A group of astronomers at ESA’s ESTEC site in the Netherlands were testing some solar observing equipment on 6 September and serendipitously captured a solar flare, which turned out to be one of the Most Powerful observed in the last decade! The image here was taken with an iPhone (don’t try this at home! 😉 ) through a special interference H-alpha filter (centred at the wavelength of Hydrogen emission) mounted to a small dedicated solar telescope at 13:09:26 GMT. An X9.3 flare was observed on the Sun by space telescopes at 12:02 GMT, meaning that this image was taken as the flare was in the gradual decay phase. See http://www.esa.int/spaceinimages/Images/2017/09/Solar_flare_catch
