This 3rd Order Fresnel Lens was used in the Old Point Loma Lighthouse.
Made in 1850 it weighs 1,895 lbs = 900 kg. When used with three lamps it could be seen from 20 miles = 32 km away.
The image above was taken for this weeks Totally Informal Transglobal "Thursday" Challenge: "Crystal Clear".
Check out images of other participants here
All images © 2004-2016 by Walter Otto Koenig, Images may not be copied, downloaded, or linked. All rights reserved.