7" f/12 iStar folded refractor 28: Stainless steel objective handles.

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My stainless steel handles for my bayonet fitting objective system have just arrived. Of marine quality and probably intended for yachts and boats these Roca handles are literally, solid stainless steel throughout. I was quite shocked at the weight and even considered using them as dumbbells. The sturdy handles are almost unique in having the solid 12mm diameter grips usefully cranked at 45 degrees to push them well away from the huge 10" diameter dewshield.

The handles will probably add another pound to the 10lb weight of the objective on its bayonet fitting plate. Though they will provide a vastly improved  grip than trying to hold the awkwardly round objective cell or the sharp cornered bayonet plate.

Here I have used temporary screws to hold the handles to the bayonet plate. The cranked, handle offset is ideal to allow a firm, unencumbered  grip even when the dewshield is in place. The ease with which the heavy lens can be carried about and bayonet mounted, onto and off the OTA, is quite a revelation.

There proved to be plenty of room for nuts between the bayonet and OTA front plate. So I shall have to find some smart, countersunk, hex-socket head screws in stainless steel  for a neat, permanent fix. By sheer luck I had no need to move the bayonet location screws. Though I had to trim the stand-off pads on the back of the plate to allow room for nuts.

Now with the short dewshield from the long tube, 'classical' OTA, propped in position. The short dewshield provides a very firm support for the longer dewshield as well as offering considerable protection to the objective lens in its own right. The question is whether I really want to permanently increase the bulk of the objective assembly for indoor storage. If I cut down the depth of the short dewshield it will lose its ability to protect the lens from dew.

The handles fit under the dewshield recess without obstructing the short dewshield in any way. I laid the dewshield in place before marking out potential positions for the handle bases. The cranked form proved to be remarkably flexible in allowed positioning.

I had made a plywood plug for the dewshield so that the long OTA could rest on its nose in storage. Probably overkill for a removable lens bayonet system.

Straight on view of the lens fitted to the bayonet plate with handles fitted.

The subtle, green anti-reflection coating is visible in this view.


An oblique view of the objective fitted to the bayonet plate. I am very pleased with the quality of these handles but would have preferred they were hollow tube for weight saving. They will tend to make the OTA even more nose heavy.

I wasn't able to find any stainless steel, socket head, countersunk screws for the handles locally. So I went with A4 SS CSK cross-head screws instead. Which were too long and had to be shortened in the lathe. I bought some Nyloc nuts and M6 stainless steel butterfly nuts as well.

So the collimation screws, bolts and nuts are all rustproof. While the 'bayonet' plate handles are now firmly attached with SS screws. I have yet to find some more, stainless steel, hex socket head screws for the objective's collimation 'pull' screws.

A simple, foolproof means of locking the bayonet plates together still eludes me. I have set the task to be free of fitting screws or adding nuts. A compact, spring-loaded, locking pin would be idea but I know of no such beast readily available in the DIY market.

Click on any image for an enlargement.

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