Astrovelo

Hi Steve, As for your shellac, this should be obtainable from John Boddy`s fine wood and tool store in Boroughbridge in North Yorks

John.

Thanks for that, John. Boroughbridge is just down the road from me.

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?

Hi Richard,

Thanks for the compliments on the 'scope. I was going to refer you to a discussion I found on the Cloudy Nights forum but I see YOU were the author of the comments I found were of interest! I found your website and the gallery of pics really interesting, especially the 'scope you found for the famous rock guitarist!

Actually, I was a research chemist before I retired and worked on metal corrosion so you may have something there. If there was galvanic corrosion caused by the junction of two different metals in the lens mount then maybe the metal corrosion product might attack the Schott glass. This would be very slow but over the years humidity might transport the corrosion product through the lens assembly if it was soluble.

Or maybe the sprung lens just kept the glass junction tighter?

Steve

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?

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