Half Hours with the Stars
Half Hours with the Stars INTRODUCTION ON THE USE OF THE MAPS.MAP I. NIGHT SKY.—DECEMBER AND JANUARY.MAP II. NIGHT SKY.—JANUARY AND FEBRUARY.MAP III. NIGHT SKY.—FEBRUARY AND MARCH.MAP IV. NIGHT SKY.—MARCH AND APRIL.MAP V. NIGHT SKY.—APRIL AND MAY.MAP VI. NIGHT SKY.—MAY AND JUNE.MAP VII. NIGHT SKY.—JUNE AND JULY.MAP VIII. NIGHT SKY.—JULY AND AUGUST.MAP IX. NIGHT SKY.—AUGUST AND SEPTEMBER.MAP X. NIGHT SKY.—SEPTEMBER AND OCTOBER.MAP XI. NIGHT SKY.—OCTOBER AND NOVEMBER.Copyright
Half Hours with the Stars
Richard A. Proctor
INTRODUCTION ON THE USE OF THE MAPS.
It is very easy to gain a knowledge of the stars, if the
learner sets to work in the proper manner. But he commonly meets
with a difficulty at the outset of his task. He provides himself
with a set of the ordinary star maps, and then finds himself
at a loss how to make use of them. Such maps tell him nothing of
the position of the constellationson the
sky. If he happen to recognize a constellation,
then indeed his maps, if properly constructed, will tell him the
names of the stars forming the constellation, and also he may be
able to recognize a few of the neighboring constellations. But when
he has done this he may meet with a new difficulty, even as
respects this very constellation. For if he look for it again some
months later, he will neither find it in its former place nor will
it present the same aspect,—if indeed it happen to be above the
horizon at all.It is clear, then, that what the learner wants is a set of
maps specially constructed to show him in what part of the sky the
constellations are to be looked for. He ought on any night of the
year to be able to turn at once to the proper map, and in that map
he ought to see at once what to look for, toward what point of the
compass each visible constellation lies, and how high it is above
the horizon. And, if possible (as the present work shows is the
case),onemap ought to suffice
to exhibit the aspect of the whole heavens, in order that the
beginner may not be confused by turning from map to map, and trying
to find out how each fits in with the others.It is to fulfil these requirements that the present maps have
been constructed. Each exhibits the aspect of the whole sky at a
given day and hour. The circumference of the map represents the
natural horizon, the middle of the map representing the part of the
sky which lies immediately overhead. If the learner hold one of
these maps over his head, so as to look vertically upwards at it,
the different parts of the horizon marked in round the
circumference being turned towards the proper compass points, he
will see the same view of the heavens as he would if he were to lie
on his back and look upwards at the sky, only that the map is a
planisphere and the sky a hemisphere.But although this illustration serves to indicate the nature
of the maps, the actual mode of using them is more
convenient.Let it first be noted that properly speaking the maps have
neither top, bottom, nor sides. Each map may be held with any part
of the circumference downward: then the centre of the map is to be
looked upon as the top for that part of the circumference. The
portion of the map lying beneath the centre represents the portion
of the sky lying between the point overhead and a certain part of
the horizon—the part in fact corresponding to the particular part
of the circumference which is turned downwards. Thus if on any
night we wish to learn what are the stars towards the north, we
look for the map corresponding to that night. At the hour named the
stars toward the north will be those shown between the centre of
the map and the top; and, of course, we hold the map upside down so
as to bring the centre above the northern part of the
circumference.But this matter will be more clearly understood by comparing
the account of any of the accompanying maps with the map
itself.Again, it must be noted that, although the maps are
necessarily arranged in a certain order, there is in reality no
first or last in the series. The map numbered I. follows the map
numbered XII. in exactly the same manner that the latter follows
the map numbered XI. The maps form a circular series, in
fact.The only reason for numbering the maps as at present, is that
the map numbered I. Happens to exhibit the aspect of the sky at a
convenient hour on the night of January 1st. It will be found that
the dates follow on with intervals of seven or eight days right
round the year, the end of the year falling in the left-hand column
of the table under Map I., while the beginning of the year is in
the right-hand column of the same map.[*]
