Building the Octagon Pt.25 Pier pressure.

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It is now Thursday and I have had to uncover all the wood to check for wetness after yesterday's continuous downpour. Some rain did get in through the cheap tarpaulins and anything wet has been left standing up against the building to air in the weak, sunny periods. It was good to be able to check what timber and floor boarding I had left to play with. The 19' long 4"x4" pier posts were also buried right at the bottom of the mixed heap. I need to measure up and cut those to nominal length. That's the problem with repeated visits to the timber yard. The new stuff tends to go on top of a rather mixed heap. The sky keeps going dark so I shall have to keep an eye out for more rain!

In the image I have propped up two 3.6m [12'] lengths 4"x4" posts [outlined in red] of the intended four. This was to check for clearance issues with the Obs. floor aperture. The posts are rather taller than needed by at least 8" and, quite possibly, more.

The temporary [angle iron frame] pier [right] is only a meter tall but might enjoy a little extra ground clearance, at the zenith, with the long tube refractor. Hence the extra height of the pier mock-up. There is always the option of the folded refractor OTA. Particularly if I want to incorporate the 10" f/8 reflector on the same, heavy mounting.

There is an absolute height limit of 1.5 meters [5'] above the rotation ring if the inside of my dome/roof follows a typical hemispherical form. This height could be exceeded with certain Declinations of the OTA around the Polar Axis. The long dewshield, when on the long tube telescope format, has quite a reach at high pointing altitudes. From very fuzzy memory it reaches 11' above the ground with the OTA pointing at the Pole. The image right shows the naked, 7" f/12 telescope tube without its objective, dewshield or focuser.

I am repeating myself here because the 3m diameter [10'] observatory size was specifically chosen to house the long tube refractor. Talking of which: I now have access to aeroplane plywood in various thicknesses. I could save some OTA weight and perhaps reduce some theoretical, thermal issues by rolling a new tube from this material. I made a tube for my 5" f/15 refractor which was remarkably stiff and light. Whether a new tube is really worth the effort is another matter when it is permanently mounted. I would certainly use Epoxy this time around rather than waterproof, resin powder, wood glue. Still, there is no haste to get involved in yet another project until the observatory is completed.

Click on any image for an enlargement.

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