Collimation: Help please!

[Supay]

I have had a Cheshire collimator arrive and I am trying to correctly collimate my scope.

It is a Skywatcher Explorer 200P. The manual with the scope is a bit dodgy as it seems to be designed for many scopes rather than the one I bought and hasn't even got the right number of parts in the images.

I just can't seem to get it lined up correctly and have been working on it for ages.

Here is my current positioning when viewing through the Collimator. This whole lot is pretty much bang on in the centre at the moment but I can't get them aligned with each other. To the top right I can also just make out one of the primary mirror clips, but not the other at the top left or the bottom one.

That thickly bordered circle in the bottom right I assume is the centre of the primary mirror, as I can see it if I look down the tube, but no matter what I adjust I can't get it to align in the centre.

Please can someone advise, it's driving me mad.

[yeti monster]

Have you checked the secondary position?

Have you checked astro babes collimation guide?

[Ben Ritchie]

Please can someone advise, it's driving me mad.

Mine arrived miles out of collimation, so it can be a pain at first. Once you're there it holds collimation well, so don't despair!

Astro Babys Guide to Collimation

[TheThing]

Andy's Shot Glass is the easiest guide to collimating I've found so far.

[yeti monster]

Ah, found it:

Astro Babys Guide to Collimation

This time I've also bookmarked it..........

[yeti monster]

I see I'm late again.........

[Supay]

Thanks for the quick responses guys, I'm plodding through it now.

Not sure why they bother printing the manual it came with, it's blumming awful for teaching you this and has had me adjusting all kinds of screws.

[Ben Ritchie]

I see I'm late again.........

Boring afternoon in an empty office

[Supay]

I can't get the secondary mirror to show as all the guides say. No matter what I do I can't get the primary mirror clips to show. One occasionally creeps into view, but that's the best I can achieve.

[Doc]

Loosen the centre bolt on the secondary only a little until the whole secondary twists. look through your cheshire and move the secondary around until all three mirror clips are seen and then tighten centre bolt.

[daz]

Put a sheet of white paper inside the tube, opposite the focuser. This will help identify what you are seeing when you look down the focuser

Is your secondary centered within the tube itself?

Where abouts in the country are you?

Are you going to Kelling?

[Supay]

Loosen the centre bolt on the secondary only a little until the whole secondary twists. look through your cheshire and move the secondary around until all three mirror clips are seen and then tighten centre bolt.

I've tried that, but no matter how I tilt or rotate the secondary, there simply isn't enough viewable area to get all 3 primary clips in view at the same time. I can see one, but the others are out of view, or I see none.

[Supay]

Put a sheet of white paper inside the tube, opposite the focuser. This will help identify what you are seeing when you look down the focuser

Is your secondary centered within the tube itself?

Where abouts in the country are you?

Are you going to Kelling?

The secondary is definitely centred within the tube and is the only successful part of my calibration so far. I live in East Sussex, Bexhill and unfortunately am not going to Kelling.

I've not lived here long and I believe the local astronomy society is meeting again soon. i might have to go along and plead for assistance!

[Doc]

Maybe the cheshire sight tube is to narrow, I use a collicap and I can see the clips in that.

Or maybe you might have to slacken the three collimations bolts a bit as well to give you enough tilt.

Also measure your spider vanes they should all be exact.

Until you get your three clips visible you will struggle with the rest of thr procedure.

[Supay]

Spider vanes are exactly the same length in all 4 directions.

When setting up I measured the vanes first, then I centred the secondary mirror in the focuser. Now I am stuck as, using both a home made collicap and the Cheshire, I cannot see the primary clips whatsoever.

I'm usually pretty patient with stuff like this, but I'm starting to get a little annoyed with the tube!

[Patrick1948]

I found this link to a short movie VERY helpful with Collimation of a Newtonion...hope it helps... Collimating a Newtonian

[Supay]

My primary mirror has a little circle right in the middle which I can see. By adjusting the secondary I can get that in the centre. Does that achieve the same effect as being able to see the primary mirror clips? Is it there as a visual aid because I am not able to see the clips in this scope?

[Supay]

Haha, it would appear that this is the purpose of the circle. If I align the secondary using the little circle to place in the centre instead, I can make out the tiniest sliver of each primary mirror clip on the edges in the right spot using my collicap.

Nice that the manual for the scope itself fails to mention this completely and tells me the clips are the important bit, yet you can't see the blumming things!

[Supay]

As far as I can tell, it is now collimated. Not utterly perfect, but a lot better than it was and I can now see the circles all aligned in the middle, the vanes centred and the clips in the corners.

Thank you for all the links and assistance, you've saved me from having a tantrum!

[Doc]

Well done, it's harder then it actually looks, now mess it up and start again

You can manage to line up your donut Ok but the secondary still be out. Does the secondary look perfectly circular when looking down the cheshire, the more circular the better.

[Supay]

Well done, it's harder then it actually looks, now mess it up and start again

You can manage to line up your donut Ok but the secondary still be out. Does the secondary look perfectly circular when looking down the cheshire, the more circular the better.

It does. I went back to the start once I had made the progress I did in managing to get the clips in view and began from scratch to ensure that all was correctly aligned. It's probably still not perfect, but for my first go, and considering the shocking alignment it was in, I'm pleased with the result.

I'm not sure why the clips weren't showing initially, but it all seems good now.

[Mikea]

Only one thing to do now.....star test!!

[Supay]

Had a go this evening. Unfortunately, while the skies are clear of cloud, it's blumming hazy up there and really humid this evening. It seems to be collimated properly but until I get a good night I won't be able to tell for sure.