Some Fullerscopes instruments

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A British amateur astronomer has kindly been in touch to offer images and details of some Fullerscopes equipment. Some he owns, or once owned and Fullerscopes instruments belonging to other amateurs.

First is a very rare image of an even rarer 6" Fullerscopes refractor on a MkIV mounting. Very few of these instruments can have been made and sold. It is said that Wildey made the objectives. This imposing instrument belonged to another British amateur who tragically died before his time.

The classic lines of a long focus refractor is the usual image conjured up when astronomical telescope is mentioned. Such large instruments were very expensive relative to similar sized reflectors at that time. Only recent Chinese mass production has finally reduced the price of such large refractors. This instrument has a well equipped MkIV and a "proper" rack and pinion, refractor style, focussing mount. Albeit of 1.25" size it has an offset, knurled and turned brass focussing wheel. These focusers were traditional in fine instruments of the previous century. Known as the era of "brass and glass." Fullerscopes actually offered all brass refractors. At a price. Who knows how many were made? One 6" all brass refractor was illustrated in the Fullerscopes catalogue for many years.

Now some images of a 10" Fullerscopes reflector and its MkIV mounting: From top to bottom:

Here we see many typical features of a Fullerscopes reflector. A white painted PVC tube is a sign of a de-luxe model. An unpainted model was available at lower cost. Export models were of the highest standard and had polished brass crews and finer optics.

An elasticated vinyl cover for the top of the tube keeps dust, dew and spiders out.

Quite a large finder/guide telescope is fitted in adjustable, centring rings.

A large rack and pinion focuser with slow motion to one control knob is fitted. Modern focusers tend to be much shallower than this example. Allowing a slightly smaller secondary mirror to be fitted. A smaller mirror blocks less light and affects the image quality slightly less.

A so-called, "slip ring" is fitted. This was tightened firmly around the tube to stop it sliding through the twin supporting rings. Thus the tube could be easily rotated if the holding rings fasteners were left slightly loose. There would be no danger of the OTA (Optical Tube Assembly) falling out of the holding rings. Nor would the very slight slackness in support affect alignment.

Top and bottom cast rings keep the tube round and stiff.

An access door is provided at the bottom of the tube. This is for removing the primary mirror, protective cover.

Here is a close-up of the original Fullerscopes cap, finder and focusing mount.

The adjustable screws, with locking rings for centring the finder are clearly seen. I believe this may be a 60mm finder. In keeping with the needs of a 10" reflector and its greater light gathering power.

The focusing mount shows the slow motion mechanism behind the upper control knob. This looks like the Fullerscopes 2" focusing mount. Though focusers of this size are commonplace today they were considered a luxury when this instrument was built.

And now onto the MkIV mounting:

The short, sturdy pier on Heavy Duty cast iron feet provided plenty of stability for this larger instrument.

This MkIV has the "Pot Base" adaptor for fitting the mounting firmly onto a heavy 6" pipe. Screws spaced 120 degrees apart would hold the mounting firm on its pedestal. While still allowing the two to be separated at will. This made for a lighter load if the instrument had to be packed away after an observing session.

The 365 tooth bronze worm wheels are present with synchronous motors in protective brass cans to drive the slow motion worms.

The declination shaft looks like stainless steel. It has the large Fullerscopes engraved circles in place. With two collars to keep the counterweights from sliding off. While allowing removal, if necessary, to reduce the weight of the various components for transport.

Another view of the MkIV showing the original wrinkle paint. The large ring is lined with green felt to protect the tube and allow easier rotation. Rotating the tube made the eyepiece more accessible on a German equatorial mount like this.

Note how the polar axis is pivoted between two screws. Smaller altitude locking screws work in arcs cut in the ears of the pot base.

The protective, brass, motor cans are well seen in this image.


Another view of this smart MkIV showing details of the 2' long cradle for carrying the instrument via the large holding rings.

The bronze worm wheels and the long, threaded drive locking screw (with plastic knob) are better seen here.

The drive lock pushed a nylon plug against the inner surface of the worm wheel ring. This acted as a clutch. Allowing the drive from the worm wheel to drive its respective axis. In other words: The worm wheel became solid with the casting on which it normally rotates freely.

A drive lock and knob is provided on both axes. Loosening allowed rapid movements of the instrument without dragging the worm wheel teeth across their respective  worms. Power slewing is a relatively modern phenomenon.

Click on any image for an enlargement.

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