Unlike the western division of the Zodiac great
circle into 360º composed of twelve signs of 30º each, the Tibetan
measurement of the astronomical circle relies upon a division of the great
circle into 1620 Gyukar chu ser (Tib.rgyu skar chu tsod) composed of 27
GyuKar (Skt. Naksatra ; Tib: rGyu sKar) or constellations each containing
60 rgyu skar chu tsod. Each of the Gyukar contains 4 feet (Skt. pada;
Tib. rkang pa) and so as in the table below.

each chu tsod is divided into 60

WESTERN = TIBETAN

360º
= 1620 Gyukar chu tsod

1º
= 4.5 º = 4º30"

TIBETAN

each sign (30º) has 9 rknag pa 135 chu tsod 8100 chu srang amd so on

ghatika

dal rkang =

0 (rkang sdom)

6 (yang gyur chu tsod)

53 (yang gyur srang)

2 (dbugs)

80 (cha shas)

*

each dbugs is divided into chas shas and has a different division according to the planet concerned in any particular calculation. These are caled cha shas of the planet and are very important in calculation.

There are very interesting reasons for these divisions which relate to the Kalacakra Tantra and the Mandalas. More on this to be added.