Humans have produced star maps, charts, drawings and other records of the unchanging night sky above us going back to ancient times. However, even the most talented artists were limited to what could be seen with their eyes.
Early pioneers of using the telescope for astronomy quickly discovered they needed to record and share their discoveries with others. What they were viewing through even these early instruments had not been seen before! Of course the Moon was often the first target they pointed the telescopes towards. We remember Galileo and not an earlier Lunar observer, Thomas Harriot, possibly as Galileo published his works and Harriot didn’t.
The Moon drawn by Galileo
Sketching what can be seen at the eyepiece remained with only way to record telescopic images until the advent of photography in the 19th century. It’s actually a technique still used by some amateur astronomers.
Inventors started to develop ways to record images in the early part of the 1800s. John William Draper is thought to have produced the first image of the Moon in 1840. (His son, Henry Draper, also photographed the first spectrum of a star in 1872 which showed absorption lines.)
The Moon by John William Draper 1840
Astronomers continued to make advances capturing the light from stars. The first images of the Sun were made around 1845.
The Sun by Hippolyte Fizeau & Léon Foucault
A major limiting factor for early astrophotographers was that photographic plates had to prepared by pouring chemicals over them just prior to use and then needed to go through another process to develop and “fix” the image. Hard to do in daylight and a difficult task in the dark at the telescope. The “dry plate” process allowed photographic plates could be prepared beforehand away from the telescope and then used when needed.
Using the new dry plate technique, Henry Draper photographed the first deep sky object, The Orion Nebula (M 42) using an 11 inch refractor in 1880
First photo of M42 by Henry Draper
Those of you who’ve seen M42 through a telescope will quickly realise that at this point astro photos weren’t capable of recording what a could be seen visually. That changed only a few years later 1883 when English astronomer, Andrew Ainslie Common, produced an image that was the result of years of experimentation. For the first time a long exposure photo of a deep-space object showed stars that were too faint to be seen at the eyepiece.
Long exposure image of M42 by Andrew Ainslie Common 1883
Paul Henry & Prosper Henry used a 33cm refractor at the Paris Observatory to capture the first photos of the gas giants, Jupiter and Saturn. Part of the issue capturing details on these planets during the long exposures needed with the photographic plates of the time was variations in the view caused by atmospheric conditions. The same bumpy journey through the air that causes the light from stars to twinkle often causes planets to “shimmy” when viewed or photographed through a telescope. We’ll cover more on how modern cameras and software helped solve this.
Jupiter and Saturn in 1886
Astronomers around this period were also starting to catalogue stars and their brightness using standardised equipment.
What was becoming clear towards the end of the 1800s is that cameras could capture more than the eye can see through a telescope and this opened up new areas of research and discovery. We’ll next cover some of the major telescopes built in the 20th century and how they changed our place in the Universe. We’ll go over also the move from film to digital imaging – and telescopes in space!