LIBRARY
UNIVERSITY OF CALIFORNIA.
GIFT OF
Class
V
By Starlight
\ and Moonlight
With the Warner & Svvasey
Prism
Terrestrial Telescope
The Warner & Suasey C
CLEVELAND
Price 25 cents
BY STARLIGHT
and MOONLIGHT
With the Warner & Swasey
Prism Terrestrial
Telescope
Some Easy Astronomical
Observations
The Warner & Swasey Company
CLEVELAND, OHIO
Copyright, 1909, by The Warner &> Swasey Co.
Cleveland, Ohio
"// adds a precious seeing to the eye," 1
Shakespeare ; Love s Labour s Lost.
194838
THE WARNER & SWASEY PRISM TERRESTRIAL TELESCOPE
Complete with
ALT-AZIMUTH MOUNTING, FOLDING TRIPOD
AND CARRYING CASE
OF THE
UNIVERSITY
OF
The Warner C&> Swasey Prism
Terrestrial Telescope
This Porro Prism instrument represents the
highest development in Terrestrial Telescopes.
Its relation to the ordinary telescope is the same
as that of our Prism Binocular to the old type of
field-glass. It is remarkable for its large field,
brilliant illumination and clear definition.
The objective is 2 inches in diameter, clear aperture. Two
eye-pieces are provided, magnifying respectively 25 and 50 diam-
eters. The telescope tube and the alt-azimuth mounting are made of
aluminum. The folding tripod is of carefully selected ash. All are
contained in a neat leather-covered carrying case; total weight
only twelve pounds. Weight of telescope with its tripod and
mounting, apart from case, but six and a half pounds.
The high quality of its optical equipment, and the simplicity
and adequacy of its mechanical provisions, make it superior to any
similar telescope upon the market for the camper, the traveler, the
motor-tourist, the surveyor, or the marksman upon the rifle-range.
It is especially adapted for porch, seaside and general use.
While thus designed strictly as a terrestrial telescope, its
purchasers have also found it of much interest and value in the
field of amateur astronomy. It is not presented as in the tech-
nical sense an astronomical telescope; and yet its quality is so
superior that its efficiency is actually greater than that of many
larger astronomical telescopes heretofore offered to the public.
The ease with which it can be moved from place to place in the
observation of moon and stars, its sharp definition and breadth of
field, combined with the precision and steadiness with which the
instrument may be "pointed" and controlled, have brought many
expressions of satisfaction from those who having first purchased
it as a terrestrial telescope have subsequently tested it in their
observations of celestial objects. To respond to the interest and
the demand thus indicated, and to illustrate, for beginners, some
of the simple astronomical uses of the Warner & Swasey "Prism
Terrestrial," this little booklet has been prepared.
Our long experience in making "Optik Tubes" of all sizes,
from the great Lick and Yerkes Telescopes to the Telescopic Gun
Sights, Range Finders, Sextants, etc., used by the Army and Navy,
especially qualifies us to develop from both a scientific and prac-
tical standpoint, the highest type of Porro Prism Telescope.
By Starlight and Moonlight
WITH THE WARNER C& SWASEY
PRISM TERRESTRIAL TELESCOPE
Introductory
The beginner naturally asks, "What is there to see? What
objects in the sky will my telescope reveal?" It will help toward
an appreciation of what his little instrument will do for him, if
we can first help him to understand some of the things which even
the largest telescope in direct proportion to its excellence will
not do for anyone.
There are results which are mathematically as impossible for
an optical instrument as for a fine watch to tick seventy-five sec-
onds to the minute. Your telescope cannot work well through a
misty atmosphere, or through air heavy with cloudiness or smoke.
It will not work well if you permit the steadiness of your tripod
to be affected by the winds, or if when you place it on your
porch the floor on which it rests is shaken by heavy walking.
Inasmuch as the atmosphere close to the earth is more subject to
disturbance and impurity than the air a little higher up, your in-
strument will work better on objects at a slight altitude than on
objects lying close to the horizon.
Yet even this two-inch instrument (modest indeed as com-
pared to those largest telescopes of the world the great instru-
ments made by The Warner & Swasey Company for the Lick and
the Yerkes Observatories) will give you gratifying results. There
is a peculiar fascination in being easily able to point your instru-
ment at a bright star and to find perhaps to your surprise that
it is not a single star, but a "double" or a "triple." It is even more
charming to be able to discern in a double star the contrasted colors
of the components, one, perhaps, being a golden yellow, the other
a distinct blue or a delicate emerald.
A few of the coarser doubles may be divided by a field-glass,
but everyone knows the difficulty in holding a field-glass steady;
and the power commanded by this little telescope is so much
greater than that available in a binocular that many doubles which
no field-glass can divide will yield instantly to its persuasion. And
as your tripod does the holding, you can gaze at your leisure and
comfort into a steady field.
When Halley's comet comes again into view (it is scheduled to
reappear late in 1909, becoming still more conspicuous in 1910) the
possession of an adequate telescope, even though a small one, will
add much to one's pleasure in following its course. Objects, more-
over, that are quite familiar to us such a star-cluster for example
as the Pleiades assume through this little instrument a scope and
brilliancy quite unsuspected by the naked eye. Clusters, also, like
those in the sword-hand of Perseus and like the "Bee-hive" in
Cancer; nebulae like those in Andromeda and Orion; the four
greater satellites of Jupiter; the ring-formation and at least one
of the satellites of Saturn, and much of the strange and beautiful
topography of our own moon are brought within the range of
vivid interest and appreciation. A telescope that will easily divide
such double stars as Castor, and the Gamma in Virgo; that will
reveal so clearly the contrasted colors of such doubles as Mizar
and Albireo, and that will show even with a power of 50 the
trapezium in the sword of Orion, is not to be despised by anyone,
and holds for the beginner many possibilities of pleasure.
10
Part I.
Single Stars Double Stars
The Planets
Symbols
% First Magnitude Stars
Second Magnitude
Third Macjnifudf and Under
O Cluster
A Nebula
GUIDE MAP No. I.
This Map of #ie Northern Sky Joins, and overlaps the tops of
Maps II, III, IV.
On some evening when the air is clear and steady, place your
telescope on its simple mounting, and come with it out of doors.
Bring with you, for your greater comfort while observing, a plain
straight-backed chair, preferably without arms.
Let us face directly north, to get our bearings by the Great
Dipper and the North Star. During May, at 9 o'clock in the
evening, for example, you will find the Dipper just before you,
directly to the northward and very high up. During July and
August, you will see it further to your left in the northwest, the
handle following the bowl and the bowl turning slowly downward,
as its stars make their apparent revolution about the pole of the
heavens. Late in the autumn, you will find it low down, directly
to the north, its bowl turned upward; and in the winter, you will
see it climbing upward to your right, in the northeast, but with its
bowl turned toward the west.
In noting this apparent revolution of the Dipper, we have
taken 9 P. M. as the hour of observation. As it takes approxi-
mately twenty-four hours to complete its turning, we shall find it
at 8 P. M. less far advanced upon its course; at 10 P. M. or at 11
P. M., we shall find it proportionately further forward. A few
minutes' observation for an evening or two will make these direc-
tions clear ; but as many may wish to study more fully the motions
of the stars, and as all ought to have larger knowledge of the im-
portant constellations (an easy and delightful subject of popular
information) some elementary books of reference are given on
page 37 ; see also paragraph 9, page 36.
12
First let us look at Mizar, the star marked Zeta () in the
bend of the Dipper's handle. The reader who is not familiar with
the characters of the Greek alphabet will quickly pick them up as
we go along; some of the stars have no other designations.
Quite near to Mizar you will note, if the air is clear, a little star
that may sometimes be seen with the naked eye. Using your 25 x
eye-piece, turn your telescope upon them. Be sure to get a clean,
sharp focus. You will observe at least four objects in the field.
You will see Alcor, the smaller star to which we have referred, and
another fainter star, and by looking closely at Mizar (the brightest
of the group), you will discover that it is a "double." Now, having
once found these in your telescope, slip in the 50 x eye-piece, and
the division between Mizar and its close companion will be clearer
still. (The magnitudes of the components are 2.4 and 4.2.)
Now let us look somewhat further from the pole, near the edge
of our little map, at a star which the Dipper's handle (if it were
continued in a curve) would quite enclose. This is Alpha in "The
Hunting Dogs" (Canes Venatici). It is sometimes called Cor
Caroli, the Heart of Charles, in honor of Charles I of England.
Your 25 x will show it to be a charming double. (The magnitudes
of the components are 3.1 and 5.7.)
In searching for a star with the telescope, it is well to use the
less powerful eye-piece. Having found the object, you can then
slip in the higher power if you desire. Let us now follow with our
eyes the general direction indicated by the "Pointers" in the bowl
of the Dipper. Not stopping, however, at the Pole Star, let us
continue the imaginary line as far again, right across the northern
sky. We are now in the neighborhood of the constellations Cepheus
and Cassiopeia. Almost at the center of Cepheus, we shall find
the little star Xi () ; magnitudes 4.4 and 6.5. You may find it a
little difficult. Turning, however, to one of the corners of the
house-shaped figure, we shall find an especially easy and very pretty
"double" in the star Delta (8) ; magnitudes 3.7 and 5.1, and we
shall find another in the head of Draco, the Dragon. From the
star Delta (8) in Cepheus let the eye project an imaginary line
to Alpha (a) in the same group continuing it approximately
the distance of the Dipper's total length. You will thus come
readily to the stars that mark the Dragon's head. The star Nu
(v) is the faintest of the four ; but even with your 25 x eye-piece
you will be rewarded by the brightness of its two components,
(magnitudes 4.9 and 4.9).
And now before leaving the northern stars let us return again
to the region right across the northern sky from the Great Dipper.
Still using your low-power eye-piece, sweep through the rich fields
of Cassiopeia till you reach the neighborhood of the star Alpha (a)
in Perseus. This is one of the most brilliant sections of the sky.
Note especially the star-clusters marked (X) and (h). They have
symbolized for ages "the sword-hand" of the hero Perseus. Of
course a larger instrument would give a more adequate impression
of their scope and splendor, but our little telescope will reveal much
of the beauty of the scene.
13
Joins Map X
GUIDE MAP No. II. T/i/s Map Overlaps Map I at the Top and
Map III and IV at the Sides.
We have already spoken of the region of the sky in the neigh-
borhood of the star Alpha (a) in Perseus. We find Perseus in
the northeast late in August and the early autumn; in the north-
west during February and the early spring. At the right side of
Map II toward the top, you will find this part of the sky repeated,
for the tops of the oblong maps we now employ are "overlaps"
connecting the circumpolar stars with the other stars of the sky.
You will also see the star Beta ((3) or Algol, by name and you
will note that a line drawn from Beta (/?) to Alpha (a) will form
a right angle with one drawn to the star Gamma (y) in Androm-
eda. The latter is one of the most charming of all the double
stars (magnitudes 2.2 and 5.0) ; the colors of its components are
orange and a delicate emerald. It will repay close observation with
both your eye-pieces.
Next let us look at the well-known group called the Pleiades.
They appear in the east in the early evenings of late September,
reach their highest point above us early in January and continue
till April in the western sky. They are so far distant that their
light, traveling at the rate of more than 186,000 miles a second,
takes more than two hundred years to reach us. The average
unaided eye can discern but six or seven ; turn your little instru-
ment upon them using your 25 power eye-piece and you will see
the shining of hundreds.
Now let us turn our telescope upon the region about Alde-
baran, the red eye of Taurus, the Bull. The stars that here make
14
the V-shaped figure which we see in our little map the point of
the V being at the star Gamma (y) are called the Hyades. The
group is not so compact as the Pleiades, but it is well worth exam-
ination. Note especially the little star Theta (0) quite near
Aldebaran (mags. 4.0 and 3.6). Many can divide it with the un-
aided eye.
Early in November, the stars of Orion begin to be seen in
our eastern sky. There is no other constellation quite so impres-
sive ; and from November till late in April, when it sinks below the
western horizon in the early evening, it is well-placed for easy
observation. Here as always begin with your eye-piece of low-
est power. First note the uppermost of the three bright stars in
Orion's belt the one marked Delta (8). It is an easy "double"
(mags. 2.4 and 6.8). Then turn to the little star just below and
to the right of the lowest star of the belt. We refer to the un-
marked star near to Zeta (). It is a "multiple" star (Sigma, <r)
and even with our little instrument you can clearly discern at least
three of the components (mags. 5, 6.8, 6.3). Next let us look a
little lower still, at the star Theta (0). This is a region of be-
wildering interest. Here you will clearly observe especially if the
moon be not shining so bright as to obscure the light of other
objects the beautiful, mysterious halo of the "Great Nebula of
the heavens." Almost at its center, if you will now use your 50 x
eye-piece, you will discern Theta's four components, for the star
is a "quadruple" (mags. 6.8, 7.9, 5.3, 6.8). Small as they will
seem, you will clearly observe them as separate points of light.
They form an irregular square the famous "trapezium" lying
close together in a dark space at the core of the enfolding radiance.
Just below, note the star Gamma (y) in Lepus (mags. 5.6 and
6.4) ; and to the left of Orion note the star marked 8 (mags. 4.6
and 6.7); and that marked 11 (mags. 4.3 and 5.7). These are
easy and pretty doubles.
We have looked at two of the clusters easily seen with the
unaided eye; now let us look at two which but for the telescope
not so many eyes would find. You will see the place of the first
of these, marked with the little circle, just below the bright star
Sirius. A little searching with your low-power eye-piece will soon
be rewarded by the sparkle of its "star-dust." The second is shown
nearer the top of our map, in the constellation Cancer. Its name
is Praesepe, "The Manger." You will find it slightly to one side
of an imaginary line drawn from Castor to Pollux and projected
southward. The myriad little stars of the cluster seem so busy in
their twinkling that it has often been called "the Bee-hive."
Among the "doubles" in this quarter of the sky are the star
Iota ( i ) just above the "Bee-hive" (mags. 4.2 and 6.6) ; the star
Zeta () in Gemini (mags. 3.7 and 7.0), and Castor itself, one of the
most beautiful of telescopic objects (mags. 1.9 and 2.8). The two
components form a "binary" system, being in slow revolution
about a common center. The companion stars will seem very
close together in so small a telescope, but with the 50 x eye-piece
and on a clear night, a good eye will easily divide them.
15
Joins Ma/a I
G VIDE MAP No. HI. This Map Overlaps Map I at the Top, and
Maps IV and II at the Sides.
As with the other oblong maps, the top of this map joins Map I,
partly overlapping it and therefore showing some of the stars
that we noted on p. 12. Among these is the pretty "double" not
far from the Dipper's handle marked Alpha (a) in the constella-
tion Canes Venatici. We may now note also the very easy double
quite near it marked 15; its components being magnitudes 6.2 and
6.4. These stars are shown here near the upper border of our map,
about midway between the two sides. They come into good posi-
tion at the northeast about the middle of February, and though
rather high up in May, June and July, they are again well placed
for observation at the northwest during the evenings of August and
September.
Just to the south of them you will observe the pretty groups
or strands of stars called "Bernice's Hair." The name does not
appear, but you will see them on our map just to the right of
Arcturus. Sweep through them with your low-power eye-piece,
and you will be delighted with the spectacle.
Through the early evenings of spring we shall also find the
constellation Leo in our eastern sky. Leo is rather high up during
the evenings of April and May, but is again in good position in our
western skies during June and July. You will easily recognize it
by the "sickle" formed from the stars Regulus, Eta (77), Gamma
(y) , etc. First using your lowest power, let us look at the star Gamma
16
(y). You will note quite near it a little neighbor-star, not its
double for it is connected with the larger star only in the line of
sight yet it presents a pleasing contrast in size and color. Now
change to the highest power eye-piece you have. This, if you have
a good eye and the atmospheric conditions are favorable, will show
you that Gamma (y), the larger star, is also a real double, a binary
the two components (mags. 2.6 and 3.8) being in slow revolution
about a common center. With the star Gamma (y) in Virgo (mags.
3.6 and 3.6) you will also need your highest power, but as the dis-
tance between the components is greater, even the beginner if the
night is good will be delighted with his success. With the power
of 50x, in our little instrument, it is one of the most charming
objects in the sky.
One of the easiest of the "doubles" among the early evening
stars of the spring and summer is Alpha (a), mags. 5.3 and 2.9, in
the constellation Libra. Libra rises in the southeast during May
and continues in our southern skies till it sets at the southwest in
October. We may also try the star Delta (8) in Corvus, though we
shall find this more difficult. Returning now to the top of our map
let us look in the region near Arcturus at the star Pi (TT) in
Bootes; mags. 4.6 and 6.0; and at Delta (8), mags. 3.5 and 8.2, in
the same constellation. Next, and to the left, you will see the stars
of Hercules. While this immediate region of the sky is too di-
rectly overhead for easy observation in the early evening of August,
it is in good position at the east during the early spring and at the
west during the early autumn. We shall need our highest power
in looking at Alpha (a) mags. 3.4 and 5.3, but even with our
25 x eye-piece we shall find a pretty double in the star Kappa (K),
mags. 5.3 and 6.5. And now let us follow the line indicated be-
tween Eta (77) and Zeta () till we come to the cluster indicated
by the little circle lying between them. It is globular in form,
and in a large instrument is most impressive. The elder Herschel
estimated the presence within it of 14,000 stars.
Turning again to the lower half of our map, at the left, let us
next note some of the objects in Scorpio. Rising at the southeast
in the month of May and continuing at the south through the early
evenings till they set in September at the southwest, the stars of
this superb constellation are always in fine position for the observer
of our summer skies. Use first your low-power eye-piece in sweep-
ing through the whole field of these stars. Then look using each
eye-piece in turn at the double star marked Nu (v), magnitudes
6.4 and 4.2; and then at Beta (), magnitudes 2.9 and 5.0. These
are easy to divide and yet sufficiently close to be very interesting
objects of their class. Follow, then, with your low-power eye-piece
the course of the Scorpion's tail. You will find the star Mu (//,)
and the region just below it well worthy of your study. The star
clusters of Scorpio and of Sagittarius (Map IV), some of which
are marked in our maps by the little circles, are not brilliant in a
small telescope, but the finding of a few of them will add much to
your appreciation of this region of the sky.
17
Joins Map I
GUIDE MAP No. IV. TMs Map Overlaps Map TVo. 7 af the Top, and
Maps II and III at the Sides.
As we begin with the stars in Map IV let us again turn for a
moment to No. I, and note the position of the Dipper in relation
to some of the stars near the lower border of that map. As the
Dipper looms above us in the evening skies of May you will see,
low down and to the right, the stars of Lyra rising at the northeast.
In Map IV, at the top, you will now observe the repetition of
some of the objects of this region; you will note that Vega, the
leading star in Lyra, is between the constellation Hercules, on the
one hand, and Cygnus on the other; and you will see, further, that
all these stars hold always the same fixed position in reference to
the great Dipper. When the Dipper is high up these are in the
northeast; as the Dipper sinks toward the west these rise to the
meridian ; as the Dipper itself wheels again into the northeast, they
sink below the horizon at the northwest. To the beginner such
descriptions (see also p. 12 and par. 9 on p. 36) may sound a
little "complicated," yet if he will look for an evening or two at
the actual skies, glancing now and then at his little maps, he will
find few things more pleasurable than "the simplicity of the stars."
On a clear night Vega can always be identified by the rhomboid
("the slanting oblong square") formed by the stars Delta (8),
Gamma (y), Beta (f3), and Zeta () Of these, all except the second
are double stars, the first named being the easiest to divide. The
components of Delta (8) are magnitudes 5.5 and 4.5. Beta is a
"multiple," only two of the components being within the range of
our instrument (magnitudes 3.3 and 6.7). The magnitudes of
18
Zeta () are 4.2 and 5.8. We will now direct ourselves to the little
star Epsilon (e). It is a very easy double, magnitudes 5.0 and 6.0,
but of much more interest is the fact that each of these components
is itself a double, the two pairs being in very slow revolution about
a common center. The doubling of the doubles is beyond the
power of so small an instrument, but the knowledge of a fact so
unique in stellar history always gives a peculiar interest to them
as telescopic objects.
Not far from Lyra we find those stars of Cygnus, the Swan,
which form the Northern Cross. No star in the sky makes a more
beautiful or more satisfactory object for our telescope than "Al-
bireo," marked as Beta ((3) at the foot of this cross. The magni-
tudes are 3.2 and 5.3, and the contrasted colors a golden yellow
and a smalt blue make an especially fine contrast. The star
Omicron (o) is also an easy double (magnitudes 4.9 and 3.9), and
the star marked 61 (magnitudes 5.5 and 6.2) while perhaps requir-
ing your 50 x eye-piece for its division, is of interest as being the
nearest to our earth of all the stars in the northern sky. So far
away is it, however, that its light requires approximately eight
years in which to reach us!
Southward from Cygnus you will find another beautiful double
in Theta (6), magnitudes 4.5 and 5.1, of the constellation Serpens.
You can find it by extending an imaginary line from Eta (rj) to
Delta (8) in Aquila, and continuing it an equal distance. Still
further to the southward you will find a very easy double in Alpha
(a) of Capricornus; many can divide the components, magnitudes
4.5 and 3.7, with the unaided eye. A closer and more interesting
double is Beta (/3) of the same constellation, magnitudes 3.2 and
6.0; the colors being an orange yellow and a sky blue.
The stars of this region are well placed for observation
throughout the summer, rising at the southeast in July and con-
tinuing in our evening skies till they set in November at the
southwest. In Aquarius you will find that Zeta () the central star
of the little Y which marks the water-jar is a double, though rather
difficult; mags. 4.5 and 4.2. Gamma (y) in the small constellation
called Delphinus is more easily divided; mags. 5.4 and 4.4.
Among the most conspicuous landmarks of the sky is "the
Great Square of Pegasus," shown here and shown also in Map II.
It is made by three of the brighter stars of Pegasus in combination
with the Alpha (a) of Andromeda. It is at the east in the evening
skies of August, is directly above us in November, and sets at the
west in early February. The star Epsilon (e), magnitudes 2.5 and
8.5, is a double, but a little difficult. In the neighboring constella-
tion of Pisces or The Fishes, the stars Zeta (), magnitudes 5.5 and
6.4, and Psi (i//), magnitudes 5.5 and 5.8, are easier to divide.
Starting at one of the northern corners of the Square of Pe-
gasus, from the star Alpha (a) of Andromeda, let us now follow
the line which leads through the latter constellation. We shall
find here the easy doubles Pi (?r), magnitudes 4.5 and 8; and 56,
magnitudes 5.8 and 6.0; and at the position indicated by the little
triangle near the small star Nu (i/) we shall be able to distinguish
Andromeda's great nebula. Use your eye-piece of lowest power,
19
for you will want a large field. Choose a night clear, but not
flooded by the moonlight, for you will want the benefit of contrast.
This nebula is the largest of the spiral type, its diameter having
been estimated as 500,000 times the distance between the earth
and the sun, "light requiring eight years to travel across it." It is
decidedly oval in shape, brighter at its center than at its edges.
In a small instrument it is not so impressive to a beginner as is a
cluster, like the Pleiades ; but in its own way, in the far reaches of
its faint luminous glow, it is, to the discriminating observer, quite
as interesting.
The Planets
The planets are of our own family, and revolve
with our little earth about the sun. They are not
1909 themselves great self-luminous suns, as are the
"fixed stars" we have thus far studied. Because the
i9ii planets are thus near, and because they chiefly shine
by reflected light, they show an appreciable disc, or
1913 surface outline, within the telescope, though only
Venus, Jupiter and Saturn are of special interest in
a small instrument. Mars, indeed, is worth observ-
ing, for his ruddy glow and perhaps one of his more
conspicuous markings, but the much-discussed "canals" are for
larger glasses. Saturn, however, even in a small instrument, is an
object of surpassing interest.
You can easily identify Saturn by the steadiness of its yellow
light. Your 25 x eye-piece will distinctly show the existence of the
ring formation, but you can here use the 50 x with greater advan-
tage. With the higher power you will see the chief peculiarity of
the planet more clearly, though not on so large a scale as in our
little cut, and you will also see Titan, the largest of the nine satel-
lites. But Saturn's chief attraction is shown in our illustration, a
phenomenon unique so far as our knowledge goes in the whole
range of our universe. Because of the changes in the relative posi-
tions of the planets in reference to each other, the rings of Saturn
are sometimes turned "edge on" toward the earth and are then
difficult to see. This was the case in 1907, as shown in the first
figure of our little illustration. But through 1909 and 1910 the
rings gradually open out, permitting a more satisfactory telescopic
view. They are composed of "swarms of meteors" in revolution
about the planet as a center. The extreme diameter at the outer
edge is more than 172,000 miles.
20
Venus, so splendidly beautiful to the unaided eye, has no satel-
lite to interest us and no marked peculiarity of form. These facts,
together with its excessive brilliance in a glass, make it a disap-
pointing telescopic object. Most interesting, however, is the ob-
servation of the planet when she assumes her crescent phase, for
there are periods of the year when she puts on this aspect of the
new moon. It is an aspect of her charm which will be presented
when she shines at her brightest in the west during the evenings
of January, 1910, and in the east during the mornings of March
and April, 1910.
Jupiter and his satellites will form a delightful and inexhausti-
ble source of interest and pleasure. Even with the 25 x eye-piece
four of the eight moons are distinctly visible in our little instru-
ment, and the field of view is so large and so well lighted that the
spectacle is peculiarly satisfying. With the 50 x eye-piece they are
brought out even more vividly ; and by a good eye, under favorable
conditions, the cloud-belts across the body of the great planet may
be discerned. The movement of the satellites is so rapid, as they
revolve in their orbits, that we can see them change their relative
positions almost from hour to hour; one night three will be upon
one side the planet, one upon the other; the next night there will
be two on either side; and, yet again, as the satellites are hidden
by the body of the planet, or are eclipsed, or are in transit across
his huge disc, one or more of them will be wholly hid from view.
References to familiar sources of information for the easy find-
ing of the planets, together with other inexpensive literature con-
cerning their nature and their movements are given in note 10,
paragraphs 2 and 4, p. 38.
21
OF THE
UNIVERSITY
Part II.
The Moon
The Moon
Some Interesting Lunar Objects
The user of our Prism Terrestrial Telescope will find especial
pleasure in the observation of the moon. Not only does the ex-
cellent definition of the instrument show the lunar topography with
remarkable clearness and fullness of detail, but the very fact that
a terrestrial telescope does not invert the image as is the case
with astronomical telescopes is of much satisfaction to a begin-
ner. Our halftone engravings and our miniature key-map are pre-
sented, therefore, "right-side-up," in harmony with the view as
observed in a terrestrial instrument and in conformity with the
natural expectations of the eye.
As you look at our first photograph of the moon you will see
that the objects on its surface are made distinct to us by the lunar
shadows. As the sunshine dawns or dies away over plains and
mountains, the objects near the edges of the advancing or receding
light are brought into sharp relief. In the direct illumination which
obtains when the moon is "full," we can see little detail, for shad-
ows are then largely absent. Looking at each of our photographs
in turn, you will now be able at once to understand why the same
object such as Copernicus, the huge crater-mountain marked No.
28 in our key-map should present so different an aspect at differ-
ent times. These ceaseless changes caused by the different angles
at which the sun's light strikes the surface make one of the chief
fascinations of lunar study.
But in order to show clearly all of the chief objects on the
moon by the photographic process, we should thus have to present
dozens of pictures instead of two. These two, however, are enough
to explain the constant changes of illumination and to illustrate
the value of our little key-map. Without the key-map and this
accompanying explanation you might possibly infer from the pho-
tographs themselves that the objects lying outside the shadows in
the darkness, or in the confusion of the direct light are always
hidden from observation. On the contrary, the region of the moon
toward the reader's right, which seems obscured in the moon at
nine and three-quarter days by the direct glare (the objects num-
bered 1, 2, 3, 4 in the key-map) are as clear when the moon is
younger (two to four days old) as is Copernicus (No. 28) in our
first engraving.
25
The Moon at Nine and Three-quarter Days
With the moon, as with the stars, do not assume as beginners
are so apt to do that the more powerful eye-piece is necessarily
the first that should be employed. As the lower powers always
afford a much larger field of vision, it is always well to use the 25 x
in locating the object in the telescope. Then the 50 x eye-piece
may be substituted. If there is haze or mist, the lower power may
well be retained; if the atmospheric conditions are good, you will
of course gain with your higher power a greater fullness of detail
and much larger magnification.
Early in our study of the moon let us mentally mark and note
the general position of some of the greater "seas," not seas in fact,
but dark plains upon the lunar surface. Their quaint names were
given them many generations ago. That marked No. 1 was named
26
,fe/\
(*K )
"The Sea of Crises," or "The Sea of Conflicts." We roughly trans-
late the Latin titles. That marked No. 5 is the Sea of Fecundity;
No. 6 is the Sea of Nectar; No. 7 is the Sea of Tranquility; No. 8
is the Sea of Serenity; No. 21 is the Sea of Showers.
The Sea of Conflicts, No. 1, seems to be longer from north to
south (up and down) than from east to west. This, however, is
an optical illusion, due to foreshortening; its width, from north to
south, being about 280 miles, and the distance from its eastern to
its western boundary being over 350 miles. Two craters may be
readily discerned within it the lower
having the name Picard, the upper be-
ing called Peirce. These are so small
that while they may be readily seen with
the telescope when the Moon is about
(V?\ four days old, they are not indicated in
^ the key-map. No. 1 and its neighboring
objects as already stated are seen in
clear and beautiful detail in the very
new moon. This great oval plain com-
prises about 66,000 square miles. Just
Key Map above it, marked No. 2 in the key-map,
is Cleomedes, a smaller formation, a walled plain 78 miles in
diameter. A little way below No. 1 is the crater Langrenus, No. 3,
with its terraced ring over 9,500 feet high. The next crater except
one which we do not mark is Petavius, No. 4, the eastern side of
its great double rampart being 11,000 feet in height. All these
objects, as has been said, are too directly lighted to be well seen
under the illumination of the nine or ten day moon, so they appear
only as bright patches in our first photograph.
In the objects numbered 10, 11, 12 we again find almost
"drowned in light," three peculiarly interesting craters which in
the younger moon at about six days old are superbly clear. In
this particular case, however, we find recompense in our second
photograph. For, ten days later, in the receding light of the sun,
these objects Theophilus, Cyrillus and Catharina are again de-
fined in the lines of grateful shadow.
Theophilus, No. 10, is probably the deepest of the moon's
craters, the general line of the ring being from 14,000 to 18,000 feet
above the chasm. Of this triple group, it "first catches," says
Webb, "the rising sun, and I have seen it far beyond the ter-
minator (the shadow line) and even without the telescope, five
days after new ; it is a grand object when filled with night, through
which its glittering central peak comes out like a star." In our
27
The Moon at Eighteen and a Half Days
second photograph, in the now retreating shadows of the sun, you
can clearly see the bright cap of this central peak.
Cyrillus, No. 11, is even larger; and Catharina, No. 12, is
perhaps the largest of the three, irregular in character but more
than 16,000 feet deep. As with all the objects of our study these
craters should be observed under different illuminations. If pos-
sible, it is well to make two observations on the same evening
one at an early hour and another somewhat later. And in using
the little key-map, each object specified should be examined with
the aid of both our photographs.
As our little telescope will clearly show more than three hun-
dred objects upon the moon's surface each having its own distinct
28
and proper name it is obviously impossible here to indicate them
all. And upon the beginner the effect of so much detail would be
confusion and discouragement rather than information and pleas-
ure. We confine ourselves to approximately forty objects. Even
this number will seem bewildering to the novice. We suggest,
therefore, that for the first few evenings of his observation he
rigorously confine himself to four or five. Let him get these well
in mind. Then, with these as landmarks, he will be surprised and
delighted to see how rapidly his information will advance.
We have already spoken of the
objects 10, 11, 12 conspicuously
lighted in our second photograph as
well as in the six and seven-day moon.
In the nine-day moon we shall find an-
other triple group (23, 24, 25 in the
key-map) called Ptolemy, Alphonsus,
and Arzachel. This group is shown in
both our photographs. Quite near the
edge of Alphonsus you will observe
the smaller crater called Alpetragius
Miniature Key Map Qne o f the deepest On the mOOn. To
the right, No. 26, is Albategnius. One cannot but feel a strong
desire to change some of these formidable names!
We have hastened to speak of the triple group 23, 24, 25 chiefly
to prevent its confusion with 10, 11, 12. We will now return to
some of the earlier numbers. In No. 9 of our key-map we again
have an object shown in our photographs under two different light-
ings. This is Posodonius, a walled plain about 62 miles across,
containing a small but sometimes brilliant crater. No. 18 is
Manilius, and to its right is Pliny. The former is over 7,500 feet
deep and about 25 miles in diameter. No. 13 is Aristotle, No. 14
is Eudoxus ; a superb pair of craters, the terraced wall of the former,
over 11,000 feet high, being crowned by two turrets of 15,000 feet.
In this great cavity, says one authority, the Mount Etna of our
earth could stand. No. 19 is Cassini, a ring-plain with a small
deep crater. No. 20 is Plato, well shown in both our photographs, a
great ring-plain 60 miles across. Above Plato lies the Sea of Cold;
below Plato is the Sea of Showers, and within the latter we have
marked for special consideration the objects numbered 15, 16 and
17, Archimedes, Autolycus, and Aristillus. The range of moun-
tains terminating at Eratosthenes (No. 22) is known as the Apen-
nines, a chain somewhat like the mountains of the earth. Its length
is 460 miles. To the left of No. 22 lie the Carpathian Mountains,
and in No. 28 we have one of the most superb of lunar spectacles,
29
the huge crater Copernicus, 56 miles in diameter. It is the center,
as may be seen in our second photograph, of one of those systems of
light radiation which form one of the most striking features of the
moon's aspect. Another center of these radiations, as you will see,
is Kepler, No. 36. No. 27, Aristarchus, is usually regarded as the
most brilliant single point upon the moon. No. 34, Grimaldi, is by
contrast the darkest of the lunar craters.
In No. 29, seen far better in our first photograph than in our
second, we have Bullialdus, a great crater, 9,000 feet deep and 38
miles across. No. 35 is Rheinholdt. We turn now, however, to the
southern or lower quarter of the moon's surface in order that we
may close our brief descriptions with a word concerning a few of
the objects in the neighborhood of No. 30, Tycho, "the metropolitan
crater." The whole region is one of mighty cataclysm, of appalling
heights and depths. Longomontanus, No. 31, is apparently one of
the oldest of volcanic formations, its great walls having been rent
and shattered by recurrent explosions. Maginus, No. 32, is one
of a number of lunar objects which, while presenting a superb spec-
tacle under certain phases of illumination, are entirely invisible at
full moon. Clavius, No. 33, is especially interesting by reason of
the craters within its limits; their shadows are finely outlined in
the lunar sunrise. This, and many objects which must necessarily
be omitted from a list as brief as the present one, may be further
studied in some of the publications cited in par. 10, p. 38.
The great crater Tycho, No. 30, is not only of unique interest
in itself, but is the central point for the most splendid system of
radiations on the moon. In both our photographs the reader can
partially see the spreading of these lines of light. So brilliant do
they become when the moon is full that this huge crater dominates
the scene, the light-streaks extending from it in all directions.
Webb calls Tycho "a most perfect specimen of the lunar volcano,
roughly figured by Galileo in the earliest telescopic representations.
Its diameter is 54 miles, its depth 17,000 feet or nearly three miles,
so that the summit of our Mont Blanc would drop beneath the
ring. Its vicinity is thronged with hillocks and small craters so
that for a long distance not the smallest level spot can be found;
further off the craters increase till the whole surface of the region
resembles a colossal honeycomb."
"There are," says Noble, in his "Hours With a Three-inch
Telescope," "few more curious, instructive, nay even startling
sights in the heavens than the occultation of a fixed star, or
30
more rarely of a planet, by the moon. When this occurs at the
dark limb of our satellite, its suddenness is such as not infrequently
to extort an exclamation from the observer who witnesses it for
the first time. . . In describing her monthly path over the
celestial vault, it is quite obvious that the moon must pass be-
tween us and such stars as lie in her course ; the stars being
for our present purpose at an infinite distance, while she is only
some 239,000 miles from us. . . Travelling thus, as I have said,
from west to east, her eastern limb is, of course, the leading one,
or that which covers, hides, or occults objects lying in her path.
From new moon to full moon this limb is unilluminated, and the
effect of the extremely sudden extinction of a star when the dark
limb hides it is, as I began by saying, of an absolutely startling
character. 'In a moment, in the twinkling of an eye,' the star
which shone as a brilliant point in the sky is blotted out; and its
place seemingly knows it no more, until it reappears from behind
the opposite or illuminated edge of the moon. After full moon,
of course, the eastern limb is illuminated, so that the disappearance
takes place at the bright edge, and the star on its reappearance
starts instantaneously from behind the dark limb." The more
interesting occultations are fully predicted and enumerated in the
Whitaker's almanac mentioned in the closing paragraph of note 10,
page 38.
In addition to the literature concerning the moon, as mentioned
in note 10, page 38, we also refer to "The Moon in Modern Astron-
omy" by Philip Fauth, with an introduction by J. Ellard Gore,
F. R. A. S. ; published by the Van Nostrand Co., New York. With-
out endorsing, necessarily, some of the theoretic contributions of
the volume we are sure the amateur astronomer will find much
pleasure in its illustrative and descriptive matter.
31
Part III.
Notes and Suggestions
Notes and Suggestions
1. Readers of this booklet are advised before beginning the
specific use of any particular part of it to read it through as a
whole. The suggestions made at one point will often prove helpful
in other connections.
2. Our half-tone engravings of the moon are reduced from
direct contact prints of negatives made with the great 40-inch
Yerkes telescope, designed and constructed by The Warner &
Swasey Company for the University of Chicago at Williams Bay,
Wisconsin. As all photographs taken with an astronomical tele-
scope show the object inverted in the field of view, the above prints
are presented "erect" in this booklet, in conformity with the re-
quirements of a terrestrial instrument.
3. The user of a camera expects to make a few failures before
getting the best results, the user of any form of mechanical equip-
ment whether it be the bicycle, the automobile or even a pair of
roller skates expects to put a little thought and care into the
mastery of the machine. It is so with a telescope. While far
simpler than the "modern creations" which we have mentioned, the
beginner should not begrudge the expenditure of a little thought
and time if he would gain intelligent command of the instrument
itself and of the resources which it will bring him.
4. It is to aid the beginner in one department of its use that
this booklet has been prepared. Yet it is not intended as a library
on astronomy or as a complete telescopic manual. The little maps
are necessarily inadequate and are not presented as a substitute for
such a "star atlas" as the advanced amateur will desire. In maps
so small many stars must necessarily be omitted; other and per-
haps smaller stars because of some special telescopic interest, or
because of their connection with the constellation figures have
been included. The diagrams are offered just as rough approximate
guide-maps for elementary telescopic work.
5. While our references to particular stars are so clearly given
as not to necessitate the memorizing of the Greek alphabet, that
alphabet is here printed as a matter of convenience to the beginner.
A general familiarity with the characters is easily acquired and
indispensable in the use of larger star-maps: Alpha, a; Beta, /?;
Gamma, y ; Delta, 8; Epsilon, ; Zeta, ; Eta, ??; Theta, 0;
Iota, t ; Kappa, K; Lambda, A; Mu, /*; Nu, v; Xi, ; Omicron, o;
Pi, TT ; Rho, P ; Sigma, o- ; Tau, r ; Upsilon, v ; Phi, <f> ; Chi, x ; Psi, \j/ ;
Omega, o>.
35
6. As already suggested on p. 12, the use of a plain straight-
back chair, without arms, will be of much service to the observer
employing so light an instrument. As he takes his place in the
chair the instrument may be drawn toward him, and sitting al-
most directly beneath the tripod, a leg of the tripod falling naturally
into position at each side of him he will be able with very little
adjustment of the telescope to command almost any altitude. Stars
obscured by mists at the horizon or inconveniently high up may be
permitted to wait the observation of those at better range. If the
beginner will early learn to take what Fortune brings, he will
always find that Fortune, whatever her negligences, will surely
bring the stars again. At a later hour on the same evening, or at
the same hour on a later evening, he will be rewarded.
7. Among the interesting astronomical phenomena of 1909-
1910 is the return of Halley's comet, after an absence of nearly 76
years. The comet in October, 1909, will be not far from the little
star marked Nu (v) in Orion (Map II). You will see this star
just above the bright star Betelgeuse, and a little to the left. Pass-
ing westward through the constellation Taurus the comet will
move along the southern part of the constellation Aries, and from
thence as we watch it from week to week we shall see it pass
into the region of Pisces, the Fishes. A telescope will probably be
needed for its observation during the autumn of 1909, but by the
early spring of 1910 it is likely to be a conspicuous object even to
the unaided eye. Its visible advance into our skies will, of course,
be first heralded by those commanding larger instruments ; the pos-
sessor of our two-inch terrestrial will thereafter find much interest
in observing its first appearance and its gradual brightening under
the modest powers of his own telescope.
8. Some one has well said that "the most important part of
a telescope is the man at the small end of it." This is but a recog-
nition of the fact that there is such a thing as a trained eye as well
as a trained hand or a trained will. The beginner may be sure,
therefore, that as he extends his familiarity with his instrument
and as he gains in clearness and accuracy of vision, his telescope
will be an increasing satisfaction. Two of the personal conditions
of good-seeing may be especially commended: Work in comfort,
and work with deliberation. Holding the telescope in trying posi-
tions, getting the head or body into fatiguing or unnatural attitudes,
are directly embarrassing to clear, accurate seeing. And because
we thus see with the mind as well as with the eye, much of the
reward of exquisite vision is found in deliberation. Do not rush
from star to star. In looking, for example, at a beautiful double
star like the Gamma (y) in Andromeda see p. 14 quiet, thought-
ful observation, after you have secured a sharp focus, will add much
to your real pleasure in what you see. In this case, you are looking
at two splendid suns thousands of millions of miles distant from
our earth, so different in their chemical constitution that their con-
trasted colors are at least partially conveyed to us through all the
intervening space.
9. In our little map at the top of p. 12 the Dipper is shown
in its approximate position for the early evening of May 1st. As
36
it turns westward (to the observer's left), the two stars marked
"The Pointers" (no matter what the position of the Dipper), will
always indicate the direction of the bright star, Polaris, or the
Pole Star, which lies nearest to the polar "hub." All the stars in
our little map, ever keeping the same permanent relations to each
other as though fixed on the respective spokes of a great wheel
revolve also, as does the Dipper; but Polaris lies so near the pole
of the heavens that its motion is almost unappreciable ; it seems to
the "wayfaring man" to stand ever fixed at the true north. It is
also, as you can see, the leading star in the "Little Dipper," part
of the constellation called "Ursa Minor."
Still looking at our first map, you will see that the further a
star is from the pole the larger must be the circle it describes, as
the great wheel revolves ; and that the stars located further out on
its spokes (to continue our figure) will, with the wheel's turning,
dip below the horizon for a shorter or longer period. Those, how-
ever, that lie within about forty degrees of the pole are never
carried quite out of the sight of observers in the latitude of Cleve-
land and New York; they are called the stars of the "circumpolar
constellations." These are roughly indicated in Map I, and are
always in our night sky.
The stars that are further from the pole are indicated in Maps
II, III, and IV. They pass out of our night skies for shorter or
longer periods of time ; and as we come to study them we shall see
that our figure of speech must be changed. For, as we look toward
the true north, we are gazing not strictly at the hub of a flat wheel,
but toward the pole of a hollow sphere, its apparent axis the pro-
jection of the earth's axis, and its equator the projection of our
own equator. We may imagine the spokes of the revolving wheel
as they extend gradually bending inward toward us, and forming
the ribs of a vast including globe. We stand enclosed as it were
at the sphere's center.
The circumpolar stars turn with the sphere itself, but as they
lie so near its pole, the circle of their revolution never carries them
below our horizon. Sometimes, for example, we see the Dipper
above the North Star, sometimes below it; sometimes it is a little
to our left, the bowl slowly turning downward, sometimes it is
toward the right with the bowl climbing upward, but it is always
in our northern sky. Yet, with the sphere's turning, the stars
further from the pole (Maps II, III, IV), like bright points fixed
on the inner surface of its concave sides as these arch themselves
above and below the horizon appear and disappear according to
their hours and their seasons. A few minutes of actual observa-
tion for a couple of evenings will make this subject clear, even to
children of grammar-school grades. An admirable and much fuller
exposition of the diurnal motion of the stars will be found in
Newcomb's volume, mentioned on p. 38.
10. The beginner may wish to supply himself with a few
volumes that will help to enlarge his knowledge. First, he will
enjoy gaining some measure of familiarity with the chief constella-
tions. Among the best helps here are Olcott's "Field Book of the
37
Stars," published by Putnam's, New York; and Serviss's "Astron-
omy with an Opera Glass," published by D. Appleton & Co. A
Planisphere will be found a most useful device for ascertaining the
positions of the stars from night to night. An inexpensive one is
sold by Thomas Whittaker, 2 Bible House, New York. As a
substitute, readers of French may prefer to use one upon the same
plan as Whittaker's, called the "Carte Celeste," published by Burk-
hardt, 2 Place du Molard a Geneve, to be had through any of
Brentano's book-stores.
Readers of German will find attractive star maps and ex-
cellent descriptive matter in the Stern-Atlas of Jacob Messer. The
"Himmel Atlas" of Schurig is less expensive and the new edition
is extremely useful even to those who do not read German. Both
volumes may be had of G. Steckert, 129 W. 20th St., New York.
Among English atlases may be mentioned "The New Star Atlas,"
by Proctor, published by Longmans, Green & Co. ; and Sir Robert
Ball's "Popular Guide to the Heavens," published in New York
at $4.50, by Van Nostrand. The latter contains not only a star
atlas, but charts showing the position of the stars from month
to month, simple tables for finding the planets, photographs of
clusters and nebulae, and admirable maps of the moon, etc.
Among the many interesting books upon the general principles
and facts of astronomy, we may mention S. P. Newcomb's "Popular
Astronomy," published by the American Book Co. It is especially
clear and able in its expositions. Among other admirable text-books
may be mentioned those by Todd, Young, and Moulton. Our little
cut of Saturn on p. 20 is drawn from a portion of a cut in Prof.
Todd's "New Astronomy," the American Book Co., New York. In
the use of the telescope, whether in observing the moon or the stars,
the advanced amateur will want some such volume as "Webb's
Celestial Objects for Common Telescopes," 2 vols., $1.75 each;
London and New York, Longmans, Green & Co. Much of it will
be too advanced for the beginner, but even very early in his work
he will find a great deal in it to give him pleasure. Among
more popular books, Noble's "Hours With a Three-inch Telescope"
(Longmans, Green & Co.) is especially useful and interesting for
its chapters on the moon.
In following the course of the planets the beginner will find a
good almanac almost indispensable. The astronomical matter pub-
lished in the New York Tribune almanac and in the almanac of the
Brooklyn Eagle usually presents a simple table showing in which
constellation each planet may be found from week to week through-
out the year. The best almanac, however, for the amateur astron-
omer is undoubtedly the English "Whitaker's," published at 12
Warwick Lane, London not to be confused with the American
house publishing the planisphere. This almanac may be secured
through any large bookseller. Its tables of the interesting as-
tronomical phenomena for each month are especially full and
valuable ; and the movements of the planets and the configurations
of the satellites of Jupiter, etc., are presented with simplicity and
38
clearness. "Whitakers" may be had in several editions, ranging
from about 30c to $1.00 in cost.
11. After the beginner has become familiar with his instru-
ment and with the telescopic objects already mentioned, he may
find it interesting to try some additional double stars. The follow-
ing list is, of course, not complete, and of the objects enumerated
some are easy and others are more difficult. If you do not succeed
with a specific star on one evening, try it on another. Changes in
atmospheric conditions are more frequent and more important than
many amateurs realize. In Map I, try in the constellation Draco
the star Psi, \j/ (mags. 4.9 and 6.0) ; and the star Omicron, o
(mags. 4.8 and 7.6). In Cassiopeia, try Iota i (mags. 4.8 and 8.1).
In Perseus, note Eta (>?), mags. 3.9 and 8.5. In Ursa Minor, the
star Pi, -a (mags. 6.9 and 7.6) ; in Cepheus, Beta, /? (mags. 3.5 and
8.0). In this constellation, the star Mu, /x, while not a double is
one of the most famous of the red stars called by Herschel a "gar-
net." In Map II, try in Auriga the star 14, mags. 5.1 and 7.2; in
Aries you will find easy doubles, both in Lambda, A (mags. 4.8 and
8.0); and Gamma, y (mags. 4.8 and 4.7). Note the Lambda, A, in
Orion (mags. 3.6 and 5.5). In Eridanus, try the stars marked 6
(mags. 5.7 and 8.0), 55 (mags. 6.0 and 7.1), and 32 (mags. 4.8 and
6.4); and in Cancer, the star Zeta, (mags. 4.8 and 6.5). In this
case as well as in a few others, the star appearing as a double in a
small telescope is really a triple or a multiple as viewed in a larger
instrument. It may also be interesting to note two of the im-
portant "variables" shown in Map II. We have already spoken
of the star in Perseus marked Beta, /?. The regular variations in
the brilliancy of its light are so remarkable that the Arabs called
it "Algol," the Demon. At minimum it sinks to fourth magnitude,
but it so remains only about 15 minutes, when, within 5y 2 hours,
it becomes again a second-magnitude star. Another remarkable
variable in our map is Mira, in the constellation Cetus, the Whale.
Its "period" is longer, being over 331 days, but it varies regularly
from absolute invisibility, for the naked eye, to a star of the
second magnitude! Toward the bottom of Map IV, at the right,
you will note the Alpha (a) and Beta (/3) of Sagittarius, the Archer.
The star /?', if you are living far enough south to command a view
of it, is an interesting and easy double (mags. 4.2 and 7.2).
12. The beginner, in noting the little table of symbols (Map I),
will see that the smaller the value of the numeral the higher the
magnitude of the star. A first magnitude star is a very bright one,
an eighth magnitude star is a very faint one. Little attempt has
been made in the maps themselves to secure absolute accuracy as
to these magnitudes the drawings are necessarily too small for
the varied use of many different symbols. But in the text of our
descriptive matter the magnitudes of the components of the double
stars are given according to the revised Harvard Photometry for
1908; or, in the cases of a few small components not included in
that list, according to the "Sternverzeichnis" of Ambronn, Univer-
sity of Gottingen, 1907. The "magnitude" of a star has no neces-
sary relation to its actual size ; the term refers solely to its apparent
brightness as seen from our earth itself. Many of the fainter stars
39
may be actually larger and more luminous than those we classify as
first magnitudes, their apparent faintness, in such cases, being due
only to their greater distance.
13. This factor of distance in the observation of the stars is so
great that it wholly transcends all our ordinary conceptions of
space. Yet a lack of knowledge upon this point is the occasion
among beginners of much disappointment in the first using of a
telescope. Do not expect your telescope, however large in size
or fine in quality, to lend a large surface image or a broad sensible
disc to any of the "fixed stars."
With the moon and with the planets, as we have seen, things
are slightly different: these are relatively very much nearer to the
earth. But so remote are the hosts of the stars proper (the very
nearest being over twenty-five millions of millions of miles distant)
that no telescope, however great, will ever make them in the popu-
lar sense any "bigger." The highest power usually provided with
our little instrument is 50 diameters. Let us suppose, however,
that we were able to use a telescope affording us a magnifica-
tion of 5,000 diameters. As such a power would magnify all
the conditions of atmospheric obscurity or disturbance (as well
as the star) there are few of us who could get any satisfaction
from it. But on the assumption that we could use it under
fine atmospheric conditions what would it mean to us? It would
bring a star that might be 50,000 million miles from us to a distance
of 1,000 million miles! That is not very near, is it? But there is no
star so near as 50,000 million miles: nor any so near as 500,000
million miles. The very nearest, as we have said, is 25,000,000 mil-
lion miles away and no star even so near as that is visible to us
north of our tropic latitudes.
Astronomers, accordingly, ignore the mile as a unit of measure.
Their unit is the light-year, the distance traversed by light speed-
ing at 186,330 miles a second in a year of time. Our North star,
for example, is at a light distance of 40 years that is to say the
light by which the mariner may now take his reckoning (1909)
was started on its way toward us in 1869. As you bear these dis-
tances in mind you will not find fault with your little telescope if
it does not make a star assume the proportions of a dinner-plate.
But if you will employ your instrument under some of the simple
instructions of the preceding pages, you will find that it will give
you results even more interesting than the mere enlargement of
size.
40
Specifications
Objective clear aperture
Powers two eye-pieces
Length of telescope
Weight of telescope
Weight of tripod and alt -azimuth mounting
Weight, complete with carrying case
Dimensions of carrying case
2 inches
25 and 50
. 21^ inches
2}^ Ibs.
4 Ibs.
12 Ibs.
12x6^x4^ inches
41
THE WARNER & SWASEY
PRISM
TERRESTRIAL
TELESCOPE
The Warner & Swasey Company
Cleveland, Ohio, U. S. A.
Circular .4-251909
SPECIFICATIONS
Objective clear aperture 2 inches
Powers two eye-pieces 25 and 50
Length of telescope 21 ^ inches
Weight of telescope 2^ Iks.
Weight of tripod and alt-azimuth mounting 4 Ibs.
Weight, complete with carrying case 1 2 Ibs.
Dimensions of carrying case - 24x6>4 x4^ inches
THE WARNER & SWASEY PRISM
TERRESTRIAL TELESCOPE
T
'HE 2-inch Porro Prism Tele-
scope is designed expressly for use
as a terrestrial instrument. Its large
field, high magnification and superior
construction represent the highest de-
velopment in terrestrial telescopes. As an example of
its excellence, it will show clearly so delicate an object as
the moving second hand of a watch at a distance of 300
feet. At from five to seven miles, in good atmospheric
conditions, it will reveal the time of day by the town
clock in the old meeting house tower, while at ten miles
or more what appeared as mere specks are sharply
brought out as recognizable objects ; that white dot is a
quarry of building stone, not a house. In other words,
the 2 5 -power eyepiece brings the object apparently twen-
ty-five times nearer and the 50-power eyepiece fifty
times nearer. Of course, atmospheric conditions modify
the " seeing." On a clear day, with no wind, an object
can be seen farther and better than in hazy weather, but
under any conditions The Warner & Swasey Prism Ter-
restrial Telescope enables the user to see more and better
and farther. It is the ideal instrument for terrestrial use.
THE WARNER & SWASEY PRISM TERRESTRIAL TELESCOPE
Complete with
ALT-AZIMUTH MOUNTING, FOLDING TRIPOD
AND CARRYING CASE
HOME USE
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