Help please ;) Skyliner 250 collimation

[Woking]

Hi

We are having a real struggle collimating the skyliner 250.

Using Astrobaby's guide and

- both refer to viewing the primary mirror clips on the edge when centering the primary onto the secondary mirror, but this seems impossible as the the primary reflection is just too big.

Anybody else with a skyliner 200 manage to align using the primary mirror clips or just rely on the small centre cirle?

We are also having problems getting the secondary centred in the focuser (using a cheshire), it seems stuck to one side and no matter how many times we adjust the phillips or allen key screws just can't get it centre. Thinking of adjusting the spider vanes now.....

Worth a try but is there anybody in the Castle Donnington, East Midlands area who can help?

[NGC 1502]

If you cannot see the primary mirror clips, have you racked the focuser out ? If the focuser is too far in, that could be part of the problem.

Or perhaps this may help ?

http://stargazerslounge.com/topic/181796-collimation-help/

Hope you sort it, Ed.

[Woking]

We followed Astrobaby's guide so did have the focuser racked all the way out but fear we may have made a school boy error........believe it or not we did'nt notice what appears to be an extension tube between the end of the focuser tube and EP (is this a reducer / flattner? I don't know as never used one with my frac!).

So with this in we had given up on trying to fit the clips in the focuser/secondary view and carried on with the collimation. Taking it out for a star test we did see slightly out of focus stars but there was insufficient back focus, this is when we noticed this 'extension tube' the EP was in! We removed it but still could'nt achieve focus even with the EP plugged directly in the end of the focuser tube, which confused the hell out of me as surely this would have solved the back focus problem.

Ideally want to know the sure if we've identified the problem and should recollimate without this 'extension tube' thing, before starting the whole process again. It's been a few hours, it's late and it's frustrating clear but the moon is rising......fresh minds and a new day required

Hope none of the Surrey Observers dob mob read this, as this frac boy is hanging his head in shame

[jabberwocky]

The secondary is much easier to do with a collimation cap rather than a Cheshire, less to look at.

as for the extension tube as you describe it, I assume this is the ep adapter and needs to be in otherwise the Cheshire may hit the secondary.

just to check you aren't using both adapters? The 2 inch and the 1 1/4, only use one at a time

[umadog]

The secondary is adjusted with a sight-tube. The primary with a Cheshire.

[Stargazer_00]

I can't see the clips on mine either. Haven't played with it much to work out how pain full that's going to be. Not sure how close I out of view they are but it shoes mean that not all the mirror is hitting the secondary. Dunno Why that is as I haven't adjusted it much since it came from the factory.

[Woking]

The secondary is much easier to do with a collimation cap rather than a Cheshire, less to look at.

as for the extension tube as you describe it, I assume this is the ep adapter and needs to be in otherwise the Cheshire may hit the secondary.

just to check you aren't using both adapters? The 2 inch and the 1 1/4, only use one at a time

That's exactly where we went wrong, we were using both the 2" and 1.25" adaptors

Pic attached of this 2" adaptor, couple with the rather long 1.25" adaptor and the focuser fully racked out, no wonder we were struggling with the cheshire I'm used to star diagonals and the 1.25" adaptor being inset into the 2".

I've looked through various dobs and Newts and obviously not paid enough attention.

Well hopefully once we retry collimation with just the 1.25" adaptor in, all should be well as we've definitely learned collimation the hard way.

Just very frustrating as there were a good few hours of clear skies last night before the moon put in it's appearance, if it wasn't for a very silly error we could have been making the most of it.....

[Stargazer_00]

I didnt see clips using a 50mm extension, the standard 1.25" converter is 35mm if i recall correctly. It didnt bother me though as my collimation is currently spot on using a lazer. I havent had to tinker much with my secondary as it present a good circle to the EP (even though I cant see clips) and centres well using lazer. Star tests show perfect as well so im not inclided to argue with it yet. I'll do that next week once I've flocked it.

[Woking]

Hope you have an easier time with it than us.

It didn't help that all the guides and diagrams we were referring to showed the clips perfectly on the edge within the primary reflection on the secondary, this really threw us off course and in the end just relied on getting the small primary centre circle slap bang in the middle. The stars we tested with were just a frustrating focus tweak away and not being able to backfocus enough must have been down to collimating with both 2" and 1.25" adaptors attached in tandem. Obviously will not know for certain until we attempt the whole process again, but at least the secondary looks spot on.

[Stargazer_00]

Made a thread about the clips issue here:

http://stargazerslounge.com/topic/182072-250px-issue-is-the-supplied-secondary-mirror-too-small/

Has a video on it I just made showing the issue.