4 Example of observations

The USO video magnetograph is being used for near-simultaneous observations of longitudinal magnetic field, photospheric, and H$\alpha$ chromospheric activity. Figure 7 shows an example of a typical video magnetogram and the corresponding image in the blue wing of CaI 6122 Å line. During the best seeing conditions, the fine magnetic features of about 2 - 4 arcsec could be observed. The minimum detectable field was found to be 15 Gauss as obtained from the background noise level. Figure 8 shows an example of video magnetogram, CaI 6122 Å and H$\alpha$ images of active region NOAA 7843 obtained on 19 and 20 February 1995 in a single cycle of operation.