The Sun in the H-Alpha Band

©ESA/Michael Khan

Sun in the H-Alpha Band.

This picture of the Sun was taken on 14 August 2013 at 09:00 CEST from the premises of ESOC, Darmstadt.

The image was taken using a H-Alpha filter (a narrow band filter that lets through only those wavelengths that are very close to 656.28 nanometers, the Alpha emission band of hydrogen, an element that is abundant in the Sun. The H-Alpha wavelength happens to be in the red part of the visible spectrum, which is why the Sun appears very red in this image. This is something different from the red Sun we see at sunrise and sunset.

The image is a composite of two images taken within a short period of each other, one with a longer exposure time, so the fainter prominences in the corona become visible, the other with a shorter exposure time to render the surface detail visible. These two images were then super-imposed to obtain the composite you see.

The telescope used is a Coronado PST, an amateur telescope with a H-Alpha filter that allows observations of the Sun (and nothing else). The camera is a Canon EOS 1000D digital single lens reflex camera.

On the surface several extended sunspot regions are visible. Also visible are prominences (also called protuberances) around the visible rim and filaments on the surface, which are prominences seen from above. They appear like extended darker strings against the bright background.

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