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Posts Made By: Alan French

December 6, 2011 12:21 AM Forum: Refractors

3-3/8" f/3 Achromats: Origin and Use?

Posted By Alan French
I have a pair of 3-3/8" achromats of 9" focal length. Mounted, they'd probably be 3" f/3 lenses.

They were acquired long ago with some other optics, and I have no clue as to either their origin or original purpose. Anyone have any thoughts what they'd be useful for? They seem a bit short even for big binoculars.

Also, any thought of what they could be used for. A 25mm eyepiece would yield about 9x, a 5 degree field (if 50 AFVOV), but an overly large exit pupil. I'm guessing an f/3 achromat is not going to do well with a wide field eyepiece.

They are interesting. The edge thickness of the flint is the majority of the thickness of the pair, and that of the crown is very small.

Clear skies, Alan

March 30, 2012 06:19 PM Forum: Solar System Observing

Venus by Eye in the Daytime Sky

Posted By Alan French
The Moon provided a nice guidepost to spotting Venus by eye on March 26, and I've been following Venus every clear day since. It is still fairly easy to spot by eye alone. A planetarium program will show its position relative to the Sun and first quarter Moon (today). Sitting in the shade to the east of a building helps.

Clear skies, Alan

April 18, 2012 12:32 PM Forum: Refractors

Chester Brandon and Earl Witherspoon

Posted By Alan French
Hi Folks,

Chester Brandon advertised 3, 4, and 6-inch f/15 achromats in 1947 (as Brandon Scientific Development) and 3 and 4-inch objectives in and around the mid-1950s (as Brandon Instruments).

A gentleman named Earl Witherspoon advertised f/15 achromats in the Sky and Telescope classifieds for along time, in the 1950s, and, I believe, early 1960s.

I've seen one telescope with a Witherspoon objective, but have never seen a Brandon.

Does anyone own any of these objectives, used one, or seen one in the field?

Thanks, and clear skies, Alan

April 18, 2012 12:32 PM Forum: Refractors

Chester Brandon and Earl Witherspoon

Posted By Alan French
Hi Folks,

Chester Brandon advertised 3, 4, and 6-inch f/15 achromats in 1947 (as Brandon Scientific Development) and 3 and 4-inch objectives in and around the mid-1950s (as Brandon Instruments).

A gentleman named Earl Witherspoon advertised f/15 achromats in the Sky and Telescope classifieds for along time, in the 1950s, and, I believe, early 1960s.

I've seen one telescope with a Witherspoon objective, but have never seen a Brandon.

Does anyone own any of these objectives, used one, or seen one in the field?

Thanks, and clear skies, Alan

May 8, 2012 12:18 AM Forum: Global Warming - REAL or NOT

Little Wolf Lake

Posted By Alan French
http://www.boston.com/news/local/new_hampshire/articles/2012/05/05/ny_lakes_freezing_and_thawing_shows_warming_trend/

May 10, 2012 03:10 PM Forum: Solar System Observing

Naked Eye Sunspot

Posted By Alan French
Sunspot 1476 is easily visible by eye alone through a shade #14 welder's glass. So if you have a shade #14 welder's glass, or proper solar filter, check it out.

While spots are more detailed through a properly filtered solar telescope, it's always fun to see them without optical aid.

Clear skies, Alan

August 21, 2012 12:17 PM Forum: Global Warming - REAL or NOT

Arctic Ice Expected to Hit New Low

Posted By Alan French
http://www.bbc.co.uk/news/science-environment-19330307

August 26, 2012 06:34 PM Forum: Global Warming - REAL or NOT

The Conversion of a Skeptic

Posted By Alan French
http://www.gocomics.com/bc/2012/08/26

September 5, 2012 10:45 PM Forum: Global Warming - REAL or NOT

The Lengthening Growing Season

Posted By Alan French
One response to a warming climate...
http://www.npr.org/blogs/krulwich/2012/09/04/160554150/what-s-with-frosty-why-isn-t-he-showing-up-on-time

Clear skies, Alan

September 5, 2012 11:04 PM Forum: Global Warming - REAL or NOT

The Loss of Arctic Ice

Posted By Alan French
http://www.bbc.co.uk/news/science-environment-19496674

Clear skies, Alan

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