The refractor was developed and designed in ISTP SB RAS according to the original optical scheme. An interference-polarization filter (manufactured by Bernhard Halle Nachfl. GmbH, Germany) installed in the telecentric ray path allows us to observe the Sun in the H-alpha spectral line at 656.3 nm. Having the half-width of 0.05 nm, the filter passband can be displaced within ± 0.1 nm.

The main parameters

In 1981-1999, 80-mm film was used to obtain images of the solar disc; there is a film archive. In 2000-2002, we used the Princeton Instruments CCD camera having 2048×2048 pixel array format. Image archive on FTP server. Since 2004, we have been using the 8-megapixel Konica Minolta DiMAGE A2 to observe separate active regions.

Images of the solar chromosphere in the H-alpha line

The most significant results:

• A flare is a loop system where glowing gas flows down the loop tip on each side. Subjacent loops start glowing at the beginning of the flare; then the disturbance is transmitted to higher loops, and the underlying ones stop glowing. So flare cores in loop bases seen in projection against the solar disc move away from the polarity boundary.
• Three days before a powerful flare, a long large-scale path forms in the active region. Activation of chromospheric fine structures along and nearby the path precedes the flare. The chromospheric structure activations mainly occur within 1 hour before the flare: we observe variation in intensity of dark nodes in the region of the flare ribbon formation as 3 - 4 minute pulsations, preflare appearance of dark vortex structures around regions of the flare ribbon formation, appearance of dark ribbon channels over large areas in flare regions before the flare commencement, and other phenomena.
• Existence of alternate turbulence (multifractal structure) in the chromosphere of active regions has been shown. We have revealed characteristic properties of time variations in scaling parameters of structure functions prior to flares, which provides a new method for their early detection.