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)
Note that the above fit is very dependent on the weights assigned to each observation.
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.
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.
[Top of Page][Return to Home Page]