Andhra wedding muhūrta: of the present day are to the minute. The jeelakarra bellam ritual must take place exactly then.
However, in vēdānga jyotişam, ie., astronomy applicable to vēdā: , the muhurta duration is 48 minutes long.
How do we arrive at this?
The moon-sun separation of 360 degrees is divided into 30 tithis each of which, represents, on average, 12 degrees.
From new moon 0 deg seperation to full moon, 180 degree separation, we have 15 tithis.
Every day, the moon rises later by an amount of time equivalent to a 12 degree separation.
(24 * 60) minutes/ 360 degrees * 12 degrees gives us 48 minutes.
Every day, the moon rises 48 minutes later than the previous day.
And this is the duration of a muhūrta: .
Therefore there are 30 muhūrtā: in a day. We can expect the names to have changed over time and geography and to have acquired different luck-significance.
Muhurta names are from : http://www.veda.harekrsna.cz/encyclopedia/astrotables.htm