“In addition to helping the crew organize its time, the second HP-41 computer was kept ready for flight-critical, deorbit-burn calculations. Once during each orbit around the Earth, the shuttle has an opportunity to land at one of six contingency locations. During a routine flight, Mission Control supplies the shuttle crew with deorbit-burn information. Should the shuttle encounter an emergency, however, the astronauts would rely on the HP-41 for these calculations.”
– “HP-41’s Again Aboard Columbia.” HP Key Notes, March-May 1982.
To prepare an orbiting Space Shuttle for re-entry through the Earth’s atmosphere it is critical that the spacecraft be “balanced” by taking into account the mass of the fuel left in the tanks at the end of a mission. An astronaut would use a handheld computer or programmable calculator to determine how many minutes and seconds of fuel to burn to get the center of gravity correct for a smooth descent and landing. The “personal computing system” used for this was made by Hewlett Packard in the 1980s. NASA donated one of these, a model HP-41CV, to Ladd Observatory after the retirement of the Shuttle program. Continue reading Flight-critical calculator→
“In Philadelphia I dragged out a colorless and an unhappy existence till September, 1904, when to my delight I was ordered back to New England, and this time nearer the centre of civilization. (Of course by that I mean Boston, which is the “hub of the universe” the “Athens of America”, the “Centre of Culture”, and last but not least, the home of the humble baked bean and the sacred codfish). I was sent to Providence, R. I., and have remained here ever since and hope to continue my residence here. By a happy combination of circumstances I have lived in the classic halls of Brown University ever since my arrival in Providence. The location and environment are eminently satisfactory.”
“This is truly scientific magic. Just think of it! You want to know the true time to the fraction of a second, and all you have to do in order to get it is to open your electric ear to these sounds, which seem to drop out of the sky, as if Old Time himself were speaking to you!”
During 1913 the Washington Naval Observatory and the Observatoire de Paris attempted to exchange wireless time signals. The experiment was used to calculate the difference in longitude between the two locations more accurately than was possible with other techniques. They were also trying to measure the velocity of radio waves through space. The goal was to improve communication with ships at sea which used the time signals to calibrate the chronometers used for celestial navigation. For most of the year atmospheric conditions prevented the reception of the signals sent across the ocean. The conditions improved in November and the two observatories were then in regular contact by radio. Prof. Winslow Upton of Ladd Observatory was listening in on the transmissions.
When news of Léon Foucault’s demonstration of the Earth’s rotation reached the United States in 1851 there was great interest in repeating the experiment in Providence. Two members of the Brown faculty arranged for a public demonstration in the Providence railroad depot. Alexis Caswell was a professor of natural philosophy, mathematics, and astronomy. William A. Norton was professor of civil engineering and natural philosophy. The pendulum bob weighed a little less than 40 pounds and was suspended from the end of a wire 97 feet long. The report on this experiment was published in the Proceedings of the AAAS along with an account of the Harvard demonstration in the stairwell of Bunker-Hill Monument. Continue reading “The pendulum of eternity”→
The site chosen for Ladd Observatory was at the top of the highest hill in the city of Providence. The hill lost that distinction in 1919.
The borders of Providence have changed a number of times. The settlement of Silver Lake was originally part of Providence, but the residents decided that this agricultural community had more in common with rural Johnston and choose to secede in 1759.
Prof. Winslow Upton tapped a telegraph key as he watched the planet Mercury transit the Sun. The signal was sent to a chart recorder where an electromagnet moved a pen on a slowing turning drum of paper to record the observation. The instrument is called a chronograph. This one was made by the Warner and Swasey Company of Cleveland in 1890. Primarily it was used for calibrating the astronomical regulators (precision pendulum clocks) to set the time accurately. It was also used for timing events such as lunar occultations of stars. Continue reading Timing the transit of Mercury, 1907→
The Leonid meteor shower was approaching and as the astronomers prepared cameras to capture the event they must have wondered: will the skies be clear tonight?
Prof. Winslow Upton taught astronomy at Brown from 1883 until his death in 1914. He also had a keen interest in meteorology. He had been a professor of meteorology at the Weather Bureau of the U.S. Signal Survice from 1881 until 1883. In 1884 he was one of the organizers of the New England Meteorological Society and operated a weather station at Ladd Observatory starting in 1890. We can gain some insight into how he might have forecast the cloudiness of the sky by noting a curious instrument to the left of the cameras in the photo above. Continue reading Observing the “rain-bands”→
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.
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→
During the Blizzard of Feb. 8-9, 2013 there were reports of thunder and lightning amidst the heavy snowfall and high winds. The lightning detector on the roof of Ladd Observatory recorded a great deal of activity late Friday night into Saturday morning with the peak occurring just before midnight. Most of the strikes were along the southern coast of Rhode Island, but some were observed about 350 miles to the south over the ocean. For more information about thunder snowstorms see Scientific American.
The Geminid meteor shower peaked on Dec. 13 – 14, 2012. At Ladd Observatory we operate an automated camera on the roof which takes an image of most of the sky every 10 seconds. There were many small meteors and a number of medium meteors that we captured during the night. Here are the four best images. Each is a 10 second exposure with a field of view of about 140 by 90 degrees. North is at right and west is at bottom.