Fullerscopes 4" Refractor.

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Here is a complete 4" Fullerscopes refractor on a MkIV mounting sitting on a heavy pipe pier with original cast iron "heavy duty" feet.

Fullerscopes usually offered their 4" refractor on the MkIII. This one enjoys the great pondus, stability and sheer class of the timeless MkIV.

A closer look at the 4" OTA (Optical Tube Assembly) on the MkIV. This achromatic refractor is longer than many of the Chinese offerings of today. Theoretically this provided sharper images with less chromatic aberration and coma. Another advantage with long focal lengths is the ability to use comfortably long focal length eyepieces while still enjoying high powers. This in turn offered increased eye relief without one's eyelashes smearing the surface of the eye lens or obscuring the edges of the field of view.

Now there's a nice point of view! Lots of polished and lacquered brass and black wrinkle paint. Fullerscopes made the classical rack and pinion focussing mount in the same style as the great 19th Century makers. The heyday of brass and glass when makers vied with each other to produce microscopes and telescopes for those who could afford them. The upper and middle classes were the only customers who could afford such luxuries back then. Beautiful refractors like that shown here would grace stately homes and doctors, lawyers and bankers detached, country homes. This may not have been strictly true of Fullerscope's products but they still required a considerable investment for that time. Prices for refractors have fallen dramatically in recent years as Chinese products overwhelmed home markets for these instruments.

These much earlier instruments could also be found in the fee paying (public) schools of the wealthy. The telescopes were often housed in domes like the one shown above which protected a 5" classical refractor in the grounds of a public school. An all brass 6" refractor was stored at the same school but had suffered a broken crown element in the objective lens. The workmanship of the entire instrument was of the quality which only the very best makers could manage. With lots of intricate brass and bronze castings all skilfully hand finished and deep gold, hot lacquered to maintain the superb finish for a lifetime and well beyond.

Another view from the business end of the 4" Fullerscopes refractor. The counterweight might be improved to be more in keeping with the perceived quality of the instrument by fitting a simple, cylindrical, bored turning in steel or iron. A few minutes work for anybody with a lathe and the raw materials.

A closer view of the mounting showing the 6" bronze wormwheels and slip-ring RA circle with metal pointer. These are presumably of a later date than my own MkIV. The main castings were designed to maximise stability by using widely spaced sleeve bearings supplemented by large surface areas on the thrust faces. PTFE sheet was used to reduce friction between these faces. Offering a light, buttery smooth motion without backlash provided the telescope is not too massive. The MkIV could carry up to 15" reflectors but friction may have increased beyond the comfort level when fine pointing the telescope by hand. These castings look rather rough suggesting that they have been cleaned up with a very coarse file by somebody in a hurry.

The large plastic knob jutting from the declination casting actuates a simple clutch via a long screwed rod. This forces a nylon plug against the inside of the relevant wormwheel. There are two knobs. One for each axis. The slow motion worm housings look rather later than my own and these seem to have evolved over time.

The beautifully tapered main castings are strictly to the book. Maximum stiffness where the loads are highest. Reducing in diameter where the loads are least. Russell W Porter, the brilliant designer of the 200" Hale Telescope, suggested this arrangement in his designs for the castings of telescope mountings used prior to the erection of the Hale Observatory. These (and others) were shown in the classic three volumes of "Amateur telescope Making" published by Ingalls around the middle of the last century and earlier. These books can probably still be found in major libraries and specialist bookshops. Particularly those with online search facilities. They are now rather dated but full of useful information for the creative amateur astronomer. Particularly one who likes to build and make things for themselves.



The lacquered, adjustable brass cell showing the first surface of the achromatic objective. (below) It is believed that Wildey was responsible for Fullerscope's refractor objectives. His work is legendary and, if he really was the maker, probably resulted in a very fine lens.

The massive cross sections of the MkIV mounting provide the stiffness and resistance to flexure so essential to real telescope mountings. The eye may be quite forgiving of wobbly mountings but can these cope with photography or imaging? No problem here.

An unconventional view of the instrument. Perhaps the one seen after one has just fallen off a high stepladder while trying to view something near the horizon? ;-)

What is there not to like about this classical refractor on a sturdy, well-designed mounting?

My gratitude for all the images above goes to Richard at Skylight Telescopes of London. I have enlarged his original images in Photofiltre to allow closer views. Any faults in the enlarged images are entirely my own. Richard is a specialist vendor and restorer of quality, older instruments. His website is well worth a visit for those with an interest in instruments of the last century and beyond.

www.skylightelescopes.co.uk

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