The following adjustments must be made before doing the experiment with spectrometer:
(i) Adjustment of the eyepiece
The telescope is turned towards an illuminated surface and the eyepiece is moved to and fro until the cross wires are clearly seen.
(ii) Adjustment of the telescope
The telescope is adjusted to receive parallel rays by turning it towards a distant object and adjusting the distance between the objective lens and the eyepiece to get a clear image on the cross wire.
(iii) Adjustment of the collimator
The telescope is brought along the axial line with the collimator. The slit of the collimator is illuminated by a source of light. The distance between the slit and the lens of the collimator is adjusted until a clear image of the slit is seen at the cross wires of the telescope. Since the telescope is already adjusted for parallel rays. a well-defined image of the slit can be formed, only when the light rays emerging from the collimator are parallel.
(iv) Levelling the prism table
The prism table is adjusted or levelled to be in a horizontal position by means of levelling screws and a spirit level.