On the quality of 19th century lenses.

[Mark Sawyer]

Those of us who appreciate still use 19th century lenses, even in the 21st century, often marvel at the quality achieved by the old craftsmen. Considering the technological knowledge and expertise of that period, such creations as the Petzval, the Globe lens, etc. seem hardly possible, seeming far more advanced than the times they came from. And I'm pretty sure I've figured out how the ancient lens-makers were able to create those sophisticated marvels of optical engineering.

Aliens.

I'm thinking of writing an episode for The History Channel about it...

[Tin Can]

LOL you have been reading my private emails

just minutes ago!

actually lens making was done for centuries improving constantly

maybe

[Mark Sampson]

Well, once the aliens finished building the Pyramids, they needed a new challenge, yes?

[jp]

That explains how we have the Radar lens before radar was even a noun amongst humans. Old tech for the aliens.

[pgk]

Try reading "Prism & Lens Making" by F Twyman FRS, published by Hilger, originally during WWII, although its not exactly a 'light' read. It describes the almost unbelievably exacting and laborious processes involved in making lenses. There is also the book "Victorian Telescope Makers" (about the Grubbs), by Ian Glass which explains how large objectives would take months or even years to gring and were subject to irrevocable damage due to a few minutes inattention. Victorian lens makers were extraordinary people IMO, with levels of understanding and patience that I marvel at. As for photographers like Samuel Bourne who actually used a Grubb C lens to shoot 12" x10" wet plates at 18,600 feet altitude in the snow of the Himalayas in 1865, well what can you say?

[Tin Can]

Just bought the book, cheapest with shipping was NOS for $20

Thanks for the tip!

Try reading "Prism & Lens Making" by F Twyman FRS, published by Hilger, originally during WWII, although its not exactly a 'light' read. It describes the almost unbelievably exacting and laborious processes involved in making lenses. There is also the book "Victorian Telescope Makers" (about the Grubbs), by Ian Glass which explains how large objectives would take months or even years to gring and were subject to irrevocable damage due to a few minutes inattention. Victorian lens makers were extraordinary people IMO, with levels of understanding and patience that I marvel at. As for photographers like Samuel Bourne who actually used a Grubb C lens to shoot 12" x10" wet plates at 18,600 feet altitude in the snow of the Himalayas in 1865, well what can you say?

[Drew Bedo]

I have watched those History Channel episodes on Ancient Leans from time to time too. Always fascinating untill they leave the observable ruins and ggo off on wild unsupported speculation.

My question: If ancient space ailens actually helped the Egyptians build the pyramids around 2,500 BC, why didn't they also teach them how to build a stone ARCH? Or give them the wheel or show them how to make Bronze?

[Chauncey Walden]

Maybe Jim Galli's alien friends have historical records that were kept;-)