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Transcript
North Central Florida’s
Amateur Astronomy Club
29°39’ North, 82°21’ West
September/ October
Issue 109.1/110.1
Member
Astronomical
League
Member
International
Dark-Sky Association
Saturn: Shadows of a Seasonal Sundial
Image Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA Explanation:
Saturn's rings form one of the larger sundials known.
This sundial, however, determines only the season of Saturn, not the time
of day. In 2009, during Saturn's last equinox, Saturn's thin rings threw almost no shadows onto Saturn, since the ring plane pointed directly toward
the Sun. As Saturn continued in its orbit around the Sun, however, the
ring shadows become increasingly wider and cast further south. These
shadows are not easily visible from the Earth because from our vantage
point near the Sun, the rings always block the shadows. The above image
was taken in August by the robotic Cassini spacecraft currently orbiting
Saturn. The rings themselves appear as a vertical bar on the image right.
The Sun, far to the upper right, shines through the rings and casts captivatingly complex shadows on south Saturn, on the image left. Cassini has
been exploring Saturn, its rings, and its moons since 2004, and is expected to continue until at least the maximum elongation of Saturn's shadows occurs in 2017.
First Light
Sep / Oct / 2011
1/ 15
Presidential Comments
Bob Lightner
AAC President
Hello Everyone!
The temperatures here in north central Florida may be cooling down a bit from the hot
summer, but things here in the AAC are really heating up! We have many great astronomy events taking place throughout the remainder of 2011. The AAC is alive and
well. I am so excited to see so many of our members involved in such a wide-variety of
projects. Our beehive is really buzzing!
This month we have several club star parties planned. We started this month off with a
star party at St. Madeline’s Catholic Church in High Springs. Chuck Broward wooed
the crowd with his slide show on his trip to see the total solar eclipse in Easter Island. Then Mike Toomey,
Tandy Carter, Chuck and myself showed the congregation the moon, stars, constellations and galaxies
through our telescopes.
A big annual club star party was held at Fred and Lucille’s Stargate Observatory up in Live Oak. Goldhead
Branch State park is the site for another club star party later this month.
We are also gearing up for our huge annual event at the museum called Starry Night. This year we will be
involved once again in an effort to introduce the public to astronomy by setting up our telescopes in the
field in front of the museum, along with the UF Astronomy Department and Santa Fe College Astronomy
students.
Our School Outreach is boiling over with activity! We have three school star parties planned for this year
with at least two more for early 2012. The few open slots on the calendar that remain will most-likely be
filled as well. Thanks, Tandy for all of your efforts!
Bob O’Connell’s LOG group will be involved in the Lunar Club 100 project. This is an exciting and FUN
educational opportunity.
Chuck Broward’s ATM group is involved in designing a sundial for our observatory. Our Eagle Scout candidate, J.P. Organ, finished his project at the observatory, making and installing six nice benches to complete our original master plan for the facility.
Our new club website is really developing and many members are now posting interesting forum content. The site continues to improve as people get used to the new format. We held a special workshop at
our general membership meeting this month and many people attended.
Several of our club members continue to show up and assist at the University of Florida’s Campus Teaching Observatory each Friday evening. Astronomy students and the general public flock to this nice campus
location to look through the UF’s telescopes.
Our members have been treated to many wonderful speakers at our club meetings this year. One final one
will be presenting next month on the Kepler Mission to discover Exoplanets near Cygnus.
One final important piece of work remains to be done. Our club is in the process of searching for new officers to fill the slate for 2012. If you know someone who is willing to serve our club in any capacity, please
encourage them to contact one of our three nominating committee members, Rich Russin, Ivo Rabell or
Pam Mydock. Perhaps YOU might like to step up to the plate and serve!
2 / 15
Sep / Oct 2011
First Light
Alachua Astronomy Club, Inc.
2011 Officers
President: Bob Lightner
Phone: 352-373-3055
Email: [email protected]
Vice-President: Marlene Grabbe
Phone: 352-732-2767
Email: [email protected]
AAC Meeting Location - AAC regular meetings are held on the
second Tuesday of each month at 7:00 p.m. at the Florida Museum of
Natural History, Powell Hall, in the Lucille T. Maloney Classroom, on
UF campus, unless otherwise announced. All meetings are free and
open to the public. Join us for some great discussions and stargazing
afterwards. Please visit our website for more information
(floridastars.org). There is no monthly meeting in December.
Treasurer: Ivo Rabell
Phone: (352) 665-9381
Email: [email protected]
Secretary: Paula McLain
Email: [email protected]
Board of Directors
Howard Eskildsen
Bill Helms
Pamela Mydock
Chairs and Committees:
Star Parties: Paul Griffin
Email: [email protected]
Programs/Promotions: Andy Howell
Phone: (352) 505-4852
Email: [email protected]
Outreach Coordinator: Mike Toomey
School Liaison & Outreach:
Tandy Carter
Email: [email protected]
ATM SIG: Chuck Broward
Phone: 352-373-7527
Email: [email protected]
Astronomical League Correspondent:
Charles S. Broward
Phone: 352-373-7527
Telescope Custodian: vacant
Email: [email protected]
Lunar Observing/SIG: Bob O’Connell
Phone: 352-475-1586
Email: [email protected]
Webmasters: vacant
Email: [email protected]
FirstLight Editor: Arne Reykowski
Phone: 352-562-3387
Email: [email protected]
Submitting Articles to FirstLight
The AAC encourages readers to submit articles and letters for
inclusion in FirstLight. The AAC reserves the right to review and
edit all articles and letters before publication. Send all materials
directly to the FirstLight Editor.
Materials must reach the FirstLight Editor at least 30 days
prior to the publication date.
Submission of articles are accepted by e-mail or on a CD. Submit as either a plain text or Microsoft Word file. (In addition, you
can also send a copy as a .pdf file but you also need to send
your text or Word file.) Send pictures, figures or diagrams as
separate .gif or .jpg file.
Mailing Address for Hard Copies or CDs
Note: Since our mailbox is not checked daily, mail materials well before the deadline date. (Hence, submission by e-mail is much preferred!)
c/o FirstLight Editor
The Alachua Astronomy Club, Inc.
P.O. Box 141591
Gainesville, FL 32614-1591 USA
By E-Mail: Send e-mail with your attached files to
[email protected]
FirstLight is the bi-monthly publication of the Alachua Astronomy Club, Inc.,
Gainesville, Florida. © Copyright 2011, Alachua Astronomy Club, Inc.
FirstLight is copyright by the AAC. No part of FirstLight may be reproduced by any
means, nor stored in retrieval systems, transmitted or otherwise copied without written
permission from the AAC.
First Light
Sep / Oct / 2011
3/ 15
SPECIAL EVENTS - 2011
Event
See the AAC website for details
Date
Location
Check the website for directions
Saturday,
December 3
Holiday Party
Barnett residence in
Gainesville
Start/End Time
TBD
STAR PARTY / OBSERVATION SCHEDULE: Upcoming Events - 2011
Event
Star Party
Date
Location
Saturday,
December 17
Start/End Time
Newberry Star Park
5:00pm-11:00pm EST
School Outreach Program: Upcoming Events - 2011
School
Date
Location
Check the website for directions
Start/End Time
Williams Elementary
School
Wednesday,
November 9
1245 SE 7th Ave,
Gainesville
Begin:4:30pm
End: 10pm
Chiefland Elementary
Thursday,
Dec 1
1205 NW 4th Avenue,
Chiefland
Arrival Time: 16:30
Start Time: 18:00
Aurora Over Greenland
Image Credit: Copyright: Juan Carlos Casado.
4 / 15
Sep / Oct 2011
First Light
Mare Nectaris Oct. 3, 2011
First Light
Howard Eskildsen
Sep / Oct / 2011
Board Member
5/ 15
Mare Humorum
6 / 15
Howard Eskildsen
Sep / Oct 2011
Board Member
First Light
October Club Meeting
Speaker:
William E. (Bill) Carter, Research Professor, Civil and Environmental Engineering, University of
Houston Adjunct Professor, Civil and Coastal Engineering, University of Florida
The Astronomer, the Clockmaker, and the Sea-Captain Extraordinaire
Preview: The names Nevil Maskelyne, John Harrison, and James Cook will forever be entwined
by the roles they played in "solving" the problem of determining longitude at sea, during the age
of sail. In recent years much attention and credit have been focused on John Harrison, including
the dedication of a memorial in Westminster Abbey, in 2006. Unfortunately, much of the effort to
heap more credit on Harrison and his clocks has come at the expense of denigrating the contributions of Nevil Maskelyne and his astronomical solution to the problem. The obvious question: Are
these realignments of credit justified by historical facts? Those who have read Dava Sobel's book
"Longitude, the True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His
Time" may be surprised, dismayed, or pleased by the content of this talk, but hopefully few will
leave believing that Harrison single-handedly solved the longitude problem.
About the Speaker: Bill Carter was born in Steubenville, OH, and grew up in western PA, near
Pittsburgh. He studied Civil Engineering at the University of Pittsburgh, receiving a B.S. Degree in
1961. He served 8 years in the U.S. Air Force, as a Geodetic Officer, and then as a graduate student at Ohio State University where he earned an M. S. Degree in Geodetic Science, before being assigned as a Minuteman Missile Launch Control in Montana. After leaving the Air Force Bill
worked for the Air Force Cambridge Research Laboratory and earned a PhD in Civil Engineering
at the University of Arizona, while helping to build a Lunar Laser Ranging Station at the summit of
Mount Lemmon. Later positions included: Research Geodesist, University of Hawaii, and Chief of
Geodetic Research and Development Laboratory, National Oceanic and Atmospheric Administration. Moving to St Augustine, FL in 1996, Bill became an Adjunct Professor at UF, and helped
found and develop the National Center for Airborne Laser Mapping (NCALM) at the University of
Houston, where he is a Research Professor. Bill has published several papers and two books
(Latitude, How American Astronomers Solved the Mystery of Variation, and Simon Newcomb,
America's Unofficial Astronomer Royal) with his daughter, Merri Sue Carter, who is an astronomer at the US Naval Observatory Flagstaff Station, AZ.
Left: JoAnn Stevener, our lady of
refreshment, who
provides wonderful goodies each
meeting.
Right: Andy Howell presenting Bill
Carter, who gave
us a look at 18th
century sailing
and navigation
techniques, with
a AAC coffee
mug.
First Light
Sep / Oct / 2011
7/ 15
August ATM Meeting
Chuck Broward
ATM
These are four pictures
of the August 2011
ATM meeting at Rich
Russin's home in west
Gainesville.
The picture above
shows Rich and Clint
looking at focuser problems on one of Rich's
many scopes.
A fine dinner was
served, and we spent
some time learning
about various Aps for
IPads...presented by
Rich Russin, Larry
Friedberg,
Paula
McLain, and Barbara
Stanton.
About half a dozen
members attended. We
also assisted another
member with repairs to
his telescope.
8 / 15
Sep / Oct 2011
First Light
September ATM Meeting
Chuck Broward
ATM
The pictures are of the September
ATM meeting at
Chuck Browards house.
Featured was Greg Beckner
who presented eight ATM'ers
with a discussion of grinding
his own 8 inch mirror. He
hopes to have a working
'scope by November.
Greg is a DOT engineer, active in scouts, and a skilled
archer.
First Light
Sep / Oct / 2011
9/ 15
Comet C/2009 P1 Garrard
Byron Bergert
AAC Club Member
Web Master
The photo is comet C/2009 P1 Garrad taken on August 29, 2011. This small comet was moving
in the sky over 2 arc seconds per minute so a single luminance exposure of 5 minutes binned 2x2
was made.
10 / 15
Sep / Oct 2011
First Light
Star 8
Mike Toomey
Club Member
In the last edition of First Light, Dr. Howard Cohen asked how many avid sky watchers have seen an object that defied explanation. The following is a true story...
7:51p.m. EST, March 5, 1997
My Backyard
Morriston, Florida
Earth
At dusk, on an unseasonably warm and clear evening, I was setting up my recently delivered 12-inch
Schmidt-Cassegrain telescope. At this point, I was required to identify two “guide” stars for the telescope's
computer alignment. Scanning around, I recognized the Big Dipper rising in the northeast.
But there was something amiss with this all-too-familiar asterism – instead of 7 bright stars making up the
bowl and handle, there were 8!
The mystery star brightened slowly until reaching about magnitude +2, almost identical in brightness to
nearby Dubhe (Alpha Ursae Majoris). It remained at this brightness for 8 to 10 minutes, without ever moving – not perceptibly, anyway. “A supernova!” my mind raced. “The brightest in a thousand years! This is
every astronomer's dream!” My astronomy text book states that we are 500 years overdue for a supernova in our stellar neighborhood. “What an amazing stroke of luck!” I thought. “Call the press! Call everyone!”
Alas! It began to dim, and within a minute, it had disappeared entirely; curious behavior for a supernova.
Was there some other type of variable star I was unaware of? Do gamma ray burst possess a visible
component? Once the initial excitement wore off, I had to assure myself that the explanation was probably quite mundane. Any light source outside of our own solar system seemed far-fetched, and any source
outside of earth's immediate vicinity would probably not survive scrutiny either.
For the next several days, I systematically eliminated one explanation after another. There were no
launches from Cape Canaveral or any other space port. A weather balloon is common enough but it did
not sit well – even in the telescope, the object appeared star-like (i.e. it had no form or "disk"). There was
little or no motion – certainly a balloon would have demonstrated some drift during the time span observed. I detested the idea that this was some top secret military deployment that would stymie any sort
of investigation. After all, if whatever hypothesis I came up with was correct, then the observation might
be repeatable.
I had read that geostationary satellites may brighten to naked eye visibility despite being located some
25,000 miles above Earth. This is especially true near the equinoxes (the vernal equinox was just 2
weeks away). The problem with this explanation was that the "satellite" was observed at 63 degrees north
declination. This object was no where near the geostationary belt. In fact, any satellite residing outside of
about 10 degrees of declination should exhibit some movement... right?
Even so, I revisited the possibility of an artificial satellite. Over the next couple of weeks, I had digested
every article on the satellite observers' web site, as well as hundreds of archived mailings. I downloaded
several satellite tracking programs, learned how to plug and play Keplerian elements (the numbers that
describe an object's orbit), and verified the accuracy of the predictions with actual observations.
Still, “Star 8” seemed elusive, but now having observed many types of satellites and their sometimes peculiar behavior (glinting, flashing, flaring, formation-flying!), I felt that I was on the right track. Now I just
needed to scrutinize thousands of artificial satellites in an effort to find a match. Thank goodness for computers!
First Light
Sep / Oct / 2011
11/ 15
There never was a eureka moment. It took a while to fit the pieces together. While Star 8 was, in
fact, an artificial satellite, there is a rather interesting explanation attached to it. The object was
one of several Russian communication satellites that occupy a special orbit call a molniya, named
after the first satellite system to use this orbit.
Russia possesses a couple of disadvantages in communication technology, both owing to its
northerly latitude. The first is that their primary space port, Baikonur Cosmodrome, is at 46 degrees north latitude. (For comparison, Cape Canaveral is at 28.5 degrees north latitude). It takes
the Russians considerably more fuel to inject a satellite into the geostationary zone (an area that
roughly lies above the Earth's equator), which places greater demands on their rocket technology
(i.e. it drives up the costs). But this is of less consequence than the fact that most of Russia lies
above 50 degrees north latitude (in fact, half of Russia lies above 60 degrees north latitude). The
line of sight from Russia to the geostationary zone is of such a low angle that satellite transmissions are weak to non-existent. Enter the molniyas.
A satellite in a molniya orbit is highly elliptical (or eccentric). In any type of orbit, an object spends
more time near apogee (farthest from its parent body, in this case, Earth), and less time near
perigee (closest to Earth). If an object has a rather circular orbit (the International Space Station,
for example), then there is little discrepancy between apogee and perigee. However, with a
highly elliptical orbit, there can be a considerable difference in the amount of time a satellite
spends near each of these points.
The result: a satellite with a highly elliptical orbit, such as a molniya, will give the observer on the
ground the impression that the satellite is stationary or hovering above Earth for minutes or even
hours at a time while it is near apogee. The satellite then spends a relatively brief period in a
slingshot around the Earth before resuming its high altitude mission. From this lofty perch, the
satellite can beam signals back and forth with Earth's high latitude clients. The gap in coverage
(while the satellite is in “slingshot” mode) can be mitigated by launching multiple satellites into the
same orbit with different timings. This constitutes a satellite “constellation.” [The best known satellite constellations are the Global Positioning System (GPS), and Iridium, which provides satellite
phone service worldwide].
On this particular evening in 1997, I happened to be standing in the right place at the right time to
detect a sun glint from a rather large Russian molniya satellite at a remarkable distance of 25,000
miles! (Bear in mind, satellites do not emit any light of their own; any observation of a satellite is
made possible by reflected sunlight. This is what makes it possible to observe the space station
or the Hubble Space Telescope pass overhead during twilight hours.) While I've seen only one
bright molniya since that time, I along with other AAC members have made several observations
of other high earth orbiting satellites at our star parties – without any visual aid!
This mystery served as a wonderful catalyst for exploring a new field. The following year, I gave
the astronomy club a presentation about observing artificial satellites. I developed a web site
dedicated to observing satellites over North Florida. I even landed on the front page of the
Gainesville Sun in the build-up to the re-entry of the Russian space station Mir. I rediscovered
the benefits of binoculars as an astronomical tool – ideal for hunting down satellites – which, in
turn, has reinforced my knowledge of the stars and constellations.
No little green men were harmed in the recounting of this story.
12 / 15
Sep / Oct 2011
First Light
Molniya orbit
From Wikipedia, the free encyclopedia
Figure 1: The Molniya orbit. Usually the period from perigee + 2 hours to perigee + 10 hours is
used to transmit to the northern hemisphere
Molniya orbit is a type of highly elliptical orbit with an inclination of 63.4 degrees, an argument of
perigee of -90 degree and an orbital period of one half of a sidereal day. Molniya orbits are
named after a series of Soviet/Russian Molniya (Russian: "Lightning") communications satellites
which have been using this type of orbit since the mid 1960s.
A satellite in a highly eccentric orbit spends most of its time in the neighborhood of apogee which
for a Molniya orbit is over the northern hemisphere, the sub-satellite point at apogee having a latitude of 63.4 degrees North. As the apogee altitude is as high as 40000 km it will therefore for a
considerable period around apogee have an excellent visibility from the Northern hemisphere,
from Russia but also from northern Europe, Greenland and Canada.
To get a continuous high elevation coverage of the northern hemisphere at least three Molniya
spacecraft are needed.
The reason why the inclination should have the value 63.4 deg is that then the argument of perigee is not perturbed by the J2 term of the gravitational field of the Earth but stays -90 deg.
First Light
Sep / Oct / 2011
13/ 15
Variable Start of the Month
Andy Howell
Programs/Promotion
Variable Star of the Month – Omicron Ceti
By Matthew Templeton
Reprinted by permission of the American Association of Variable Star Observers (AAVSO)
Omicron Ceti, also known as Mira, is justifiably one of the most famous of the variable stars, and dear to many variable star observers -- especially those who use our website, mira.aavso.org! Omi Cet, discovered in 1596, was declared 'miraculous' by its early
observers for appearing and disappearing from view with a regular cycle of around 11
months. We know today that omi Cet and the other Mira variables are very evolved, giant
stars undergoing large-amplitude pulsations that make them periodically brighten and dim
by several magnitudes. These stars are giant in size -- most are comparable in diameter
to the orbits of Earth or Mars -- but at the same time have masses only slightly larger than
that of the Sun. They're all nearing the ends of their lives, too, and their remaining lifespans as 'stars' is measured in tens or hundreds of thousands of years rather than millions or billions. After the Mira phase, they'll soon become planesize. They're among the
most numerous variable stars known since their great amplitudes made them easy to
find. The AAVSO has light curves for several hundred of them spanning many decades,
of which Mira's itself is the brightest, and among the best-observed.In 2011, Mira reached
one of its brightest observed maxima in history, reaching m(vis) ~ 2.2 in mid-September.
For more information visit:
Mira Revisited: http://www.aavso.org/vsots_mira2
Cetus Finder Chart: http://www.aavso.org/sites/default/files/finder_charts/CET.GIF
14 / 15
Sep / Oct 2011
First Light
In, Through, and Beyond Saturn's Rings
Image Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA
From Astronomy Picture of the Day: http://apod.nasa.gov/apod/ap111026.html
Explanation: A fourth moon is visible on the above image if you look hard enough. First -- and farthest in the background -- is Titan, the largest moon of Saturn and one of the larger moons in the Solar System. The dark feature across
the top of this perpetually cloudy world is the north polar hood. The next most obvious moon is bright Dione, visible in the
foreground, complete with craters and long ice cliffs. Jutting in from the left are several of Saturn's expansive rings, including Saturn's A ring featuring the dark Encke Gap. On the far right, just outside the rings, is Pandora, a moon only 80kilometers across that helps shepherd Saturn's F ring. The fourth moon? If you look closely in the Encke Gap you'll find a
speck that is actually Pan. Although one of Saturn's smallest moons at 35-kilometers across, Pan is massive enough to
help keep the Encke gap relatively free of ring particles.
First Light
Sep / Oct / 2011
15/ 15