Whats the vote on this one?

[spaceboy]

http://www.ebay.co.uk/itm/MASSIVE-VINTAGE-LENS-21cm-Diameter-5-5-Kilos-/280940856786?pt=UK_Collectables_Scientific_MJ&hash=item41696145d2 I'm guessing it's off an old ships compass?? Would be a mighty fine frak at 8 1/2" if it was out of a scope though.

[Prador]

The lens looks like it has quite an extreme change to the angle of the light path. All I can imagine is possibly a chart weight and/or desk magnifier?

I would make quite an impressive objective if from a refractor though

[Capricorn]

Depends what it's focal length is.

If it is long as in 30-40 ft then it is probably off a periscope.

Used to have to use one that had a focal length of 42' 4.5" .

It was somewhat similar diameter if I recall (30+ years back)

Unfortunately at focal lengths like that they are not much use for a scope as simply too damn long for practicallity.

If it were f/10 then possibly useful length as the tube would be just over 2 meters, at f/12 then around 2.5 meters.

Need some idea of the focal length.

It looks ex-MOD as they built in big solid brass holders.

If anyone has an Ebay account ask if the focal length (even approximately) is known.

It might be written on it somewhere so ask if the holder has any numbers/markings.

[sologuitarist61]

That is certainly some piece of kit regardless of what you can use it for. Is there any easy way to determine the focal length? I wouldn't mind it just as a piece to have hanging around the house - all that glass and brass - lovely, and I am sure my partner would come to love it as well.

[Chris]

I was thinking the same thing the other week:)

http://stargazerslou...r/#entry1598148

[NGC 1502]

As post #1, I reckon it's from a ships compass or something similar. Too steep a curve on the glass for it to be a refractor lens.

Would look nice on the mantelpiece if the Chief Officer in your house allows

Regards, Ed.

[JamesF]

Stick it in the front door. You'd be able to see who was ringing the doorbell from the end of the garden

James

[alexog]

Looks like a very short focal length and possibly a simple lens (one element) but hard to tell. I'd guess part of some kind of projection system.

I've got optics from Epidiascopes, Periscopes etc. They're good fun but with no markings on I think we'll never know.

[LeeB]

it looks like an agfa or similar photo enlarger lens and if so will be small f probably 1.7 to 2 so difficult to use as a fract.

[faulksy]

Stick it in the front door. You'd be able to see who was ringing the doorbell from the end of the garden

James

good idea james, but as you said you would be able to see who is ringing from the end of the garden but they would have to have long arms wouldnt they :grin:

[melsky]

Looks like a condenser lens from a large format enlarger. Way back in my darkroom days I remember 10x8 inch enlargers with these set just above the negative holder.

[faulksy]

this item sold for £206 just thought i would let you all know

[JamesF]

What's the odds on seeing it up for auction again soon?

James

[petermarknimmo]

Wow! Imagine the chromatic abberation if that thing was on a telescope