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03/25/2005 10:23:02 AM · #1 |
On today's Astonomy Picture of the Day is a photo of an old lens used by Christiaan Huygens many hundreds of years ago. It's focal length is "10 Rhineland feet".
Anyway - with it he discovered a moon of Saturn, most probably Titan. Next time I think I need one more lens or one more accessory to take a better photograph, maybe I'll remember this and try improve my techniques before buying new gear!
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03/25/2005 10:32:27 AM · #2 |
Keep in mind that the incredibly long focal lengths of early telescopes was because they had not yet learned how to make glass that minimized the chromatic distortions caused when light refracts through a lens. A pair of Civil War binoculars had lenses that were far superior to anything Huygens ever used.
BTW, his most powerful telescope at a focal length of 123 feet! See it here. |
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03/25/2005 11:11:56 AM · #3 |
| Those fellows were determined astronomers! The focal ratio of Huygens telescope was about f/720. The exit pupil from the eyepiece must have been difficult to find. I have an odd lens, 120 inch focal length with a 3 inch diameter. It is achromatic but I have never attempted to use it in a telescope. Thought I might make a camera obscura with this lens. |
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03/25/2005 11:57:13 AM · #4 |
Originally posted by joebok:
On today's Astonomy Picture of the Day is a photo of an old lens used by Christiaan Huygens many hundreds of years ago. It's focal length is "10 Rhineland feet".
Anyway - with it he discovered a moon of Saturn, most probably Titan. Next time I think I need one more lens or one more accessory to take a better photograph, maybe I'll remember this and try improve my techniques before buying new gear! |
Sorry. The site changes the picture.
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03/25/2005 11:59:47 AM · #5 |
Originally posted by nsbca7:
Sorry. The site changes the picture. |
Yes - but I linked directly to the 3/25/2005 page.
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03/25/2005 12:03:44 PM · #6 |
Originally posted by joebok:
Originally posted by nsbca7:
Sorry. The site changes the picture. |
Yes - but I linked directly to the 3/25/2005 page. |
My bad. My bad eyes. I just glanced and thought it was a drawing of a moon.
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