7" f/12 iStar refractor 11: Curing that sinking feeling.

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After endless struggling to move my welded pier around the lawn I suddenly had a new idea. The small, solid tired, castors which I had been using sank far too easily into the soft lawn.

Then I noticed the nose [or jockey] wheel on my trailer. A local discount store sells complete nose wheel assemblies including the fixing clamps and the screw jack posts. I just need to fix a jockey wheel clamp to each leg of my massive steel pier and I shall have the mobility I have been seeking for years.

Leveling, raising and lowering can be all be easily achieved with a spin of the handles on the screw jacks. Locking of the wheels, if necessary, is easily done. The screw jacks allow a considerable change in pier height as the tubular body is allowed to slide through the clamp. Once jacked up with the screw, the leg can rest on a lump of timber to allow the jack to be rewound and then slid down through the clamp. Once the clamp is re-locked the screw jack can lift the pier off the timber props for even more height. Ideal when viewing high overhead to avoid muddy knees. When viewing at lower altitudes the pier height can be just as easily lowered again to avoid climbing a stepladder. 

The wheels turn and castor freely to allow rapid changes in direction in a confined space. Handy for rough polar alignment.  The 260x85 [10" x3.5"] pneumatic tires have 150kg capacity. Each well beyond the weight of the complete instrument.

I revisited the rotating focuser to remove the slack. There were a couple of burrs left on the back plate cut-out which were easily sanded away. Re-assembly resulted in smooth, slop free rotation.

I shall need to fix the 8 x 50 finder support stalk directly to the main tube. When the dovetail was fitted to the focuser slot the finder was physically blocked by the 8" [20cm] back plate diameter.

I have cleaned the algae from the pier. The dark blue Hammerite paint has lasted remarkably well considering it has been standing out of doors and exposed to the weather for years. A scrub with a washing up brush and a little washing up liquid quickly cleaned back to the paint. I am uncertain whether I want to repaint it in another Hammerite colour or leave it as it is. The Fullerscopes MkIV mounting could also do with a repaint. Which leaves me wide open to a complete update in appearance. Many modern mountings are often light coloured. Though I rather an favour overall grey as a tribute to famous, classical refractors from Clarke and Cooke. Lighter coloured pier legs/feet would certainly be far more visible in the dark. Though the shiny plated surface of the wheel jacks should help to make them much more visible.

After searching for details on repainting old Hammerite I discovered that its properties had changed dramatically since environmental and safety issues had altered its original ingredients. Opinions on a boating forum were very negative about the more recent product on rust protection of their highly vulnerable trailers.  

I would also like to arrange control rods for the slow motion axis locks/drive engagement. The original "radio" control knobs are often difficult to find in the dark and are sure to become harder to reach due to increased pier height. Most classical refractors had long control rods coming right back to the eyepiece to allow the observer to easily make such adjustments. Connection will require flexibility or universal joints to be connected to the present short stalks on the mounting.

The Fullerscopes MkIV uses a threaded rod [stud] to press a nylon plug against the inside of each, ring-like wormwheel. This locks the shafts by using the worm itself to deny rotation to the 6" 359t wormwheels. Because the locking takes place between the castings and wormwheels it simultaneously engages the drives if the synchronous electric motors are actually running. Not quite on a par with a dedicated screw down friction lock [MkIII] or circumferential clamps. The worms can slip against the very fine wormwheel "teeth." This can most easily occur under conditions of serious imbalance and should not be automatically trusted without some prior thought.

Having much easier mobility for the entire instrument opens up the distinct possibility of parking it under a secure, overhanging structure. Provided it is sheltered but not tightly covered the birds should stay away. The excellent weather proofing, wind shelter and security from predators seems to make protective tarpaulins act as bird magnets.

Click on any image for an enlargement.

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