Transit of Mercury, by Kevin Reardon (Arcetri Observatory), Imaged with the IBIS instrument mounted at the Dunn Solar Telescope of the Sacramento Peak Observatory, National Solar Observatory / NSF – in CaII

Published October 18, 2015 at 800 × 470 in Transit of Mercury

Transit of Mercury, by Kevin Reardon (Arcetri Observatory), Imaged with the IBIS instrument mounted at the Dunn Solar Telescope of the Sacramento Peak Observatory, National Solar Observatory / NSF – in CaII