Photograph showing the interior of one of the domes of the Palermo Observatory, Sicily in 1876. This building houses an equatorially mounted refracting telescope of 25 cm aperture made by the German maker Merz of Munich around 1860. The telescope was first used by Pietro Tacchini (1838-1905) to observe and record sunspots. Later the telescope was used with a spectroscope to observe solar prominences, red protrusions, normally only visible at solar eclipses. These can be viewed with a spectroscope if its slit is placed tangential to the Sun and opened slightly. Later in 1879, Tacchini left the Palermo observatory to take a post at the Collegio Romano observatory in Rome.
© Science Museum / Science & Society Picture Library