AstroNotes 1963 December Vol: 2 issue 10

EDITORIAL . Meteor Counts . Deep Sky . Galileo Among the Paperbacks . Papers for the 1964 General Assembly .

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AstroNotes

The Newsletter of the Ottawa Centre, RASC

Vol. 2  Issue 10    1 December, 1963

Editors: George Brunton 2565 Elmhurst   828-1473, Howard Harris  620 Keenan     728-6044

EDITORIAL

This issue of ASTRONOTES marks our first anniversary.

Since it was conceived as an in­formal vehicle of the Observers' Group for the exchange of information and advice on star-watch­ing, its circulation was restricted to that corps
of activists who turn up regularly at the meet­ings of the Observers' Group. After the first few months, however, popular demand forced us to increase our circulation to  include the whole membership of the Ottawa Centre of the R.A.S.C.

From this popularity we may perhaps draw the inference that the Ottawa Centre is full of would-be observers who, because they lack proper equipment, are too diffident to call themselves Observers. If there are indeed any such para­gons of modesty, we urge them to come out to our meetings and be filled---with advice on telescope making, with information about the Constella­tions, planets, deep sky objects and with coffee.

This may be an appropriate time to thank our small but faithful band of regular contributors. Over the course of the past year they have pro­duced a great deal of valuable and interesting material, and Astronotes could not have survived without them. These people have become so much the backbone of the magazine that we consider them as part of the staff. But we do need more contributors, and we know that there are a good many others in the Group who are capable of pro­ducing good articles. In particular, we urge the coordinators to report activities of the Observers' Group in their respective fields, or if there are no activities to report, to give us general information on their observing special­ities and news about upcoming sky events worth watching for.

MERRY CHRISTMAS TO ALL!


Meteor Counts

by Gord Grant

A method of collecting data on meteor rates during meteor showers is to take advantage of the reflection qualities of the ionized trail left by a meteor. The degree of  ionization will depend to some extent on the size of the meteor and the material in it. By selecting a distant trans­mitter on a frequency of 40 mcs or higher and located at a distance greater than the normal ground wave image, total counts and the duration of bursts of the reflected signal can be made using a simple antenna and a moderately sensitive receiver.

There are a number of suitable transmitters already operated for other purposes that can be used to this end. Exact frequency at the receiver end must be known, however, since there is normally no opportunity to ’tune-in’ the receiver signal. If more elaborate antenna systems are used, they may be directed to the general area of the sky where the greatest number of meteors will appear. These rates should be related to visual count rates where possible and to the time of day.

A piece of equipment that is commonly avail­able in the average home is your TV set. It is an adequately sensitive receiver of sufficient bandwidth so that tuning is no problem and antennas are available in a range of prices. The distant transmitter is also no problem in the myriad of TV stations in the large urban centres. It may be necessary to wait until the local transmitter signs off to have a quiet channel, and then to sit in front of the blank screen counting the bursts of picture from the distant station. Jack Horwood has used this method locally and obtained some interesting count rates.

An F-M receiver tuned to a distant station (300 to 1000 miles) can be used for the same purpose. These equipments are readily avail­able and provide an easy way to make a start in Radio Astronomy.


Deep Sky

by John Stairs

Seven galactic clusters of considerable
interest are:
Name                             Distance (L.Y.)               Age(years)
h and Chi Persei             7300                             I million
Pleiades (Taurus)            410                              50 ”
Praesepe (Cancer)          515                              500 "
Hyades (Taurus)             130                              1 billion
M67 (Cancer)                 2700                            10   "
NGC 188 (Cephus)         5000                            15   "

At present the two in Cancer are visible only after midnight but they will be up before 12 by mid-December.

A number of interesting articles have appeared on these clusters in recent years and readers are referred to:

Journal of the RASC 49, 13 (1955)
Sky and Telescope, Nov. 1962
Scientific American, Nov. 1962

It must be emphasized that the age and distance figures given are by no means final but they do represent the trend of thinking at this time.

Determination of age is done by plotting the HERTZSPRUNG-RUSSELL diagram of each cluster.
This diagram shows a measure of the absolute magnitude of the star against a measure of the star’s temperature and gives curves similar to those shown in Fig. 1. There is a main sequence of stars from upper left to lower right with curves breaking away from this at different points. Calculation shows that the breakaway point is related to the age of the cluster.
The double cluster in Perseus is made up of young giants, many of them 25,000 times brighter than the sun. By contrast, NGC 188 is a faint cluster 5 deg. from the pole, made up of stars of brightness similar to the sun and perhaps 15,000 times older than the double cluster. Some globular clusters are believed to be even older.

Pig. 2 shows how to locate NGC 188. The Sky and Telescope already mentioned (Nov. ’62) has a photograph of this cluster and its sur­rounding field and this has been found to be very useful when searching for this difficult object.

FIGURE 1 COLOUR INDEX - BLUE M INUS VISUAL MAGNITUDE
FIGURE 2 HANDLE OF LITTLE DIPPER


Galileo Among the Paperbacks

by Howard Harris

Anyone can build up a sizeable library quite
cheaply these days by using paperbacks. Two of
the best paperbacks I ’ve found on Galileo are
Discoveries and Opinions of Galileo, by Stillman
Drake (Anch or, $1 .4 5 ), and The Crime of Galileo,
by Giorgio de Santillana (Phoenix, about $2.00).
These two books complement each other nicely,
and anyone like myself who starts with a pretty
sketchy knowledge of Galileo’s life would we
well advised to read Stillman Drake’s book first.
This book contains translations of four of
Galileo’s most important works: The Starry (or
Sidereal) Messenger, Letters on Sunspots, Letter
to the Grand D uchess Christina, and The Assayer.
Mr. Drake supplies a clear interconnecting text
which explains the discoveries and controversies
which led up to each of these works; and the
translations themselves are a treat to read.
Aside from his merits as a scientist, Galileo
must be one of the greatest scientific pro­
pagandists who ever lived. The only one I can
think of to compare him with is Thomas Huxley,
who did for natural selection in the 19th cen­
tury what Galileo did for astronomy in the 17th.
Stillman Drake leaves off before the publi­
cation in 1632 of Galileo’s Dialogue on the Great
World Systems, the work that finally got Galileo
into deep trouble with the Church establishment.
This work, with the controversies and intrigues
that led up to it, and the consequences that
followed, is the subject of The Crime of Galileo,
The book is primarily about politics rather than
science. Its great merit is to show that the
Church is not a monolithic structure, however
much it may look like one from the outside.
Galileo’s chief enemies were the Peripatetic
scholars (the followers of Aristotle) and a few
obscure priests.

Right up to his condemnation
the great body of influential Jesuits and most
of the higher church officials were on his
side. But the Dialogue had offended Urban VIII, and the clamour raised by the scholars
and some of the priesthood gave Urban sufficient
justification to ask the Inquisition to proceed
against Galileo. However, even the backing of a
Church with absolute secular power did not make
the proceedings easy for the Inquisitors. It is
particularly instructive to see the desperate
shifts they were put to in order to give the trial
an appearance of legality.

Mr. de Santillana writes like a professor,
and sometimes like a professor determined to prove
that he is every bit as subtle as the most prac­
tised Renaissance casuist, but this tendency is
only an occasional annoyance in a book that makes
fine reading.


DON'T FORGET the meeting of the OBSERVERS' GROUP
on Saturday, December 7th at 8.00 p.m., usual place.


Papers for the 1964 General Assembly

The usual session for papers has been
scheduled for the General Assembly in Ottawa,
May 15-17, 1964. Members are urged to prepare
papers on such topics as historical astronomy,
observing equipment, results of observational
programmes, etc. An abstract of 200 words or
less should be sent not later than 15 March, 1964
to Dr. Ian Halliday at the Dominion Observatory.
The complete manuscript should also be forwarded
by 1 April, Authors should indicate the size of
any slides they intend to use or any special
facilities they may require for demonstrations.
If the author is unable to attend but wishes his
paper to be read for him this should also be
stated. Papers presented at the Assembly will
appear in complete or abstract form in the
RASC JOURNAL.