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This home-made Newtonian on a Dobson mount is frequently used from my home at St Dennis, Cornwall, chiefly for deep sky observations. The Dobsonian mount is made from 3/4 inch thick plywood, treated with wood preservative and overpainted with weatherproof paint. The rocker box bearings are 8-inch diameter PVC tube, internally strengthened with plywood discs. The bearings are covered with smooth kitchen worktop edging strip and ride on PTFE pads. Surrounding the bearings on the tube box itself there are circles of smooth PVC adhesive tile which bear against smooth PVC furnture bearing circles attached to the inside of the rocker box. This is meant to make it easier when lifting the tube box in and out of the rocker box, and to facilitate some tension in the altitude axis on turning a knob a the side of the box (yet to be fitted) which contacts the tube box circles. The tube box is fitted with a digital inclinometer giving tenths of a degree accuracy, making the finding of faint fuzzies easier when used in conjunction with a live PDA astronomy program (giving the current altitude of any desired object). The base of the ground board is fitted with four castors which ride on a fold-down drawbridge-type ramp which makes it possible to move the whole instrument with little effort from the garden shed to the observing area. The 12-inch f/4.6 mirror was ground and figured by me at home, and gives a respectable image.
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When I lived at Rednal, south Birmingham, these were my two most frequently used telescopes — the ETX-125 for quick grab-and-go sessions, the LX90 for more in-depth views of the Moon, planets and deep sky objects. Both were used mainly on their tripods, but they could also both go onto the pier that I made for the 200mm Dynamax (see below). The photograph shows the expert lunar observer Nigel Longshaw (at left) and me on 27 August 2005.
I wanted a pier to accommodate both my 150mm f/8 Helios refractor and my 200mm Dynamax SCT. The refractor requires a high pier. The SCT requires a low one. I built a dual-purpose pier. The main pier is a 4-square section of glued and screwed 4x4s. This is bolted to a small, thick square concrete slab which in turn is bolted to a larger, heavy square concrete slab which lies on a level screed. Between the two slabs are two wooden slats (not depicted in diagram) to cancel vibrations. It is quite stable, despite not having deep foundations, due mainly to the weight of the base slab and its large footprint. The wooden pier is square hollowed to take a 4-foot length of 4x4 to which is attached the equatorial head for my refractor. When used, this is secured for use by two large side bolts that fasten onto metal discs set into the wood. The SCT rests on a tiltable platform that is offset from the main pier so that the wedge does not interfere with the secondary refractor pier. Adjustment of the wedge is therefore possible using with the four corner nuts. The SCT just slides onto the pier and fastens into position with a single bolt. A heavy duty polythene bag covers the pier when not in use. Here it is shown during an observing session, with SCT and binocular eyepiece - note the highly offset SCT counterweight because of the heavy binoviewer!
