An astronomical oddity, from the Sidereal Messenger, June 1890:

On the evening of April 25th, 1889, at about 8:30 p.m., I was examining Saturn with a power of about 180 on a 4 1/8-inch achromatic by Brashear, when, much to my surprise, I found the shadow of the globe on the rings curved the wrong way, i.e. from the globe, as shown in the following drawing. Thinking my eyes might be deceiving me I called my wife, and without telling her what I had seen, requested her to describe the shape of the shadow. She described the shadow as having its right hand edge curved away from the planet.

I wrote to Professor Comstock of the Washburn Observatory about it, and was informed by him that while my observation of Saturn was unusual, it was far from being unprecedented; that the same appearance was observed in 1875 with the 26-inch achromatic at Washington, and that Webb, in ‘Celestial Objects for Common Telescopes,’ says: ‘The outline of this shadow has often been found curved the wrong way for its perspective.’ Professor Comstock also adds, ‘I do not know that any satisfactory explanation for this anomaly has ever been given.’

William Corliss notes a flurry of similar observations between 1886 and 1914. I think this must have been explained by now, but I haven’t been able to find a source.

(Jenks, Aldro; “On the Reversed Curvature of the Shadow on Saturn’s Rings,” Sidereal Messenger, 9:255, 1890.)