Removing incorrectly placed center spot.

[Stonius]

After much tail chasing, I finally realised why I was having difficulty getting an exact collimation - my centre spot is about 2mm out - as supplied by the manufacturer.

I know the procedure for putting a centre spot on, but taking one off? How do I get this off without damaging the objective?

Many Thanks

Markus

[Stonius]

Or does it matter, since the centre dot will be hiding behind the secondary in practice?

[barx1963]

Markus
With removing it, process is just remove it. as you said, the area where it is is in the shadow of the secondary so if you do happen to slightly damage the coating it is not the end of the world.
To get a new spot, just get a reinforcing ring (they sell packs of them at the newsagent. Then get some suitable paper (wrapping paper works fine) use a compass to trace a circle the same size as your mirror. This also puts a hole right in the centre. Place the paper over the mirror and with a texta, mark the centre of the mirror through the hole in the centre. Then place the ring as carefully as possible over that mark.

Job's done!!

Malcolm