I've hit a collimation problem

[Ogri]

With a Cheshire collimator that has the cross hairs.

Nothing wrong with the Cheshire (a very nice bit of kit tbh), it's my eyes, I lose the cross hairs and the bits I want to line up.

Spent hours on it, and I'm pretty sure I have everything in the '9 ring' but just can't seem to get a good enough focus on things to get it all '10 ring'ed up'.

I also found I am getting an 'egg shape' with the concentric circles (why I had to give up competitive smallbore rifle shooting, as it was no longer possible to put every round through a cigarette lengthways), but persevering seems to have paid off in that regard, and I am not too unhappy with the concentricity.

Sadly it's thick cloud here tonight so I can't look at any stars to see what the effect is.

So:

Would '9 ring' accuracy of alignment have a particularly bad effect on the views?

And

Would a laser collimator get me around some/most of the problem?

TIA

[Ogri]

Update: Pheeew! Obviously I was worried I might be lumbered with a 'Close, but no cigar' situation, but it looks like '9 ring' collimation accuracy I can live with.

Woke up about 5:00 am and the sky was clear! Betelgeuse and Orion clear as a bell to the South!

By the time I had the 'scope out, I could see it was rapidly starting to get light though, so not even a chance to let the 'scope cool properly.

Had to lift the extension tube in the focusser to get focus on Beltelgeuse, but it came up pretty sharp with the 32mm Meade 4000 SP. Popped the 20mm erfle in and I could see the light was increasing fast now, so a quick first hello to Orion's Belt for the new season, then pack up fast and in for a coffee.

Not just a Pheeew, but a DOUBLE Pheew!

[Moonshane]

hi Ogri

sounds like you got it nailed in the end. personally, I have found that collimation is one of those skills that seems really hard when you start but once it all clicks you wonder what you worried about.

star tests are a good way to tweak the final 5% of accuracy out of the collimation but you really need good seeing for this to do it right. maybe a 'false star' is the way to go. might have a think about this myself.

[Ogri]

Obviously there's the 'how does this work then?' aspect, hehe, but I was getting on pretty well (John sent me a link to a nice little video which was a good help, plus A_B's guide helped too) until all the things started to get close together in the view - then my eye problems kicked in.

I literally lost them altogether, once they got into the central concentricity area. Things went invisible on me.

I knew they were 'about there' as I could see them until they got close, then it was a case of 'hide and seek' and I couldn't find.

Yes I should think a false star might well be an option!

[callisto]

Hi Ogri,

What was the video link John sent you if you dont mind me asking

Mark.

[Ogri]

It was this one Mark - Collimating a Newtonian

[callisto]

Thanks for that

Cheers, Mark.

[Moonshane]

Yes I should think a false star might well be an option!

always good to know how what you are using works

re artificial stars I have done some digging on the net and it seems that unless you can get it well distant (100m or more) they are not too useful.

[Jason D]

I also found I am getting an 'egg shape' with the concentric circles

If by "egg shape" you are referring to the secondary mirror shadow then that is normal. Check attachments.

Jason

[Ogri]

Thanks for that Jason, I figured what I see of that is fairly normal, I get the 'telrad type' rings in the bright centre egg shaped as well though.

My eyes really are a crock . . . . .

eta: see the centre dot, then white ring, then grey ring before the first of the thick white rings? As soon as anything gets anywhere close to that central grey ring, I lose it. So that's what I call '9 ring' accuracy. I can't tell where anything is from there to the very middle.

Given the way a laser collimator works, that should allow me to get a result in that region (I think a false star might work too)?