सिद्धान्तशिरोमणि: गणिताध्याय (भास्कराचार्य - ग्रहगणित, मध्यमाधिकार व स्पष्टाधिकार सटीक)

340
Fig. 64
the Sun, for an observer 'O' on the surface of the Earth,
the Moon is not in the line of sight namely OS but hangs
down that line (लम्बते अनेनेति लम्बनम् = That phenomenon
by which the Moon hangs down the line of sight). Hence
it is not sufficient to say that the Sapātasūrya has a
longitude of 7° to conclude the occurence of a solar
eclipse for a place. If the Sapātasūrya be less than 7°,
certainly there will be a solar eclipse for some place on
the earth but not for all places. So, to decide whether
there will be a solar eclipse for a given place, we are
to take into account the phenomenon of parallax. At
every New Moon, the longitudes of the Sun and the
Moon will be no doubt equal; yet the Moon may not
obstruct a vision of the Sun, not being situated in the
ecliptic plane. He may be above the ecliptic plane or
below it and if he be within 32' from the plane, a part of
the Moon's globe may hide a part of the Sun's from the
vision of certain observers who are situated about the point
o' of fig. 64. But suppose an observer is at O. For him.
there is no eclipse at all as could be seen from the figure,
As the observer moves away and away from O' towards O,
the effect of parallax will be greater and greater in longi-
tude, whereas, as the observer moves away and away from
O' towards O₁ (where O₁ is the geocentric pole of the circle