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SW 150P collimation help

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When I purchased my scope I was told that it would be factory collimated but looking around on the net it soon became clear that it is worth checking the collimation anyway. So after various how too's and tutorials I finally plucked up the courage to give it a go. When centered on a bright star I took the scope out of focus the halos that appear were going off to one side of the stars position so, using a home made collimating cap (35mm film case) it was clear that the primary mirror was a fraction out (could see all the primary mirror clips in the secondary so left the secondary alone) so I adjusted the primary and it is now spot on in terms of visual allignment however when I performed the star test again the out of focus "halo" around the star still goes off to the side of the stars actual position. Have I missed something? I thought the halos that appear should radiate out with the star at the centre?

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hi there

I am no expert with star testing but it's vital that the star is exactly in the centre of the field and stays there. for this reason Polaris is a good one to use.

if I were you, I'd invest in a Cheshire eyepiece as this will allow you to be more accurate with collimation - I collimate my scope every time I use it (at least the primary - the secondary does not often need any adjustment).

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Yep, have looked at the cheshire and it is going on my ever lengthening shopping list. I did try to collimate the primary whilst veiwing the star to try and centralise the halo but had no luck and ended up throwing the mirror way off. Still its all good practise!!

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The collicap may get you close, but the slightly out of focus star test tells the truth.

From what you have said, the secondary is ok, so the primary adjustments are the

ones to sort it. And Shanes post (#2) is important too, after each tweak on the screws,

centre the star to check.

To decide which screw to adjust, if you place a finger over the front edge of the

tube (with the star way out of focus) you can see your finger, try different positions

to decide the appropriate screw. As you get closer to correct collimation, the adjustments

are quite tiny.

Regards, Ed.

Edited by NGC 1502
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