Observations of the occultation of SAO 96908 by (704) Interamnia
on 2003 March 23 from near the ends of Maui

1.  Rebecca Sydney video recorded the occultation from a site
just north of Highway 30 near Honolua Bay, south of Lipoa Pt.
near the north end of Maui.  She used her C8 with a
Supercircuits 164C camera, recording the event with a Sharp
camcorder.  As best I can tell from http://www.topozone.com,
she was at

longitude 156 deg. 38' 25" west
latitude   21 deg. 01' 09" north
altitude  160 ft.

Since topozone uses the 1:24,000-scale map of the area, I assume
that these coordinates are on the Old Hawaiian Datum, but I am not
sure of that.  In any case, they are considerably different from the
GPS measurement that Becky provided:
longitude 156 deg. 38.56', latitude 21 deg. 00.65'
which, when plotted on topozone, is well inland, away from Hwy. 30.
Maybe the difference is just the difference between the WGS 84 datum
of the GPS and the Old Hawaiian Datum, but Becky was using a small
GPS receiver for hiking; I think it would be useful to go back to
the site with a good averaging GPS receiver like the one Ed Mahoney
loaned me to make another GPS measurement, averaged for at least
5 minutes.

The videotape was time-inserted with a Manly time inserter to
provide the following event times (UTC, from WWV, triggering from
the 1000-Hrz minute tone, without correction for propagation delay):

 h  m  s
 9:56:30    start observing
10:01:28.08 start of disappearance
10:01:28.18 0.5 brightness (center of star)
10:01:28.42 end of disappearance
10:02:11.23 start of reappearance
10:02:11.38 0.5 brightness (center of star)
10:02:11.43 end of reappearance
10:02:58    end of recording

The event durations are consistent with the expected angular
diameter of the star, 0.63 mas from the Warner relation (that is 3.8
times the Fresnel fringe spacing, so Fresnel diffraction is
negligible; the center of the star, or 0.5 brightness, should be
used for the geometric occultation by the edge of Interamnia).  The
faint companion of the star reported by Japanese observers is not
evident in the recording, but might be found with digitization of
the tape to produce a photometric record of the events.
_______________________________________________________________

I video recorded the occultation from a site near the
south end of Maui, from the road leading south from Makena,
surrounded by the Makena Golf Course northeast of Puu Olai.  I used
a 50-mm telephoto lens attached to a 2nd-generation image
intensifier and Panasonic video camera, recorded with a Sony digital
camcorder; it recorded down to about 8th mag. over a 12-deg.-wide
field.  The observing site was 7 yards west of the center of the
road and 12 yards south of the center of an underpass for a small
road, apparently linking the west and east sides of the golf course,
that passed under the road I was on.  Using the GPS receiver
borrowed from Ed Mahoney, the WGS 84 coordinates of the site,
averaged for about 10 minutes, are:

longitude 156 deg. 26.649' west
latitude   20 deg. 38.424' north
altitude   50 ft. (from www.mapmart.com)

The GPS receiver gave the accuracy as 22 to 39 feet.
This agrees well with the position for the site determined from
http://www.mapmart.com that shows both roads.  The USGS map on
www.topozone.com does not show these roads, but only an older,
straighter road that is not very close to the coordinates above.

I thought I had 4 microphones, but Becky and Ed each had one, and I
left one at a remote station (see below), and I could not find one.
So I did not have sound (or WWV) during the occultation observation,
but before and after, I switched to the camcorder to record WWV
along with the camcorder clock, and then relied on the latter for
the timing of the occultation.  Unfortunately, I could not get the
Manly time inserter to trigger to the 9:57 minute tone before the
occultation, only to the 10:07 tone afterwards.  So the camcorder
clock is calibrated only after the event, and the running time
insertion display showed an unusually large rate difference from the
camcorder clock, as well as some apparent irregularity of the
latter.  This introduces larger errors in the times than I expected;
they can be improved if the 9:57 minute tone can be made to trigger
the Manly time inserter, or that might be calibrated by Frank Anet
with his analysis of the digital record, which I will send to him,
if I can't get the Manly time inserter to trigger.  A calibration of
the camcorder clock was also possible from another occultation
observed on March 8, showing a difference of 8.42 seconds.  That
implies a rate correction over the 5 min. from the Interamnia
occultation to the 10:07 UTC calibration of a negligible 0.002
seconds.  So for now, assuming the camcorder clock rate is correct
over the time interval in question, the event UTC times are:

 h  m   s
10:01:27.28 disappearance
10:02:24.35 reappearance

I think these times are accurate to about 0.2 second, the scatter in
the rate that I observed, but they can be refined by accurately
calibrating the camcorder clock with the 9:57 UTC minute tone from
WWV, which should be possible.
___________________________________________

I also set up another telephoto lens with a Watec camera about 100
feet north of a bus stop near the end of Hwy. 31 in Wialea.  I did
not have time to properly point that system, so it ended up
recording the target star for only 30 seconds about 5 minutes after
the occultation.  Although that was a failure, the position
determined with the GPS reciever of the site, longitude 156 deg.
25.876', latitude 20 deg. 41.312', is far east of Hwy 31 (rather
than west of it, as the bus stop is located) when plotted with
www.topozone.com.  I should compare that with www.mapmart.com, which
seems to have more up-to-date roads.

David Dunham, 2003 April 3