibly from RASNZoccsec) so they can get a feeling of what to expect to see.  

It was delightful to sit back and watch the screen while sipping on a nice hot cup of coffee 
while the video camera did it's work instead of peering into an eyepiece through wattery eyes.


CHORD 3:
Observer's Name                  : Roger Giller
Aperture (cm)                    : 20
Focal length (cm)                : 100
Type (e.g. SCT; Newtonian)       : Newt.
Magnification                    : 100
Observing site name              : - 
Longitude (DD MM SS ; East +ve)  : +151 00 28.9
Latitude (DD MM SS ; South -ve)  : -34 01 37.8
Height above Sealevel (metres)   : 127
Geodetic Datum (e.g.WGS84,NZ1949): WGS84
Height Datum (if known)          : WGS84
Sky Transparency (Delete two)    : Good 
Star Image Stability (Delete two): Good 
Time Source (e.g. WWVH, GPS)     : Telephone & stopwatch
Recording method (e.g. tape)     : Tape
Could you see the Asteroid?      : Yes, during occultation only
Approx. Limiting Magnitude       :
                                            | Estimated  |
                             Universal Time | Reaction   | Accuracy,
Remarks
                                h  m  s     | Time (sec) |
Started Observing          :   18:20:00.0
Star and Object Merged     :   18:20:00.0
Disappearance At           :   18:24:07.6        1.0  ± 0.5
Reappearance At            :   18:24:25.0        0.5  ± 0.2
Stopped Observing          :   - 

Was your reaction time (also known as Personal Equation) subtracted from
any of the above timings?  : Individual PE applied to D and R (surprise at D!)
If YES, state value        : 1.0 and 0.5 sec

ADDITIONAL COMMENTS:

Everything worked except I could not get a time signal from WWVH. It was OK on 10 MHz in the 
afternoon but nothing on any frequency at 4 a.m. My backup was the stopwatch on my wristwatch 
but I messed that up. Fortunately the tape recorded the stopwatch beeps so I quickly went to the 
phone and called the Telstra talking clock. I held the phone to the recorder until it cut out to 
get a measure of tape drift. I applied this drift to the event duration and the interval from R 
to the time recording. I did not wait for secondary events or separation as I wanted to get to 
the phone ASAP
 

CHORD 4:
Observer's Name                  : Albert Brakel
Aperture (cm)                    : 20 cm
Focal length (cm)                : 200 cm
Type (e.g. SCT; Newtonian)       : SCT
Magnification                    : 77x
Observing site name              : "Edgecliff", Bellmount Forest
Longitude (East +ve)             : +149 15' 39"
Latitude (South -ve)             : -34 55' 33"
Height above Sealevel (metres)   : 665 m
Geodetic Datum (e.g.WDD84,NZ1949): AGD66
Sky Transparency (Delete two)    : Good
Star Image Stability (Delete two): Good
Other Conditions:  
     (Wind, Clouds, Lights, etc.): Dark sky site, clear sky
Time Source (e.g. WWV, VNG)      : WWVH
Recording method (e.g. tape)     : Tape
Could you see the Asteroid?      : Yes
Approx. Limiting Magnitude       : ca. 12
                                          | Estimated  |
                           Universal Time | Reaction   | Accuracy, Remarks
                              h  m  s     | Time (sec) | 
Started Observing          : 18:22
Disappearance At           : 18:23:56.9		1.0	 Fluctuations first 6 sec
Reappearance At            : 18:24:08.8		0.5	 Sudden brightening
Stopped Observing          : 18:28

Was your reaction time (also known as Personal Equation) subtracted from 
any of the above timings?  : No

ADDITIONAL COMMENTS: 

When the asteroid was sighted 30 minutes beforehand when still separated from star, 
it was almost invisible with direct vision. At the start of the occultation I was therefore 
surprised to see the asteroid (minus the star) significantly brighter than the earlier sighting. 
This together with some brightness fluctuations (lasting about 6 sec) caused a momentary hesitation, 
which is why I assign a PE of 1.0 sec to the D. The R was a sudden brightening to the normal merged 
brightness. The change in apparent asteroid magnitude is probably due to the glare of the nearby 
star 30 min before the event. The moderate brightness fluctuations during the occultation may have 
been seeing related.


CHORD 5:
Observer's Name                  : John Morland
Aperture (cm)                    : 15 cm
Focal length (cm)                : 120 cm
Type (e.g. SCT; Newtonian)       : Newtonian
Magnification                    : 48
Observing site name              : In Backyard (Curtin, ACT)
Longitude (East +ve)             : 149d 04' 51"E
Latitude (South -ve)             : 35d 19' 56"S
Height above Sealevel (metres)   : 595 m
Geodetic Datum (e.g.WDD84,NZ1949): GDA94
Sky Transparency (Delete two)    : Good
Star Image Stability (Delete two): Good
Other Conditions:  
     (Wind, Clouds, Lights, etc.): Suburban sky site, calm clear sky
Time Source (e.g. WWV, VNG)      : WWVH
Recording method (e.g. tape)     : watch and stopwatch
Could you see the Asteroid?      : did not really notice it
Approx. Limiting Magnitude       : not sure, about 11
                                          | Estimated  |
                           Universal Time | Reaction   | Accuracy, Remarks
                              h  m  s     | Time (sec) | 
Started Observing          : 18:17
Disappearance At           : 18:23:59		1.0	 dimmed down quickly
Reappearance At            : 18:24:06.9		0.5	 Sudden brightening
Stopped Observing          : 18:27:30

Was your reaction time (also known as Personal Equation) subtracted from 
any of the above timings?  : Yes

ADDITIONAL COMMENTS

My observation of the disappearance is some 3 minutes later than Albert Brakel. 
I was using an analog quartz watch (set at the right signal time the evening 
before) and a stopwatch. As the star blinked out, I started the stopwatch.  
When it reappeared I stopped it.  The time recorded was 7.39 seconds.  Then 
I immediately (within a 2-3 seconds) stopped the analog watch by pulling out 
the time adjuster (on the right hand side of the watch which also adjusts the 
time if you twist it) with my fingernail.  I think I may have accidentally 
"adjusted" the time by slightly twisting the wheel as I pulled it out.

Otherwise I may have missed the primary occultation but found a "moonlet" (a 
rather big moonlet as the occultations lasted over lasted over 7 seconds (unlikely 
outcome).

Another explanation is (perhaps) I did not see the occultation, and the 
disappearance is due to high statospheric winds that could momentarily make the 
faint star fuzz out. However I don't think this is likely as the other faint stars 
around in the same field of view were unaffected.

ADDITIONAL NOTES FROM ALBERT BRAKEL:

You will note that his times are 3 minutes after mine, and that he thinks he
may have inadvertently altered the minutes shown by the analog watch as he
stopped it. I discussed this with him, and he was able to replicate the
effect, on one occasion adding two minutes to that shown, without altering
the seconds. We may be able to use this result on the assumption that 3
minutes were accidentally added to the watch, if the chord seems reasonable
alongside the other chords. Note that there is also a 2-3 sec delay between
stopping the first stopwatch and stopping the second watch.

Conclusions:

The value of using a recording method - such as video - which does not contain inherent human reaction time problems has again been amply demonstrated. All observers are urged to seriously consider the relatively small outlay necessary to acquire and use one of the PC-164C low-light video cameras used by Dave Gault, or alternatively, if a CCD is already available, learn how to use the CCD 'drift-scan' technique pioneered by John Broughton. Links to further information about both these methods are available from our home page.

Psyche has only once previously been observed at occultation (on 2002 March 22) when one observer in Mexico saw a 17.5 second event.

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