RASNZ OCCULTATION SECTION MEETING - 2004 JULY 3 06:00 UT
NZ International Campus, Upper Hutt, Wellington
(Compiled from notes taken by Bob Evans)
were 34 people in attendance.
start of the meeting Graham Blow made available copies of the Section’s News
and Minor Planet Circulars.
- Graham asked how many people
had seen a total or grazing occultation.
About 50% indicated 'yes'. He
then asked how many had seen one in the last 2 years. Only a very small number of people
indicated so. Graham noted that a
few years ago Australia and NZ were, per capita, behind only the U.S. in
the number of these events observed, but that was no longer the case. Graham emphasized that observing total
and grazing occultations was still valuable, with an additional reason now
being that they provided good practice for reducing observers’ reaction times
which are now the major factor limiting the accuracy of minor planet
- Graham noted that occultation
predictions are now easily available via OCCULT software written by David
Herald. This software will predict
occultations for any site, perform on-line reductions, and supply graze
profiles, etc. Graham indicated
that copies of OCCULT were available at the meeting and that updates would
be posted to the Occultation Section website.
- Graham asked how many people used
the ‘Upcoming Minor Planet Occultations’ page in the News Circulars and
whether there was any value in retaining it. No-one appeared to use the page and
Graham indicated that it would be dropped in future.
- Graham noted that at present
~100 minor planet occultation predictions by Edwin Goffin are published annually as hard copy, with
many more events listed on the Section website. Previously, members had asked to retain
the hard copy MP Circulars. However
he noted that next year there would likely to be 200 to 250 events
predicted by Edwin Goffin (because of fainter stars being used: down to
12th magnitude), which had cost implications for the Section. Further, some of the fainter events
would not be visible to those without larger telescopes. Since there was some feeling to retain the
MP Circulars, Graham suggested that hard copies of only bright events be published. This will be discussed with other Section
- Graham asked whether the finder
charts for MP events published on the website were being used. Few people appeared to do so. Some people mentioned that they produced
their own charts in preference.
- John Drummond mentioned that
WWV was sometimes difficult to pick up, and he would like a more reliable timebase. Graham noted that this was a problem
also faced by a majority of Australian observers. Further, it was difficult to source good
quality shortwave receivers in NZ at a reasonable price.
Russell (from Australia) noted that the VNG User’s Consortium was planning to
make available a device which would use GPS data to emulate VNG signals. However the project had been under
development for two years now and there was as yet no timeframe as to
completion or commercial manufacture.
Hudson asked whether the Radio Shack WWV TimeKube receivers were still
available. Graham indicated that they
were not. Gordon undertook to
investigate whether he, together with his son Rick, might be able to
manufacture some for sale through the Section.
then indicated that the GPS-based KIWI system developed in Christchurch would
be an answer to the timebase problems and handed the meeting over to Brian and
- Brian explained that Geoff
Hitchcox of Christchurch has produced software (“KIWI”) to generate a time
signal to millisecond accuracy from GPS signals. GPS signals can be obtained from surplus
U.S. GPS chips, but KIWI requires a computer running pure DOS. KIWI generates time pips similar to
those produced by the now defunct VNG.
A KIWI device was demonstrated to the meeting. Its features are:
- GPS position to about 0.1”
accuracy. Height accuracy to about
- Time pips are produced and
sound similar to VNG signals, but without voice announcements. There is a higher tone pip every 10
seconds, the 56th, 57th and 58th second pips are shorter, the 59th pip is
missing and the minute pip/tone is longer. Time is read out on the computer screen. John Drummond asked if this readout could
be enlarged so that it would be more easily seen in the dark, but the
answer was 'No'. Brian also noted
that an LED, which could be put down the end of a telescope tube, could
be connected to the system. The LED would flash once a second and be
recorded on a video camera connected to the telescope, thus providing a
timebase for video observing.
- A facility to remind the
observer that the occultation time is approaching.
- A 'stopwatch' facility. Every time a button (on the end of a
cable) is pressed, the time is recorded and saved to a text file along
with positional data. It was
noted however that to save this file the program must be run from a hard
disc, not from a bootable floppy.
- Reaction time programs for
both disappearance and reappearance.
concern was expressed about having to rely on a computer running only DOS. (KIWI
cannot be run from a DOS window in the Windows OS because Windows does not give
enough CPU cycles for the application to meet spec). However it was noted that
any PC would be suitable so long as it could be booted from a DOS floppy which
also contained the KIWI software (subject to the restriction noted above that
the text file of time and position data cannot be saved to the floppy).
Christie declared that there was a way around Windows. Bill Parkin said that FreeDOS, a substitute
for Microsoft DOS, was being developed and was soon to be available. He will keep Graham appraised of this.
about the KIWI system is available from Geoff Hitchcox’s website at:
Loader’s “Beeper Box”
- Pauline Loader then
demonstrated her portable “Beeper Box” which can be synchronised
automatically with UT from KIWI, or synchronised manually from another
time source. The box produces VNG
style time-pips, is small and portable, and costs about $20 in parts. It is designed to be synchronised with a
timebase and then be taken into the field for a grazing or minor planet
occultation. It is essentially a
replacement for a shortwave radio and can be used in conjunction with a
tape recorder to visually time events.
(The beeps can be muted during transport to and from a remote
noted that every 10th second pip is longer, the 56th, 57th and 58th second pips
are shorter, and the 59th second is muted.
The minute is a long beep where the beginning of the beep marks the
minute. As with the KIWI system, an LED can be attached.
box automatically synchronises itself once it is plugged into the KIWI System. Accuracy is better than 0.01 seconds. As long
as it hasn't been turned off, it can be rechecked afterwards against KIWI to
determine any drift. The box can also be
synchronised (manually) with a radio time pip. The 4 x AA batteries powering
the unit last about 20 hours. When
organizing a grazing occultation expedition a number of boxes could be
synchronised from one KIWI or radio and then distributed to party members.
box’s 10 MHz chip is temperature sensitive but can be calibrated for a
particular temperature. Pauline Loader
is happy to supply the circuit and to program the main chip. More information is available at: http://www.occsec.wellington.net.nz/videotime/beeper.htm
to the meeting Bill Parkin of Wellington indicated that he would be happy to
investigate building a trial run of ~20 beeper boxes].
- Brian Loader then described the
use of his video camera for timing occultations. He uses a 0.0003 lux Supercircuits PC-164C
which fits into the eyepiece holder of his scope. It has a ¼” CCD chip, runs on 12 V, and
he can reach to about magnitude 11.5 on his 10" Meade. The field of view is 5 arcmin. Brian felt that a C8 would probably have
only a half magnitude brighter limit.
A cable from the camera is connected to a small black and white
monitor and a VCR, and Brian plugs a small microphone and amplifier into
the audio input of the VCR so he can record voice comments. He uses a KIWI-based flashing LED inside
the telescope tube to provide the timebase. He noted that each flash lasts
for about 2 frames. However as the
camera is NTSC (not PAL), the VCR must be able to record in NTSC.
system (with photos) is described at:
- Graham mentioned that the Watec
902H camera (www.watec.net) is also
very suitable. The advantages of
the Watec camera are that it has higher resolution than the PC-164, it is
a PAL camera so an NTSC VCR and TV are not required, and the chip is
larger at 1/3” (so there is a larger field of view). The cost of the camera is about $NZ420
and it is available through Hill’s Industries in Lower Hutt.
asked those who might be interested in a bulk order of Watec 902H cameras to
put their names on a list. Eleven people
- In reply to a suggestion about using
a Philips ToUcam webcam, it was stated that the sensitivity of this camera
was much lower which would limit observation to only bright stars.
- Graham suggested that if people
were concerned about spending several hundred dollars on a system suitable
only for MP occultation work, it is possible that the system could be made
much more versatile by installing a frame-grabber card in a computer and
then using the camera and computer to grab and stack frames as is done
with traditional CCDs. (No-one has yet tried out this option to our
- It was noted that for observing
other than MP events (e.g. lunar grazing occultations, where there can be a
considerable difference in brightness across the CCD) it might be
desirable to override the automatic gain control in both the PC-164 and
Watec 902H cameras. Such
modifications can be made for the PC-164 by Sandy Baumgartner in the
US. [Subsequent to the meeting it
was determined that the Watec camera does indeed appear to have a manual
gain control within its housing and that in the simplest case, a hole
could be drilled in the case to allow access to this].
- Graham mentioned that Geoff
Hitchcox has recently developed an On-Screen Display (OSD) unit which
overlays each frame of the video with millisecond accurate time plus
positional information. Although
there are already commercial units which do this, the advantage of Geoff’s
system is that the circuit is very simple, it is extremely cheap to make,
and the system includes considerable error-checking and redundancy which
commercial systems do not possess.
A prerequisite is that the observer has a small GPS unit and Graham
mentioned that Deluo Electronics (http://www.deluoelectronics.com/customer/home.php)
make such a unit for $US80. Brian said that he was hoping to see
Geoff’s OSD next week. Geoff’s OSD
is described at: http://www.geocities.com/kiwi_36_nz/kiwi_osd/kiwi_osd.htm
closed at 7:10 pm.