File talk:NewtonsTelescopeReplica.jpg

6 inch aperture or focal length?

The original text with the picture stated:

At 6 inches in diameter, it was also one of the largest telescope of its day.

To which another user responded:

Don't be fooled: Newton's original Telescope and its faithful replicas may be 6 inches long or tall, but the diameter of the mirror is more like 1 or 1.5 inches. -- en:User:BjKa 14:23, 12 September 2007 (UTC)

I found a reliable source[1] which states that it is 6 inches long. By scale it appears the aperture is about 1 - 1½" (25 - 40mm). I modified the text with reference.

The confusion seems to be related to how telescopes used to be routinely described:

"It was the custom in those days [circa 1777, and presumably earlier] to refer to telescopes by their focal length rather than aperture, as we do today." (Richard Baum. The Haunted Observatory: Curiosities from the Astronomer's Cabinet. Prometheus Books: Amherst, New York, 2007. p. 139. ISBN 978-1-59102-512-2)

— Eoghanacht ^talk 13:47, 9 January 2008 (UTC)

Modified description some more to add ref'ed description and to point out that this is a replica of Newton's second telescope. 75.196.227.115 15:37, 11 March 2009 (UTC)