The Shastamsa (that’s 1/60th part of a sign , or half a degree each = 0.5 x60=30 degrees).That is the 60th divisional chart(D-60).
To calculate the Shastamsa Lord ignore the sign position of a planet and take the degrees etc. it has traversed in that sign . Multiply that figure by 2 and divide the degrees by 12. Add 1 to the remainder, which will indicate the sign , in which the shastiamsa falls. The Lord of that sign is the planet that rules, that’s 60th harmonic.

For odd signs the names of Shastamsa divisions:

1. Ghora
2. Rakshasa
3. Deva
4. Kuber
5. Yaksh
6. Kindar
7. Bhrasht
8. Kulaghna
9. Garal
10. Vahni
11. Maya
12. Purishak
13. Apampathi
14. Marutwan
15. Kaal
16. Sarpa
17. Amrit
18. Indu
19. Mridu
20. Komal
21. Heramba
22. Brahma
23. Vishnu
24. Maheshwara
25. Deva
26. Ardr
27. Kalinas
28. Kshitees
29. Kamalakar
30. Gulik
31. Mrityu
32. Kaal
33. Davagni
34. Ghora
35. Yama
36 Kantak
37. Suddh
38. Amrit
39. PurnaCandr
40. Vishadagdha
41. Kulanas
42. Vamshakshaya
43. Utpat
44. Kaal
45. Saumya
46. Komal
47. Sheetal
48.
Karaladamshtr
49. Candramukhi
50. Praveen
51. Kaalpavak
52. Dhannayudh
53. Nirmal
54. Saumya
55. Krur
56. Atisheetal
57. Amrit
58. Payodhi
59. Brahman
60. CandraRekha (InduRekha).

The reverse is the order for even signs (starting from ChandraRekha,Brahman etc).