5 Summary

A video magnetograph using a voltage tunable LiNbO₃ Fabry-Perot etalon has been designed and constructed and is operational at Udaipur Solar Observatory. The instrument is used in f/40 beam of the telescope with an objective aperture of 15 cm and an imaging relay lens in telecentric mode. The comparison of USO magnetograms with SOHO/MDI data shows the consistency of our measurements. The preliminary data show the capability of the instrument to take high spatial and temporal resolution observations which can be used to undertake study of various problems related to the magnetic field and flare productivity in active regions. This instrument is the first such facility in the Indian longitudes and fills an important gap for continuous coverage of observations of solar active regions.

Acknowledgements

Our thanks are due to Prof. F. Kneer for his valuable comments. The financial support for the present work comes from the Department of Space (DOS), Government of India and Indo-US scientific collaboration (NSF Grant INT - 9710279). The SOHO/MDI magnetogram used for the comparison is kindly provided by SOI-MDI group. The high voltage switchable power supply for KD^*P modulator was designed and fabricated at the Space Application Center (SAC), Ahmedabad, for which we acknowledge the contribution of Dr. S.S. Rana, Mr. R.K. Arora and his group members. Dr. D. Balasubramaniam and Dr. Vyas from SAC are acknowledged for their help in optical coating. The mechanical components were fabricated by Mr. B.L. Paneri of USO.