Restoration of 3" equatorial Negretti & Zambra

[Roberto]

After the 2020 restoration of the 3" Dollond, last November I came across a nice vintage equatorial telescope being sold locally.  It was described as in good condition, including no blemishes on the objective.

Here are some original pictures from the seller:

[Roberto]

A few days later I collected it and took some pictures comparing it to the 3" Dollond:





It is a shorter tube but with very similar focuser.  The finder is a lot better in the N&Z.  It came with four eyepieces, including what looks like a pancratic tube.   

Here are some pictures of the mount in its original state:





The tripod was in worse state than the mount but the telescope was functional and with very, very good optics.  I only tested it during daytime and posted about it in the Groups.io forum for the Antique Telescope Society as I had not been able to find this particular model in any of the N&Z catalogues available online.





The experts in the Antique Telescope Society forum suggested it may have a Cooke lens (!) and although I could not see any markings upon disassembling it, it looks very similar to a picture showing on page 68 of a History of Cooke, Troughton & Simms telescopes by Anita McConnell:



Knowing I had not the weather nor the time to work on it, I put it away until this year.

[Roberto]

As the scope was in such good state I decided to work on it only recently and started by disassembling and cleaning the mount:





And the worm wheel before cleaning it:



And after:



The patina was nice but the dials and brass work was pretty oxidised so I gave it a good scrubbing with Mothers' polish.

[Roberto]

In mid-March there was forecast for a warm early spring day so got to work on the tripod and mount:







The counterweight was a lead cylinder in a brass jacket:

[Roberto]

After plenty of elbow grease things started to clean up:





and with the sun still shining there was time to prime the parts for painting:

[Roberto]

At night there was time to work on the telescope fittings using Renaissance wax using the mototool.  I didn't clean it a thoroughly as the mount as the telescope had obviously lived much of its life inside its transit box with the mount spending less time as protected.

Before:





And after:



The focuser has a nice baffle with a fixing bracket:

[Roberto]

The paint - which was difficult to find a good match for - was between a pale olive green and grey.  Both the telescope tube and tripod had the same paint.   I stripped the paint from the OTA and saw no clear indication of lacquer on the brass or old patina so I assume it had always been painted. But that's just a guess:





There was minimal damage to the OTA:

[Roberto]

The Easter weekend gave me a chance to prime the telescope tube and paint other parts:



Tripod legs and mount parts:

[Roberto]

At the end of March I started work reassembling the mount after cleaning and regreasing all parts as necessary:

[Roberto]

Here's the mount reassembled in the kitchen:

[Roberto]

Well, after having come back from the eclipse trip to Mexico, I worked on the OTA.

First it was primed and painted:



I had put all bolts, screws, brackets, parts, etc in separate boxes.  The mounting rings for the finder had to be put back in a specific order for the whole thing to fit.  It took me some time to get everything together, particularly the front element as I may have sprayed too many layers of paint and lacquer so it was tight fit!

Inside the box (which I still need to work on):

[Roberto]

The fully assembled OTA with focuser (no eyepieces) but with finder and caps weighs in at close to 4.4kgs:

[Roberto]

And here are a few pictures outside in between passing clouds:

[Roberto]

Finally, a comparison with the Alt-Az Dollond:

[Roberto]

Last ones promise:





I now need to test it under the stars.  A simple comparison with the Dollond on far away branches, leaves and some chimneys implies better optics for the N&Z (potential Cooke).  The Dollond is no slouch under the stars so I guess I shall know more when I can manage to test it.

Roberto