From our “Plan of the Week”
————
August 12 & 17 1877 – Asaph Hall discovers the moons of Mars. From Halls’ notebooks: I repeated the examination in the early part of the night of [August] 11th, and again found nothing, but trying again some hours later I found a faint object on the following side and a little north of the planet. I had barely time to secure an observation of its position when fog from the River stopped the work. This was at half past two o’clock on the night of the 11th. Cloudy weather intervened for several days.

On 15 August the weather looking more promising, I slept at the Observatory. The sky cleared off with a thunderstorm at 11 o’clock and the search was resumed. The atmosphere however was in a very bad condition and Mars was so blazing and unsteady that nothing could be seen of the object, which we now know was at that time so near the planet as to be invisible.

On August 16 the object was found again on the following side of the planet, and the observations of that night showed that it was moving with the planet, and if a satellite, was near one of its elongations.

Until this time I had said nothing to anyone at the Observatory of my search for a satellite of Mars, but on leaving the observatory after these observations of the 16th, at about three o’clock in the morning, I told my assistant, George Anderson, to whom I had shown the object, that I thought I had discovered a satellite of Mars. I told him also to keep quiet as I did not wish anything said until the matter was beyond doubt.

He said nothing, but the thing was too good to keep and I let it out myself. On 17 August between one and two o’clock, while I was reducing my observations, Professor Newcomb came into my room to eat his lunch and I showed him my measures of the faint object near Mars which proved that it was moving with the planet. On August 17 while waiting and watching for the outer moon, the inner one was discovered. The observations of the 17th and 18th put beyond doubt the character of these objects and the discovery was publicly announced by Admiral Rodgers.
————

This was from a time when the Observatory was located at Foggy Bottom — it was about 16 years later that it was moved to its current location. But the same telescope is still in use.

(And it’s probably a good thing Hall didn’t discover the moons as a university professor, because then the Astronomy building named after him would be Asaph Hall Hall)