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You want to get it so that everything is circular and everything except the secondary shadow is centred under the crosshairs. I would give it another go tomorrow and see if you can improve.

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It think i have broken my telescope because i think both my mirror are out and i cant fix it.... Tried everything online but still cant get it back to how it was... Can anyone help before i get rid of it 

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32 minutes ago, Anthony1979 said:

It think i have broken my telescope because i think both my mirror are out and i cant fix it.... Tried everything online but still cant get it back to how it was... Can anyone help before i get rid of it 

Have you got a local astro' society nearby to help, maybe Peter Drew at Todmorden Observatory would be prepared to help, not too far from you.

Dave

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No you're OK you haven't broken it don't panic. 

Collimation of a scope is somewhere between a skill and an art. Primary collimation (the big mirror) is easy and takes a few seconds: secondary collimation (the little one) is a real pain and can take hours the first time - and I do mean hours. But luckily you don't need to do it very often. 

Deep breath, cup of tea, go slow and you'll get it. 

This guide is absolutely brill and takes you through the whole process:

http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/

Niall

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Ive tried following online instructions but dont seem to be getting anywhere... I on the job now but getting really frustrated because i dont no what out of align 

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best take a break if its getting frustrating, that path can lead to over adjusting and more frustration. Then when you restart, find a couple bits of coloured card/paper so you can blank off the primary (insert it partway into the tube below the secondary) and behind the secondary so its easier to see its shape. Then get the secondary central under the focuser as a first step and concentrate on the effect of the 3 tilt screws. You may have to shift it up/down the tube using the central lock screw and then adjust the tilt screws to get it true. The gently nip up the lock screw to secure it in place.

Once the secondary is central remove the cards and get the secondary aligned to the primary with small tweaks on the tilt screws, you should be able to see the 3 clips on the primary carrier evenly spaced, ignore the shadow of the focuser tube. Lightly nip the lock screw up to secure that position and then you can look to adjust the primary. Undo the lock screws just a little and then observe the movement in the eyepiece as you turn each of the primary adjusters, you're now aiming to get things aligned to the centre spot. you may well have to go back and tweak the secondary slightly again just a little. Once done, nip up all the lock screws and recheck, repeat etc.

Can take a bit of effort and a LOT of patience but once done you should get nice sharp focus across the FoV, only way to know for sure will be a test on the stars, you may still find a small tweak is needed. That said tho, don't fret about it, enjoy the views for now and look to sort it laterwhen the patience quota has restored a bit 😉

 

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Good stuff, you can see what you're doing now! This does just take time+practice, don't worry. You basically can't break a scope doing collimation - just make sure not to touch the secondary mirror surface and you'll be fine.

It doesn't look that far out of plumb - you probably want to move the secondary "up" and then might need to move it closer to the front of the tube (done by slackening all three adjustment screws off a bit, then tightening the centre screw - gentle forces on all of this). That'll get the secondary centred in the cheshire.

Then take out the white card and have a look at your primary to get that well aligned. The various online guides with photos will help here, http://www.astro-baby.com/astrobaby/help/collimation-guide-newtonian-reflector/ is for your type (and nearly the exact same model) of scope.

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Posted (edited)

Are you following astrobaby's guide?

Basically you tackle it in two stages:

1. Secondary;

  • The reflections from the primary to the secondary give you a massive headache and are very confusing. That's why you use a piece of paper to block off the primary (like you've done), and ideally a different coloured piece of paper behind the secondary so you can tell the difference between what you are looking at. The secondary has three axis of adjustments - forward/back angled up/down and spun side/to-side.
  • Your first mission is to make sure the forward/ back movement is right eg; you can see the whole secondary mirror through the collimator. That is relatively straight forward - you do that by adjusting the big screw in the middle of the vanes.
  • Your second mission is to make the shape of the edges of the mirror exactly circular; you've got an elliptical mirror angled at 45 degrees. So you know that when it appears circular then the light from the main mirror will be bouncing perfectly at 90 degrees up into your eyes.
  • The third stage is adjusting the twist and angle so that you can see the edge of your primary mirror clips; so you'll need to take the pieces of paper out. Ignore everything but the edge of the mirror clips. You'll need to loosen off the three screws in the centre of the vane for this so you've got a bit of play. Avoid touching the mirror if you can but its not the end of the world if you do. It's important that you remember you aren't trying to "line anything up at this stage" as your primary may be out still (we'll get to that later)
  • If you can't see your clips at all - there's a chance that you have moved your secondary too close to your primary, or possibly your vanes aren't straight and tight but yours look fine. Try racking your focusser out all the way if you are using a Cheshire collimator, this sometimes helps. But either way the clearances are quite tight, with some scopes you can only just see the edge of the clips. Then tighten everything up.
  • There's a chance that these adjustments mean that your secondary mirror doesn't look quite circular anymore - so have another go.
  • This whole process is very very painful and time consuming. It really is a case of back and forth and back and forth and back and forth. The good news is that as long as you are reasonably gentle with your scope its only something you need to do every couple of years.

As a rule - collimating a scope usually only involves adjusting the primary, and this takes a few seconds and is only a tiny job.

2. Primary

  • Now looking through the collimator all you have to do is line up the centre dots of the main mirror with the cross hairs on your collimator. If your scope is f5 of lower then the crosshairs wont necessarily all line up perfectly due to something called the "offset" but that doesn't matter - just get the circle aligned with the cross hairs using the three adjustment screws at the bottom of the scope.
  • When done you should have: a nice circular looking secondary mirror, the mirror clips of the primary should be more or less equally visible, and the centre spot of the mirror should be in the middle of the crosshairs.

It's time consuming, it really is. But once you've done the whole thing once it gets much easier. And as above, a typical collimation only usually requires the primary adjustment which is dead easy.

Don't lose heart.

 

Edited by Mr niall
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ok, first you needed to adjust the secondary tilt to get the primary fully centred to the secondary - as in the full primary mirror and edge clips evenly in view. After that you adjust the primary tilt. You're aiming to tease the secondary just a little when looking into the eyepiece to get the primary fully in view, so small undo on one screw and tighten on another till you get the tilt where it needs to be.

From the image it looks like the secondary isn't getting a full image of the primary so while you've centred the dohnut marker the mirrors are still out of alignment.

It can be a painful process, I know. Tho saying that, nothing like shimming prisms in a binocular to get that aligned, each step was dismantle, try making another slightly thicker/thinner, reassemble and retest... took me something like 5-6 hours on that pair. You certainly learn patience, the value of a gentle/light touch and v fine movements and just when you feel like giving up you hit the right setting and suddenly it feels great to have beaten it.

Maybe take a break for a bit? At least once its done you'll only really have to tweak the primary occasionally and the secondary rarely once you've got it sorted :) 

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