My Impressions of the Spica Graze of 6/09/95
Robert L. Sandy
bobgraze@qni.com
To ALL My Avid Graze Observers: The first thing I would ask is that before
reading any further, please link onto my web page at
http://www.qni.com/~bobgraze/pr.htm which explains how to interpret what
you are looking at when viewing my Pictorial Reductions.
Now on 6/09/95, 48 observers in 5 separate expeditions in the states of
California (three seperate CA expeditions), Arizona, (it is VERY noteworthy
that AZ had ONE expedition made up of observers from FIVE different
clubs!!), and New Mexico (one expedition) were successful in observing the
EXTREME Lunar Longitude Libration graze of Spica (Z.C. 1925) near the lunar
south pole. There were ten observers in California, twenty-eight in
Arizona, and ten in New Mexico. Of these, a total of 50 accurate timings
were made in California, 110 in Arizona, and 49 in New Mexico, for a total
of 209 timings! On the PICTORIAL REDUCTION (P.R.), I was able to plot 8 of
the 10 observers in CA, 10 of the 17 observers (some of the 28 observers in
AZ "teamed" up at some of their sites, leaving 17 individual sites) in AZ,
and 8 of the ten observers in NM, for a total of 26 observer tracks plotted
on the P.R., thusly making this the second LARGEST/DETAILED undertaking by
this writer in drawing a Pictorial Reduction; the FIRST being that of the
Rho Sagr. (Z.C. 2826) graze of 9/05/95, also showing 26 observer "tracks".
And MANY hours were spent by this writer in correspondence with Expedition
Leaders, AND in drawing the Spica Pictorial Reduction.
P.R. Facts: (1) The predicted profile (shown in black) was plotted using
the limb datum shown on Dr. M. Soma's Grazing Elements (G.E.'s) NECESSARY
to draw SUBJECT P.R. This limb data is ALSO the SAME as that shown on the
pre-ACLPPP profiles the Expedition Leaders received PRIOR to SUBJECT graze.
(2) Please note that for this graze, the Moon's LONGITUDE libration (L) was
-6.78-deg. for the CA observers, and -6.90-deg. for the NM observers. In my
"study" of what EFFECT the SMALL 0.12-deg. CHANGE in the Longitude
Libration might CREATE with regard to any CHANGE in the PREDICTED Watts
Limb Datum plotted on the P.R., I found a MAXIMUM of ONLY 0.04" of VERTICAL
limb datum VALUE change BETWEEN CA and NM, --a pretty insignificant amount.
There was NO CHANGE in the Moon's Latitude Libration (B=+2.08-deg.) BETWEEN
CA and NM. (3) BECAUSE the Moon's Longitude libration was EXTREME, almost
ALL the ERROR BARS were of value=1; a few error bars are shown on the P.R.
ERROR bars could be placed every 0.2-deg. ALONG the entire P.R.-Predicted
Limb, except that in doing so would "CLUTTER" the P.R. too much (please pay
close attention to the error bar values shown at the BOTTOM of the P.R.).
(4) It has been established that virtually ALL observers saw "bright" Spica
make contact with the Moon's SUNLIT features, yet even though the Moon was
highly GIBBOUS (79% Waxing) , the star Spica was bright enough to offset this.
THANKS: Thanks are in order to Derald Nye and Don Stockbauer for their time
spent to do TIME-INSERTION for observers Don Lynn, B. Gill, J. Sanford, and
W. Johnson (all in CA), and G.Lucas, D.Nye, T.Polakis, P.Schwaar, and
D.Wrigley (all in AZ). These people videotaped Subject graze.
Apologies: Unfortunately since there were so many observers OUT for this
graze AND many of them LESS than 0.05" (vertically) apart from one
another (each SMALL square on the P.R. IS 0.05"), and even though I used
a 2x template, it was impossible to plot EVERY observer. So apologies go out
to the several observers that I could NOT plot.It may be a "consolation"
to the non-plotted observers that I HAVE compared their reported timings in
"relation" to the P.R.-plotted observers, and found that their timings CLOSELY "agree".
CREDITS: Whether INTENTIONAL or not, special thanks to Obs. Tom Seddon (NM)
for going "deep" into the Moon to COVER the W.A. range from 170.4 thru
181.1-deg.; it would have been nice to have had ADDITIONAL observers a
little SHALLOWER than he. Also CREDIT is given to the AZ observers for
establishing the PEAK of the feature located at W.A. 177.2-deg. Also,
special thanks go to Alan Hale (of Comet Hale-Bopp fame) for observing this
graze in NM expedition. Boy, this is getting to sound like the Academy
Awards (pun)!! Dave Brown (AZ) definately established the TIP of the
mountain centered at W.A. 173.3-deg., reporting a 1.0-sec. BLINK using
video-recording. Derald Nye (AZ; not plotted), who was located just 0.064"
"below" Brown, observed a 3.2-sec. occultation using video, and Tom Polakis
(AZ-plotted) located just 0.095 "below" Brown, observed a 4.4-sec.
occultation. The NM TEAM "discovered" a unpredicted (not shown on either
the Watts charts OR the ACLPPP) feature centered at 172.55-deg. BOTH AZ and
NM observers "discovered" yet another unpredicted VERY small feature
centered at 173.85-deg. THE POINT HERE IS, as usually the case, that MORE
events are observed than PREDICTED, due to small features that are
UNPREDICTED on the Lunar-Predicted PRE-graze profiles. CA observers
"verified" the fairly small PREDICTED feature centered at 175.95-deg. The
VERY large "mountain" centered at W.A. 174.6-deg. was well-verified by ALL
obseving TEAMS. Observers from ALL three states "saturated" the predicted
peak at W.A. 177.2-deg., AND well-determined its TRUE outline, and also
showing it to be somewhat WIDER than predicted. AND Observer Brian Vorndam
(AZ) using a 6"-f/8 clockdriven Newtonian "established" the EXTREME flat
top of it. Observer Brian Gardner (AZ), the next DEEPER observer, saw
several rapid events starting at W.A. 176.91 and ending at 177.11-deg.,
definately indicating that the TOP of this large feature WAS "slanted" as
PREDICTED. It is also interesting that Observer Fulton F. Wright using a
5"-f/10 SCT at 100x, saw a Flash at W.A. 177.32-deg. This writer believes
that because he was using a fairly small-aperature scope, and that ALL
major lunar features were sunlit, that SOME of his timings were slightly
LATE, even after this writer applied his estimated Personal Equation of
-0.25-seconds to his RAW timings.
SPECIAL NOTE: This writer believes that Alan Rishel's FIRST reappearance
timing to be LATE by a good 3-4 seconds of time from that REPORTED to me.
He reported that "seeing deteriorated markedly DURING the Graze Period,
with much jitter and color and intensity fluctuations". He VISUALLY
observed SUBJECT graze using a C-8 at 275x! It is this writer's belief that
MAGNIFICATIONS of OVER 150x is TOO MUCH for ANY graze observing, whether
the graze occurs on EITHER the dark/bright side, since the HIGHER the
magnification, the more atmospheric turbulence is magnified (the Moon/Star
was ONLY 18-deg. above the horizon, and therefor turbulence). This bad
seeing turbulence creates the graze "target" star to become blown out of
proportion, even at the BEST possible focus, thusly making it look FAINTER
than it is, and therefor harder to see, OR "follow" during the graze period.
DISCOVERIES: The MAIN discovery for SUBJECT graze was the very noticeable
left-to-right HORIZONTAL shift of ALL observers' ACTUAL observed events vs.
the predicted star Spica CONTACT points! This left-to-right discrepancy
CANNOT be contributed to any star position error, BECAUSE the position
(R.A. and Dec.) for Spica was taken from the Hiparcus Catalog, and is
EXTREMELY accurate. NOR can it be contributed to a Cassini Region Graze,
since even though the graze occured WITHIN 7-deg. of the Moon's true South
Pole, the Moon's Latitude Libration (B) was +2.1-deg.; in order for a graze
to be "rated" as a Southern Cassini Region graze, the Moon's Latitude
Libration has to be in the HIGH MINUS value, NOT plus value. So what caused
the horizontal shift (?); the answer lies in the fact that the Moon's
Longitude Libration was EXTREME (i.e., -6.8-deg.;--see P.R. caption), and
thus creating longitudinal error in the Predicted Watts Profile! Dr. Dunham
is in agreement with this writer that it was the EXTREME Longitude
Libration that caused the left-to-right shift.
In a email letter addressed to Spica Expedition Leader Warren Offutt (NM)
dated 8/18/98, Dr. Mitsuru Soma (Japan) stated (quote) "As Bob Sandy wrote,
your observations provide good profile data, and they are very valuable
BECAUSE the Watts** limb data for THIS lunar limb region have POOR
accuracies due to the NEARNESS of the libration limit, and we did NOT have
any observed profile data for this limb Watts Angle region in the ACLPPP
limb data files. Thanks for observing and reporting them to us."
After receiving some final data from graze leaders, who covered a
slightly different Watts Angle limb region, it was obvious that my
prediction was correct.
SPECIAL REQUEST: This writer makes a plea to all graze team leaders to
move quickly to finalize their post graze reports. Other graze
expedition leaders could use your same observed profile information for
locating their observers in relation to the Predicted Graze Limit. I am
well aware that the post graze followup and reporting time is the
hardest thing for an expedition leader to do, but the data collected is
useless if it is not reported in a timely fashion so that others can
benefit from their efforts.
NOW, ANOTHER INTERESTING TIDBIT (per David Dunham): Did you know that the
Moon's B-Libration (i.e., Lat. Lib.) values are STAR POSITION related??!!
Yes, this means that when the Moon occults a certain star, like Spica for
instance, that the Moon's Latitude Libration (B) value AND sign (+/-) is
ALWAYS (i.e., within less than 0.4-deg.) the SAME B-value!
So the point here is that EVERY time the Moon grazes Spica for instance,
the B-value (and sign) is ALMOST IDENTICAL. So THIS paragraph strongly
RELATES to my "Special Request" directly above with respect to LET'S ALL
GET OUR GRAZE REPORTS COMPLETED PRONTO!!.
**The Marginal Zone of the Moon by Dr. C.B. Watts (deceased); U.S. Naval
Observatory; A.P. Volume XVII
Robert L. Sandy
IOTA Pictorial Reduction Plotter
4901 S. Valley View Rd.
Blue Springs, MO 64015
816/795-8116
bobgraze@qni.com
P.S. If there is ANYONE of you LISTED in the TO: or CC: think
would like to receive a copy of THIS email Spica COVER LETTER, and who is
NOT shown in the TO: or CC's ABOVE, let me know what their email/snailmail
addresses are, and I will send them a copy. Also IF you are listed ABOVE,
but do NOT have a copy of the Spica P.R., let me know BY email. The Spica
P.R. AND THIS cover letter WILL be "POSTED" on EITHER the IOTA Main Web
Page OR this writer's Web Page at http://www.qni.com/~bobgraze/ AND
possibly in a FUTURE IOTA Newsletter.