telescopes on the hill

[Foss]

Mackensen - this is extremely helpful thank you. I'm definitely going to carefully have a go this weekend with some new brushes etc. I'll take care with the threads etc as you suggest and let you know how I get on. Seriously appreciate it. When's the book coming out?!

OK - remember three things: these were meant to be stripped in the field by soldiers so they are robust and well-made; the lens glass is soft so be gentle when cleaning them - use a soft, clean cloth and a little lens cleaning fluid or else some of the proprietary lens wipes that you can buy in any opticians; finally, remember that the threads are fine and of soft brass so be very careful when re-assembling not to cross them!

Remove the first draw (narrowest tube) by unscrewing the milled flange that joins it with the second draw. At the front end, you will find the "erector" lens (which turns the received image the right way up). Remove it and clean it. Now, at the eyepiece end, unscrew the eyepice, then, holding the lens, unscrew the large, milled flange that holds it. You can now clean that lens properly too. If the lens is badly scratched or hazed. or if it has fungus badly, it may be beyond rescue - you would be surprised how much wear and damage the large objective lens can take without affecting the image too much but damage to the eyepiece lenses will have a marked effect. The large objective lens is an "achromatic doublet" - that is, two lenses next to each other and they can also be removed for cleaning by unscrewing the milled ring at the very front of the telescope (with the sun shield fully-retracted). If it hasn't been stripped for years you may have to get it started in a vice, using a cloth in the jaws and being very careful not to pinch it!

Hope this is of use - I'd better shut up now or the Moderators will accuse me of hogging this thread, which wasn't really about old stalking glasses at all!

 

[Brithunter]

Negretti were still in the instrument business in the 1980's based in Croydon. In fact optics too as they built and serviced high speed cameras for the RAF recon planes. They also built the instruments for the Sea Harriers I had a friend who worked there for many years. I doubt many people took notice as they were tucked away behind a load of shops in the middle of Croydon. A dark ally being the only bit seen from the road as I recall but then I only met him at the entrance a few times after he was working sat mornings. I believe they were known as Negretti Aviation by then.

Steve had to give up work due to ill health which finally claimed his life last year. Sad for one so young as he was younger than I am. We met and became friends during technical College.

 

[Mr Lewis]

I use an Optolyth 30x75 draw scope on both the hill and in woodland.

Personally I do not know how anyone can properly assess Roe Bucks age and quality without one.

 

[Heym SR20]

Dont worry it's definately being kept as its engraved with his name and initials of the scope tube.

 

[Foss]

Mackensen et al - I had a very satisfying and successful cleaning session of the old spy glass thanks to Mackensen's encouraging advice. The lenses (all 6 or something of them) are honestly like new pieces of kit. What I thought was deterioration of the old lenses was in fact black spots / tiny flakes from the inside coating of the scope tubes. The cleaning session has brought an entirely new life to the glass and I am really pleased. I'm looking forward to using it again soon (especially the low powered lense). What I also found interesting was that the tubes are not in fact lined with baize / felt as I previously thought. This means that I will have more confidence in just taking the glass out in the wet (and peat) and having the ability to strip it down afterwards. A very rewarding experience and a great example of knowledge being shared on the forum. Thanks Mackensen!

BTW - If anyone else is planning on stripping down their old telescope I found that, when putting it back together, the brass threads found each other the moment I held the pieces vertically (as opposed to carefully trying to find the correct match holding them horizontlly).