Now what do I do?

[Zachariah]

I am trying to collimate my SW skyliner 150. But the screws holding the secondary mirror are so tight I cannot budge them, despite holding the mount tightly. Looking through the eypiece with a cap everything looks not to bad. But using a laser the secondary is out and the primary. If I grt the primary right everything is out looking down the focus tube

If I cant shift the screws in the secondary is it best to get as near to perfect using a coll cap and looking diwn the focuser?

[Kai]

If you undo the screw in the centre of the secondary 1/2 a turn this will lessen the pressure on the adjustment screws so you can use them.

HTH

[Zachariah]

Thats the screw that I cant budge. I very nearly twisted the spiders.

[sabana]

Hi

Just hold the vane with the other hand. If it then still insists on twisting, you're at the end of the the thread for the bolt that holds the vane, and then you need an extra washer between the tube and the bolt .(This is a common probem so an extra washer is oten advisable).

[Zachariah]

Well tried that and the ****** will not shift.

[Kai]

The im afraid that you are going to have to remove the secondary from the vanes and use a bit more force in holding the secondary (maybe clamped in a vice).

[Zachariah]

Thanks. But I would have to remove the secondary and the vanes by using the 4 nuts on the outside of the tube. Pretty drastic. I dont have a vice either. Why do they make them so tight

[stevetynant]

can you carefully put some WD40 on the nut and let it soak - a very small amount I'm talking and use the straw and perhaps some kind of shield to ensure you don't get any on your mirrors?

[Kai]

Pretty drastic. I dont have a vice either. Why do they make them so tight

Ive found that it the over adjustment of the three grub screws that is the problem rather than the middle screw.

If you want to loosen them then you are going to have to bite the bullet im afraid.

I dont think that WD40 will work as the screw on the outside are under compression and the middle screw is under tension rather than seized.

[Mr Q]

Before you go banannas with the secondary, do a star test to see if the amount the collimation is off is worth the trouble. The link below shows the effects of bad collimation on planetary detail.Thierry Legault - The collimation

[Peter Drew]

You have far more chance of freeing one of the three adjusting srews rather than the centre one. The centre screw is being held with the combined pressure of the other three, either one of which, onced freed should release the others.