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Electronic Journal of the ASA (EJASA) - September 1994
Author: Larry Klaes
Date: Tue, 13 Sep 1994 22:29
Date: Tue, 13 Sep 1994 22:29
1147 lines
58749 bytes
58749 bytes
THE ELECTRONIC JOURNAL OF
THE ASTRONOMICAL SOCIETY OF THE ATLANTIC
Volume 6, Number 2 - September 1994
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TABLE OF CONTENTS
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* ASA Membership and Article Submission Information
* A History of Meteorology at the Pic du Midi Observatory
- Emmanuel Davoust and Jacques Damiens
* Mirror Making Class of 1993: A Review - Paul Dickson
* You Call It What? - M. Leon Knott
* Up All Night: Observing the Perseid Meteor Shower of 1994
- Michael Hann
* Announcing a New Publication: SETIQuest Magazine - Carl Helmers
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ASA MEMBERSHIP INFORMATION
The Electronic Journal of the Astronomical Society of the Atlantic
(EJASA) is published monthly by the Astronomical Society of the
Atlantic, Incorporated. The ASA is a non-profit organization dedicated
to the advancement of amateur and professional astronomy and space
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ASA membership application is open to all with an interest in
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For information on membership, you may contact the Society at any
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or telephone the Society Recording at (404) 636-3642 to leave
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ASA Officers and Council -
President - Eric Greene
Vice President - Jeff Elledge
Secretary - Tex Ratcliff
Treasurer - Cindy Weaver
Council - Frank Guyton, Larry Klaes, Ingrid Siegert-Tanghe,
John Stauter, Wes Stucky, Harry Taylor, Gary Thompson,
Bob Vickers
ARTICLE SUBMISSIONS
Article submissions to the EJASA on astronomy and space exploration
are most welcome. Please send your on-line articles in ASCII format to
Larry Klaes, EJASA Editor, at the following net addresses or the above
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You may also use the above addresses for EJASA back issue requests,
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When sending your article submissions, please be certain to
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Back issues of the EJASA are also available from the ASA anonymous
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DISCLAIMER
Submissions are welcome for consideration. Articles submitted,
unless otherwise stated, become the property of the Astronomical
Society of the Atlantic, Incorporated. Though the articles will not
be used for profit, they are subject to editing, abridgment, and other
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Society of the Atlantic, the Electronic Journal, and the author(s).
Opinions expressed in the EJASA are those of the authors' and not
necessarily those of the ASA. No responsibility is assumed by the
ASA or the EJASA for any injury and/or damage to persons or property
as a matter of products liability, negligence or otherwise, or from
any use of operation of any methods, products, instructions, or ideas
contained in the material herein. This Journal is Copyright (c) 1994
by the Astronomical Society of the Atlantic, Incorporated.
A HISTORY OF METEOROLOGY AT THE PIC DU MIDI OBSERVATORY
Emmanuel Davoust
Observatoire Midi-Pyrenees,
14 Avenue Edouard Belin, 31400 Toulouse, France
davoust@obs-mip.fr
and
Jacques Damiens
Meteo France,
1 Quai Branly, 75007 Paris, France
Summary
Meteorology was the main activity of Pic du Midi Observatory until
astronomy prevailed around 1937. Three directors, Vaussenat (1882-
1892), Marchand (1892-1914), and Dauzere (1920-1937), ensured smooth
running of this Observatory, which was often caught in storms and
lightning at an altitude of 2,880 meters. They gathered and
successfully analyzed the numerous meteorological data obtained by
the two observers at the summit.
Introduction
Pic du Midi Observatory, located near Lourdes in the center of
the Pyrenees Mountain Ridge in southern France, owes its international
renown to the remarkable astronomical observations that were carried
out there. However, its vocation for astronomy is recent. The
Observatory's long ties to meteorology are worth recounting. In fact,
from its founding in 1882 to the naming of an astronomer as director
in 1937, meteorology was the principal, and for a long time the only,
activity at this Observatory.
The Observatory at Sencours Pass
The project of establishing a meteorological observatory at the
summit of the Pic du Midi dates from 1872. The project was launched
by the Societe Ramond, a group of men interested in the Pyrenees
Mountains. Charles Champion du Bois de Nansouty, a retired general,
was named as the head of the project, and Celestin-Xavier Vaussenat, a
civil engineer, was charged with presenting the project to the public
and collecting money, since the financing of the construction and
the running of this private Observatory was to come from private
donations.
A temporary meteorological station was established at the Sencours
Pass, at an altitude of 2,366 meters, just below the summit of Pic du
Midi, in 1873. The observers were lodged at the inn that had been
built a few years earlier. The instruments were placed on the
Plantade knoll, named for an astronomer who had died there in 1741.
Measuring instruments were also placed at the summit of the Pic du
Midi.
General de Nansouty, observer Baylac, and a cook spent six winters
at the pass. Every day they took four series of six to ten meteorological
readings at the Plantade knoll, at 7 and 10 a.m. and 4 and 7 p.m.. Once
each day, observer Baylac would climb to the summit of the Pic to take a
reading at 12:43 p.m. (7 a.m. in Washington, D.C.). The results were
transmitted to General Albert Myers, Chief of the United States Signal
and Meteorological Service, following the recommendations of the Congress
of Vienna.
In 1880, observers could stay in the permanent buildings at the
summit of the Pic du Midi. The Observatory was officially inaugurated
in 1882 and donated to the State on that date, on condition that the
State would take over the 45,000 Franc debt, and that it would give
30,000 Francs a year for the observers' salaries and to maintain the
building. Vaussenat was named director.
The Organization of the Observatory
The Pic du Midi Observatory's exceptional location at an altitude
of 2,880 meters was not without constraints. The whole story has to
be known in order to understand its history until 1952, the date at
which the Observatory was linked to the rest of the world by two cable
cars, drastically changing life at the summit.
Map of the Access to Pic du Midi Observatory
+ Bagneres
\
------ road \
...... path \
= pass \
O lake \ 12 km
+ town \
x cascades \
(2880m) altitude \
4km distance \
\
\
+ Sainte
/ Marie
* Observatory (2880m) / de Campan
4 km . /
Oncet lake O = . . /
Sencours pass | . /
(2400m) | ................... + Gripp (1100m)
3.5 km | . /
| . / 2.5 km
| . x/ Arizes cascades
Tourmalet pass = ------+------------------- |
(2115m) 4km La Mongie (1800m) \ _|
x
At the summit, the personnel was composed of two assistant
meteorologists and two general helpers. The first observers were
Leandre Ginet and Sylvain Latreille. They carried out both
meteorological and astronomical observations. After a preliminary
reduction, they transmitted them to Bagneres de Bigorre, where the
Director exploited them. In the 1930s, the two assistant meteoro-
logists, Hubert Garrigue and Joseph Devaux, were more than just
observers: Both were preparing a thesis on atmospheric electricity
and on glacier snow, respectively.
There were more people at the Observatory during the brief summer
period, when access was easier. The director, visiting astronomers,
naturalists, and physicists stayed there while doing their research.
It was at this time of year that the annual inspection (until 1920) by
two scientists named by the Central Meteorological Office in Paris
took place.
The director ran the Observatory from Bagneres (altitude 550
meters), a small spa in the valley about 27 kilometers away from the
Observatory. He was linked to the summit by a telegraph line that was
often cut by bad weather conditions. The director was responsible for
administration, management, and scientific observations (meteorological,
seismological, magnetic, and astronomical). His hardest job was
certainly ensuring the smooth running of life at the top, managing
supplies (especially when the weather blocked access), human problems,
and the correct functioning of the instruments, most of the time from
a distance.
A position of assistant meteorologist was created in Bagneres in
1900, which Jean Dort held until 1934. Joseph Bouget, the Observatory
botanist, never had a permanent position. He took care of botanical
gardens at the summit, in Bagneres, and at several intermediate
altitudes. Bouget often observed when one of the incumbents was sick
or on vacation. In Bagneres, occasional employees paid by the hour
worked as secretaries, accountants, or librarians.
There was an important intermediate stage between Bagneres and the
Pic: The Brau Inn at Gripp and the Observatory's depot, 2.5 kilometers
after Gripp. Jean Brau, and later his sons, played an essential role
in the Observatory's daily life. It was they who organized the
conveying of men and food to the summit, in winter as well as in
summer. The road suitable for vehicles joining the Tourmalet Pass to
the Laquets (altitude 2,600 meters) was built only in 1934 and can
only be used in the summer (this is still the case!). Before that
date, the only path to the summit was a mule trail. In the winter
until 1952 this trail had to be followed to the top, sometimes at the
risk of being carried away by an avalanche. Three porters died in
this way in November of 1882.
Five to eight hours were needed to climb on foot or skis from
Gripp to the summit, depending on weather conditions. Ascents usually
took place once each week, but often bad weather prevented them. In
the history of the Pic, it very often happened that men would be
blocked at the summit without getting supplies for one month or more.
Most of the supplies - canned food, wine, fuel - were carried by mules
between July and September. The rest of the time, porters carried the
supplies on their backs. Since this was very expensive, portages were
limited to fresh food and indispensable equipment.
Life at the Summit
Life at the summit was very difficult during the winter, which
lasted eight to ten months. Snow fell in October at the latest, and
melted only at the beginning of July. At the end of the winter there
were often several meters of snow on the terraces (this is still the
case!). The buildings were badly heated, poorly insulated against bad
weather, and let dampness and even snow come into the structures. The
roofs had to be cleared when the weight of the snow threatened to make
them collapse, and tunnels had to be dug in the snow to let the light
in when the windows were buried.
In an 1886 letter to Eleuthere Mascart, director of the Central
Meteorology Office, Marcel Brillouin, a renowned French physicist,
describes one of the observers: "Ginet got there such terrible
rheumatic pains that he could not put his feet down without suffering.
(...) A crack in the vaulted ceiling loaded with snow let water drip
into his room until the summer, as long as the snow could not be
cleared; and to make sure that everybody else followed the rules, he
nevertheless stayed in that room, whose dampness you can imagine."
After the cold and the snow, the main problem facing the men at
the Pic was lightning. It is in fact still a problem today. A
network of lightning rods, linked by a cable 1,200 meters long to
Lake Oncet (below Sencours Pass), ensured a minimum of security and
channeled away most of the lightning. This network also eliminated
accidents, previously quite frequent, caused by lightning in the upper
parts of the valleys leading to the Pic. It sometimes happened,
however, that the lightning came up to the summit along the telegraph
wire, despite the lightning rods installed all along it.
Storms were (and still are) spectacular at the Pic, as witnessed
in a letter from Vaussenat to Mascart, dated July 12, 1887: "Last
night, from 9 p.m. to midnight, we were able to observe the most
grandiose storm that we have ever seen, and which hit the central
Pyrenees and came within a kilometer of our peak. The Pic was
unharmed, thanks to our set of lightning rods and their good
conductors. But never had we seen the St. Elmo's Fire with such
intensity; there seemed to be real fixed, luminous, blue and red
centers. The envelopes themselves were luminous. It was fairy-like,
it hailed abundantly."
Vaussenat's Direction (1882-1892)
Vaussenat was mainly concerned with improving the installations at
the summit, enlarging the terraces, building new shelters or permanent
buildings. He was interested in everything that happened at the peak,
and carefully noted all the phenomena which attracted his attention:
Frost on the windows, on the metal of the doors, St. Elmo's Fires,
lightning bolts, and rings around the Moon or the Sun. Vaussenat
wrote about them in his letters to Mascart.
Daily meteorological observations were the summit's principal
activity, but they did not seem to be well done, according to Marcel
Brillouin who inspected the Pic in 1886. "The actinometric observations
never made any sense. (...) The anemometer and the weather vane do
not show anything in the winter, and mean nothing in the summer. The
barometer was empty, and even though observed carefully, the thermo-
meters too. As for the hygrometer and the pluviometer, I believe they
need special precautions to work correctly."
An important function of the Observatory was to forecast bad
weather and to warn the population, a service appreciated by the
administration and by farmers. Indeed, the Pic du Midi's privileged
location, an isolated peak in the Pyrenees chain, allowed observers
to forecast atmospheric disturbances, storms, and also floods of the
Garonne, Adour, and Gave de Pau Rivers. Unfortunately, the lack of
communications did not always let these warnings be given rapidly.
An important experiment in atmospheric physics was attempted
between 1884 and 1887: The Lemstrom experiment, named for the Swedish
scientist who tried to produce artificial Aurorae Borealis in 1882.
This experiment was suggested by the Central Meteorology Office in
1883 and carried out at the Pic du Midi by Vaussenat. The Pic's
summit was covered with a network of 400 square meters of wire
("the Lemstrom network"), in order to tap atmospheric electricity.
Unfortunately, the network mostly attracted lightning, with disastrous
results for the equipment and danger for the personnel. The
experiment had to be given up before giving any scientific results.
Marchand's Direction (1892-1914)
Emile Marchand, the Observatory's second director, established a
meteorological station at Bagneres. He also perfected a simple code
so that the observers at the summit could give a rapid (less than one
quarter of one hour), succinct, but precise description of the cloud
cover (with the speed and the altitude of the clouds) several times
each day. In this way, he obtained simultaneous readings at two
altitudes (550 and 2,880 meters) that were completed by readings at
intermediary altitudes taken during ascents of the Pic. He also
continued the seismological and magnetic measurements started by
his predecessor.
These initiatives let him gather very numerous and complete data
which Marchand spent years analyzing. He was thus able to acquire
great knowledge of the atmospheric and meteorological phenomena in the
neighborhood of the Pyrenees chain. He would make weather forecasts
for the next 24 hours, which were reasonably correct ninety percent
of the time.
Among Marchand's works we should mention: A lifelong study of
the correlations between solar activity, earthquakes, geomagnetism,
and atmospheric physics, a method for establishing a local weather
forecast (1911), the effect of the Pyrenees chain on the rainfall and
the asymmetry of the region's valleys (1903), and a long study of
the temperature and the tension in water vapor (1894-1898). He
presented all his works in talks at many colloquia. Unfortunately,
most of his works were published in the proceedings of the various
colloquia and in obscure publications, like the Bulletin of la Societe
Ramond, where they are still waiting to be read.
One of the observers, Sylvain Latreille, was also supposed to make
astronomical observations, to take daily readings of sunspots, Moon
observations (to search for a lunar atmosphere), Jupiter and Saturn's
satellites (ephemerides), and to map the zodiacal light.
It was under Marchand's direction, in 1906 and 1907, that a real
astronomical station was installed at the summit of the Pic du Midi by
Benjamin Baillaud, who was then director of Toulouse Observatory. A
fifty-centimeter equatorial reflector telescope was brought up to the
summit in the course of two summers, thanks to the efforts of a group
of soldiers of a regiment in Tarbes. It was reserved, though, for
astronomers from Toulouse and for visiting astronomers who had to ask
permission from Toulouse Observatory's director. This reflector,
which was very inconvenient to use, was hardly used until 1942, when
it was completely transformed.
Marchand died in April of 1914 and was only replaced at the end
of the First World War (1918) by Joseph Rey, a former naval officer
who resigned in 1920.
Dauzere's Direction (1920-1937)
The Observatory suffered from the lack of maintenance during the
war. Camille Dauzere not only repaired the buildings and the terraces,
but also improved living conditions at the summit, built other buildings,
and attracted scientists of all kinds.
In 1926, the Observatory became an "Observatory and Institute of
Terrestrial Physics", like those in Paris, Clermont-Ferrand, and Algiers.
Dauzere was a physicist. He took up Marchand's meteorological
works and, being particularly interested in lightning and hail, tried
to link these phenomena to the air's electrical conductivity. He
worked more closely with Bouget, who for the past thirty years had
been making a detailed study of all the lightning bolts that he knew
about in the region. They were thus able to establish some simple
rules:
"Lightning preferably strikes certain privileged places, that
are not necessarily protuberant points of the ground. The location
of those places that are often struck by lightning is related to the
nature of the rocks that make up the ground. The areas most exposed
to lightning are often located on contact lines between two different
geological terrains. (...) Places where hail originates (...) are
linked with places where lightning strikes."
The Pic du Midi's astronomical renown began in the 1930s, with
Bernard Lyot's work on the solar corona outside periods of eclipse.
In 1937, the naming of Jules Baillaud (Benjamin Baillaud's son) as
director of the Observatory confirmed this conversion to astronomy.
Conclusion
This brief survey of the history of the Pic du Midi Observatory
shows that it was always a high point of interdisciplinary studies.
Thanks to the will of several men and to the courage and perseverance
of many others, this Observatory allowed scientific progress in very
different fields: Meteorology, botany, astronomy, atmospheric physics,
particle physics, cosmic rays, physiology, etc. It would be extremely
regrettable that the present economic difficulties should lead to its
abandon, because its history holds much promise for its future.
Acknowledgments
We would like to thank Mr. J. P. Legrand who told us about the
existence of documents on the Pic du Midi Observatory at the archives
of Meteo France. This paper has been published in French in "La
Meteorologie".
Was this brief history of any interest to you? Please send your
comments to Emmanuel Davoust at davoust@obs-mip.fr.
Related EJASA Articles -
"Amateur Astronomy in Spain", by Jordi Iparraguirre - April 1990
"The Mayall Four-Meter Telescope", by Don Barry - May 1990
"A Southern Travel Diary: An Observer's Tale", by Don Barry -
August 1990
"Kitt Peak and McDonald Observatories: Impressions", by Russell
Whigham - October 1990
"A History of Ohio's Perkins Observatory", by Earl W. Phillips, Jr. -
February 1992
About the Authors -
Emmanuel Davoust (davoust@srvdec.obs-mip.fr) is an astronomer at
Midi-Pyrenees Observatory. He does research on the morphology and
dynamics of galaxies, mainly based on observations obtained at Pic du
Midi Observatory. Emmanuel is also working on the history of French
astronomy and that of Pic du Midi Observatory in particular. He has
published a book on the search for life in the Universe titled THE
COSMIC WATER HOLE (MIT Press, 1991).
Jacques Damiens is an archival officer at the main library of the
French Meteorological Office. He is interested in the history of
meteorology and has published several papers in that field.
MIRROR MAKING CLASS OF 1993: A REVIEW
by Paul Dickson
From the February, 1994 issue of the Saguaro Astronomy
Club's newsletter, SACNews, in Phoenix, Arizona
Last summer, fifty people gathered together at Scottsdale
Community College in Arizona to grind mirrors for telescopes.
Although it was called a class, no grades were given, as the goal was
to learn how to build telescopes from the mirror blank up. The class
typically met twice each week, with exceptions when the school was
closed for holidays or when the East Valley Astronomy Club (EVAC) had
their monthly meeting. The class was taught/led by Leon Knott with
assistance from his wife Fannie.
In the Beginning
The class held its first meeting on April 29, 1993. This first
meeting covered basic mirror math, enough so that class members could
choose the f-ratio of their mirror as well as ordering the mirror
blanks in the sizes we wanted. Mirror sizes built by the class
ranged from four inches up to twenty inches.
The first working meeting was in June, after the mirrors blanks
had arrived. In this meeting we beveled the mirror edges to prevent
chipping while we did the rough grinding. Those who were still unsure
of their f-ratio were given another overview of how to compute the
grinding depth needed in the glass.
The class met informally. It was not required that everyone
attend all meetings. In fact, with the large size of the class, a few
missing people gave everyone else a little more elbow room. For the
most part, all of the tools for our mirrors were poured from dental
plaster during the first couple of nights. "As much plaster as a
dental lab uses in six months", according to Leon.
The meeting after pouring the tools, ceramic tiles were epoxied
to the tool. The epoxy was the single most expensive item after
purchasing the glass. But it was well worth it: If the tiles were
not held in place, then a lot of work could be lost, as one person
found out who did not use epoxy.
The Grind
Generating the curve of the mirrors was done with 80 grit
particles. This was used to get within a few thousandths of one
inch of our desired depth. Those who had mirrors sixteen inches
and larger had their mirrors pre-generated to almost the correct
curve, allowing them to skip this first step, which could consume
a lot of time for them.
After reaching nearly the correct depth, we switched to 120 grit.
After this point, we switched to the next smaller grit size when the
surface had a uniform smoothness under a 30X magnifier. The next
sizes in sequence were 220 grit, 40 micron, 25, 12, 5, and then 3
micron.
At this point polishing pads were then used with 1 micron serum to
accelerate the polishing before moving to the pitch lap. We were told
by Leon that he had experimented with the polishing pads in previous
classes and their use significantly cut down the number of hours on
the pitch lap, but did not replace the pitch lap.
The pitch laps were poured on the ceramic tools when Leon did not
already have a tool of the correct size. They were covered in pitch
with channels cut to form small squares of pitch maybe 0.75-inch
on one side, separated by narrow channels.
The Test
By the time we were well into using the polishing pads, we could
now see a reflection off the surface of the glass. It was time to use
the Ronchi tester to determine the rough shape of the glass surface.
The goal in polishing the mirror was to get the surface as smooth as
possible and get the surface spherical. The polishing pads left the
surface with a roughness as well causing some zonal errors. These
needed to be removed before figuring could take place.
In the Ronchi tester, when the mirror was spherical, the lines
in the tester would appear as straight vertical lines. If the lines
converged in the center, the center was too high relative to the rest
of the mirror's surface. If the lines diverged, then the center was
too deep. After making the mirror spherical, figuring would parabolize
the shape and the resulting mirror would have lines that diverged to
some degree. First, though, we all had to get our mirrors spherical.
The Ronchi tester also showed the roughness of the mirror. On a
smooth spherical mirror the vertical lines of the Ronchi tester would
appear clear and sharp. The roughness would appear as a haziness at
the edge of the vertical lines.
After the mirror was spherical and as smooth as your patience
allowed came the figuring. This was done with star laps. The star
laps where the same pitch laps but had a four (or more) pointed star
cut in the pitch. The center of the star was the center of the pitch
lap. The full size lap was still used but a smaller star lap was
also used for finer work.
The Strokes
Leon had the class do two different strokes with the pitch laps.
The most common was to take the smaller lap and do an edge-to-edge
stroke, centering over the part of the mirror where the most work was
to be done. This center started at the center of the mirror and moved
outward. Since both the mirror and tool were rotated this made the
work uniform around the circumference of the mirror. The problems
with this is that the smaller tool could do too much if not monitored
frequently and could easily add roughness.
The other stoke Leon had the class use was the W-stroke. This
stroke moved the tool over most of surface in a W or M fashion. If
you got lazy, it could be called a Z-stoke. This used the full size
lap and worked quite a bit slower. The points of the stoke were at
the points you wanted to do the most work. If you wanted to work out
the center then the center of the tool was moved to the edge of the
mirror. If you wanted to work the ring midway from the center to the
edge, then the tool would only uncover that part of the mirror that
was outside the ring.
During the class, Leon would perform the Focault test at home
between sessions. This would allow the mirrors time to equalize with
the temperature of the testing environment.
The class lasted four months and several people finished their
mirrors before the class ended. Most finished theirs shortly after,
while a few are still working as you read this. By the end of May
1994, even the twenty-inch mirror was getting its final figuring (the
physical plant is huge). Case in point is the author, who has had
first light but still has not finished the mounts.
An Example
When I started in the mirror making class, I didn't really want to
make a large telescope and I already had an eight-inch instrument. So
I decided to make a five-inch one so I could have a telescope that was
really portable. Around this same time, an article appeared in SKY &
TELESCOPE magazine about a small solar telescope. This left me
undecided on which direction to go, but with the cheapness of the
five-inch mirror blanks, I decided to grind two mirrors.
I decided to grind one blank first and later, after completing the
first mirror, I would start the second. This would allow me to learn
from any mistakes I might make rather than duplicating them as I
progressed.
It took nearly one week to get started with the rough grinding.
First was pouring the dental plaster tool and letting it dry. The
tools was hard within a few minutes, but it took time for it to dry
completely. After it had dried, we had to epoxy ceramic "bathroom"
tiles on to the tool surface. These were allowed to dry pressed
against the mirror protected by wax paper. At the beginning of the
second week of class, the grit started flying.
On my first mirror, I planned on a f/5.5 which meant I had to
grind out 0.057-inch of glass from the center of my mirror. It may
not look like much, but it took me seven class sessions to get to
depth and start using the Ronchi tester. I also took home sore arms
and wrists during the first weeks of rough grinding.
Problems
It only took two more sessions of polishing to completely polish
the surface. The surface was really smooth. The trouble was I had a
zone on the surface that I could not seem to get rid of. I attempted
to polish it out but all attempts only pushed the zone closer or
further from the edge.
At this time, everyone else was testing their mirror, too. So the
testing cycle with the Ronchi grating was a few minutes of polishing
followed by tens of minutes waiting for the tester. At this time, the
last few sessions of class, I decided to start my second mirror. I
could work on mine with the few others who were still working at 80
grit, far away from those polishing and figuring. I reserved my
working on the first mirror to when I was over at Leon's.
After playing with the zone on the mirrors surface for over thirty
hours of work, I spent twelve hours at Leon's with his turntable and
finally removed the zone. From a nearly spherical mirror, it took less
than five hours of work. The resulting mirror was f/5.4 with a surface
wavefront error of 1/14-wave done in a total of 72 hours of work.
The Second Mirror
The second mirror was entirely different in both design and
implementation. It was supposed to be a five-inch f/8 solar
telescope. The reflecting surfaces would be uncoated. Making this
mirror had all sorts of surprises. First I used the f/5.4 tool from
my first mirror. This caused my second mirror to grind down to
0.057-inch when I really only wanted 0.039-inch. I had ground, in
two class sessions, a second f/5.4 mirror. I then had to continue
grinding another session to get back to 0.039-inch, adding glass to
the middle by actually removing it from the edge.
From beginning to end, my second mirror took just less than 25
hours of work. It is a five-inch f/7.75 with a surface wavefront
error of 1/54-wave. Leon's Focault tester is only good to 1/16-wave
in resolution, though.
Now I just have to build the physical plants for the telescopes.
I looked into a coelestat for the solar telescope so I can mount video
equipment on a unmoving telescope, but I decided on an English Yoke
instead.
Throughout the class Leon and Fannie remarked on how well the
class went. The only problems encountered by class members were minor
and easily fixed. No one had serious problems with their mirror
surface. My own problems were fairly minor and resulted in doing and
undoing work until I understood which direction I needed to take. The
class had one mirror break while being ground (a six-inch) and one
person - who did not use the epoxy - lost his tiles while grinding.
The polishing pads did introduce zonal problems on to a large
number of class member's mirrors. This did not happen in previous
classes that Leon has taught and he is not sure why it did occur.
The use of polishing pads will require more experimentation.
The Next Telescope
While waiting for parts and money for completing these two
telescopes, I am researching designs for my next telescope: A
ten-inch Gregorian convertible Newtonian. It even sounds impressive.
Related EJASA Articles -
"The CHARA Multi-Telescope Telescope", by Hal McAlister - August 1989
"Amateur Telescopes, Yesterday and Today", by Bill Bagnuolo -
September 1989
"A Living Legend: The Alvan Clark Refractor", by Alan Fleming -
May 1990
"A Comparison of Optical and Radio Astronomy", by David J. Babulski
- June 1990
"Low-Budget Astronomy", by Tony Murray - October 1990
"Aperture Arrogance", by Eric Greene - March 1991
"How to Make a High-Quality Fifty-Millimeter Finderscope", by Robert
Bunge - December 1991
"The Elusive Dot", by John Stauter - December 1991
"Telescopes: A Novice's Guide", by Steven M. Willows - March 1992
"Astronomical Optics: Exploring the Definitions", by Nils Turner -
May 1994
"1993 Arizona Messier Marathon", by A. J. Crayon - June 1994
"1994 Arizona Messier Marathon", by A. J. Crayon and Paul Dickson -
June 1994
About the Author -
Paul Dickson has been a member of the Saguaro Astronomy Club (SAC)
since 1988 and has been the Editor of SACNews for more than three years.
Paul is currently a student at Arizona State University. Paul has
contributed a number of articles from SAC to the EJASA. His network
address is p.dickson@asu.edu.
Paul is the author of the following EJASA articles:
"Grand Canyon Star Party" - May 1993
"181st American Astronomical Society (AAS) Meeting" (with Mike
Willmoth) - July 1993
"The Perseids from Arizona" - September 1993
"1994 Arizona Messier Marathon" (with A. J. Crayon et al) - June 1994
YOU CALL IT WHAT?
by M. Leon Knott
From the March, 1993 issue of the Saguaro Astronomy
Club's newsletter, SACNews, in Phoenix, Arizona
Well, here we are, class. Summer, with its hazy skies and too hot
temperatures has given way to blessed fall, with cooler temperatures
and incredible skies. Now is the time to take out those new
binoculars, telescope, star charts, or books you just could not
resist, as you begin mining the riches of the night time sky.
Right away, with the general cussedness and perverseness of life,
you face a seemingly impossible task. All those stars have such
unusual names and just how do you really pronounce something like
Betelgeuse and some others even worse? After all, one does not wish
to appear unknowing about such elementary things when in the company
of friends, spouses, students, ministers, and school teachers, right?
I recently experienced such a problem when visited by the late
well-known Walter Scott Houston, author of SKY & TELESCOPE magazine's
"Deep Sky Wonders" column for nearly 47 years. Sitting in our living
room, we were talking about galaxies, clusters, and nebulae when I
happened to mention the beautiful double star in Orion we know as
Rigel (rhymes with a well-known antacid). Mr. Houston looked at me
and said, "It's Rigel (rhymes with regal)." To which I replied,
"Rigel (rhymes with that well-known antacid)."
At that point the famous Walter Scott Houston glared at me and
said, "How many advanced degrees do you have?" When I answered that I
had one degree and that it did not amount to very much, he said "Well,
I have three degrees and two fellowships. It's Rigel (rhymes with
regal)."
Glancing up, I could see my wife Fannie and two daughters, Dottie
and Kana, smirking at me, and believe me I know how to pronounce
"smirking." Well, Mr. Houston has gone back home, and in the spirit
of modest correctness, I hereby affirm that the proper pronunciation
of Rigel is Rigel (rhymes with that well-known antacid).
So, in an attempt to share with you my grammatical, syntactical,
and pronounciational expertise, and in order to help you become better
acquainted with the names of several famous stars, I have drawn up the
following short list. If you learn to pronounce the names of these
stars properly, you can hold your head high in any crowd and put to
shame anyone who might presume to correct you, whether PhD, school
teacher, or even high school kid. If someone does try to push too
hard, just tell them you read it here and that ought to be good
enough to silence even the most adamant and obdurate.
Let us begin with the bright stars in Orion, since that brilliant
constellation commands the fast approaching winter skies. This starry
warrior has beacons marking out his shoulders, his belt, and of
course, his left foot (Rigel - you already know how to say that),
along with his right knee. The bright star that does signify Orion's
right knee is Saiph. You will be perfectly safe in pronouncing it
"safe" with just a tiny bit of emphasis right in the middle of the word;
you know, as if you suddenly realized that an insect had entered your
mouth and was conducting extensive and probing explorations in there.
Orion's right shoulder is Bellatrix, and you might say Bellatrix
is for kids. On the other hand, his left shoulder is Betelgeuse, and
I defy anyone to pronounce it "Beetle Juice" within my hearing. I
just simply will not stand for it. You had be much safer in pronouncing
it as if it were spelled "Bet Old Joy." Now, doesn't it feel really
good when you get it right?
The three stars making up Orion's belt are very famous and are
known as Mintaka, Alnitak, and Alnilam. I dare you to say all three
name, quickly as you can, three times in a row! These stars point to
the eastern direction and help us locate the brightest star in the
heavens. This star is seriously bright and is named Sirius. You might
even call it Seriously Sirius, if you know what I mean.
Letting the belt lead us in the opposite direction will point us
to the glaring red eye of Taurus (like the well-known automobile) the
Bull. This bright red star is named Aldebaran. Here, you might say
"The Bull attacks us....Al, Deb, and I run (Aldebaran) while Ann
tarries behind (Antares, the name of the Scorpion's heart, seen
during the summer. I threw it in for free)." Poor Ann.
Well, you have been marvelous students and this is enough for a
first session. Later we will cover such important names as Arcturus,
Zubeneshamali, Algenubi, Mirach, and perhaps, even Uranus. Being an
amateur is fun and informative. It can also give rise to some
justifiable pride and perhaps even some gentle snob appeal, especially
when we can pronounce all those tough words correctly, with confidence
and verve arising out of knowing we are right and all those other guys
are wrong.
Related EJASA Articles -
"Orion: Winter's Mighty Hunter", by Michael S. Wiggs - December 1989
"In Search of the Horsehead Nebula", by Eric Greene - April 1991
"Astronomy and the Family", by Larry Klaes - May 1991
"The Hyades: A Star Cluster Rich in Myth and Astronomy", by Ken
Poshedly and Don Barry - June 1992
"Celestial Favorites of Autumn", by Bruce Bowman - October 1993
About the Author -
M. Leon Knott is an amateur astronomer interested in observing and
telescope making. Recently from the U.S. East Coast, he is now living
in Mesa, Arizona. He has written for SKY & TELESCOPE, ASTRONOMY, THE
MOTHER EARTH NEWS MAGAZINE, and TELESCOPE MAKING. In addition he is
an Associate Editor of the new AMATEUR TELESCOPE MAKERS JOURNAL and
Newsletter Editor for the East Valley Astronomy Club (EVAC).
Mr. Knott is author of and discussed in the following EJASA articles:
"Cometary Conundrums" - June 1993
"Hunting for Comets: One Observer's Success Story", by Michael
Janes - March 1994
"1993 Arizona Messier Marathon", by A. J. Crayon - June 1994
"1994 Arizona Messier Marathon", by A. J. Crayon and Paul Dickson -
June 1994
"Mirror Making Class of 1993: A Review", by Paul Dickson (this issue)
UP ALL NIGHT: OBSERVING THE PERSEID METEOR SHOWER OF 1994
by Michael Hann
Courtesy of the Astronomy Club of Tulsa, Oklahoma newsletter
A good Perseid meteor shower was observed by three hardy Astronomy
Club of Tulsa members who maintained their watches from dusk to dawn
at the RMCC observatory at Mounds, Oklahoma (35 degrees 45 minutes
North Latitude, 96 degrees West Longitude) on August 11-12, 1994.
The sky was cloudless, though a thin haze reduced the limiting
magnitude to 5.5. A generous portion of bright meteors were seen
as the shower's peak approached, including one brilliant, bluish -7
magnitude Perseid which left a thirty-second train. A -5 magnitude
bluish Perseid appeared to be sparking as it traversed the sky, flared
at the end of its path, and then exploded. I observed a Zenithal
Hourly Rate (ZHR) of 98 during the interval of 3:30-4:30 a.m., the
peak of the shower as observed at Mounds (see the following comments
about preliminary reports from California).
Note that the ZHR is a rate corrected for limiting magnitude and
shower radiant angular altitude and is not the same as the total
number of meteors one observes in one hour. Twenty-six percent of the
Perseids I observed were accompanied by trains - persistent, glowing
trails.
The Perseids were supplemented by meteors from other radiants,
including Kappa Cygnids, Capricornids, and Pegasids. One "meteor"
slowly streaked across the sky for a full ten seconds, moving from the
southeast to northwest. I assume this to have been some artificial
space debris falling back into Earth's atmosphere.
The following histogram represents the number of Perseids I observed
in each of the hourly intervals. Data for meteors from other radiants
is not included. I did not observe in earnest until 11:30 p.m. (4:30
UT), as the shower was not very active earlier. Central Daylight Time
(CDT) is five hours behind Universal Time (UT), the reference time
used in all the following data.
Hour Interval
----------------
2:30 - 3:29 UT | 1
3:30 - 4:29 UT | 1
4:30 - 5:29 UT | 12345678901
5:30 - 6:29 UT | 1234567890123456
6:30 - 7:29 UT | 123456789012345678
7:30 - 8:29 UT | 1234567890123456789
8:30 - 9:29 UT | 1234567890123456789012345678901234567
9:30 - 10:29 UT | 12345678901234567890123456789012345
------------------------------------------>
Number of Meteors Observed
--------------------------
The ZHRs for each of the hourly intervals beginning with the
interval 4:30 - 5:29 UT are given next. I calculated the ZHRs
following the method presented by Neil Bone in his book METEORS.
ZHR = count*(1/sin(angular altitude))*(r^(6.5 - LM)) +- Error
Error = +-ZHR/SQRT(hourly count)
Where r is the population index factor. I calculated three sets
of ZHRs based on r = 2.2 (per the Royal Astronomical Society of Canada's
Observer's Handbook 1994), r = 2.35 (per Neil Bone), and r = 2.6 (per
the International Meteor Organization, IMO).
ZHRs
Hourly Interval r = 2.2 r = 2.35 r = 2.6
--------------- ------- -------- -------
4:30 - 5:29 UT 46 +- 14 49 +- 15 54 +- 17
5:30 - 6:29 UT 55 +- 14 59 +- 15 65 +- 17
6:30 - 7:29 UT 54 +- 13 58 +- 14 64 +- 15
7:30 - 8:29 UT 51 +- 12 54 +- 12 60 +- 13
8:30 - 9:29 UT 92 +- 15 98 +- 16 108 +- 18
9:30 - 10:29 UT 86 +- 15 92 +- 16 102 +- 18
These rates compare well with peak rates of other Perseid showers.
The following histogram represents the magnitude distribution
observed during the shower.
Magnitude Range
---------------
(+5.5) - (+4.6) mag | 1234
(+4.5) - (+3.6) mag | 123456789012345678901234
(+3.5) - (+2.6) mag | 123456789012345678901234567890123456
(+2.5) - (+1.6) mag | 1234567890123456789012345678
(+1.5) - (+0.6) mag | 123456789012345678901234
(+0.5) - (-0.4) mag | 1234567
(-0.5) - (-1.4) mag | 123456
(-1.5) - (-2.4) mag | 1234
(-2.5) - (-3.4) mag | 12
(-3.5) - (-4.4) mag | 1
(-4.5) - (-5.4) mag | 123
(-5.5) - (-6.4) mag |
(-6.5) - (-7.4) mag | 1
------------------------------------------->
Number of Meteors in Magnitude Range
------------------------------------
The average meteor brightness in each of the hourly intervals
beginning with the interval 4:30 - 5:29 UT are given next.
Hourly Interval
---------------
4:30 - 5:29 UT : 3.8 magnitude on average
5:30 - 6:29 UT : 3.1 magnitude on average
6:30 - 7:29 UT : 3.1 magnitude on average
7:30 - 8:29 UT : 1.9 magnitude on average
8:30 - 9:29 UT : 1.2 magnitude on average
9:30 - 10:29 UT : 1.3 magnitude on average
It is acknowledged that the Perseid shower now has two peaks: A
traditional peak and an earlier peak which is associated with a higher
portion of bright meteors as well as higher ZHRs. The peak I observed
was the new peak, as evidenced by the increased average brightness
during the peak hour interval.
Joe Dellinger, one of the hardy three who stayed up all night at
the observatory, and who has recently moved to Tulsa from Hawaii, sent
me E-Mail reporting that ZHRs reached a peak of 250 as observed at
Honey Lake, California, after dawn had broken in Mounds.
Related EJASA Articles -
"Astronomy and the Family", by Larry Klaes - May 1991
"Perseids 1993: Shower or Storm?", by Peter Brown - June 1993
"The Perseids from Arizona", by Paul Dickson - September 1993
"In Pursuit of Comet Swift-Tuttle", by Harry Taylor - September 1993
About the Author -
Michael Hann developed an interest in amateur astronomy as a child
growing up in rural Illinois. This interest lay dormant for a long
time until reawakened several years ago while laying in the autumn
leaves of his backyard, looking up at the sky with his two year-old
son. Michael is now a member of the Astronomy Club of Tulsa and
enjoys leading observation sessions for public groups at the club's
RMCC observatory - which houses a sixteen-inch Newtonian reflector
telescope - observing with his 10x70 binoculars, and watching meteor
showers.
Michael works as a software engineer. He intends to design and
construct a forward scatter radio meteor detection system during the
next year and welcomes any advice you might wish to give him on this
topic. Please send E-Mail to mikeh@ssd.fsi.com.
ANNOUNCING A NEW PUBLICATION: SETIQUEST MAGAZINE
by Carl Helmers
SETIQuest is a new quarterly print/electronic mail (E-mail)
periodical containing news, technical information, and tutorials
devoted to bioastronomy and its subset, SETI (Search for
Extraterrestrial Intelligence).
SETIQuest is published for professionals, serious amateur
astronomers, and individuals curious about this fascinating field of
observation. SETIQuest fills the need for a specialized astronomical
publication devoted exclusively to the on-going search for evidence
of life in the Universe. Such evidence could be intentional or
inadvertent signals of other civilizations. Such evidence could be
found in spectral signatures of biological activity on extrasolar
planets or in the interstellar medium.
SETIQuest is written and edited for the scientifically literate
individual taking part in the progress of our technological
civilization, with articles by amateur and professional scientists.
SETIQuest includes information about hands-on observational programs
that can be carried out by individuals and groups of amateur
astronomers at radio and optical wavelengths.
SETIQuest is filled with articles covering topics such as:
* Tutorials about bioastronomy and SETI
* Microwave or optical SETI as practiced by amateurs
* "Do-it-yourself" participation in bioastronomy and SETI activities
* Book reviews
* Regular commentary on issues relevant to SETI and bioastronomy:
SETI and the political milieu
Philosophical issues regarding the prospects of success and
failure in the search
SETI as a parable of science versus pseudo science
Publications Watch: Summaries of recent scientific/general
publications relevant to SETI
For your FREE issue of SETIQuest (Volume 1, Number 1), send us
your postal address by fax, E-mail, or conventional mail to:
SETIQuest Inquiries, Department EX
Helmers Publishing
174 Concord Street
Peterborough, NH 03458-0874
U.S.A.
Telephone: (603) 924-9631; FAX (603) 924-7408
Internet E-mail: SQINQNET@pixelacres.mv.com
Related EJASA Articles -
"Does Extraterrestrial Life Exist?", by Angie Feazel - November 1989
"Suggestions for an Intragalactic Information Exchange System",
by Lars W. Holm - November 1989
"Radio Astronomy: A Historical Perspective", by David J. Babulski -
February 1990
"Getting Started in Amateur Radio Astronomy", by Jeffrey M. Lichtman
- February 1990
"A Comparison of Optical and Radio Astronomy", by David J. Babulski
- June 1990
"The Search for Extraterrestrial Intelligence (SETI) in the Optical
Spectrum, Parts A-F", by Dr. Stuart A. Kingsley - January 1992
"History of the Ohio SETI Program", by Robert S. Dixon - June 1992
"New Ears on the Sky: The NASA SETI Microwave Observing Project",
by Bob Arnold, the ARC, and JPL SETI Project - July 1992
"First International Conference on Optical SETI", by Dr. Stuart A.
Kingsley - October 1992
"Conference Preview: The Search for Extraterrestrial Intelligence
(SETI) in the Optical Spectrum", by Dr. Stuart A. Kingsley - January 1993
"Detectability of Extraterrestrial Technological Activities",
Part 1, by Guillermo A. Lemarchand - December 1993
"Detectability of Extraterrestrial Technological Activities",
Part 2, by Guillermo A. Lemarchand - January 1994
About the Author -
Carl Helmers, President and Editorial Director, Helmers Publishing,
Inc.. Publishers of SENSORS, ID SYSTEMS, and SETIQuest magazines (what
else do you do after starting BYTE?).
INTERNET: carl@pixelacres.mv.com
SNAILMAIL: 174 Concord Street, Peterborough, NH 03458, U.S.A.
TELEPHONE: 603-924-9631; FAX: 603-924-7408
THE ELECTRONIC JOURNAL OF THE ASTRONOMICAL SOCIETY OF THE ATLANTIC
September 1994 - Vol. 6, No. 2
Copyright (c) 1994 - ASA
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