Tweaking the Celestron 11"

A friend of mine ask me to make some modifications on his Celestron 11 Fastar, below there are the steps. Starting from a solid 20 mm plexy I made a ring with my big lathe. It will be used for the primary mirror lock.

The ring will be placed behind the primary mirror to "restore" the plane where (and without) the locking screws hit the glass. Ther's a groove on it for the original focuser bracket.

The ring placed behind the mirror with a glass glue.

Section of the primary mirror with the ring. The ring have a 20 cm external diameter and a average thickness of 12 mm.

Making the alluminium axle box for the locking screws using my little lathe.

The back plate where I made 3 holes (12 mm) for the mirror lock screws.

Internal view of the back plate. The axle box and the screw (6 mm) are placed. 

Starting from a solid 40 mm alluminium tube I made 3 screw knobs. Mirror lock work finished. Obviously with this modification will be better to use an external electronic 2" focuser like the Optec TCFS or FLI DF2.

This is the C11 secondary mirror on my lathe, I used a Stabilo pencil to make a perfect centered circle on it. This will be very useful to allign the corrector and the mirror to the optical axis using a laser collimator.

The secondary hole on the corrector plate is a little more large than the secondary support, so I place some adhesive paper to fit it well.

Collimating the laser collimator. Without the secondary mirror I pointed the telescope to a white wall, then I rotated the laser and verified that the beam always hit the same point. 

Centering the corrector plate and the secondary mirror. The laser beam hit out the little circle, so I moved the plate until the beam hit the center, then I locked the plate.

The secondary mirror and the corrector plate are centered, the laser beam hit the center of the circle, but the secondary mirror seems to be a little out of collimation.

Now the secondary mirror should be collimated, the laser beam return back to the source, but a star test is needed to verify the collimation. Test soon..

These are  the mods on my Meade 10" SC (sold), I add 5 knifes edge light stop inside the tube, 2 inside the dew shield and 3 inside the primary mirror tube, 2 PC fans in the back plate, all the internal surfaces were covered with a flat black adhesive paper.

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