Fame

The telescope which is most closely associated with the Harvard College Observatory is the ‘Great Refractor’. This was the largest telescope in the world at that time (together with its ‘’twin’ at Pulkovo Observatory). It was this telescope which was used to carry out some of the earliest pioneering work in astrophotography. It was at this time that William Cranch Bond in collaboration with John Adams Whipple had begin to experiment with astrophotography, and the use of daguerreotypes to obtain images of celestial objects. On December the 18th 1849, William Bond and John Adams Whipple took their first image of the Moon using the Harvard College Observatory’s 15” (38cm) refractor with a 40 second exposure. However prior to 1850, nobody had ever successfully imaged a star or other Deep Space Object. On the 17th July 1850 William Cranch Bond and John Adams Whipple succeeded when they took a 100 second exposure of the bright star Vega in the constellation of Lyra using the ‘great’ refractor. However in the field of astrophotography, the Harvard College Observatory saw important pioneering work carried out by William Cranch Bond, his son George Phillips Bond and John Adams Whipple. It was at Harvard that the first successful photograph of a star was taken on the 17th July 1850. On March 22nd 1851, William Cranch Bond recorded in his notebook: “Succeeded in Daguerreotyping Jupiter. Six plates were taken by Whipple and could distinguish the two principal equatorial belts – Time about as long as the Moon required or not much longer”. On the 8th and 9th October 1857 Whipple photographed Jupiter using wet collodion plates, with similar results. This pre-dates the planetary images of the Henry Brothers (1885-6) by over 30 years. It was John Adams Whipple who may well have been the first person to successfully image a Planet, and not the Henry Brothers. Unfortunately his images of Jupiter have not survived and it is therefore not possible to verify the notebook entries made by William Cranch Bond.

Sponsor

The principal driving force behind the commissioning of the 15” ‘Great Refractor’ was William Cranch Bond (1789-1859), an amateur astronomer and renowned Boston Clockmaker. William Cranch Bond had been born on the 9th September 1789 at Falmouth (now Portland), Maine, United States. His family had originally emigrated from the Parish of St. Dominick, Cornwall, England in 1786 to live in Plymouth, Maine. He grew up to become one of the early pioneers of astrophotography and was the first Director of the Harvard College observatory (from 1839-1859). His father William Bond became a clockmaker after his lumber shipping had failed, and young William learned the trade from him, becoming himself an expert. He built his first clock – ship’s chronometer, when he was fifteen and eventually took over his father’s business. His mother Hannah Cranch was from a Devonshire family renowned for their artistic, literary and musical talents, and for a great love for learning. It was in an atmosphere of mechanical work coupled with the quest for knowledge that William Cranch Bond was raised, and which was to be a great catalyst for his future career. He became interested in Astronomy when he was seventeen years old, after he had witnessed the Solar Eclipse which took place in 1806. Afterwards he became an avid amateur astronomer, building in 1813, a transit instrument made of a strip of brass nailed to a wall with a hole in it! In 1811 he independently discovered a comet when he viewed it on April 21st, it had been discovered earlier in Europe on the 25h March. At that time William Bond had no telescope and he had an unusual way of adapting his eyes to the dark - " been in the practice of going to a deep well, and, shading his eyes from stray light, would direct his eyes toward the bottom for some minutes"!

Construction

The ‘Great Refractor’ at Harvard Observatory was a 15” German Refracting Telescope so called because when it was purchased it was equal in size to the largest in the world. It was constructed in 1847 by the Munich Firm of Mertz and Mahler, who in 1839 had built an identical telescope for the Pulkovo Observatory in Saint Petersburg, Russia. It arrived at the observatory on the 11th June 1847. The first observation with the Great Refractor was of the Moon on the afternoon of June 24, 1847. A number of significant achievements quickly followed. It is amusing to relate that prior to its arrival the telescope used by the observatory to first observe the newly discovered planet Neptune was a refractor with an object glass of 2.75” in diameter! Even great observatories have to start somewhere! The ‘great’ refractor was first used on the 24th June 1847 when it was pointed at the Moon. The telescope was put to good use when on the 19th September 1847, the eighth satellite of Saturn, later named Hyperion was discovered by William Cranch Bond, and his son George Phillips Bond who had first observed it two days earlier but was uncertain as to its true nature. The astronomer William Lassell had independently confirmed its discovery on the same night in England. In 1850, Saturn's crape, or inner, ring was first observed, again by the Bonds. That same year, the first daguerreotype ever made of a star, the bright Vega, was taken by John Adams Whipple working under William Cranch Bond, following several years of experiments using smaller telescopes. The earliest photograph of a double star, Mizar and Alcor in the handle of the Big Dipper, was achieved in 1857, using the wet-plate collodion process. The Great Refractor was active for nearly three-quarters of a century. During the first 30 years, the work was chiefly determination of stellar positions and the visual observation of planets, variable stars, comets, and nebulae. After the appointment in 1877 of the observatory's fourth director, Edward C. Pickering, the telescope was employed almost entirely for photometry. For the past 50 years, the Great Refractor has been used only for public Observatory Nights and an occasional student or special research project. It is now being restored to nearly its original form and, with renovation of the building, will stand as an outstanding example of 19th century scientific, engineering and architectural achievements.

Specification

The 15-inch-diameter lens for the Great Refractor was ordered that year from Mertz and Mahler of Munich; it was to be a twin of the one completed in 1839 for Pulkovo Observatory in Russia. Land was purchased at the present Observatory Hill site on Garden Street, to which equipment from Dana House was moved in 1844, while construction proceeded on the Sears Tower to house the refractor, a residence, and various other buildings. The Sears Tower surrounds a granite pier that rises 43 feet to the observing floor from its 22-foot-diameter base 26 feet below ground. The pier, in turn, is topped by an 11-foot-high, 11-ton granite block that carries the telescope mount. Originally, doors on three sides of the dome led to small iron balconies on which portable telescopes could be set up. Only the north balcony remains and probably is original. The 30-foot dome, weighing approximately 14 tons, is of frame construction, reputedly built by a whaling shipwright and is sheathed in copper. The eight 8-inch iron spheres, which served as bearings on which the dome turned, were replaced in the early 1940's by a more modern support system. One of the "cannon balls," flattened from wear, is on exhibit in the dome; the rest were donated for scrap metal during World War II. The wooden tube, veneered with mahogany, is some 20 feet long, tapering from about 16 inches at the objective (upper) end to l2 inches at the eyepiece. The unique observing chair rolled around the telescope on circular tracks, and could be raised or lowered to put the observer into position at the telescope eyepiece.