Part 2: 12" Fullerscopes Newt-Cass restoration

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Back to this restoration project of a 12" Fullerscopes Newtonian-Cassegrain in Australia. The previous image shows the instrument as found on its MkIV mounting in a white GRP dome.

 The cast rear backplate houses the primary mirror cell and the Cassegrain focussing mount.

The original condition does not inspire great confidence. The paint is oxidised and the metal parts corroded.

No doubt the focusser needs careful dismantling and restoration too. The focuser has its own alignment screws. Which will need great care.

Rusty screws must be treated with patience. By applying easing oil well before any attempt is made to remove them.

 There is a lot of messy work removing old finishes even when great care is required. You can't just attack the components without the risk of damaging the original finish or fine details.

A mask is essential to avoid inhaling possibly toxic finishes from the past.

 Here is the finished and painted backplate.

Even the Fullerscopes logo has been picked out in gold. A nice touch which adds a hint of sophistication.

I believe the paint is Hammerite "Metallic Charcoal."

The Fullerscopes MkIV mounting before restoration. The paint is dull and weathered. 

The details are all badly in need of smartening up. 

Supporting the parts on a sturdy working surface with protective cover avoids unnecessary damage to finishes and parts.

Restoration requires thought, patience and care. Simply pulling a rusty shaft through a bearing can do a lot of damage.

Here the components of the MkIV have been disassembled.

The main castings now have their shafts exposed. We see the slow motion worm wheels (actually rings in this case) and their drive worms in their cast housings.

The large Declination circle is the perforated casting in the foreground.

On the right are various bolts, screws and the slow motion locking wheels and threaded rods. Two white circles are thin sheet PTFE. (Teflon)
This helps to reduce friction between rubbing surfaces.

A collection of small parts undergoing examination and restoration. Note how everything is kept tidy in shallow trays to avoid loss of vital, original parts.

Even obtaining bolts and screws with original threads can be difficult in this time of almost universal metric threads. Some of the original fasteners have coarse threads to maintain strength and holding power in the soft aluminium alloy castings. Metric threads of similar dimensions have very poor holding power in such soft castings.

Some of the weakest parts of the MkIV design are the Polar Axis pivot bolts. These pass through 'ears' on the base casting and screw into the Polar Axis casting itself. A heavy instrument or any out of balance forces can easily strip these threads. This is where an inexpensive turn-buckle is so useful. It removes the need for the pivot screws to resist unbalanced loads around the pivot screws.

This is part two of the 12" telescope restoration. The next post will show the main tube, guide telescope and their restoration.

Here is a link to Xavier's own MkIV restoration:

http://support.internetmarketingsolutions.be/gallery3/index.php/Fullerscopes-MK-IV/fullerscopes_mkiv01

Click on any image for an enlargement.

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