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

439 parallax in latitude, so that it is a variable. We are to make a correction for this variability, both in the com- putation of Sthiti-khanda, Bhuja and Iṣṭa-kāla. The formula for the Sthiti-khanda is √(R+r)² - β² / (m₁ - s₁) where β is the latitude of the Moon at the moment of conjunction. The value of MN at the moment of conjunction will not be equal to its value at any intermediate point because parallax in latitude differs from position to position of the Moon. In other words β is variable. The formulae given for the rectification of the Bhuja B or the Iṣṭakāla I are B' = (B × T') / T and I' = T' - √(R+r - g)² - β² / (m₁ - s₁) × T / T' where T' is the Sthiti-khanda rectified for the variability of β, B' is the Bhuja rectified for the same whereas T and B are the values of the Sthiti-khanda and Bhuja computed taking the effect of parallax in longitude above. The effect of parallax in longitude is to prepone or postpone the moment of first contact as well as that of conjunction. The verse under commentary uses two terms Sphuta-Sthiti-khanda and Sphuteshuja-Sthiti-khanda. The former is the Sthiti-khanda rectified for parallax in longitude whereas the latter is that rectified for parallax in latitude ie. by adopting β' instead of β in the formula √(R+r² - β²) / (m₁ - s₁) where β' = β ± effect of parallax in latitude. Suppose on account of parallax in longitude the moment of first contact t₁ becomes t₁ + δt₁, and let the moment of conjunction t₂ become t₂ + δt₂. Then the Sthitikhanda unrectified for parallax in longitude will be (t₂ - t₁) whereas that rectified for parallax will be (t₂ - t₁)

• (δt₂ - δt₁). This rectified Sthitikhanda is called Sphuta-Sthiti-khanda. Now the verse under commentary gives a procedure to rectify the Bhuja, and Iṣṭakāla in the