Aspasia Occultation Timed from 2 Mid-Atlantic Sites
- Updated 2005 Oct. 5
The path shifted north by 0.7 path-widths (1.9 sigma) so the
s. limit must have been over Baltimore, maybe the n. side of it
Skies were clear in Maryland and northern Virginia, but too cloudy
for observation farther west
The story of this event is recounted in the messages below,
with the most recent first.
______________________________________
From: David Dunham [dunham@starpower.net]
Sent: Sunday, October 02, 2005 12:44 AM
To: Roelle, Curtis W
Cc: IOTAoccultations@egroups.com; Dunham, David;
jsedlak@bellatlantic.net
Subject: Large north shift for Sept. 29th 409 Aspasia occultation
Curt,
Since you have an approximately 4-sec. occultation at 100 km
north of the predicted center line at Marston Obs., and John Brooks had
only a 1-second event at Stephens City, VA at 87 km north, that means
that he must have been within only a few km north of the southern limit
of the occultation, which must have been around 80 km north of the
predicted center. So the path must have shifted about 0.7 path-widths,
or 1.9 sigmas, north of Steve Preston's prediction. That means that
the actual southern limit must have passed north of Phoenix, AZ;
near Socorro, NM; and near Carrs Mill, MD and Wilmington, DE, while
the northern limit was near Flagstaff, AZ; Santa Fe, NM; St. Louis, MO;
n. of Columbus, OH; and near Albany, NY and Portland, ME. The times
that you and John Brooks reported for the star's disappearance were
very close to Steve Preston's prediction for the time.
I finally played back the tape I recorded at Point Lookout, MD.
The recording around the time of the occultation was very good,
showing the target star rather well and even fainter stars barely;
WWV at 10 megahertz was clearly recorded with a Timekube.
It was not occulted at that site 75 km s. of the predicted center,
which is consistent with the large north shift deduced from the
other observations. The GPS WGS84 location was:
Long. 76 deg. 19' 21.3" W., Lat. +38 deg. 02' 28.1", h 3m above
sea level. The curious thing is that the star followed a path
near the center of the fixed (in alt./az.) field of view, but
went out of the field at the right edge of the video display
at 1:41:54 UT, only 0.1 min. after the predicted time. That was
closer to losing it than I'd like, but o.k. for a miss observation
since your and Brooks' times indicated that the actual occultation
occurred 0.05 min. or less later than the predicted time. The
star took at least a minute to cross the video field of view.
I pointed the telescope a couple of arc seconds north of
34 Librae at 0:14.9 UT; I double-checked that calculation to
confirm it. So the target star should have been near the center
at the predicted time rather than at the right edge. I was using
a radio shack clock that self-sets to WWVB, and it was changing
its minutes in synch with WWV's minute tones, so I'm sure it was
right; maybe I read the clock wrong, but I don't think so. The
only other explanation is that the telescope tripod was set up
in sand; during the 1.5 hours between setting it at 34 Librae
and the appulse, it must have shifted a little, either from
my motions near the scope as I changed to the long-duration
analog camcorder and started it with the radio in the telescope
box; or from the wind (blowing rather steadily from the east;
I didn't put on a dew cap since the telescope was pointed low
(so the corrector plate was only 10 deg. off of vertical) and
that would increase problems with the light wind, which also
would prevent dew from forming, and none did; or from a passing
deer. I don't plan to play back the 1.5 hours of tape to
listen for/look for those possibilities (but it would be
possible from that to tell when the shift occurred, or if it
was there even at the beginning). In the future, I'll try to
put the tripod on a stronger surface, or if only a sandy
surface is available, push the tripod legs down into it as
far as they'll go.
I also played back the tape made at my other site at
Mechanicsville, near 19 km south of the predicted center,
where I ran a McAfee GPS time inserter for timing, confirmed
with the Radio Shack WWVB-setting clock. It
showed no stars around the time of actual closest approach,
so I don't think it was pointed right, as I suspected before.
But also the focus, and possibly the optical collimation, was
not as good as with the other 8-in. SCT at Point Lookout.
But judging from John Brook's observation, no occultation
occurred there with high probability.
David
______________________________________
From: David Dunham [dunham@starpower.net]
Sent: Wednesday, October 05, 2005 12:15 AM
To: Curtis Roelle
Cc: Dunham, David; jan.manek@worldonline.cz
Subject: Re: Better times for the Aspasia occultation?
Curt,
Many thanks for the times below.
David
Date: Sun, 2 Oct 2005 17:50:59 -0700 (PDT)
From: Curtis Roelle
Subject: Re: Better times for the Aspasia occultation?
To: David Dunham
--- David Dunham wrote:
> Curt,
>
> Could you play back your tape to determine
> your D and R times
> to 0.2 seconds or better? Maybe it'll need to be
> processed with
> Limovie, the Japanese occultation video processing
> software, to do
> this, as John Brooks did.
David,
I thought I submitted the form to
http://sorry.fse.cz/~ludek/mp/results/report.html .
first time I used Firefox browser and it didn't work.
Then I tried it with Netscape and it brought up an old
e-mail program I don't use any more that's configured
with an ISP I no longer use.
So I cut and pasted the addressee, subject, and text
info into another e-mail and sent it. I requested
that it be sent to IOTA and to myself, but never got a
copy.
In any event, here's the results for Aspasia:
D: 01:41:40.8 09/20/2005 UTC
R: 01:41:45.8
Pretty close to the maximum expected duration of 5.6
secs even though I was on the N100 km radius just 22
km S of the northern limit.
---
By the way, for what it's worth, here's the times I
also tried submitting via the web form for the
occultation of 328 Gundrun and TYC 2382-01036-1:
D: 07:44:40.2 08/11/2005 UTC
R: 07:44:43.8
Curtis Roelle roelle1@yahoo.com
______________________________________
From: David Dunham [dunham@starpower.net]
Sent: Friday, September 30, 2005 1:53 AM
To: Roelle, Curtis W
Cc: IOTAoccultations@egroups.com; Dunham, David;
jsedlak@bellatlantic.net
Subject: Re: Aspasia success at MTO Sept. 29 UT
Curt,
Thanks for your observation described below; glad you were
able to time it. John Brooks also video recorded it from Stephens
City, VA, in the northern Shenandoah Valley, a little south of your
chord.
Hopefully, I'll have a 3rd southern chord to add to yours and
John's, but am very busy trying to meet a couple of deadlines, and
after losing time to observing last night, I won't have time to
review the tapes carefully for a couple of days. I found a good
site on the driveway of a friendly young couple overlooking a
large field northwest of Mechanicsville, MD, at about 19 km s. of
center, and set up one of my 8in. SCT's there an hour before
sunset. Then I drove to the end of the highway, at Cape Lookout
where the Potomac River meets Chesapeake Bay. About half a
dozen fishermen were there, but I found a secluded place just
a couple of hundred feet away and set up my other SCT there,
getting it pointed in the right direction with the help of some
7th-mag. stars in Libra a little more than an hour before the
event, that at 75 km s. of center. Then I drove the 40 miles
back to the Mechanicsville site, and made the mistake of starting
to find the star field before polar aligning. I finally did
that, but then missed the opportunity to pre-point that scope
to an 8th-mag. star at the same Dec. as the target star several
minutes of RA west (and of time before) the faint target star.
So I only managed to get to the other 8th-mag. star half a
deg. southwest of the target, and with my narrow field of view,
just blindly offset towards the northwest, but I think I
missed the target at the critical time, and never saw it for
sure. When I returned to the scope at Point Lookout, I found
that everything worked there, stars were still in view on
the camcorder screen and WWV was still playing (not too loud,
with the camcorder and Timekube in the telescope case that
muffled the sound, as well as dense vegetation between the
location and any people, but with a great view to the
horizon over the Potomac). Playing back the tape showed that
it had recorded to the end of the tape well after the event
occurred. A few clouds passed over now and then, coming
from the east over the Chesapeake, but rarely reaching the
target star area. There's a chance one was over the star
at the critical time, or that a deer bumped the scope (but
no evidence of that); I'll let you know after I get a
chance to play the tape to the part around the time of the
occultation. Possibly the path shifted far enough north
that a miss occurred there, but that would be useful to
know.
Joe Sedlak tried to observe the event from Bowie,
MD, but looking to the west from there over the lights
and haze of Washington, DC prevented finding the star.
Another 100 miles down the Shenandoah Valley from
John Brooks was John Goss at Fincastle; haze (probably
thin cirrus) from the front approaching from the west
made it impossible for him to observe the event (from
Cape Lookout, I thought I could see some of that very
low on the horizon, maybe up to 3 deg. or so altitude,
but at the 10 deg. altitude of the target star,
the sky remained quite clear there,
when there weren't the occasional low clouds
from the east). Farther west, in central Tenn., Scott
Degenhardt said it was raining, and other observers
who tried farther west were also clouded out.
David
At 10:21 AM 9/29/2005, you wrote:
David,
A successful event for the (409) Aspasia occultation was observed from
Marstown Observatory in Carroll County, Maryland. According to your
updated site-specific predictions the observatory was situated on the
+100N km radius, 22 km S of the northern limit.
The 4-5 second event was observed starting around 01:41:41 UTC. It was
recorded on VHS video format and was imaged using the StellaCam EX, with
integration mode switched off, connected at prime focus to the 12.5" f6
Equatorial Newtonian.
With the camera's integration turned on it was easy to follow the
progress of the asteroid for about an hour as it approached the star
from the west until the two bodies merged five minutes before the event.
Curt Roelle
___________________________
Extensive prediction and pre-event planning information is here.