Saturnian Challenges

I recently perused a copy of the fifth edition of Le Ciel by French science writer and journalist Amédée Guillemin. Published in 1877, this profusely illustrated tome contains a beautiful lithograph depicting Saturn based on observations by Otto Wilhelm von Struve (1819-1905) in the autumn of 1851 at the Pulkovo Observatory on the outskirts of St. Petersburg.

The most striking detail of the print is a well-defined division in the faint, tenuous C ring. Struve detected this feature three-quarters of the distance from the ring’s inner edge to its outer border in 1852.