canuck

I am a new member and so coming to this thread a bit late in the day. I've had a Cooke PV 3.25inch refractor, dating from 1895, since the 1960s. The lens still looks good to me, but maybe I don't know what to look for!

I'm not sure if the tube is Cooke's own as there is no maker inscription. Interestingly, the eyepieces are labelled in mm rather than inches so maybe it's a German tube. The 'scope does need some restorative work, particularly on the rack and pinion focussing. And a respray as you can see ... The head of the tripod was replaced by a solid oak piece to exactly the same size. This needs varnishing but where do you get shellac these days!?

Steve

Wow, old thread...but what a scope! I've seen pictures of a surviving 5" Cooke triplet too. So selected 5" pv's and under seem to have been able to survive . The Europa.com article referred to above mentions that the smaller objectives had slightly modified standard cells, while the larger glass had the ingenious temperature compensating cell. I wonder of one of the metals in this large cell was a factor in the lens deterioration?

When the Cooke p-v scopes came out, they were regarded as being excellent, sadly for Cooke's, the new Schott glass that was used turned out to be reactive with the elements. A nice article on the whole episode can be seen here:

http://www.europa.com/~telscope/hdtaylor.txt

This is an interesting article, and a fascinating piece of telescope history...I've referred to it before.

Interestingly, some Cooke p/v's have survived through to present day without tarnish. It's curious that some of these lenses seem to have escaped the fate that most of their siblings suffered. I wonder circumstance rescued these select few?