Repair & Stripping

First, let me acknowledge the invaluable help I had from a good friend Brian Johnson. He joined the ranks of seriously hooked amateur astronomers a few years ago and set himself up a great observatory. Sadly he passed away in April 2015. I will miss him greatly.

He had a lovely home workshop with mill and lathe which he used to great effect. A real craftsman who knew his stuff and was always keen to help me.

The first challenge I gave him was to straighten out the split & dented tube. No problem for someone who has been a professional auto body worker! He made a custom mandrel and with a lot of patience carefully restored the tube & focuser.

I then stripped off the paint. The top was a blue coat, seemingly applied with a 6" brush. Next was a light grey coat, sprayed on.

Finally the 3rd layer was the original. This was a hard, thick, dull grey lead based paint. It had adhered to the metal extremely well.

With this layer identified I paused for a while and found the best matching paint I could. A grey undercoat/primer from B&Q had almost the perfect colour and matt finish. This layer had brush marks which I knew I would have no problem recreating!

Using Nitromors I stripped off the paint, the first two layers offered almost no resistance, the original paint took hours of soaking and scrapping.

Removing the paint revealed the craftsmanship of the original build.

The tube was made from 4 rolled sheets of tin plated iron, soldered along all seams. Re-enforcing collars had been added (one at bottom, three at top. These were all copper. Brass inserts had been added where the mirror cell , spider and focuser mounted.

An iron cradle fitted snugly around the tube and held the two elevation trunnions.

A couple of the copper ribs had become detached a little, but were easily re-soldered back in place.

The wooden (oak) mirror cell was split. This had been caused by the wood drying out and shrinking and finally splitting when the mirror was finally bigger than the hole. I glued and cramped the cell to restore it, which left an oval hole (it had only shrunk across the grain of course). Brian restored the hole to circular on his lathe.



© AstroKeith 2022