Occultation by asteroid (471) Papagena observed from 5 stations in n. MD
and s.e. PA - Updated 2007 Dec. 3, 23h UT
The path shifted about 1/3rd path-width to the southwest with the
occultation about 5 seconds late relative to S. Preston's prediction
I recorded the occultation from 3 well-separated stations
Links are now provided to my .avi files
Tony George has determined accurate times from my video tape
Times and Files from Curtis Roelle's video are now provided
Since the account below was posted on May 30th, Tony George has
analyzed my video tapes using Registax, which co-added frames to
enhance the faint images of the target star enough to determine
rather accurate event times, and then a plausible elliptical fit.
Also, Rick Frankenberger has analyzed Curtis Roelle's video using
his version of the Manly time inserter to make a time-inserted copy,
and then used LiMovie, Registax, and Excel to process it; see below,
after the account by Tony George of my observations.
Tony George wrote:
From: "Tony George"
To: "Brad Timerson IOTA" ,
"David Dunham IOTA"
Cc: "Dave Herald IOTA"
Subject: Revised Papagena OBS file -- 5-24-2007
Date: Thu, 14 Jun 2007 19:17:38 -0700
David,
Here is the revised Papagena event Occult .OBS file I created from
your video files. The data reduction was quite difficult. I had to
use VirtualDub filtering, Registax integration, and LiMovie to
reduce the data. I checked the LiMovie results with a simple 'eye'
method as well, after the videos were filtered and integrated so I
could see the target stars. The LiMovie and 'eye' results agreed to
within +/- 0.1 second (or better). So, we have changed your initial
stop watch results a bit and improved the +/- error by at least 1/2.
Your initial results were actually quite good. The greatest change
I found was just a few tenths of a second. The new OBS file does
provide quite a nice fit and agrees amazingly well with the shape
and size observed in the Papagena event of 1-24-1987 listed in the
events summary in Occult. I recommend the circular size filed with
the original file be discarded in favor of the newer shape and size
provided in the file attached.
Let me know if you have any questions. You can now take Papagena
off the list to be checked and processed.
Tony George
Umatilla, Oregon
Note added Sept. 5: The Occult .OBS file originally posted here was
corrupted, and has now been replaced with a correct version copied
from Tony's message.
______________________________________
The original (unprocessed) .avi files that Tony George used are
below (my recordings); they range in size from 71.9 to 76.6
megabytes:
Northeastern station near Nottingham, PA
Central station at Poplar Grove, MD
Southwestern station at Bagley, MD
______________________________________
The account below is unchanged from May 30th
I recorded the Papagena occultation from two remote stations in
n.e. Maryland and also at an attended station near Nottingham, PA,
just n. of the MD border, my 2nd 3-station-positives success. The
occultation was also recorded by Dick Sauder at Narvon, PA, well
east of my locations, and by Curt Roelle, well to the west, and a
little outside the predicted western edge, showing that the path
shifted west (further confirmed by Brad Timerson's miss).
________________________________________________
This is the 2nd time I've successfully recorded an occultation
at 3 separate locations, but the first time I've done it without
help from anyone else (the first time, for 99 Dike on 2005 Dec 1, my
wife turned on the camcorder of the prepointed telescope at home)
and the first time for me with 3 successful chords that none of the
stations were at home. I really had to scramble, since there was
less than 3 hours of good enough dark time (by that, I mean good
enough to see Polaris without much difficulty to approximately polar
align my scopes by eye). Because of this, I wasn't able to get as
wide a separation as I had (80 miles) for the (19) Fortuna event
last month, but still managed to obtain useful separations. I first
found a suitable site for the southern station at about sunset, then
travelled 10 miles up US 1 to find the second (center) site where I
set up the first telescope and prepointed it with the help of a 5th-
mag. star near the Auriga/Gem. border. I then went back to the
southern site and set up and prepointed the second telescope there,
with help from sigma Geminorum just north of Pollux (I just missed
that good opportunity, but it got me close enough to star hop to
fainter stars that allowed an accurate pre-pointing). I started the
Video Walkman recording there, then stopped at the center station
for a final prepointing (with help from faint stars just north of
iota Cancri; I had to adjust the previous pre-pointing since
removing the front end cover and adding a dew cap moved the scope a
little), then attaching and starting a camcorder there. By then, it
was less than an hour to the event; I had wanted 1.5 hours. I drove
up US1 to the 1st exit in Penn. about 20 miles from the center
station, and then had only about 25 minutes to set up the northern
station. I had wanted to go about 8 miles farther, but had to
settle for this, a good-enough separation, anyway. Unfortunately,
US1 in Maryland is not interstate quality; most stretches have only
2 lanes (1 each way) with a fair number of stop lights. I used a
5-inch SCT with image intensifier there; the combination just barely
worked with the bright background from the Moon 23 deg. away, and I
got everything running and on target with only a couple of minutes
to spare. 8-inch SCT's were used at the other stations, those
without image intensifiers, but all with PC164C cameras and f/3.3
focal reducing lenses.
About half an hour before the Papagena occultation, Curt Roelle
was watching (471) Papagena approach the target star with his
integrating Astrovid camera and thought of calling my cell phone.
But then he thought, "Dave's probably scurrying around setting up
his stations now and probably doesn't want to be interrupted" so he
didn't. I appreciate that; only if you are in danger of loosing an
observation and might be able to use some advice should you try to
call me during the hour before an event. As noted above, I was
quite busy then. When I first set up at the central station,
twilight washed out the fainter stars in my finder, but I was just
able to see Polaris to polar align that telescope. Then I was able
to set it on sigma Gem, easy to find about a deg. n. of Pollux, and
then move my scope in RA westward using setting circles to find the
5th-mag. stars near the Aur/Gem border that were only faintly
visible in the finder. In any case, I had to be focused on Papagena
the whole time; I didn't have time for either the (96) Aegle appulse
or 45 Leonis lunar occultation, both of which occurred a little
more than an hour before the Papagena occultation. But those of you
who only observed from one place might have tried those other
opportunities. I think Brad Timerson was the only one who actually
observed the Aegle appulse.
I believe this now brings the total number of positive chords I've
timed to 81, I claim more than anyone else, although Paul Maley has
timed more individual events than me. But I beat him for chords
since 13 of the occultations that I've observed have been from 2 or
more stations. Of course, Roger Venable still holds the record for
number of stations for a single occultation, having obtained 4
chords for an occultation by Pallas last June. As noted above, two
others were successful in recording the occultation, and two others
have reported misses - see the summary below, where the occurrence
of an occultation or not is indicated with + and -, respectively.
Joe Sedlak travelled farthest for this occultation, from his home in
Glenn Dale, MD n.e. of Washington, DC to southern New Jersey. He
had the star in view before and after the occultation, but lost it
for about 20 seconds at the critical time due to bright headlights
of a passing car. So when possible, try to find a site where this
won't be a problem, at least in the direction of the target star,
and possibly have a dark towel or cloth that you can drape over your
head and the scope eyepiece if you can't set up far enough off the
road. The occultation occurred several seconds late at my
locations (Dick Sauter has determined the times from his video,
showing that the occultation occurred 5 seconds late relative to
Steve Preston's last prediction).
P
r
Dist. o U.T.
from b 4h 0m Star
center. Location, observer and Alt
km % s o
115 50 *** Northern limit ***
71 72 - NEWARK NY BRADLEY TIMERSON 16 26
0 89 **** Centre Line ****
-7 89 + Narvon PA Dick Sauder 27 24
-37 + Nottingham PA David Dunham
-60 + Poplar Grove MD D Dunham remote
-77 + Bagley MD D Dunham remote
-115 50 *** Southern limit ***
-126 44 + Marston MD Obs.,Curt Roelle 30 24
-186 16 ** Southern limit plus 1-Sigma **
_____________________________
Curt Roelle's observations from Marston, MD (added 2005 Dec. 4)
Some time ago, Curtis Roelle sent me the CD that Rick
Frankenberger sent to him, with the full .avi file and a shorter one
processed with Registax, and Excel sheets from the LiMovie analysis
that he made of both tapes. Only recently I tried to unzip the .zip
files on the CD, and that worked except for the full .avi file,
which my WinZip said was corrupted. From the Excel frames file, I
obtained the following times for Curtis Roelle's observatory:
Disappearance: 4:00:31.55 +/-0.03s UTC
Reappearance: 4:00:34.35 +/-0.03s UTC
I confirmed these times to within a frame both from the 5-frame
average Excel file (where the event is very clear, but the time
resolution needs to be degraded a little) and from visually
examining the frames of the short .avi file with LiMovie.
The relevant files are:
"short" 1.3 Gigabyte .avi file
Rick Frankenberger's description of his files and work
Rick Frankenberger's Excel file and LiMovie plots
Zip file with short Huffy files needed to view the .avi file
_____________________________
Extensive prediction information and pre-event plans, including the
last station list before the event, are here.
David Dunham, 2007 Dec. 3, 6 pm EST
Phones home 301-474-4722; cell 301-526-5590; office 240-228-5609
office e-mail david.dunham@jhuapl.edu (& Blackberry)
home e-mail dunham@starpower.net