17th April 2016 Spring cleaning.

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While trying to make room in the shed for the folded refractor and 10" f/8 rebuild I decided to check my assorted achromat refractors. These all stand on their dewshields in storage which means they collect dust inside from leakage around the focuser drawtubes. The no-name 60mm x 700mm, Bresser Skylux 70mm x 700mm and Vixen 90M 90mm x 1000mm all badly needed the backs of their objectives cleaning.

The DIY 5" f/15, in the spiral steel tube, was in rather a poorly state with thick fungus growing on the plywood baffles. So I removed the objective and focuser back plate and slipped the baffle tree out. I now have a plain steel tube for the 5" of exactly the same size to replace the spiral tube. It needs a new objective cell backplate because the original plywood ring has delaminated. The lens also needed cleaning.

This image shows the relative scale of objectives and dewshields. Photography and bright sunshine makes things look worse than they are!

Next up is the Celestron 6" f/8. The lens needs cleaning on the back. Fortunately I can unscrew the lens cell to avoid removing the glass elements. The same with the Vixen which required Prussic loops and opposed battens to loosen the [very firmly] screwed cell from the main tube. Trying to drop the glass elements out of a fixed cell is really asking for trouble. Or chips at least.

All of these refractors were bought secondhand except for the Bresser which was incredibly cheap on special offer, with mounting and tripod, from Lidl supermarket. A check through the empty focuser of the Bresser showed the black plastic drawtube had never been blackened inside. So out came an old toothbrush and I quickly painted the inside with blackboard paint. The toothbrush reaches in easily to such small [1.25"] tubes and leaves concentric rings when the tube is spun against the toothbrush bristles. These act as tiny screw-like baffles and help to kill glancing reflections.

Leaving the bare focuser out in the wind and sunshine soon dried the paint to a flat, matt black. The drawtube is baffled but it was easy to see the high shine surrounding the baffle before it was painted. Shine kills contrast by reflecting stray light into the eyepiece. The difference is very obvious with a 'milky' view in daylight.

The plan was to mount these various refractors as guide-scopes or finders on the bigger instruments but they added weight and vulnerability during carriage. Each produces decent enough images so they really ought to get more use. The problem is that having a larger instrument available spoils the desire to look though anything smaller.

I now have an Amici prism 45 degree, terrestrial diagonal which should mean the refractors getting more use for distant bird watching. At which they excel but at the cost of greater length and weight [7lbs with Vixen rings and dovetail] than the very expensive, but ultra-compact, short focus, lightweight, prismatic, spotting scopes.

Sitting on my sturdy, Bogen, video tripod I have used the Vixen 90 for both eclipses and transits. I plan to use the Vixen 90 on the MkIII Fullerscopes mounting for the Mercury transit on the 9th of May 2016 [in Europe] using a DIY, Baader Solarfilm filter. Or I could mount the 5" Solarfilm filter on the folded 7" refractor somehow. Or use it, as intended, on the 6" f/8 objective stop. Or, I could just sit indoors watching the rain pouring down and feeling very sorry for myself.

Click on any image for an enlargement.

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