The method of finding the Lagna (Ascendant).

The method of finding the Lagna (Ascendant) for the birth time. The sign of the Zodiac rising in the eastern horizon at the time of birth is the Ascendant or lagna, that is to say, the rising Sign at birth is the ascendant. At sunrise on each day, that sign named after the Hindu solar month (in which the day falls) will be rising in the eastern horizon. This is because during each month the Sun would be in the corresponding sign of the Zodiac. For example, during the solar month Maesha, the Sun occupies, (it apparently moves through) the sign Maesha (Aries). Thus, on the first day of Maesha, the Sun and the sign Maesha would rise together and the sign Moesha would be at the eastern horizon for about 1/12 of a day (2 hours) from Sunrise. On the second day of the Maesha month, Sun apparently would have moved I degree in the sign Maesha, so that the sign Maesha would be I degree up in the eastern horizon at Sunrise. Thus, the sign Maesha would be 4 minutes earlier than the Sun (since I degree corresponds to 4 minutes). Hence Maesha sign would be in the eastern horizon from 4 minutes before sunrise till 1 hr. 56 min. after sunrise. Hence on the second day the rising time for Maesha is Ihr. 56 min. after sunrise. Similarly on the 16th of Maesha, the Maesha Sign would be in the eastern horizon only. 4 min multiplied by 15 = 1 hr after Sunrise. Thus, the rising period or the rising of a month would gradually fall at the rate or 4 minutes per day and will reduce to zero after the 30th day that month. 30 x 4 min. = 2 hrs. This means that the Sun has crossed over to the next sign and the month also would have changed. The rising period on each day of the rising sign can thus be calculated, and it is called the udayaathpara, meaning balance of the sign after sunrise, rising period of that sign in that date. After fixing the time of rising of the rising sign, the next 2 hrs. will be the rising period of the next sign and so on, till the next sunrise. This is only an approximate method of calculation, because, due to the shape of the orbit and the difference between the latitudes of each place on the to place, depending on the latitude. The riing period of each sign, called raasimaana has to be for each place and these data are usually available in the conventional almanacs. These a usually in Ghatis and Vighatis, which can converted into hour-minute (1 Ghati=24 mins,  1 Vighati = 24 Seconds). Further the sunrise for each day also varies from place to place and from day to day. The time of sunrise for each day is given in almanacs.