Question

How much angle accuracy is possible with a goniometer fitted with two 32400 lines radial grating?

(a) 0.1 second of arc

(b) 1 second of arc

(c) 2 second of arc

(d) 0.5 second of arc

This question was posed to me in a national level competition.

My doubt is from Optical Instruments for Angular Measurement in chapter Angular Measurement and Circular Division of Engineering Metrology

Answer 1

Correct option is (a) 0.1 second of arc

To explain I would say: Advantage of goniometer is that grating errors are entirely averaged to zero during the time of measurement thus giving the inherent accuracy. With a goniometer which is fitted with two 32400 lines radial gratings, it is possible to obtain angle measurements to an accuracy of 0.1 second of arc.