Just after lunchtime on July 28th, 1851, Julius Berkowski took the first accurate image of a total solar eclipse. As we prepare to shoot the eclipse on Monday, let's take a look at history behind this unique astrophotography.
The photo was taken in the Koenigsberg Observatory, in what was then Prussia. Unfortunately, it was destroyed during WWII, but not before the Royal Prussian Observatory commissioned a daguerreotypist to capture the total eclipse in 1851. Berkowsky attached a refracting telescope (of 60mm in diameter, no idea on focal length) to a 15.8 centimeter Fraunhofer heliometer. I can only imagine that he didn’t split the image, as a heliometer would, in order to preserve the image as a whole.
From what I can tell, he shot with an effective f-stop of f/13.3 and exposed the shot for 84 seconds. Due to Daguerreotype being so insensitive to light, the long exposure was needed. I find it astonishing that the image is so clear for such a long exposure. Surely the moon would have moved enough to blur the edges? It appears as though the image being distributed online has been edited, brightening up the image just a bit.
To put that into perspective, the eclipse that we’ll be seeing on August 21st will be moving between a speed of 1,502mph and 2,955mph, with an average diameter of 70 miles. That’s about two minutes in some areas, adding an extra 30 seconds in others. Not a lot of time for wiggle room!