### Vedic Astrology: How to calculate Sunrise and Sunset

In this post we are going to cover the calculation of sunrise and sunset. Sunrise takes place when the sun appears on the eastern horizon. The time for sunrise varies according to the location. For instance, the time for sunrise at a place located at 15 deg. North and 90 deg. East will be different from a place located at 45 deg. north and 90 deg. East.
The formula for sunrise is:
1.      tan (sun's declination) * tan( latitudes of place ) let us call this as X
2.      Now find the sin inverse of X. The product is in degrees minutes.
If the sun is in Uttarayana and the location is in northern hemisphere then. The product calculated above should be added in 90 deg. If however the birth is in Dakshinayana and the location is in northern hemisphere then the above product should be deducted from 90.
The reverse holds true when the birth is in southern hemisphere.
The product derived from above calculation should be multiplied by 4 minutes and should be deducted from 12 Noon for sunrise and added to 12 Noon for sunset.
Example:
Let us calculate sunrise and sunset on 1st July 2001 at Hong Kong and Pune.
Sun's declination as on 1st july 2001 is 23 deg. 8 min.
tan (23 deg 8 m) = 0.42724
Latitudes of Pune are 18N32 and latitudes of Hong Kong are 22N20.
tan (18 deg 32 m) = 0.33525
tan (22 deg 20 m) = 0.41081

tan(23 deg 8 m) * tan(18 deg 32m ) = 0.14323
tan(23 deg 8 m) * tan(22 deg 20m ) = 0.17551

sin inverse (0.14323) = 8 deg 15 m
sin inverse (0.17551) = 10 deg 6 m

Since both the locations are in northern hemisphere and the sun in Uttarayana both should be added to 90. Thus the above products for Pune and Hong Kong are 98 deg 15 m and 100 deg 6 m respectively.
After multiplying the above numbers by 4 (4 * 98 deg 15 m) and (100 deg 6 m * 4) we get 6 hours 33 minutes and 6 hours 40 minutes for Pune and Hong Kong respectively.
Thus the sunrise for Pune is 5 hours 27 Minutes ( LMT ) and sunset is at 17 hours 27 minutes (LMT)

Thus the sunrise for Hong Kong is 5 hours 19 Minutes ( LMT ) and sunset is at 17 hours 19 minutes (LMT)