This coelostat is made at Nehru Planetarium, Mumbai. The basic model is very similar to the one made at IUCAA.
The polar axis is made differently. We are planning to add half RPD (rotation per day) motor to the axis. Also to change the altitude of the axis there is bolt pushing both the boards.
The second mirror is fixed to a retort stand.
By adjusting the second mirror one direct the solar light to the desired direction. In this case a small telescope.
The telescope is inserted through a large size card. This casts the shadow and creates better contrast if the solar image.
This telescope has a 45 degree mirror and the sun can be focused on the stable ground. This helps in making the drawing of the solar image and to mark sunspots.
Check these links – Scaling the Sun , solar limb darkening
DIYA 