8.10.2025 Etalon adapter ring.

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  I needed to be able to use M6 machine screws. To hold the pipe clamps to the dovetail bar. Without having to make oversized holes and enlarged slots. The clamps were threaded both 8 & 10mm in the bosses. So I bought some threaded adapter bushes. 6-10mm. 

 They are rather long to fit deep enough into the clamp bosses. I have yet to see how high the bosses will stand off from the dovetail plate. Once the etalon nosepiece is centered in the FT rotation ring. If the spacing is enough then I need not modify the threaded bushes. If too short a spacing. Then I must saw off the excess protrusion of the bushes. 

 If I am lucky I can use a plate of some sort. To maintain the clamps distance from the dovetail plate. With the bosses passing though suitably sized holes. The bosses can then be pulled down tight onto the dovetail plate. Rather than onto the protruding threaded bushes. The measurement to the centre of the ring and to the centre of the nosepiece. Is really quite close to each other at 60mm. 

 15.30 I have turned a marine plywood ring. This fits snugly in the FT rotation ring. The plywood ring is being secured by the FT rotation ring's pointed screws. While holding the etalon nosepiece centralised. The pipe clamps' bosses are actually close to the correct height. Unfortunately, the threaded bushes project much too far. 

 So, should I saw off the projecting threaded adapters? It makes the most sense. I then make a plate, probably in plywood first, to ensure accuracy. To support the pipe clamps and to fix the lateral location of the projecting bosses underneath. This plate would be bolted to the long dovetail bar. With the provision to allow the Lunt etalon to slide along the axis during fine tuning. 

 I can make an aluminium plate afterwards. Once the exact location of the etalon, relative to the APO telescope's focus, is confirmed. There is considerable weight involved in the Lunt etalon housing and the following focuser and camera supports. This must all be held firmly and safely on axis. Without sag or twisting under its own weight.

 

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