400 mm telescope building

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Assembly

The final assembly consists in finding the appripriate truss tube length binding primary and secondary cases, in order to reach proper focal point. I wished to keep sufficient back-focus to keep ability to use the tube for phtoography. I eventually chose a 25 cm back focus from secondary mirror, which gives me tubes of 140 cm length (with an additional 5 cm offset taking into account of secondary thickness and mirror to binding level offset).

Then bearings are attached to the primary case, and the whole is placed over the rocker base. Good news : with the 1 kg UWAN 28 mm eyepiece, I don't need any counterwitght on the primary side to compensate for cantilever. This will be some weight less to carry ;-).

The other good news is the global stiffness of the OTA. Truss tubes are not "bent" and stay in line (thanks to CAD design for this).

Finishing

After global verification, the telescope will go through its latest finishing steps : primary mirror ventilation, putting the "QuickFinder" Telrad-like finder, as well as mirror clamps & "head up" collimation rods for primary... Then comes the painting, so that the thing will get its definitive look.

The telescope is now ready for it's first use.

Next : in use

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