The Caltech Videomagnetograph: A Report on its Design and Operation

Abstract

The present report describes the installation of the Caltech videomagnetograph at Big Bear Solar Observatory, and its initial operation during 1971-1972. When fed by a 10" refracting aperture and 1/8 Å λ5324 birefringent filter, the instrument produced an approximately 4x6 arc-minute field of view, within which high resolution (2-3 arc-second) cancellations could be electronically generated and displayed in real time on a video monitor. These cancellations reveal the structure of the photospheric velocities and magnetic fields in time lapse movies. The amount of data which can be created in this manner is impressive. Daily operation between January-September, 1972 produced some 3500' of magnetic movies and 1500' of Doppler footage (35 mm half-frame negatives), representing on the order of 700 and 200 hours of real time, respectively. In addition, a daily survey of active regions yielded an album of approximately 800 high-resolution H-alpha - magnetic pairs, showing the day-by-day development of more than 60 different solar activity centers. These data are described and catalogued. Principles of operation, details of construction, troubleshooting, and suggestions for future improvements are also discussed.