Tag Archives: Moon

“An Astronomical Blunder”

“An Astronomical Blunder. — Professor Waltemath of Hamburg recently announced through a private circular that he had discovered a second moon to our earth. The contents of the circular were the basis of sensational articles in leading newspapers… He also quotes descriptions of strange objects in the sky seen at various times since the sixteenth century, which his calculations show were probably this second moon.”

The Cyclopedic Review of Current History, 1898

Georg Waltemath
“Dr. George [sic] Waltemath. The German astronomer, who says he has discovered a second moon circling around the earth.” – Chicago Daily Tribune, March 22, 1898.
Georg Waltemath made an extraordinary claim: that the Earth had a second moon. It was supposed that it was much smaller and dimmer than the known moon. He calculated that this object orbited the Earth every 119 days and would pass between the Earth and Sun, on average, every 177 days. He predicted that on February 3rd of 1898 it would be visible in silhouette as it moved across the disk of the Sun, an event known as an astronomical transit.

Winslow Upton was skeptical of the existence of this long unnoticed moon, but nonetheless attempted to observe it. Continue reading “An Astronomical Blunder”

The dark side of the Moon

Automated instruments on the roof of Ladd Observatory monitored the sky during the total lunar eclipse of Sept. 27-28, 2015. First there is a wide field sky camera. It has a fish-eye lens which can capture an image of most of the sky above Providence. The second is a sky brightness meter which is used to monitor light pollution.

Eclipse sky
An image from the sky camera during the total phase of the eclipse. (Click on the image to see a time lapse video.)

The full Moon is usually so bright that it overwhelms the sensitive camera causing the images to be overexposed. During the eclipse the Moon was dark enough that the only artifact in the image above is a thin vertical line where one column of the digital camera was saturated by the moonlight. The camera is more sensitive than the human eye allowing the Milky Way to be seen during the total phase of the eclipse. The time lapse video contains 3,625 still images. Each second of the movie shows about 5 minutes of changes in the sky. Continue reading The dark side of the Moon