Page 256 - Lokmanya Tilak Samagra (khand 2)

THE ARCTIC REGIONS 43

horizon of the observer will be · H' H, atid the stars will : ·now
appear to move in circles inclined to his horizon, as shown in the
figure by the black lines AA',
BH' and CC'. Some of the
stars, viz., those that are
situated in the part of the
celestial dome represented by
H'PB, will be visible throu-
0 ghout the night, as their
H'f:::::::>"~-r'--~~...,.~..:::::::::_~H circles of revolution will be
above the horizon H' C' D H.
1
But all the stars, whose
Polar distance is greater
than PB or PH', will
in their daily revolution,
be partly above and partly
below the horizon. For instance, the stars at C and D will
describe circle , some portion of which will be below the
horizon H' H. In other words, the appearance of the vi ible
celestial hemi phere to a person whose zenith i at Z will be
different from the appearance pre ented by the heavens to an
ob erver at the orth Pole. The tars will not now revolve in
horizontal planes, but obliquely. A great number of them would
be circumpolar and visible during the whole night, but the
remaining will rise and set as with us in the tropics, moving in
oblique circles. When Z i very near P, only a few star will rise
and set in this way and the difference will not be a marked one;
but as Z i3 removed further south, the change will become more
and more apparent.
Similar modification will be introduced in the duration of
day and night, when the ob erver's position is hifted to the south
of the terrestrial North Pole. This will be clear by a reference to
the figure on the next page. Let P be the cele tial orth Pole and
Q' Q the celestial equator. Then ince the sun moves in the ecliptic
E' E, which is inclined at an angle of about 23i 0 ( 23° 28') to the
equator, the circles T E and E'T will corre pond with the terrestrial
1
circles of latitude called the Tropics and the circle AC with the
Arctic Circle on the terrestrial globe. Now as the sun moves
in the ecliptic E' E, in his annual cour e he will always be twice
over-head for an.observer stationed at a place within the terrestrial