Tag Archives: eclipse

Chromospheric lines

“These are some of the problems in connection with the sun which are being investigated at the present time. Their complete solution will help to interpret the mystery, not only of the sun itself, but also of that type of stars of which the sun is a representative.”

―Frederick Slocum, The Study of Solar Prominences. Popular Astronomy, July 12, 1912.

Frederick Slocum (Brown University undergraduate class of 1895) received the first Ph.D. in astronomy at Brown in 1898 and served as assistant professor of astronomy from 1899 to 1909. He then became professor of astronomy at Wesleyan University in 1914 where he planned and supervised the construction of Van Vleck Observatory. The image below shows Slocum observing with a spectroscope attached to the main telescope at Ladd Observatory.

observing with a spectroscope
Observer Frederick Slocum using a spectroscope on the 12″ refractor at Ladd Observatory. March 15, 1905.

This spectroscope was made by the scientific instrument maker John Brashear of Pittsburgh in 1891. It is used to study the spectrum of colors in starlight. It could also be mounted on a table top to examine the spectrum of a chemical which is done to calibrate the instrument. During this era professor Winslow Upton used it in an attempt to predict rain.  It uses a prism or diffraction grating to disperse the light into a rainbow pattern of colors. This reveals dark Fraunhofer lines in the spectrum that can be used to identify the chemical elements present in the Sun or a distant star. Each chemical element has a unique pattern of these dark lines where specific colors are missing.

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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.

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