Focuser alignment issue on a 10" Newt?

[tich]

Is there any way of checking that my focuser is aligned on my Skywatcher 250P as I think it's not very well aligned. It has the stock focuser with the 3 adjusting screws. When I put in a laser collimator & wind the focuser up & down the spot moves from side to side which is telling me that something isn't quite right with it.

[Dreadz]

stick some graph paper inside the tube behind the secondary and view with through a collimation cap as you rack the focusser in and out. If its not square the amount of squares visible around the secondary will not remain equal (hope that makes sense!!)

[tich]

Thanks for your help, I'll probably remove the secondary & place some graph paper under the focuser & either use a laser to check for movement or the coli cap method when moving the focuser.

[RichM63]

Why remove the secondary?

I understand what you are saying. Although I doubt that the focuser can be miles out.

I had similar problems when I bought the S/H 200P. Focuser out of kilter, secondary vanes way out.

I would first have thought that you need to be 100% sure that the laser is colimated and absolutely centered in the draw tube, otherwise the dot will move when drawing in and out.

In the end I had to opt for a DIY method due to lack of equipment.

2 bits of coloured card.

The yellow one to block the primary and the pink one placed opposite the secondary.

You will see that in the first pic my spider was way out. The PO had been playing with it.

Then after tweaking and adjusting it got better.

Using a point and shoot camera and Al's Colimation aid from an Aussie genius I managed to get to near perfect.

HTH,

Richard

[Jason D]

When I put in a laser collimator & wind the focuser up & down the spot moves from side to side which is telling me that something isn't quite right with it.

The laser beam is not parallel with the focuser axis. Several causes:

1- Your laser collimator is not aligned

2- The drawtube of the focuser is misaligned with the focuser casing

3- The laser collimator tilts when tightened in the drawtube

[tich]

I've rotated the laser collimator & the spot stays in the same place, as it's a Baader MK III it can not be aligned which leads me to believe that the draw tube is out of alignment in the focuser housing.

I had a look at the draw tube last night & it does appear to be very close to one side of the focuser housing than the other.