Measurement of Astronomical Seeing Using Long Exposure Solar Images

We extend our modified parameter search method (Sridharan, Dashora, and Venkatakrishnan, Solar Phys. 222 , 35, 2004 ) of estimating the Fried parameter ( r_0 ) from long exposure images to the images obtained from the H α -telescope installed at Merak, a cold desert on the Himalayas, with a modified criterion – the contrast ratio of the observed and the deconvolved images – to identify the true r_0 . We validated our new method by applying it to the solar granulation data and found that it is as accurate as our modified parameter search method. The median seeing at H α – estimated from the data spanning over 5 months – is ≈ 2 arc-sec and it corresponds to a median r_0 of 6 cm. About 30