Spectacular mu Arietis graze in Texas 2007 June 12 UT
Many multiple events were recorded from 9 stations
north of Hockley
The first reduction profile is here
Updated: 2007 December 14, 19h UT
On the morning of June 12, our expedition observed the graze of the
5th-mag. close double star mu Arietis = ZC 399 from several
locations along and near Hegar Rd. about 2.5 miles north of Hockley
and about 4 miles east of Waller, Texas. The graze took place well
on the dark side of the thin crescent (only 10% sunlit) Moon, which
was about 13 deg. above the eastern horizon with the Sun about 14
deg. below it, so conditions were very good. There were a few thin
cirrus clouds. An approximate tally lists the number of
occultations of the primary star observed at each station from north
to south (so the number is the number of disappearances and the
number of reappearances; multiply by two for the number of contact
events). A few more were found during the detailed analysis of the
video tapes, as well as some step events giving times for many
events of the secondary star.
Especially for the large .avi files, rather than trying to view
them directly from the Web, I suggest that you download them and
view them offline. The locations of the observers in our
expedition, and the approximate locations of the other two (one-
person) expeditions by Roger Venable and Rick Frankenberger are
shown in this Power Point file.
Note that in order to play Bob Sandy's and Don Stockbauer's now
correct .avi files, you need the freeware codec HUFFYUV on your
computer. The readme.txt file in this .zip file tells you how to
install the codec from the files that expand from the .zip file.
These .avi files are large, each about 1 gigabyte.
#
occ'ns Observer
1 Richard Nugent (4in SCT, WAT 902h Ultimate, only 1-sec.)
3 Dave Clark remote (8in SCT, PC164C, Youtube video), large .avi file, and report
2 Dave Clark (8in SCT visual with report
7 Paul Maley (8in SCT, video), LiMovie plots by Rick Frankenberger
Rick Frankenberger also provided these Excel and Word files.
7 D. Dunham remote (5in SCT, PC164C, video, 304-Mbyte .avi file)
with camcorder turned on and off by Brian Cudnik, who observed
the graze nearby visually with I think a 6-in. reflector. He
started the camcorder for my remote setup, then observed the
graze visually, trying to time the events with WWV and a
tape recorder, but that failed because inadvertantly the
voice activation switch of the tape recorder was turned on.
Michael Richmond analyzed these observations with link here,
and Zane Nitskorski made a comprehensive analysis fitting
diffraction curves to the events with Limovie in this 4-mb Word file.
6 David Dunham (4in SCT, visual)
11 Robert Sandy (8in SCT, PC23C, video) .avi file
The action-packed light curve produced by Rick Frankenberger
with Limovie is here, based on this Excel file. This version
of the Excel file includes expanded plots of many of the
events.
3 Don Stockbauer (8in SCT, PC23C, video) .avi file
Rick Frankenberger's Limovie light curve is here. His notes
about the analysis is here, and the Excel file here.
5 David Dunham remote (5in SCT, PC164C, video, 152 Mbyte .avi file)
The .avi file shows only the "D" side of the graze, which had
all of the action; there was only a single reappearance after
central graze which is not shown here.
Michael Richmond analyzed these observations with link here.
____________________________________________________
REDUCTION PROFILE (Lunar profile determined from the observations)
I am especially interested in this star since I co-discovered
its close duplicity during visual observations of a graze of the
star in St. Louis, MO (where I lived at the time) in January 1970
(it was independently found to be double by Christian de Vegt with a
photoelectric lunar occultation disappearance at Hamburg
Observatory, Germany, a month earlier; we discovered each other's
observations at an occultation symposium at the IAU General Assembly
in Brighton, England, in August 1970). In August 1973, we again
resolved the double star during a favorable graze that we observed
near the city of General Terran, Mexico, and further suspected an
8th-mag. 3rd component north of the tight pair. I was hoping that
the third component might be confirmed during our observations, now
with much better equipment & sensitive video cameras, and even
better astronomical conditions (well on the dark side of the thin
waning crescent Moon, only 10% sunlit), but we found no evidence for
it; I think we were fooled by diffraction effects of the bright pair
during the 1973 graze.
Anyway, with the help of many, not just the observers, we've
finally analyzed the observations to produce the profile in the
attached .gif and .png files (labelled and unlabelled versions).
In addition to the observers, those who helped with this effort,
included Rick Frankenberger, who created a time-inserted copy of Don
Stockbauer's WWV-based video as well as convert at least 3 of the
tapes to .avi format and perform extensive Limovie analyses of them;
Richard Wilds, Zane Nitzkorski, and Jennifer Cheng, who determined
timings and prepared reports of the observations; and Mitsuru Soma,
who reduced the observations and sent the files that J. Cheng and I
were able to use to create the reduction plots shown here in
labelled and unlabelled (.png files) and as .gif files in
labelled and unlabelled versions.
In the above plots, the horizontal scale is Watts Angle
(position angle measured from the Moon's axis of rotation as defined
by Watts and the argument used in his classic charts of the marginal
zone of the Moon) in degrees and the vertical scale is seconds of
arc at the Moon's mean distance (one unit = 1.8 km or 1.1 mile).
The Moon isn't as rugged as it appears since the vertical scale is
about 39 times the horizontal scale. Each observer had two lines
for the two components of the star, which were separated by only
0.007" +/-0.004"; they were predicted to be near periastron with the
secondary star south of the primary, and we confirmed that. The
lower line of the close pairs is the secondary star, whose events
were often difficult to notice since the primary star was always
visible when they occurred; many of the events just appeared as if
only one star was involved since either the event occurred
simultaneously for the two components within a video frame, and/or
the event was too noisy to clearly tell a different time for the
secondary star. Consequently, there are many missing secondary star
"chords" on the plot, which shows when the star was behind lunar
features. My north and south stations were remote video stations
with 5" SCT's, while my central station (just south of "D Dunham
north") was a hastily setup visual effort with a 4" SCT under less
than ideal conditions, so I only noticed the secondary star at one
event; there is a noticeable discordance (I was a little later than
my reaction time estimates indicated) of my first disappearance (on
the left side of the diagram; it occurred shortly after I started
observing when I was caught by surprise) relative to the video
observations (all of the other observations shown were video; D.
Clark observed visually with a second telescope near his video
setup, but his visual times disagreed with the video times and are
therefore not shown). Roger Venable observed near Monroe,
Louisiana, in an effort separate from our expedition, so the line
for the 5 occultations that he observed is slanted relative to the
others; atmospheric conditions were worse at his location so he only
obtained times for the primary star events.
Also here is our "official" report for the expedition, although
it is not quite in the e-mail 76 format since the 4-digit year
instead of the usual 2-digit year is given; the sequential event
numbers in col. 1-2 are truncated for those over 100. The report
was updated/corrected on Dec. 11, but Mitsuru Soma has found some
discrepancies that will be corrected soon. Dr. Soma has also
determined that 0.28s needs to be added to the times of Paul Maley
(station D) for them to line up properly with adjacent video
observations; Maley's times are then accurate to less than 0.1s.
My early mu Arietis graze trips were adventures. On the
outskirts of St. Louis in Jan. 1970, while enroute to pick up a
young observer to help with the graze, I made a stupid decision and
crossed a grade crossing when an approaching train was too close (I
thought it was farther away but was fooled by the angle of the road
to the tracks). My vehicle and I survived the close encounter
unscathed, but it was too close for comfort and it gave me more
respect for grade crossings. Then during the 1973 event, my van got
stuck in mud near the north end of the graze zone before the graze.
Afterwards, we needed all the observers to get us out, getting caked
in mud in the process. When we crossed the border back into Texas,
the customs officers wanted to search our van full of student
observers. We welcomed the chance to clean up, dumping several
pounds of dirt on the pavement. Finally, in December that year, we
made another long trip into Mexico, to Puerto Escondido southeast of
Acapulco to observe an annular eclipse of the Sun. On the way back,
we observed another graze of mu Arietis, in early January, 1974,
near Cuernavaca, but all but one of us had a miss for that event;
the predictions weren't as good then as they are now.
More details, including coordinates, about my 3 observations of the
June 12th graze are given in the messages below.
____________________________________________________
My first message about the graze is immediately below, followed by
more messages with more details.
From: David Dunham [dunham@starpower.net]
Sent: Tuesday, June 12, 2007 9:18 AM
To: Dunham, David
Cc: DWalt10100@aol.com; bennyhiker@aol.com; Rpbrpbrpb1@aol.com;
eflaspo@aol.com; pandtzimme@aol.com; MDelevorya@aol.com; ChazEH@aol.com;
CPAJohnM@aol.com
Subject: mu Ari graze successfully observed e. of Waller, TX
8 of us successfully observed the graze of mu Arietis this morning -
lots of multiple events, but not much evidence of the star's
triplicity - apparently, the bright pair was too close to easily
resolve, being near periastron (closest approach expected in
August, see below). First looks showed no evidence of the 3rd star;
either it doesn't exist, or may be 9th mag. or fainter such that it
might not be visible with the telescope/camera combinations that we
used. Richard Nugent, at the northern edge of my predicted graze
zone, had no complete occultation of the star, but possibly had an
occultation of one component of the double by the highest mountain
peaks.
Rick Frankenberger tried to observe the graze from near the center
of the graze zone near Tilden south of San Antonio. He recorded
occultations of the star by three lunar mountains before clouds
moved in, preventing observation of the 2nd half of the graze.
Brian Mason, double star astronomer at the U. S. Naval Observatory,
has provided this plot of the orbit of the mu Arietis close pair,
and these measurements.
David
____________________________________________________
Message to Bob Sandy, copied to the IOTAoccultations e-group
From: David Dunham [dunham@starpower.net]
Sent: Sunday, June 17, 2007 2:23 AM
To: IOTAoccultations@yahoogroups.com
Subject: Re: [IOTAoccultations] Mu Arietis Data
Yes, Bob, I'd like to have your tape, or a copy of it, to post on my
Web site; I don't have any graze videos with so many events that
have GPS time insertion (I think my video of the nu Vir graze that I
recorded in 2002 July from Champlaign, IL, may have as many events).
I'll post it as an .avi file so others can Limovie it - you didn't
mention that you used a PC23C camera.
But I recorded twice as many events as you at the mu Arietis graze!
At least 36 events, 18 D's and 18 R's. However, I had to run 3
telescopes to do that. The northern station, a 5-in. SCT with
PC164C, f/3.3 focal reducer, and Kiwi time insertion, did the best,
with 7 D's and 7 R's, plus I believe 1 or 2 faint flashes. The star
signal was strong, almost as good as that on Dave Clark's video.
Brian Cudnik was near that telescope and turned the camcorder there
on shortly before the graze and off a little after; he observed the
graze visually nearby. The location was about 150 yards south of
Paul Maley's station. The WGS coordinates were long. 95d 50.5144'
W., lat. 30d 04.3121 N., h 71m.
My southern station was the southernmost one that we deployed, maybe
200 yards south of Don Stockbauer's telescope. It was unattended,
also with a 5-in. SCT, PC164C, and f/3.3 focal reducing lens. It
recorded 5 D's and 5 R's, with all the action (5 D's and 4 R's) in
the early part of the graze, with some rather complex variations
over a brief period. There was also a Kiwi time inserter there, but
in the rush to get to my 3rd station, I didn't connect it, and
didn't realize that until after I turned the analog video Walkman
(no camcorder clock!) off after the graze. So there's NO UT timing
of the events, only very accurate relative timings. My hope is that
it will be possible to correlate the relative times with the UT
times at Stockbauer's station, to determine the UT times of the
events at the southern station to a second or better. The WGS
coordinates were long. 95d 50.4964' W., lat. 30d 03.8404' N., h 74m.
By the time I arrived at my central station, about halfway between
your station and my northern one, there were only a few minutes
before the graze began, just enough time to set up a 4-in. SCT on
top of my rental car and observe the graze visually. I called out 6
D's and 6 R's there, noting that one of the R's seemed to be in
steps.
The WGS coordinates were long. 95d 50.5036' W., lat. 30d 04'2284'
N., h 77m.
I've looked at my two tapes closely, and also Dave Clark's
recording, and I do not see the 3rd star. At my northern station,
there is a faint visibility for a second or so after one of the D's,
but I think that is the "toe" of the Fresnel diffraction curve of
the brighter component. If the 3rd star was 0.2" north of the tight
pair, as claimed from the observations of the 1973 Aug. graze (also
northern limit), I think it must have a period of 300 years or more,
so it should have been evident this year. I suspect that there is
no 3rd component, and that the "faint star" that was seen during the
1973 Aug. graze, where all the observations were visual, was also
just the toe of the Fresnel diffraction curve of the brighter
component.
Anyway, it was an action-packed graze that will produce a good
observed lunar profile once we analyze all the observations. A
Limovie analysis of my tapes, as well as yours, Paul Maley's and
Don's, will be interesting to see if they show step events like
those that seem to be in Dave Clark's recording.
In an earlier posting, Paul Maley said that it would not be possible
to run a remote station in Texas. Well, I proved him wrong; I even
did that successfully for another graze a few years ago in New York
City (but it was a cold Sunday morning in December close to the
beach in an area of a few blocks that had recently been demolished
for some new development). Of course, these were for grazes, not
asteroidal occultations, where the separations, and the times left
unattended, need to be longer. But I'm confident that my central
station for the mu Arietis graze last Tuesday morning, at a fenced
(but with an open door) small utility building, could have been used
as a remote station for an asteroidal occultation; if one looks
around, one can usually find lonely places that won't be visited
during the night.
David
At 12:26 AM 6/17/2007, you wrote:
>Response from Bob Sandy: For what it is worth, I used a Celestron 8"
>GOTO GPS scope along with a Mogg f/6.3 Focal Reducer for this event,
>and broke my old record of 14 events by getting 18 events. My Stability
>Code = 2 for this graze, because of low Moon Altitude, so the star DID scintillate some.
>Does anyone wish to LiMovie my VCR tape?? I can either send my original
>to someone, OR burn a DVD at the fastest speed, and send the DVD to whoever.
>
>----- Original Message -----
>From: "Roger Venable" <rjvmd@hughes.net>
>To:
><IOTAoccultations@yahoogroup
>s.com>
>Sent: Saturday, June 16, 2007 7:48 PM
>Subject: Re: [IOTAoccultations] Mu Aritis Data
>
> > Dave Herald --
> >
> > I appreciate your follow-up to my comments. However, I am impressed
> > that the uncertainties in the orbit as predicted by the speckle data
> > are magnified by the present, rapid change in the position angle of
> > the secondary as it crosses the minimum-separation point of the
> > orbit. Thus, the secondary may well be positioned more favorably for
> > detection at a disappearance than at a reappearance, notwithstanding
> > the orbit prediction. Indeed, one way to find out about this is to
> > look at Dave Clark's data! There it is! Or, there it seems to be.
> > Like you, I am not sure. Nevertheless, I think that Dave should
> > report it the disappearances as two-step events with a code of "2"
> > in column 47, i.e., "possibly spurious." I agree with David Dunham's
> > comment about estimating the 1/4 brightness point as the point of
> > 1/4 of the brightness of the star after this secondary disappearance,
> > but again, it's a matter of taste.
> >
> > This will make future grazes of this star more interesting than ever.
> >
> > -- Roger
> >
> > ----- Original Message -----
> > From: Dave Herald
> > To:
> IOTAoccultations@yahoogroup
> s.com
> > Sent: Friday, June 15, 2007 10:03 PM
> > Subject: Re: [IOTAoccultations] Mu Aritis Data
> >
> > I'm inclined to agree with this analysis. In particular, the small
> > drops before each of the two major D's are tempting. They drop by a
> > similar amount, and remain at that level for a number of frames -
> > which is what you would expect of a double star event. However the
> > absence of any corresponding steps on the reappearance side is
> > troublesome. From the orbit, we know that the direction of the
> > secondary from the primary is approximately normal to the lunar limb
> > (perhaps give or take quite a few 10's of
> > degrees) - which means
> > that it is highly unlikely for the pair to disappear at
> > significantly different times but reappear at the same time.
> > Importantly the partial reappearance (which MUST be of the primary
> > star only) shows that stellar diameter &/or Fresnel diffraction are
> > present. So my conclusion is that the two steps before the D's are
> > most likely stellar diameter/Fresnel diffraction made visible by an
> > appropriate lunar gradient.
> >
> > As further support, Roger notes that his events were 'slow' but
> > without steps. That is, he saw stellar diameter &/or Fresnel
> > diffraction effects.
> >
> > Dave Herald
> > Canberra, Australia
> >
> > ----- Original Message -----
> > From: "Roger Venable" <rjvmd@hughes.net>
> > To:
> <IOTAoccultations@yahoogrou
> ps.com>
> > Sent: Saturday, June 16, 2007 4:52 AM
> > Subject: Re: [IOTAoccultations] Mu Aritis Data
> >
> > > Dave --
> > >
> > > I think that the feature is a diffraction event in which the
> > > star's
> > light was partially
> > > visible in a lunar valley. Its peak brightness is more than 1000,
> > > i.e.,
> > more than 25% of
> > > the brightness of the unocculted star in your analysis.
> > > Consequently,
> > it should be
> > > considered to be a reappearance and disappearance. I'd report the
> > > R & D
> > times as the
> > > times at which the measured brightness is at 1/4 of 2500, or about 625.
> > >
> > > Even more interesting is the slight diminution in brightness just
> > before two of your
> > > disappearances. These partial dimmings might be the brightest of
> > > the
> > companion stars,
> > > which was occulted before primary, and may have shown up better in
> > > the
> > disappearance
> > > phases of the events as compared to the reappearance phases, due
> > > to its
> > position with
> > > respect to the primary. However, I am not sure that this is the
> > > meaning
> > of these
> > > features.
> > >
> > > (In my graph of the events of the same graze, made from northern
> > Louisiana, the noise is
> > > greater and no trace of partial events can be detected, despite
> > > all the
> > events being
> > > slow.)
> > >
> > > Thanks for sharing this most interesting graph.
> > >
> > > -- Roger
> > >
____________________________________________________
Pre-event plans and predictions are here.
David Dunham, cell 301-526-5590