12" Cass on a MkIV

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I had an email from the President of the Kent University Space Society seeking advice about an instrument in their possession. The instrument is a rather impressive 12" Fullerscopes, Cassegrain-Newtonian reflector on a MkIV with electric drives and large, Fullerscopes, plastic setting circles. The telescope appears to be housed in a high quality fibreglass dome.

The classical Cassegrain telescope uses a 'fast' concave paraboloid and a hyperboloid convex secondary to provide a long effective focal length in a fairly compact instrument. Fullerscopes used to offer a convertible Newtonian/Casegrain to make the instrument more flexible in application. This particular also appears to have a Newtonian focussing mount. The Cassegrain focuser is also visible behind the primary mirror cell. A simpler form of Cassegrain, known as a Dall-Kirkham, used the same optical layout of concave primary and convex secondary mirrors using simpler curves but could not be used (so well) as a Newtonian.

This instrument has fallen out of regular use and repair due to a lack of skilled personnel to carry out the necessary running adjustments and new observer training. Not an uncommon circumstance in the education field where there is a regular turnover of staff.

I was asked whether they should sell the complete instrument to purchase something newer. My advice was to start with the local astronomical society(s) in search of someone suitably experienced in a variety of telescopes. Hopefully they could offer expert advice free of charge or even make the necessary adjustments if the optical coatings were still usable.

An alternative to selling the whole instrument would be to keep the MkIV to carry a new OTA. Perhaps a compact Schmidt Cassegrain OTA from one of the popular US companies. No doubt savings could be made by buying a secondhand OTA which had been independently inspected prior to purchase. The existing Fullerscopes, hinged, tube rings could easily be replaced with those required for a new instrument.

The complete instrument may be up for sale but would be subject to cancellation if their plans should change. I recommended the UK Astro Buy and Sell small ads website if they wanted to reach the largest interested audience for their sale.

U.K. Astronomy Buy & Sell

It is difficult to see what all the wires and cables do from a photograph but there is a paddle and drives to both axes. The typical MkIV, bronze, 365 fine-toothed, slow motion wormwheels are clearly visible in the images. As are the Fullerscopes white plastic setting circles. A far more useful, if slightly less attractive, addition compared with finely engraved circle mounted on a slip ring on the RA wormwheel. The graduations of which require a powerful magnifying glass and reasonable light to read! The latter should be avoided in any astronomical observatory normally used at night.

If anyone in the Kent area has the real expertise to help with their instrumental problems they might like to get in touch with my contact: howard (at) phillips.fm

Note: I see this instrument and mounting are now both listed (seperately) on UK Astrobuysell seeking offers closing on the 14.9.09 no reserve. Be quick if you want a bargain. Collection only from Kent.

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