The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1896-01-26
POPULAR ASTRONOMY
THE OPERA GLASS MAY BE USED IN
STUDYING THE sKY's WONDERS.
With a Good Lens Twenty Times as
Many Stars Can Be Seen as with
the Naked Eye-The Great Bear.
Nav Proctor. in Popular Science.

scope in order to learn anything. While
this is undoubtedly an advantage. yet II Is
a luxury few possess. A telescope is bet
ter adapted for advanced students but
the most suitable instrument for COM
mencing astronomical studies is within or
binary reach. 1t is the weil-known binoc-
ular, that a sailor uses on board ship; or,
If that cannot be had, then common OPP
era glass will answer nearly as well. AL
though not powerful as a telescope, Ii
has compromising advantages. An opera
glass enables to survey a large region
OF the sky at one glance. while a telescope.
generally speaking. only presents a small
field OF view. Calico made his famous
discoveries with what was simply on OPP
era glass, and although its use was after
wards abandoned for the telescope, yet
ION account of its brilliant illumination OF
objects looked at, \and its convenience of
FORM, Serviss, who is an authority on the
subject, tells us that 1.-The opera glass is
still valuable and. in some respects. an
unrivalled instrument OF observation" The
instrument used by him in making most
of the observations had object glasses one
and sixteenth inches in diameter and a
magnifyfng power of about three and six
tenths times. In choosing an opera glass
see first that the object glasses are achro-
matte, although this caution Is hardly nee
essary. for all modern opera glasses worthy
OF the name are made with achromatic
detectives. But there are great diff
ferences in the quality of the work. II a
glass shows colored fringe around a
bright object. reject it. Let the diameter
OF the object-glasses, which are the large
lenses In the end furthest from the eve be
not Tess tnan an inch and half. The mag
nliying power should be at least three or
four diameters. A familiar way of estimat-
ing the magnifying power is by looking at a
brick wall through one barrel of the opera
glass with one eye, while the other eye
the glass. Then notice how many bricks
seen by the naked eye are required to
equal In thickness one brick seen through
the glass. That number represents the
view given by the two barrels of the opera
glass coincide or blend perfectly together
II one appears to partially overlap the other
when looking at distant object, the effect
Is very annoying. This fault arises from
the barrels of the opera-glass being placed
too far apart: so that their optical centers
do not coincide with the centers Of the OBJ
servers eyes. Don't buy a cheap glass, but
don't waste your money on fancy mount
ings. What the Rev. T. w. Webb says OF
Inferior articles may be showily got UP.
and the outside must go for nothing
UNDER THE SKY.
The right place to make observations Is
unquestionably out of doors. With due pre-
cautions as to dress nothing need be feared
from might air." that prejudice is fully
confuted by the well-known longevity OF
astronomers. even of such as have habitual-
ly protracted their watchings "till the dap
pied dawn doth rise" Do not lose time in
looking for objects under such unfavor-
able circumstances as twilight, moonlight,
and that most treacherous foe of star
gazers, the electric light. A very brilliant
night is often worthless for planets or
double stars from its blurred or tremulous
definition; it will serve, however, for ire
solvable nebulae which have no outlines
to be deranged; hazy or foggy night will
sometimes defines bright objects admirably:
never condemn such night untried, Look
for nothing near the horizon; unless, in
over or to the leeward Of a chimney in
use unless you wish to study the effect of
a current of heated air. In examining
seeing nothing by dazzling 1t Immediately
beforehand with a lamp or looking at a
book. Give it little previous rest in the
When a star is not to be seen at once do
not give Ii up without trying oblique or
averted vision. Turn the eye toward the
edge of the field, but keep the attention
fixed on the center, where the object ought
to appear. and will appear IL you are only
patient. Professor Serviss says: The eff
feet of seeing a faint star in this way,
in the neighborhood of a large one, whose
rays hide 1T from direct vision, is sometimes
very amusing. The little star seems to dart
out into view as through a curtain. perfect
ly distinct, though as UNNECESSARILY minute
as the point Of a needle. But the instant
you direct your eyes straight at 1t, presto!
it is gone And so it will dodge in and out
Of sight as often as you turn your eyes,"
If you catch a really favorable night, with
sharp and steady vision, make the most of
1t; you will not find too many of them.
STUDY OF THE DIPPER.
would suggest as a little experiment In
star-gazing with an opera glass. a glance at
Ursa Major. otherwise known as the Great
Bear in England, or as the Great Dipper in
America. Face the north. and IL you are not
just sure where the north is try a pocket
compass. This constellation consists of four
bright stars, which form a sort Of ob,ong.
while the other three represent the tail. If
it is a fine. clear night, count how many
stars there are within this oblong. They are
all very faint, but you will be able to see
a few, and, with good sight, and on a good
night, you may perhaps see ten. Next take
region, and if you will carefully count the
stars 1t shows you will find fully two hun
dred; SO that the operaglass has in this
part of the sky revealed nearly twenty
times as many stars as could be seen with
out its aid As six thousand stars can be
seen by the eye all over the heavens, we may
fairly expect that twenty times that number
that is to say, 10000 stars--could be
shown by the opera glass over the entire sky.
Look at the star in the middle of the handle
of the Dipper this handle forms the tail of
Ursa Major, and little attention will show
you that the star is double. The larger OF
these two stars is called Mizar and the
smallest Alcor-the Horse and his Rider, as
the Arabs say. Your glass will not
cor and Mizar. but also their diff
ference in color. When We speak of
Nizar as double star, it is to be under
stood that Alcor is one of the components
of the double. In the nlagnifying power OF
the opera glass Alcor is at some little dis
lance from Mizar, while Mizar itself Is
and pale green. and close together. This
is. indeed the best double star in the
heavens for the beginner TO commence his
observations upon. A larss lumber of the
double stars are perceptible through a
good opera glass, and II will afford many
a delightful evenings entertainment 10
ment. In this way We can obtain a fair
the position of the consultations. the lead
ing brilliants OF the sky and many won
ders of the heavens, which cannot be seer
know the stars. and TO be able. like Nil
tons hermit, to
est and rightly spell
OF every star that heaven do show"