Wednesday, April 2, 2014

Fizeau, Foucault and Astronomical Photography

Star trail composite image created by International Space Station
Source: NASA
On April 2, 1845, Armand Hippolyte Louis Fizeau and Jean Bernard Léon Foucault manage to make the very first photography of the Sun. Thereby, they both initiate astronomical photography.

From a previous blog post you may remember Léon Foucault's Pendulum. The instrument was used to proof Earth's rotation in the 1850s and counts to one of Foucault's biggest scientific achievements. But let's start a little bit earlier. Leon Foucault was born on September 18, 1819 as the son of a publisher in Paris. After an education received chiefly at home, he studied medicine, which he abandoned in favour of physics due to a fear of blood.

Meanwhile, astronomical photography started to establish slowly. There were not many experts in the field back then, since the very long exposures needed to capture relatively faint astronomical objects and many technological problems had to be overcome. Completely new telescopes had to be developed that were rigid enough in order to not lose the focus during exposure time. Also the telescopes had to be attached to a rotating mount that would move at a constant rate very accurately. Next to the telescope building itself, the technology of photography needed improvement as well. The daguerreotype was just introduced in 1839 and came into a very widespread use. However, for astronomical photography, the process was too slow and was only able to record very bright objects. Also, the exposure time was very limited using this method due to the wet plate collodion process.

Louis Jacques Mandé Daguerre experimented in the field of astronomical photography for quite a while already. The daguerreotype process was invented by him and soon he attempted to photograph the moon. Unfortunately, he failed to guide the telescope accurately during the exposure, wherefore the outcome was only a "fuzzy spot". The first known successful photograph of the moon was taken by the New York University Professor John William Draper about one year later using a 5-inch reflecting telescope and managing a 20-minute-long exposure with the daguerreotype process.

Léon Foucault was highly influenced by Daguerre and his work in his early scientific years and he devoted much of his time to improve Daguerre's photography techniques. Hippolyte Fizeau was born in 1819 as well and astronomical photography counted to the scientist's earliest interests, too. Both managed to take the first known photograph of the Sun in 1845 using an improved daguerreotype process. The scientists finally proved that high quality astronomical photography was possible and only six years later the first Solar eclipse was successfully recorded by a daguerreotypist named Berkowski at the Königsberg Observatory. He was advised by it's director, Dr. August Ludwig Busch. Astronomical photography was officially 'born' and Vega soon became the first star captured with the daguerreotype process by astronomer William Cranch Bond and daguerreotype photographer and experimenter John Adams Whipple.

When dry plate photography was introduced in the 1870s, scientists finally managed to use astronomical photographs as professional research tools. The English astronomer Sir William Huggins and his wife Margaret Lindsay Huggins were back then the first known scientists to use dry plate photography in their work to record the spectra of astronomical objects. On this day, astronomical photography has evolved as a popular hobby among photographers and amateur astronomers next to its significant role as a research tool for professionals.

At yovisto, you may enjoy a video lecture by Mary Dussault and Joe DePasquale titled 'Understanding Astrophotograpy: Where Science and Art meet'.



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