very old equipment term

[Brian W]

Hi all, on Feb 11, 1806 Sir W. Herschel was observing M-42 with a '10 foot reflector and a double eyepiece'.

I am guessing that 10 foot refers to the diameter but the term 'double eyepiece' leaves me totally baffled!

Any ideas?
Brian

[gbeal]

Likely a two lens eyepiece, Al Nagler hadn't invented his trademark sample then, LOL.

[acropolite]

I expect 10 foot would be the focal length.



here are some descriptions (http://amazing-space.stsci.edu/resources/explorations/groundup/lesson/scopes/herschel/index.php)

[DavidU]

Probably not the Huygens as it was the 1800's but prob the Ramsden eyepiece.

[Brian W]

well so much for my guess what the ten foot referred to. I will look up the Ramsden ep.

Thanks,
Brian