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02/21/2022 – Ephemeris – The time President Abraham Lincoln visited the US Naval Observatory

February 21, 2022 Comments off

This is Ephemeris for President’s Day, Monday, February 21st. Today the Sun will be up for 10 hours and 46 minutes, setting at 6:19, and it will rise tomorrow at 7:32. The Moon, 2 days before last quarter, will rise at 12:09 tomorrow morning.

In August 1863, during the height of the Civil War, President Abraham Lincoln and his secretary John Hay rode out to the Naval Observatory, where it was back then in Foggy Bottom. The astronomer there, Asaph Hall, showed them the Moon and the star Arcturus through the observatory’s telescope. A couple of nights later Lincoln came out alone to ask the astronomer some questions about what he saw, in including why the Moon was upside down in the observatory telescope while the telescope he used gave a right side up image.* Fourteen years later, Asaph Hall, still at the Naval Observatory, discovered the two satellites of Mars through the observatory’s then larger telescope.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.

Addendum

9.6 inch refractor

The 9.6 inch telescope through which Lincoln viewed the Moon and Arcturus on the night of August 22, 1863. From the Astronomy.com website.

Old Naval Observatory

The old Naval Observatory. From the Astronomy.com website.

* Most telescopes naturally create an upside down image. The spyglass type telescope President Lincoln was probably familiar with was a Galilean telescope that didn’t form an image within it. Telescopes like binoculars use prisms to erect the image. Astronomers don’t care if the image is upside down. Whatever is used to turn the image right side up reduces the amount of light that makes it through the telescope. For astronomers, the name of the game is to capture more light and increase the ability to see fine detail, which are both functions of the primary’s diameter. That’s why modern telescopes are measured by the diameter of their primary mirrors or lenses.