[LargeFormat] Leonid Meteor Shower

[Clive Warren]

At 11:15 am -0600 17/11/01, Michael Briggs wrote:
>On 17-Nov-01 Clive Warren wrote:
>>  As for technique - yep and thanks for the advice. I am hoping to use
>>  a 7" aero Ektar on 4x5. This has an aperture of f2.5 and is corrected
>>  for infinity - probably performs very well wide open. This is one of
>>  those times that not having a shutter is an advantage in the dark -
>>  just take the lens cap off :-)
>
>This should work.  I wonder whether a f2.5 Aero Ektar delivers more light than
>a modern f5.6 lens.  The Aero Ektars must be uncoated and the rear glass has
>turned brown from self-induced radation damage.  I am doing a historical and
>labortory study of the Aero Ektars.  Two of the rear elements contain Thorium.
>

Michael,

Thanks for the additional guidelines - as you have probably read 
there was no opportunity for even seeing the meteor shower, let alone 
photographing....

Very interested in what you had to say about the Aero Ektars. Do you 
mean that because of the radiation damage less light is allowed 
through the lens?

Have had a quick look at the two 7" aeros I have here and they 
definitely show a brown tinge to the glass. Have always wondered 
about the levels of radiation emitting from the lenses as I knew they 
contained rare elements that were not too healthy. Exactly what are 
the levels of radiation given off and is this potentially harmful?!

Would you consider publishing some of your findings on the f32.net 
web site? Would be great to have some more information available for 
general interest.  I have always wondered also how well the lenses 
are corrected for work that is not at infinity. Have read in some 
places that people dis these lenses for anything other than infinity. 
I have not yet used the lenses so have nothing to go on in terms of 
my own experience. One of the lenses is in a helicoid focusing mount 
and I was considering building it into a homebrew camera for 6x12 or 
similar..

Cheers,
         Clive