A Visit to the US Naval Observatory, continued
What did we see? Jupiter, natch! It looked wonderful in the low power eyepiece that delivered a field of view that just captured the four Galilean moons. After everyone had that view, the eyepiece was switched to a higher power, the field of view reduced to about 0.1 degree (estimated using Stellarium.) In this view, Callisto was beyond the field to the East, Ganymede was barely in to the West.
Because some cloudy weather had just moved off, the seeing wasn’t great. Jupiter actually looked better at low power. Of course a superb refractor isn’t put to its best use looking at planets in poor seeing, but it was a treat all the same.
Leaving the observatory, we were brought to the main building. There, Geoff explained the use of transit telescopes in the 19th century to set the local time.
Last stop was the astronomy library, a handsome formal circular room in the main building. Geoff showed us some of its treasures – first and second editions of books by Copernicus, Galileo, Huygens, Newton and others.
The library was originally designed by Richard Morris Hunt, who also designed the Metropolitan Museum of Art in New York. Geoff is shown in the photo toward the end of our visit.
So, what did Geoff do after the tour? He went home and made this picture himself – it was the one posted as of the time of writing on the USNO’s site, Sky This Week. Some people just can’t get enough of Jupiter.