Permanent adjustment of vertical Circle Index of transit |
The object of this adjustment is to set the vertical circle to zero when the line of sight is horizontal and the altitude bubble is centered. Test : Set an instrument in face left condition and get it temporary adjusted. Center the altitude bubble and read the vertical vernier. Now, change the instrument in face right condition and the vertical vernier after centering the altitude bubble. If the 0 of the vernier scale coincides with the 0 or 90 of the main scale , there is no vernier index error in the instrument. Adjustment : If the vernier does not read zero, loosen it and move it until it reads zero. Care should be so taken that the vernier does not bind on the vertical circle as the telescope is rotated about the horizontal axis. |