VALUABLE INFORMATION
=Photographing the Stars.=--There are some interesting things you can
do with an ordinary _camera_ in the way of photographing the stars.
A camera is made up of three principal parts, and these are (1) a
convex lens, which forms the image of the object to be photographed;
(2) a light-tight box, which keeps out all the light except that which
passes through the lens, and (3) a plate, or film holder, which holds
the sensitive plate, or film, in the camera and keeps it perfectly dark
until you are ready to have the image formed on it.
The instant the lens is allowed to form an image on the _sensitive
plate_, or _film_, we get out of the _optics_ of photography and into
the _chemistry_ of it.
The sensitive plate, or film, is coated with a thin layer of salts
of silver and bromide, heated with gelatine and a little water, and
when these substances are thoroughly mixed, an _emulsion_ results,
and this is spread on glass plates or on celluloid films. When the
plate is exposed, that is, when the image has been formed on it, it is
developed. The developing is done by placing the plate in a solution of
_pyrogallic acid_, or _hydroquinone_ and water.
The plate, or film, is now put in the _fixing bath_, which is simply a
solution of _hyposulphite of soda_ and water. This fixing bath prevents
any further action of the light on the plate, or film.
But the picture on the glass plate, or celluloid film, looks all same
like a Chinese chromo, for the light and dark parts are just the
reverse of that of the object which was photographed; in other words,
where the picture should be white, it is black, and where it should be
black, it is white, and this is the reason it is called a _negative_.
[Illustration: FIG. 180.--CAMERA POINTING TO NORTH STAR.]
To get a picture of the object, as it looks to the eye, a sheet of
paper, also coated with salts of silver, is laid flat on the negative
and held close to it in a _printing frame_ when it is exposed to the
light of the Sun.
When the paper is printed dark enough by the Sun, it is _toned_ to give
it a pleasing color and _fixed_ to make it last a long time, and when
washed and dried the image of the object, true to life, is there, a
wonderful record for all time, nearly.
This then, briefly, is how the Sun, or other source of light, makes
an image, how the image is fixed on a dry plate, or film, and how a
picture is printed from the negative, and having found out this much
let’s see how we can make it do a little star work for us.
There is not much we can do in the way of making pictures of the
things in the sky with a small camera, but the few things we can do
are mighty interesting, and show the stars in a way you can never see
them with the naked eye.
To make _star trails_ is one of these interesting things. First, set
your camera on a _tripod_, or other firm support, and focus it on a
tree or something as far off as you can see it in the daytime. Now, on
a dark night, when there is no Moon, set your camera so that the lens
is pointing directly at the North Star, as shown in Fig. 180. Set the
shutter of your camera for a _time exposure_ and open it.
[Illustration: FIG. 181. STAR TRAILS.]
You can go to bed now and let the stars work for you while you sleep,
that is if you can get up before daylight the next morning, but if you
cannot do this stay up as long as you can, three or four hours, anyway,
before you close the shutter.
Now, when you develop the plate, or film, and make a print from it
you will have a record of the apparent path of the stars, as shown in
Fig. 181, but which is, of course, due to the Earth turning round on
its axis. If you set your camera with the lens pointing toward the
ecliptic, that is, the path of the Sun, the star trails will be long,
straight lines, and this will make another interesting record.
By pointing your camera toward that part of the sky and during that
time of the year when there are showers of meteors, and opening the
shutter of your lens, you stand a chance, though it is not a very fat
one, of catching one of these wily shooting stars on your plate, and if
you do succeed--well, you will have a picture that is a curiosity.
You can photograph the Sun with an ordinary camera and make his disk
as large as you want to, but you will get nothing more on your plate
than a white spot. The Moon can likewise be photographed, but if you
focus it sharp on the plate it will not be much larger than a mere
point of light, and if you get a disk large enough to see there will
only be a small white spot on your finished print.
To make good photographs of the Sun, Moon and planets, a big telescope
driven by clockwork to offset the turning of the Earth is needed. Such
a telescope is called an _equatorial telescope_, and when it is set so
that an object in the sky is in the field of view, it will remain right
there as long as you want it, and when you make a photograph of the
object it will be as sharp and as clear as though both it and the Earth
were standing perfectly still.
If you think enough of the stars to try to photograph them with your
little camera, I should say there is a very good chance of your being
able to photograph them sometime through an equatorial telescope _for
all things come to the boy who wants them hard enough_.
=What the Stars Are Made of.=--To know what the stars are made of is to
know more about them than men knew of the Earth a few hundred years ago.
But just think of looking at a star like Aldebaran, which is so far
away that it takes 45 years for its light to reach the Earth--light
travels eleven million miles a minute--and then saying it is made
of iron, and mercury and hydrogen and sodium and half a dozen other
substances!
Now you ask, “How is it done?” And I’ll say with a _glass prism_, and
then we’ll have made a flying start. Now a glass prism is a three-sided
piece of glass--the ends don’t count--as shown in Fig. 144, and it is
just as wonderful in its way as a lens is wonderful in its way.
If you will hold a prism to your eye and look at the flame of a candle
through it, you will see the flame in all the brilliant colors of the
rainbow, and these bright colors form what is called a _spectrum_.
Now make another experiment; cover a window, on which the Sun shines,
with a sheet of cardboard, in the middle of which you have cut a
horizontal slit with a sharp knife, about 1 inch long and ¹/₂₅ inch
wide. Make the room perfectly dark except for the light which comes
in through the slit in the cardboard, and set a prism in front of the
slit, as shown in Fig. 145. The beam of sunlight which passes through
the prism will be split up, or _decomposed_, as it is called, into the
seven colors of the rainbow, but the colors will be much brighter.
If you will fix another sheet of white cardboard in a _vertical_
position so that the colors will shine on it in a band, the colors,
beginning with red at the bottom, next orange, then yellow, green,
blue, indigo and violet, will follow each other to the top bright and
beautiful. These rainbow colors, spread out in a band on the screen,
form what is called the _solar spectrum_, that is, the spectrum which
is produced by sunlight.
This beautifully colored spectrum is really made up of a great many
images of the slit in the cardboard, one for each wave-length of the
light. If the slit is made very narrow, the images of the slit will
not overlap much and you can tell whether any of the wave-lengths are
missing by looking for fine black lines crossing the spectrum. Such
dark lines are very important in finding out what the Sun and Stars are
made of.
[Illustration: FIG. 182.--BOY LOOKING THROUGH PRISM AT SLIT IN
CARDBOARD.]
All you have to do is to stand away from the slit five or six feet
and look at the beam of light through a prism just as you did at the
flame of the candle. This is the simplest form of a _spectroscope_,
that is an instrument for splitting up the light of any object which is
self-luminous, into a spectrum, as shown in Fig. 182.
When you look at the sunlight streaming in through the slit in the
cardboard you will see a number of dark lines crossing the colored
band. These dark lines are called _Fraunhofer’s lines_, because
Fraunhofer, who was a German telescope maker, was the first to show
how important they are. The chief dark lines of the Sun’s spectrum are
known by the letters of the alphabet, and, like the colored images of
the slit, they are always in the same place. They are shown in Fig. 183.
Having found out a little about the spectrum and how it is formed by
the Sun, let’s find out next how it tells us what the Sun and the stars
are made of.
[Illustration: FIG. 183.--FRAUNHOFER’S LINES.]
Now, in the Sun’s spectrum there are a pair of lines close together and
near the middle which are called the D lines--see Fig. 183--and when a
beam of sunlight is split up by a spectroscope, or rather by the prism
of a spectroscope, these D lines always appear in the yellow part of
the spectrum.
There was a time, and not so very long ago, when no one had the
faintest idea why the Sun’s light did not contain these two
wave-lengths, when the spectrum from a candle flame was a continuous
band of light without dark lines. Then two experimenters, Kirchhoff
and Bunsen, found that various substances when converted into luminous
gases in a hot flame always produced spectra which consisted only
of certain _bright lines_. Thus it was found that sodium gas gives
two bright lines in the exact positions of the D lines of the Sun’s
spectrum. This made it look as if the Sun contained no sodium. But
the experimenters did something else: they placed a very brilliant
light back of the sodium gas and on looking through their spectroscope
they saw a continuous spectrum with black D lines. This meant that
the sodium gas had absorbed from the light passing through it the
wave-lengths which it had given out when shining by itself. We now
know that the Sun is surrounded by a layer of gases which is somewhat
cooler than the interior of the Sun and that each substance in this
“reversing layer,” as it is called, takes out some of the light which
is characteristic of it and thus produces the Fraunhofer lines.
In the same way iron and other metals and sodium and other substances
which are heated until they become gases, and hydrogen and other gases
which are aflame, produce spectra consisting of certain bright lines,
and as the light from the Sun also produces black lines in the same
identical places, it is known that the Sun contains these different
substances which are heated up in it to a white heat.
[Illustration: FIG. 184.--THE SPECTROSCOPE.]
It’s the same thing with the stars. It makes no difference if the light
is made by burning some substance a few inches away from the slit of
the spectroscope, or whether it has traveled 90 millions of miles from
the Sun--which takes about 8½ minutes, or 45 years for the light to
reach it from Aldebaran, it always acts exactly in the same way; and so
we know a good deal about the stuff the stars are made of.
Let’s see now, how a real spectroscope is made, for it isn’t always
convenient to have a pitch dark room, nor is it a very exact way to
hold the prism to your eye when examining the light of burning sodium,
or hydrogen gas, or other substances.
The spectroscope is an instrument made so that the light of a
substance burned at one end will pass through a prism and will form a
spectrum on the retina of the eye at the other end. It is usually made
up of two tubes mounted on a stand at an angle with the prism between
them, as shown in Fig. 184.
In the end of the first tube, which is called a _collimator_, a very
narrow slit is cut, and it is at this end that the substance is placed
which is to be burned and whose light is to be split up and examined.
A convex lens is fitted in the other end of the collimator, or first
tube, so that the light after passing through the slit will then
pass in a beam through the prism. The other tube--the one you look
through--is called a _telescope_ and in this one is fitted a convex
object glass and an eyepiece which magnifies the spectrum made by the
prism.
When a camera is used to photograph the spectrum the eyepiece is taken
out of the tube of the spectroscope and a little camera is put in its
place. In this way the camera and the spectroscope are combined and
this helps chemists to compare the _spectra_ of different burning
substances far better than they could do with the naked eye alone.
To photograph the spectrum of the Sun the eyepiece of the big telescope
is taken out and the end of the tube of the spectroscope with the slit
in it is fitted in its place. In making a photograph of the spectrum of
a star the slit is not needed, for the light of the star itself is but
a mere point.
In photographing the spectrum of the Sun and stars three wonderful
instruments are combined, namely, the _telescope_, the _spectroscope_
and the _camera_; perhaps I should have said four wonderful
instruments, for without the _brain_ of a genius using them the Sun and
stars never would have given up their secrets.
APPENDICES
APPENDIX A
According to the official _Handbook of the Boy Scouts_, if you are a
Scout and want to win a merit badge for starcraft, you must
(1) _Have a general knowledge of the nature of the
stars and planets._
(a) By the nature of the stars and planets is meant
their colors and what they are made of. Their
sizes and their distances from the Earth in a
general way may also be included.
(b) It is easy to tell the color of both the stars
and the planets by looking at them, or by looking
them up in the foregoing chapters.
(c) The spectroscope shows that the stars are made
of metals and gases and other substances which
we have on Earth. The planets are probably
made of the same kinds of metals, gases and
substances as those which form the Earth, but
there is no way of proving this, for the planets
shine by reflected light, and in this case the
spectroscope is of little use.
(d) The stars are known to be suns as large or larger
than our Sun; while the planets are about as
large as our Earth--some smaller and some larger.
(e) All of the planets are within 2,800 millions
of miles of the Earth, while the nearest star,
except our Sun, is 25 trillions of miles from the
Earth, or 8,000 times as far away.
(2) _Have a general knowledge of the movements of the
stars and planets._
(a) While all the stars revolve in orbits and are
moving through space at high speed, they are so
far away from us that they seem to be fixed and
for all practical purposes they may be considered
to be fixed in their positions.
(b) All the planets turn on their own axes and travel
in orbits round the Sun.
(3) _Point out and name 12 principal
constellations._
(a) Twelve easy constellations are: (1) The Big
Dipper; (2) The Little Dipper; (3) Cassiopeia;
(4) Pegasus; (5) Orion; (6) Auriga and (7)
Taurus, all of which are shown in Chapters I
and II; (8) Gemini; (9) Leo; (10) Virgo; (11)
The Scorpion, and (12) Sagittarius, which are
constellations of the zodiac, and are shown in
Chapter XI.
(4) _Find the_ =North= _by means of other
stars than the Pole Star_ (_which is the North
Star_) _in case that star is obscured by
clouds._
(a) This can be done by finding the constellation of
Cassiopeia, see Chapter I; and also by Pegasus;
Auriga and Orion, as explained in Chapter II.
(5) _Have a general knowledge of the positions and
movements of the Earth, Sun, Moon, and the Planets;
and of tides, eclipses, meteors and comets._
(a) By reading the chapters on the Sun, Planets,
Earth and Moon and
(b) Other things in the sky carefully, you will be
able to pass the requirements named in No. 5.
(6) _Plot on at least two nights per month for six
months the positions of all naked eye planets
visible between sundown and one hour thereafter.
The plot of each planet shall contain at least
three fixed stars with their names or designations;
colors of planets and stars are to be recorded as
observed._
(a) How to plot the position of a planet is fully
explained in the chapter on Planets, but you
should also read the one on The Stars of the
Zodiac, and have a good star map (App. O).
APPENDIX B.
=Figures.=--When explaining the positions and forms of things, it is
often necessary to use certain terms and figures, that is to say, lines
which are either real or imaginary, but which can be drawn on paper.
See Fig. 185.
(1) A _straight line_ is, of course, a line which runs uniformly in the
same direction, and which is regular and without curves. A straight
line is the shortest distance between two points. (2) When we say that
lines are _parallel_, we mean that they lie so that every part of each
is equally spaced from the other. (3) A line is _horizontal_ when it
is parallel with the level surface of the Earth under it. (4) A line
is _perpendicular_ to the surface of the Earth when it is _plumb_,
that is, in a line with the center of the Earth. (5) A _vertical line_
generally means a plumb line. (6) A _right angle_ is formed when a
vertical, or a perpendicular, line meets a horizontal line. (7) A
_circle_ is a curved line, all points of which are equally distant from
its center. _Circular_ means round like a circle. (8) By _diameter_
is meant a straight line drawn from one side, or half of a circle, to
the opposite side through its center. (9) The _radius_ of a circle is
a straight line drawn from the center of a circle, or a ball, to its
circumference. (10) A _ring_ is a disk or object having a circular hole
cut in its center. (11) An _arc of a circle_ is a part of a circle.
(12) A _quarter circle_ is, of course, the one-fourth part of a circle.
(13) A _tangent_ is a line which touches a curve but does not cut it.
(14) An _ellipse_ is an oval figure, drawn on a plane surface. (15) The
_equator_ is a circle which divides the Earth or other ball into equal
parts, and is 90 degrees from the north and south poles. (16) The
_ecliptic_ is a circle round the Sky in whose plane lies the orbit of
the Earth.
[Illustration: FIG. 185.--GEOMETRICAL FIGURES.]
APPENDIX C
THE GREEK ALPHABET
Many of the brighter stars have names, as Aldebaran, Capella, Sirius,
etc., but astronomers now indicate the stars of a constellation by
the letters of the Greek alphabet. The usual method is to call the
brightest star of a constellation α, that is, Alpha, the next brightest
β which is Beta, and so on, but sometimes the stars are lettered in
order of position in the sky.
The following is the Greek alphabet:
α Alpha ν Nu
β Beta ξ Xi (Zi)
γ Gamma ο Omicron
δ Delta π Pi
ε Epsilon ρ Rho
ζ Zeta σ Sigma
η Eta τ Tau
θ Theta υ Upsilon
ι Iota φ Phi
κ Kappa χ Chi
λ Lambda ψ Psi
μ Mu ω Omega
APPENDIX D
STAR TESTS FOR EYESIGHT
There are a number of stars which are considered to be good tests for
the seeing power of the eyes. The faint stars of the Pleiades are a
fine test of this kind; but usually these tests are double stars and
while one will be bright and easily seen its companion will be very
faint. The test is to see the faint one, and if you can see it you may
consider you have very good eyesight.
Eyesight tests are given on the following pages:
Page
11--Mizar and Alcor
34--Spots on the Sun
94--Grimaldi on the Moon
119--Nebula in Orion
150--Epsilon in Lyra
150--Pleiades
182--Alpha and Beta in Capricornus
APPENDIX E
MAGNITUDES OF STARS
There are not nearly as many stars in the sky as you might at first
suppose. The stars are divided into magnitudes, that is, according
to their brightness. Stars of the first magnitude are the brightest
stars; stars of the second magnitude are second brightest, and so on.
The total number of stars which can be seen with the naked eye on any
one night in the United States is probably not more than 3,000. The
following table gives the number of stars of the different magnitudes
up to and including the sixth:
Magnitudes Number of Stars
1st 20
2nd about 65
3rd about 200
4th about 500
5th about 1,400
6th about 5,000
APPENDIX F
FIRST MAGNITUDE STARS
The brightness of a star is known by its magnitude. A star of the first
magnitude is one of the 20 brightest stars, and is 2½ times as bright
as a star of the second magnitude; a star of the second magnitude is
2½ times as bright as a star of the third magnitude; and so on. A star
of the sixth magnitude can just be seen with the naked eye on a clear
night when there is no Moon.
Fifteen of the twenty first magnitude stars can be seen in our
latitude, and these are:
& OF
& OF STAR CONSTELLATION
1. Sirius, the Dog Star, in Canis Major
2. Capella “ Auriga
3. Arcturus “ Bootes
4. Vega “ Lyra
5. Rigel (β) “ Orion
6. Procyon “ Canis Minor
7. Betelgeux (α) “ Orion
8. Altair “ Aquila
9. Aldebaran “ Taurus
10. Spica “ Virgo
11. Antares “ Scorpius
12. Pollux “ Gemini
13. Regulus “ Leo
14. Deneb “ Cygnus
15. Fomalhaut “ Piscis Australis
APPENDIX G
CONSTELLATIONS HAVING FIRST MAGNITUDE STARS
The following important constellations are not described in the
foregoing chapters of this book. They can be found, though, without
trouble, since a star of the first magnitude is located in each.
_Canis Major, the Big Dog_, is a winter constellation, and can be
seen on your meridian at 9 o’clock P. M. in February. Look for it in
the southern sky and you will quickly find it because of the dazzling
brightness of _Sirius_, the Dog Star.
_Bootes_ (pronounced Bo-ō´-tes), the Bear Leader, is a summer
constellation, and can be seen on the meridian at 9 o’clock P. M. in
June. It is to the north of the ecliptic, or path of the Sun. It lies
between a crown of stars and Virgo. You can’t miss it, for midway is
_Arcturus_, a red star of the first magnitude.
_Lyra, the Lyre._--Is a summer constellation, and can be seen on the
meridian at 9 o’clock P. M. in August. Look for it almost overhead, and
you can’t mistake it, for three bright stars, of which _Vega_ is one,
form a triangle.
_Canis Minor._--The Little Dog: is a spring constellation, and can be
seen on the meridian at 9 o’clock P. M. in March. It lies to the south
of the constellation of Gemini, the Twins, and Cancer, the Crab. In it
you will see _Procyon_, the Little Dog Star.
_Aquila, the Eagle._--Is a summer constellation, and can be seen on the
meridian in August. Look for it south of Lyra, and far to the west of
Pegasus. The star that put Aquila on the map is _Altair_.
_Cygnus, the Swan._--Is also a summer constellation, and can be seen
on your meridian at 9 o’clock P. M. in September. You will find it
north of Pegasus and east of Lyra, and in it you will see the _Northern
Cross_ clearly traced out with seven stars, the brightest one being
_Deneb_, a first magnitude star.
Piscis Australis, the Southern Fish, is an inconspicuous constellation
far south of the Equator. Fomalhaut, its brightest star comes only 20
degrees above our horizon and must be looked for when it is near the
meridian--about 9 o’clock P. M. in October.
APPENDIX H
COLORED STARS
You can easily notice that the stars differ in color. The following
list gives the colors of a few of the brighter stars:
WHITE STARS: Sirius, Regulus, Vega.
BLUE STARS: Rigel and Spica.
RED STARS: Aldebaran, Antares, and Betelgeux.
GREEN STARS: B Librae.
YELLOW STARS: The Sun, Arcturus, and Capella.
APPENDIX I
DOUBLE STARS
When two stars are very close together they form what is called a
_double star_, but double stars of which the two components are really
near together in space and revolve around each other usually cannot
be resolved, that is separated, into two stars without the aid of a
telescope.
The North Star; Rigel, Castor; Procyon and Sirius, are all famous
double stars.
APPENDIX J
VARIABLE STARS
A variable star is one whose brightness changes from time to time.
A great many variable stars are known, but very few of them can be
seen with the naked eye. There are different reasons given for a star
varying in brightness. Our Sun is a variable star, and we are told that
this is due to his spots. Another type of variation is perhaps produced
by pulsations--the star periodically expanding and contracting. Again a
double star formed of two bright stars which revolve round each other,
as many double stars do, may eclipse one another, and this would cause
a change in brightness. Here, then, are three good reasons for a star
being variable.
The following are a few of the _variables_ which can be seen with the
naked eye:
_Betelgeux_, in Orion.
_Alpha Cassiopeia_, that is, the brightest star in Cassiopeia.
_Beta Lyra_, that is, the second brightest star in Lyra, and
_Beta Pegasus_, that is, the second brightest star in Pegasus.
_Mira_, in Cetus.
_Algol_, in Perseus.
APPENDIX K
INVISIBLE OR DARK STARS
Stars are born, live and die, just like human beings. All the stars,
including the Sun, are either in the process of making, are at their
brightest brilliancy, are dying out, or are cold and dead or have not
yet become bright.
Procyon and Sirius is each attended by a comparatively dark companion.
Procyon and Sirius both move slowly back and forth a short distance in
the sky and this motion was attributed to the pull of satellites long
before these bodies were discovered with the telescope.
APPENDIX L
THE EQUATION OF TIME
TABLE OF THE EQUATION OF TIME
--------+---------+---------+---------+---------+---------+--------
Day of | January |February | March | April | May | June
Month | | | | | |
--------+---------+---------+---------+---------+---------+--------
|_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_
1 |S 3 31 |S 13 44 |S 12 37 |S 4 6 |F 2 56 |F 2 30
6 |S 5 49 |S 14 15 |S 11 33 |S 2 37 |F 3 27 |F 1 41
11 |S 7 59 |S 14 27 |S 10 19 |S 1 14 |F 3 45 |F 0 44
16 |S 9 49 |S 14 19 |S 8 57 |F 0 4 |F 3 48 |S 0 18
21 |S 11 24 |S 13 52 |S 7 28 |F 1 12 |F 3 38 |S 1 23
26 |S 12 39 |S 13 10 |S 5 56 |F 2 10 |F 3 15 |S 2 27
31 |S 13 35 |S 12 13 |S 4 24 |F 2 56 |F 2 39 |S 3 38
--------+---------+---------+---------+---------+---------+--------
--------+---------+---------+---------+---------+---------+---------
Day of | July | August |September| October |November |December
Month | | | | | |
--------+---------+---------+---------+---------+---------+---------
|_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_ |_m_ _s_
1 |S 3 28 |S 6 10 |S 0 6 |F 10 8 |F 16 18 |F 11 3
6 |S 4 24 |S 5 46 |F 1 31 |F 11 41 |F 16 17 |F 9 3
11 |S 5 11 |S 5 8 |F 3 13 |F 13 4 |F 15 56 |F 6 51
16 |S 5 46 |S 4 15 |F 4 58 |F 14 16 |F 15 13 |F 4 30
21 |S 6 9 |S 3 9 |F 6 45 |F 15 13 |F 14 10 |F 2 2
26 |S 6 11 |S 1 51 |F 8 29 |F 15 54 |F 12 45 |S 0 28
31 |S 6 12 |S 0 24 |F 10 8 |F 16 16 |F 11 3 |S 2 55
--------+---------+---------+---------+---------+---------+---------
As we have seen in Chapter X every day of the year is exactly 24 hours
long by our clock time. The time by the Sun is usually either ahead or
behind local clock time. The difference between clock time and Sun time
is called the _equation of time_, and a table to show how many minutes
and seconds the Sun is fast or slow, according to clock time, is given
above, taken from “The New Astronomy,” by Professor Todd, who has
kindly permitted me to use it here. In the table =S= means that the Sun
is slow, that is, that the Sun does not cross the meridian until after
the clock shows noon, and =F= means that the Sun is fast, that is, that
the Sun has crossed the meridian before the clock shows noon. =m= means
minutes, and =s= means seconds above the figures.
The table gives the average values of the equation of time, which may
differ by a few seconds from the values for any particular year.
APPENDIX M
THE KULLMER STAR FINDER
The star finder shown in the picture was invented by Dr. C. J.
Kullmer, of Syracuse, N. Y., and has been highly praised by many great
astronomers.
[Illustration: FIG. 186.—KULLMER STAR FINDER.]
You should own one if possible, for you do not need to know anything
about the stars to operate it. It is mounted on the principle of a big
telescope, but it is a naked eye instrument, an arrow taking the place
of the telescope.
The finder is placed on a table, or other level surface, with the
dial facing north. Then the pointer and dial are set for the day
and hour when you want to find the position in the sky of a certain
constellation. The indicator is turned to the name of the constellation
on the dial, and this also tells the direction to set the arrow.
This is all there is to it and the arrow points right at the group of
stars you want, whether they are above the horizon or not.
The finder can be used for many purposes, and it is a wonderful aid in
making out in the sky the path of the stars, Sun, Moon and planets,
and when they rise and set. In fact, it is a complete observatory on a
small scale. Its cost is only $5.00.
APPENDIX N
THE ELLIS SEASONAL TWILIGHT CHART
A useful chart, designed by Miss E. Rebecca Ellis, of Wellesley
College, Wellesley, Mass. It makes clear the changes in the lengths of
the day, the phenomena of the seasons, etc. Its price is $1.00.
APPENDIX O
THE CAMP FIRE SKY MAP
This map, prepared by Prof. R. S. Dugan of Princeton University, shows
the constellations as far south as the Southern Cross and is adjustable
for the time of night, date, and for the latitude. Full instructions
are given for its use. It is used in many schools and colleges. It is
sold by the Camp Fire Stores Co., price 19 cents.
DEFINITIONS OF SOME WORDS AND TERMS USED IN THIS BOOK
=Action.= The way in which a thing works.
=Affect.= To act upon; to change; to be moved or
influenced by.
=Almanac.= A pamphlet or book containing tables
showing the days of the year; also the time the Sun
and Moon rise and set; the conjunctions, eclipses
and other information concerning the things in the
sky. The word almanac is supposed to be derived
from the Arabic article _al_ and the verb
_manac_, which means to count.
=Angular measurements.= See Appendix B.
=Aphelion.= The point where a planet or a comet is
farthest away from the sun.
=Apparent.= To seem real. The daily motion of the
Sun round the Earth is only apparent, for we know it
is the Earth which turns round on its axis instead.
=Arc.= See Appendix B.
=Arc of circle.= See Appendix B.
=Aspect.= (1) Any curious appearance of an object,
especially if the object changes in appearance.
(2)The figure formed by a planet with the stars of
the constellation which it is in.
=Astrologer.= One who forecasts the life of a
person on the supposition that the stars control it.
=Astronomer.= One who is skilled in seeing the
stars and who knows them.
=Atom.= A very small particle of matter. See
Molecule; Matter.
=Attract.= To pull toward. The attraction of
the Sun and the Earth for each other is due to
gravitation.
=Attraction.= A force which pulls one body to
another.
=Attraction of Gravitation.= A force which pulls
all bodies to each other.
=Auditory nerve.= A nerve that carries the
impressions of sound which reach the ear to the
brain.
=Aurora borealis.= The Northern Lights. A glowing
light effect which takes place in the Arctic Circle.
It can often be seen from our Northern States and
sometimes from the Southern States. The same kind of
lights appear in the Antarctic Circle. These Southern
Lights are called Aurora Australis.
=Axes.= Plural of axis.
=Axis.= An imaginary line on which a body turns.
=Axis of rotation.= An imaginary line round which
anything turns or spins.
=Axle.= A wood or metal rod on which one or more
wheels turn, or it may turn with the wheel or wheels.
=Badge of merit.= A badge awarded by the
organization of Boy Scouts to members who can show a
certain amount of skill in doing certain things. See
Appendix A.
=Band.= (1) A flat strip of any material, or (2)
such a strip whose ends are joined together.
=Beam.= Rays of light which are parallel. See Ray.
=Bearing.= (1) A piece of metal, or a bit of agate
or other jewel, on which a pivot, spindle or shaft
turns. (2) A direction as found by the Sun or stars,
or by the compass, sextant or other means.
=Body.= Any separate and distinct amount of matter
when held together. The Sun and Moon are heavenly
bodies.
=Degree.= (1) The 360th part of a circle. (2)
Indicated by this sign °.
=Device.= (1) An apparatus or instrument or any
part thereof. Any arrangement for producing a
given result.
=Diagram.= A sort of shorthand picture of an
apparatus or part of an apparatus. It is used
to show in the simplest and clearest manner the
construction of an apparatus.
=Diameter.= See Appendix B.
=Direct line.= A straight line.
=Disk.= (1) A circular plane or flat surface.
Since the Sun, Moon and planets seem to be flat
their surfaces are called disks. (2) Flat and
circular like a coin.
=Dog days.= So called from the fact that Sirius,
the Dog Star, rises at the same time as the Sun.
=Ecliptic.= See Appendix B.
=Elastic.= (1) A body that will stretch and return
to its original size. (2) A thin piece of rubber.
=Ellipse.= See Appendix B.
=Equator.= See Appendix B.
=Equatorial.= Having to do with or affected by the
equator.
=Equatorial telescope.= A telescope so mounted
that its principal axis is parallel with the axis
of the earth and moved by clockwork so that it will
follow a star.
=Evening Star.= A planet which can be seen in the
west just after the sun sets.
=Fixed.= (1) Fastened securely. (2) The stars are
called fixed because they never seem to change their
positions.
=Forecast.= A prediction of some future event.
A forecast may be founded on fancy or on fact. A
horoscope of a person is a forecast based on the
fancy of an astrologer. A weather forecast is
founded on the action of a barometer, and even then
the forecast is uncertain enough. Forecasts of the
time of eclipses, the return of comets and the like
are founded on cold scientific facts and hence come
true at exactly the calculated time.
=Frequency.= How often an event occurs.
=Gas.= That form of matter which is like air.
Some gases remain in the gaseous state at ordinary
temperatures. Gases have a tendency to expand
without limit. See Vapor.
=Generate.= To produce. To set up; as a battery
generates a current; the Sun generates power.
=Gravitation.= The force which attracts all bodies
near the Earth to it and all bodies to each other.
=Heavens.= The sky. The space as far as the eye
can see about the Earth. The space in which the
stars and their planetary systems move.
=Horizontal.= See Fig. 185.
=Horoscope.= A forecast of the future of a person
made by an astrologer who pretends to read the future
from the aspect or position of the planets and stars.
=Hyperbola.= See Fig. 129.
=Hypothesis.= See Idea.
=Idea.= A notion of a plan or scheme which may be
more or less vague. =Supposition.= A clearer
conception of a plan or scheme which is based on
such facts as may be thought of. =Hypothesis.=
A plan or scheme assumed to be true and carefully
reasoned out from all the facts obtainable.
=Theory.= A plan or scheme which has been
proved true by experiment, examination or comparison.
=Illusion.= An image which deceives the eye. The
other senses can also be deceived by illusions.
=Impact.= Coming together of two objects.
=Impress.= To form on, or to affect, as light
waves impress a dry plate.
=Indicate.= To show. To point out.
=Indicator.= That which points out or shows
something.
=Limb.= The edge of the Sun, Moon or Planets.
=Lore.= Learning on any subject.
=Lunar.= Of, or having to do with the Moon.
=Magnetic lines of force.= The direction of the
force of magnetism acting in and around a magnet.
=Magnetic storm.= The Earth is a great magnet and
sometimes when sun spots of unusual size or numbers
appear, the magnetic lines of force of the Earth are
violently affected. This is called a magnetic storm.
=Mass.= (1) Amount of matter. (2) A lot of
molecules or particles of matter brought and held
together.
=Matter.= The substance of which a thing is
formed. A molecule of matter is made up of atoms,
and a mass is a lot of molecules held together by
some attractive force.
=Mercury.= (1) The name of the planet nearest the
Sun. (2) A silver white liquid metal.
=Molecule.= The smallest part of matter that can
exist separately without the substance it forms
being destroyed.
=Morning Star.= A planet which can be seen in the
east just before the Sun rises.
=Morse code.= A telegraph code of dots and dashes
invented by Samuel F. B. Morse. The Morse Code is
used for telegraph and heliograph signaling.
=Motion.= Anything that changes position. There
are two kinds of motion (a) simple motion and
(b) compound motion. _Simple motion_ can be
either _translated_ or _rotary_, while
_compound motion_ is both _translated_
and _rotary_, so that while a body is being
translated, or moved through space, it is also
rotating on its axis. The Sun and planets, then,
have compound motions.
=Nature.= Everything contained in space that has
not been shaped by human hands.
=Nautical almanac.= The American Nautical
Almanac is a book of the stars published by the
Bureau of Navigation of the United States. It is
published three years in advance and is sold by the
Superintendent of Documents, Washington, D. C., at
30 cents per copy. This is designed chiefly for
the use of navigators of ships. It gives the exact
positions of the Sun, Moon and planets and much
other astronomical information. It is based upon
the calculations made by the United States Naval
Observatory; these are printed in the Nautical
Almanac, and on this all other almanacs are based.
=Northern lights.= See Aurora Borealis.
=Obscured.= Hidden from sight.
=Official Handbook of the Boy Scouts.= A book
published by the organization of Boy Scouts and
which contains the rules and regulations of that
organization and the requirements they must meet in
order to win merit badges.
=Offset.= To equal; to balance.
=Opposition.= See Appendix.
=Optic Nerve.= The nerve that carries the
impression of light received by the eye to the brain.
=Orbit.= The path followed by a body. Atoms have
orbits as well as the stars. The paths followed by
planets and comets round the Sun.
=Parabola.= See Fig. 129.
=Parallel.= See Appendix B.
=Particle.= A bit of matter. A particle may be a
bit of matter which can be seen or it may mean an
amount so small that it cannot be seen.
=Pencil.= A group of rays from the same source of
light. See Beam. See Ray.
=Pendulum.= A body suspended from a fixed point
and free to swing.
=Perihelion.= The point where a planet or a comet
is nearest the Sun. As the orbit of a planet is an
ellipse and the Sun is in one of the foci—that is
near one end—a planet comes nearest to the Sun when
at this end of the ellipse; and when the planet is
at the other end of its orbit, it is farthest away.
See Aphelion.
=Period.= A certain interval of time which is
marked by a repeated occurrence. The period of the
Earth round its axis is about 24 hours. Its period
around the Sun is 365¼ days.
=Periodic.= Recurring regularly; as a periodic
comet.
=Perpendicular.= See Appendix B.
=Phase.= One of the peculiar aspects of a heavenly
body; as the phases of the Moon, or the phases of Venus.
=Pivot.= A pin, spindle or shaft on which a wheel,
lever or device rotates or is rotated.
=Plane.= A level surface, as a table top.
=Point.= A sharp end. A starting place.
=Pores.= Minute spaces which separate the
molecules of a substance.
=Position.= The place of a thing when compared to
the places of other things.
=Precede.= To go ahead of. That which is before.
=Precession.= The act of going ahead or preceding.
When a revolving body such as a spinning top or
the Earth is acted upon by forces which tend to
change the direction of its axis. This change in
the direction of its axis is called _precessional
motion_. The pole of the equator of the Earth
makes a complete turn round the pole of the ecliptic
in a little over 25,000 years and this change in the
direction of the axis of the Earth causes the points
of the _equinox_, that is the places where the
_ecliptic_ and the _equator_ cross each
other to move slowly from west to east and this is
termed the precession of the equinoxes.
=Prediction.= To foretell; to forecast.
Predictions may be based on fancy or founded on fact.
=Principal.= The chief one; the most important.
=Principle.= The cause of a result. That on which
a thing is based.
=Process.= (1) The way of working. (2) The course
of procedure.
=Produce.= In astronomy the word _produce_
means the lengthening of a line. It is a
mathematical term.
=Protractor.= See Fig. 98.
=Quarter circle.= See Appendix B.
=Ray.= (1) A single line of light or heat. (2) The
path of light and heat.
=Relative position.= The position of a thing when
compared with the position of something else. See
Position.
=Revolution.= The turning of a thing completely
round on its axis.
=Revolve.= (1) To turn completely round a circle.
(2) To turn on an axis, as a top, or the Earth.
=Rigid.= Firm, that which cannot be easily moved
out of its place.
=Ring.= See Appendix B.
=Rise.= To come into sight above the horizon, as
the Moon rises.
=Rotate.= To turn completely round on an axis like
a top or the Earth.
=Rotary.= Turning completely round on an axis,
like a top or the Earth.
=Roughly.= Not exactly; nearly enough for
practical purposes.
=Schedule.= (1) A tabulated statement giving items
concerning a subject. (2) A timetable of any kind.
=Seeing.= To look at. The word _seeing_
in starcraft means to observe the stars. _Good
seeing_ is to observe the stars when the
atmosphere is perfectly clear.
=Seems.= Something which apparently is true and
yet is not necessarily true.
=Sensation.= The action of one of the senses when
excited by some change in matter. Light falling on
the retina of the eye produces the sensation of
light and color in the brain.
=Set.= To sink from sight below the horizon; as
the Sun sets.
=Sight.= The power to see. See Sighting.
=Sighting.= To get the eye and two other objects,
such as a telescope and a star, in a line, as to
sight Jupiter with a telescope.
=Sign.= A mark, figure or letter which astronomers
have agreed to use to represent certain stars,
aspects of stars, parts of the zodiac, etc.
=Solar.= That which is of, or has to do with the
Sun.
=Spring stars.= The stars which can be seen best
during the spring months.
=Star chart.= A map of the positions of the stars.
=Starcraft.= Useful knowledge of the stars. Skill
shown in making the stars serve useful purposes.
=Star finder.= A device of any kind which will
enable an unskilled person to find the planets or
constellations.
=Star-lore.= Learning concerning the mythology of
the stars.
=Summer stars.= The stars which can best be seen
during the summer months.
=Supposition.= See Idea.
=Tangent.= See Appendix B.
=Tangent line.= See Appendix B.
=Telegraph code.= The alphabet of dots and dashes.
=Test.= To try out. To examine, compare or make an
experiment which will give a needed proof.
=Theory.= See Idea.
=Thumb tack.= A short, thin, sharp-pointed tack
with a large flat head which permits it to be easily
pushed into a board with the thumb. It is used by
draftsmen for fastening paper to drawing boards.
=Tilting.= Leaning from a vertical or plumb
line. The axis of the Earth is tilted from the
perpendicular 23½ degrees; this throws its equator
out of plane with that of the sun, and the circle
through the Earth that is in plane with the Sun is
called the ecliptic.
=Transparent.= Said of any substance through which
light can pass easily. Anything that may be seen
through.
=Twinkle.= To blink. To flash with varying
brightness. The twinkling of stars is caused by the
atmosphere.
=Uniform.= Being the same all through or all along.
=Vapor.= A gas produced from a liquid or a solid
and which returns to its original form at ordinary
temperatures. See Gas.
=Vertical.= See Appendix B.
=Vibration.= A to-and-fro movement, as the
vibration of a particle of matter. A constant
to-and-fro movement over the same line.
=Visible.= That which the eye can see.
=Wane.= To gradually grow smaller. Said of the
Moon.
=Wax.= To gradually grow larger. Said of the Moon.
=Winter Stars.= The stars which can best be seen
during the winter months.
=Wireless Messages.= Messages which are sent and
received by wireless telegraph stations.
=Wireless system.= An apparatus for sending and
receiving messages by wireless telegraph.
=Your meridian.= The line running due north and
south in the sky directly over your head. A meridian
of this kind is called a celestial meridian.
=Zodiacal lights.= A faint glowing light which
may be seen above the western horizon just after
twilight during the clear evenings of winter and
spring. It can also be seen just before daybreak
during the clear mornings of summer and autumn.
INDEX
Air, thickness of, around Earth, 125.
Air waves, 125.
Alcor, in the Big Dipper, 11.
and Mizar through a glass, 150.
Aldebaran in Taurus, 26, 28.
Almanac, 171.
how to read, 182.
Old Farmers’, 184.
signs in, 183.
use of, for finding planets, 61.
Alpha Centauri nearest star, 118.
Alphabet, Greek, 197.
Morse, 39.
Andromeda, great nebula in, 119.
Annular eclipse of the Sun, 112.
Antares in Scorpio, 180.
Apennines on the Moon, 146.
Apparent noon, 154.
Apparent solar day, 154.
Apparent time, 152.
Aquarius, the Water Bearer, constellation of, 63.
the Water Man, 173.
Aquila, the Eagle, 201.
Arab test for eyesight, 11.
Arc defined, 194.
Arctic day and Sun, 87.
Arcturus in Boötes, 28.
Aries, the Ram, 63, 175.
Aristarchus on the Moon, 146.
Ass’s Colts in Cancer, 176.
Asteroids, 47, 54.
Astrologer’s horoscopes, 180.
Atoms, vibration of, 123.
Auditory nerve, 125.
Autumn, 74.
Autumnal equinox, 178.
Auriga, Capella in, 24.
Auriga, the Charioteer, 23.
constellation of, 23.
of the Greeks, 24.
the Shepherd, 24.
Barometer, a simple, 35.
Barometric pressure, 35.
Belt of Orion, 21.
Beta Pegasi, 18.
Betelgeux in Orion, 28.
Big Dipper, the, 2, 4.
Alcor in the, 11.
how to tell time by the, 12.
Mizar in the, 11.
pointer stars of, 10.
position of, in autumn, 3.
in summer, 11.
in spring, 10.
in winter, 9.
through a telescope, 149.
Boötes, the Bear Leader, 201.
Boxing the compass, 78.
Boy Scout, merit badge for, 193.
Boy Scouts’ Handbook, 193.
Brain of a genius, 192.
Bull of Light, the, 26.
Burning lens, 37.
Camera, how it is made, 185.
Cancer, the Crab, 176.
Candle flame, 30.
Canis Major, constellation of, 28, 201.
Canis Minor, the Little Dog, 201.
Capella, how to find the North with, 24.
Cardinal points of a compass, 78.
Cassiopeia of the Arabians, 16.
constellation of, 14.
Castor and Pollux in Gemini, 176.
Cave man, how he marked time, 152.
Central time, 160.
Centrifugal force, 58, 90.
Chromosphere, the Sun’s, 32.
Chronograph, how made and used, 162.
Chronometer, use of, to find longitude, 85.
Circle defined, 194.
Colored stars, 202.
Colored sun glasses, 30.
Colors, how they are made, 123, 129.
Combustion, what it is, 123.
Comet, breaking up of, 116.
coma of a, 113.
Halley’s, 115.
how to find a, 112.
nucleus of a, 113.
tail of a, 113, 116.
Comets, laws of, 114.
number of, 116.
paths of, 113.
speed of, 115.
Compass, boxing the, 78.
cardinal points of a, 78.
dial, mariner’s, 78.
how to make a simple, 77.
mariner’s, 78.
pocket, 78.
Concave lens, 134.
Constellations: Aquarius, the Water Bearer, 63.
Aquila, 201.
Aries, the Ram, 63, 173, 175.
Auriga, 23.
Big Dipper, 6.
Boötes, 201.
Cancer, the Crab, 176.
Canis Major, 28, 201.
Cassiopeia, 14.
Cygnus, 201.
Flying Horse, 19.
Gemini, the Twins, 63, 176.
Great Bear, 6.
Great Square of Pegasus, 17.
having first magnitude stars, 201.
Libra, the Balance, 178.
Little Bear, 16.
Little Dipper, 15.
Leo, the Lion, 177.
Lyre, 201.
Mighty Orion, 20.
Northern Cross, 202.
Pisces, the Fishes, 63, 174.
Pleiades, 26.
Plough, 6.
Sagittarius, the Archer, 180
Scorpio, the Scorpion, 180.
Taurus, the Bull, 24, 175.
Ursa Major, 6.
Ursa Minor, 17.
Virgo, the Virgin, 177.
what they mean, 14.
Zodiac, 168.
Convex lens, 133.
Copernicus on the Moon, 148.
Corona of the Sun, 33.
Crescent Moon, 93.
Cycle of the Seasons, 75.
Cygnus, the Swan, 201.
Dark stars, 206.
Day, solar, 154.
when it begins and ends, 152.
Definitions of words used in starcraft, 213.
Degrees, dividing a circle into, 156.
Earth divided into, 81.
protractor for measuring, 79.
Denebola in Leo, the Lion, 177.
Dial of mariner’s compass, 79.
Diameter defined, 194.
Difference between true North Pole and magnetic North Pole, 88.
Dipping needle, how to make a, 79.
Dog Star, 8.
Double stars, 204.
Earth, 47, 54.
cross section of, 67.
divided into degrees, 81.
divided into standard meridians, 158.
from the Moon, view of, 104.
a great magnet, 77.
in the making, 66.
Moon eclipsed by, 107.
and Moon joined together, 89.
orbit of, an ellipse, 70.
precession of the, 173.
proof it is round, 67.
shadow of, 109.
thickness of air around, 125.
tilts on its axis, 69.
travels round the Sun, 70.
turning of, makes day and night, 69.
turning in orbit makes the seasons, 72.
turns on its axis, proof that, 68.
umbra of, 135.
when cooled off, 66.
Earth-shine, 93.
Eastern time, 158.
Eclipse, annular of the Sun, 112.
Eclipse, defined, 113, 194, 195.
of the Moon, 107.
partial, of the Sun, 112.
seeing an, 107.
of the Sun by Moon, 110.
for next 30 years, 112.
total, of the Sun, 112.
Ecliptic, the, 46, 69, 72, 170.
Ellipse, 113.
Ellis seasonal twilight chart, 201.
Epsilon in Lyra through a glass, 150.
Equation of time, 155, 207.
Equator, crossing the ecliptic, 72.
defined, 194.
Equinox, autumnal, 178.
vernal, 178.
Ether, what it is, 123, 125, 127.
Evening star, Venus, 50.
Experiment, Foucault’s pendulum, 68.
in centrifugal force, 90.
making star trails, 68.
showing, eclipse of Sun, 110.
how Moon cracked, 145.
Moon eclipsed by Earth, 107.
Moon’s crescent, 95.
Moon’s day and year, 94.
Moon’s phases, 98.
reflection of light, 131.
refraction of light, 132.
with a bell, 125.
with candle to show the seasons, 73.
with cardboard zodiac, 170.
with spinning top, 72.
with water waves, 124.
Eye, a camera, 127.
how it sees, 127.
human, 8.
light and, 129.
Eyesight, star tests for, 197.
Finding, the North Star, 2.
the North with Pegasus, 19.
Fireballs, 116.
First magnitude stars, 200.
Fixed stars, 7.
Flying Horse, constellation of, 19.
Focal length of a lens, 134.
Focus of lens, 133.
Forecasting the weather by barometer, 35.
Forecasting weather by signs, 36.
Foucault’s pendulum experiment, 68.
Fraunhofer’s lines, 190.
Frequency of vibrating atoms, 123.
Friction, 60.
Gemini, the Twins, constellation of, 63, 176.
Geometrical figures, 195.
Gibbous Moon, 93.
Girl in the Moon, 147.
Gravitation defined, 59.
Great Bear, 5.
Great Square of Pegasus, constellation of, 17.
Greek alphabet, 197.
Greenwich time, 86.
Grimaldi on the Moon, 94, 147.
Guardian stars of the Little Dipper, 16.
Handbook of Boy Scouts, 193.
Harvest and Hunter’s Moon, 98.
Heat, how it travels, 123.
Heat, what it is, 122, 129.
Heliograph, how to make and use a, 40, 41.
Horizon, a good, 153.
Horizon glass, 84.
Horizontal line defined, 194.
Horoscopes, astrologer’s, 180.
Horse and Rider, 11.
Hours, dividing a circle into, 157.
How a camera is made, 185.
How the cave man marked time, 152.
How the eye sees, 127.
How to find, Aries, the Ram, 174.
a comet, 113.
constellations of the Zodiac, 169.
focus of a lens, 133.
longitude 86.
the North Star, 83.
with dipping needle and protractor, 82.
with sticks and pail of water, 83.
power of a telescope, 143.
How to get Sun time, 153.
How to know, the stars, 14.
you are at the North Pole, 87.
How to look at the Sun, 148.
How to make, a cheap telescope, 140.
pinhole telescope, 138.
simple compass, 77.
simple dipping needle, 79.
star finder, 1.
star trails, 187.
How the Moon makes the tides, 99.
How a photograph is made, 185.
How a prism bends light, 133.
How to read the almanac, 182.
How a spectroscope is made, 191.
How the stars shine, 121.
How the stars were made, 119.
How a telescope works, 139.
How to tell, time by the Big Dipper, 12.
a true meteorite, 117.
How time is sent, by telegraph, 163.
by wireless, 165.
How to use a prism, 188.
How we see light, 126.
Hyades in Taurus, 175.
Hyperbola, 113.
Imaginary Sun time, 155.
Index mirror, 84.
Invisible stars, 206.
Jupiter, 47, 61.
nine moons of, 52.
seeing, 51.
through a telescope, 149.
Kullmer star finder, 209.
Latitude, how to find, by protractor and dipping needle, 82.
with sextant, 84.
with sticks and pail of water, 83.
Lens, concave, 134.
convex, 133.
how to find focus of a, 133.
Leo, the Lion, 177.
Libra, the Balance, 178.
Light, defined, 122.
how made, 122.
how it passes through glass, 130.
how it travels, 123.
how we see it, 126, 129.
reflection of, 131, 132.
refraction of, 132.
speed of, 188.
what makes the colors in, 123.
wave-lengths of, 123, 130.
Little Bear, constellation of, 16.
Little Dipper, constellation of, 15.
Local time, 86, 155.
Longitude, how to find it, 86.
meridians of, 86.
use of sextant to find, 84.
Lyra, the Lyre, 201.
Magellan’s voyage, 67.
Magnet, Earth a great, 77.
Magnet, steel bar, 76.
Magnetic lines of force, 76.
Magnetic North Pole and true North Pole, 76, 88.
Magnetic storms, 34.
Magnitude of stars, 199.
Man in the Moon, 93.
Mariner’s compass, 78.
Mars, 47, 49.
is it peopled? 49.
through a telescope, 149.
Mean length, defined, 154.
Mean solar time, 154.
Mean time, 152.
Mercury, 47, 48, 61.
phases of, 48.
through a telescope, 148.
Meridian defined, 18.
prime, 156.
your, 61.
zero, 156.
Meridians, fixed, 157.
of longitude, 85.
standard, 86, 156.
Meteorites, kinds of, 117.
tests for, 117.
Meteors, and meteorites, 116.
orbits of, 116.
Merit badge for starcraft, 193.
Milk dipper in the Milky Way, 181.
Milky Way, stars of the, 117, 118.
through a glass, 150.
Mizar in the Big Dipper, 11, 150.
Moon, 89.
Apennines on the, 146.
aspects of the, 94.
Copernicus on the, 148.
crescent, 93.
day and year of the, 94.
and Earth joined together, 89.
eclipse of the, 107.
eclipse of Sun by the, 110.
gibbous, 93.
Grimaldi on the, 94, 147.
Harvest and Hunter’s, 99.
how it cracked, 144.
if you were on it, 101.
imitating volcanoes on the, 91.
Man in the, 93.
motions of the, 94.
old, in the new Moon’s arms, 93.
other things about the, 106.
phases of the, how made, 94, 95, 96.
photographing the, 188.
seas on the, 144.
seeing the, with the naked eye, 92.
telling time by the, 105.
through a telescope, 144.
time marked by the, 151.
a trip to the, 101.
Tycho on the, 144.
volcanoes on the, 91.
weather, and the, 105.
where it came from, 90.
Moon girl, 146.
Morning star, Venus, 50.
Morse Code, 39.
Motions of the Moon, 94.
Mountain time, 160.
Naked eye aids, 139.
Naked eye view of the Moon, 93.
Nebula, 114, 118.
of Orion, great, 119.
Nebular hypothesis, 119.
Nebulæ, different forms of, 119.
Neptune, the outpost planet, 47, 53.
seeing, 53.
through a telescope, 149.
North, to find, by a watch, 45.
with Capella, 24.
with Orion, 23.
with Pegasus, 19.
North magnetic pole, 76.
North Pole, 8.
explorers at the, 87.
how to know you are at, 87.
shadows at, 88.
true, and magnetic North Pole, 76, 88.
North Star, 1, 2, 4.
how to find, 1, 2.
how to find latitude of, 83.
sighting the, 2.
through a glass, 150.
Northern Cross, 202.
Northern Lights, 34.
Old Farmers’ Almanac, 184.
Old Moon in the new Moon’s arms, 93.
Opera glasses, 140.
Optic nerve, 126.
Orion, of the Arabians, 22.
belt of stars of, 21.
constellation of, 20.
finding the North with, 23.
the Great Hunter, 20.
Great Nebula of, 119.
sword of stars of, 22.
Pacific time, 160.
Parabola, 113.
Partial eclipse of the Sun, 112.
Pegasus, the Flying Horse, 19.
Pendulum illustrating Sun’s attraction, 59.
Penumbra, 135.
Perpendicular line defined, 194.
Phases, of Mercury, 48.
of Venus, 50.
Photograph, how made, 185.
Photographing the Moon, 188
the stars, 185.
Photographing the Sun, 187.
Photosphere of the Sun, 32.
Pinhole sunshade, 30.
Pinhole telescope, 30, 138.
Pisces, the Fishes, constellation of, 63, 174.
Plane, defined, 55.
Planet, how to plot position of a, 61.
Planetesimal hypothesis, 119, 120.
Planets, eggshell experiment to show motions of, 57.
first aid to remembering, 57.
how held in space, 57.
how to know the, 47.
names and sizes of, 47.
path of, 170.
plane of, 55.
round the Sun, position of, 54.
the Sun’s kiddies, 46.
through a telescope, 148.
use of almanac for finding, 61.
why they spin, 60.
Pleiades, in Taurus, 26.
through a glass, 150.
Plotting the position of a planet, 61.
Plough, the, 5.
Pointer stars of the Big Dipper, 10.
Polar nights, 71.
Polaris, the Pole Star, 4.
Pole Star, the, 4, 8.
Precession of the Earth, 173.
Prime meridian, 156.
Prism, 132.
forming a spectrum, 134.
how to use, 188.
Produce, defined, 8.
Prominences of the Sun, 31.
Protractor, showing degrees, 81.
showing degrees latitude, 82.
Radius defined, 194.
Railroad time, 156.
Reflection of light, 131.
Regulus in Leo, the Lion, 177.
Rigel in Orion, 28.
Right angle defined, 194.
Ring defined, 194.
Sagittarius, the Archer, 180.
Saturn, 47.
seeing, 52.
through a telescope, 149.
Scorpius, the Scorpion, 180.
Seasonal twilight chart, Ellis, 201.
Seasons: autumn, 74.
spring, 74.
summer, 75.
winter, 74.
cycle of the, 75.
Earth turning round Sun makes the, 72.
experiment to show the, 73.
Seeing, an eclipse, 107.
the Moon with naked eye, 92.
the stars, 121.
Sextant, how to use it, 84.
Shadow of, the Earth, 109.
the Penumbra, 135.
the Umbra, 135.
Shadows, 135.
at the North Pole, 88.
Shooting the Sun, 84.
Shooting stars, 116.
Sighting the North Star, 2.
Signalling with the Sun’s rays, 38.
Signs, in the almanac, 183.
of the Zodiac, 168.
Sirius, the Dog Star, 8, 118.
Sky, things in the, 107.
Smoked Sun glasses, 30.
Solar day, 154.
apparent, 154.
Solar noon, 153.
Solar spectrum, 189.
Solar system, in perspective, 56.
top view of, 55.
Solar time, 152.
mean, 154.
Solstice, summer, 176.
winter, 181.
Sound waves, 125.
South Pole, 26.
Spectroscope, 189.
how made, 191.
Spectrum, 133.
solar, 189.
Spring, 74.
Spyglass, 136.
stars seen through, 144.
Standard meridians, 86, 156.
Standard time, 155.
zone system of, 156.
Standard time meridians in United States, 159.
Starcraft, merit badge for, 193.
Star finder, how to make a, 1.
Kullmer, 209.
Star tests for eyesight, 197.
Star time, 160.
Star trails, how to make, 187.
Stars, colored, 202.
constellations having first magnitude, 201.
double, 204.
first magnitude, 200.
how made, 119.
how they shine, 121.
invisible or dark, 206.
magnitude of, 199.
near the Sun’s path, 62.
photographing, 185.
seeing, 121.
through a telescope, 149.
variable, 205.
what they are made of, 188.
of the Zodiac, 166.
Straight line defined, 194.
Summer, 75.
Summer solstice, 176.
Sun, annular eclipse of the, 87.
arctic, 87.
attraction of, illustrated, 59.
brightest star, 29.
hot gases of, 121.
chromosphere of, 32.
core of, 32.
corona of, 33.
cross section of, 34.
eclipse of, by the Moon, 110.
how to see, 29.
layers of flame of, 31.
lighting a fire with, 37.
from the Moon, view of, 104.
stars near the, 62.
partial eclipse of the, 112.
path of the, 46, 170.
photographing the, 187.
photosphere of, 32.
positions of planets round the, 54.
prominences of, 31.
rays of, signalling with, 38.
shooting the, 84.
surface of, 32.
time marked by, 151.
through a telescope, 148.
weather and, 34.
what it is made of, 30.
Sun dial, how to make a simple, 42.
Sun spots, 31.
effects of, on the Earth, 33.
Sun time, 152.
how to set, 153.
imaginary, 155.
Sword of Orion, 22.
Tangent defined, 58, 194.
Taurus, Aldebaran in, 26.
constellation of, 24, 63, 175.
of the Egyptians, 26.
Telescope, 136.
astronomical, 138.
with convex lenses, 142.
defined, 136.
discovery of, 136.
equatorial, 188.
how to make a cheap, 140.
how to make a pinhole, 138.
how it works, 139.
kinds of, 137, 139.
magnifying power of, 143.
Mars through a, 149.
Mercury through a, 148.
Moon through a, 144.
Neptune through a, 149.
opera glass, 141.
pinhole, 30.
planets through a, 148.
Saturn through a, 149.
seeing the stars through a, 144.
of sextant, 84.
simple, 140.
stars through a, 149.
Sun through a, 148.
Uranus through a, 149.
Venus through a, 148.
Telescope lens, mounting for, 140.
Test for eyesight, Alcor, 11.
Tides, high and low, 100.
how the Moon makes, 99.
spring and neap, 101.
Time, apparent, 152.
at different cities, 161.
by the Moon, telling, 105.
by the stars, 160.
central, 160.
to change star, into solar, 163.
correct, 161.
how obtained, 162.
distributed by telegraph, 161.
by wireless, 161.
eastern, 158.
equation of, 155, 207.
Greenwich, 86.
how sent by telegraph, 163.
how to tell, by the Big Dipper, 12.
imaginary Sun, 155.
local, 86, 155.
marked by the Moon, 151.
by the Sun, 151.
mean, 152.
solar, 154.
mountain, 160.
o’ day, 151.
Pacific, 160.
railroad, 156.
standard, 155.
Sun, 154.
what is it? 151.
zone system of standard, 156.
Time ball, how made and worked, 164.
Time meridians in United States, standard, 159
Total eclipse of the Sun, 110.
Transit of a star, 162.
Transit instrument, 162.
Trapezium defined, 20, 21.
True North Pole, 76.
Tycho on the Moon, 144.
Umbra of the Moon, 135.
Uranus, Herschel’s planet, 47, 53.
seeing, 53.
through a telescope, 149.
Ursa Major, constellation of, 6.
Ursa Minor, constellation of, 16.
Vanishing Man in the Moon, 146.
Variable stars, 205.
Venus, 47, 61.
phases of, 50.
seeing, 50.
through a telescope, 148.
Vernal equinox, 178.
Vertical line defined, 194.
Vesta, an asteroid, 54.
Vibrating atoms, 123.
Vibrations of bell, number of, 125.
Virgo, the Virgin, 177.
Volcanoes, how they were made, 91.
on the Moon, 91.
Waves, air, 125.
in the ether, 127.
length of light, 123.
sound, 125.
speed of, 126.
of water, experiment with, 124.
Weather, forecasting, by the barometer, 35.
by signs, 37.
Weather, and the Moon, 105.
Sun and the, 34.
Winter, 74.
Winter solstice, 181.
Wireless, time distributed by, 161.
Wireless receiving sets, 165.
Zero meridian, 156.
Zodiac, as invented by the ancients, 167.
as we know it today, 167.
constellations of, 168.
experiment with a cardboard, 170.
how to find the constellations of the, 169.
signs of the, 168.
stars of the, 166.
what it is, 166.
Zone system of standard time, 156.