4” F15 Refractor project





For many years I have taken a keen interest in antiques and collectables, regularly visiting fairs and auctions to see what bargains can be had. Unfortunately antique and vintage astro gear is rarely seen and when it is, the prices are usually, excuse the pun, astronomical.
But in early 2010 I discovered an interesting scope and mount at a local auction house. I placed a tentative commission bid and then spent the next few days wondering if I should have bid higher. Amasingly my bid won and I became the proud owner of an early 3” Broadhurst Clarkson brass astronomical telescope together with a massive but unidentified equatorial mount. Later investigation on the mount revealed it to be a late 19th century Thomas Cooke & Sons of York Portable Equatorial Mount.

The Cooke catalogue of 1883 lists the mount as a “Portable Equatorial with fixed latitude; telescope fixing using leather straps and wood vee blocks” these were listed at the princely sum of £14 10s 0d. This mount came complete with an RA slow motion, (1883 catalogue shows price at an extra £4 00s 00d for this option). The declination axis had no slow motion controls but both axes were fitted with engraved brass setting circles.



The RA block is made of solid hardwood and shows signs of being fitted with the standard T Cooke & Sons oval nameplate on each side, these unfortunately have been lost at some point in the mounts history. The RA block also sports a pair of brass cased spirit levels to allow levelling of the mount using 3 capstan screws around the base.



The 3” brass telescope was a good example of a late 19th / early 20th century 3” Broadhurst Clarkson Starboy refractor but it looked lost on this massive mount. What the mount really needed was something bigger preferably a similarly aged Cooke refractor; unfortunately these are rare and very expensive thus an alternative was investigated. A few weeks later, after speaking with a local telescope manufacturer, I found he had a vintage 1979 4” F15 Fullescopes Deluxe refractor for sale. These scopes, even though they were produced well into the 1980s and early 90s, were made in the style of the 19th century Cooke telescopes using traditional techniques with lacquered brass components, a perfect match for my mount.

Due to the age of the mount and historical interest I did not wish to make any major modifications so I spent a few hours doing a gentle clean up and refurbishment.

However, the 100+ year old leather straps were showing signs of age and I could not trust them to support a heavy F15 scope, they were duly replaced with a pair of Fullerscopes cast tube rings that came with the scope.

Because the new scope was longer than the original 3” scope fitted to the mount I found operating the declination shaft lock difficult when viewing through the eyepiece. Therefore I manufactured an extended declination axis lock screw from brass using the illustrations in the Cooke catalogue as a guide. This modification provides convenient control of the declination axis close to the eyepiece end of the scope.



Initially I fitted the mount and scope to my Celestron CGE tripod; this being the only tripod I had that was man enough to take the combined weight of scope and mount. The CGE tripod provided a very stable platform but looked too modern; what the mount and scope needed now was a period style hardwood tripod.

Taking ideas from tripods of the late 19th century I designed my own utilising the mount base plate as a tripod head. The legs and spreader were manufactured from American white oak; mahogany would have been more in-keeping with the style of this scope but sourcing mahogany in these quantities is difficult, expensive and not environmentally pc these days.

The scope had it’s 1st public outing at the autumn 2010 Kelling star party where it promoted quite a lot of interest during the day and provided some excellent views of Jupiter at night.



I really enjoy using this scope, not only is it a pleasure to set up and look at but it is a joy to use due to its simplicity and quality. With the excellent optics and smooth and stable equatorial mount I am re discovering the delights of visual astronomy and have since taken a keen interest in double star observations. A brass 50mm Poyser Finder fitted to augment the original 25mm finder assists in finding fainter objects.

What of the 3” Broadhurst Clarkson telescope that was in the same lot as the mount? Well let’s just say that’s my telescope project for 2011.































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