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Collimation (Again :) )

littlebeagle

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littlebeagle

littlebeagle

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I'm reading Astro Babies guide and I'm certain my collimation is out.

Here is what I've done.

1) Checked the spider vanes, they were fine.

2) The secondary mirror appears as a circle through the chesire.

Now it's the third step I'm struggling with, when I look through the cheshire I can only see one of the clips holding the primary mirror in place, I was trying to adjust the tilt with an alumn key but they don't seem to be turning, the spider vanes are flexing though, any ideas? I'm scared of breaking the spider vanes holding the secondary in place.

(Skywatcher Flextube 200p)

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Leigh

Leigh

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Hi,

Not sure if its the right thing to do but I had the same with flexing spider vanes on my Omni XLT 150.

I loosened them off slightly which worked for me. It was only a very small amount, but enough to allow me to adjust the secondary.

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TheThing

TheThing

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Seeing the mirror clips is not always necessary (or possible!) for accurate collimation on some scopes.

Throw A_B's guide on the bin - it's fussy and over complicated. Google Andy's Shot Glass (seriously) for the best and easiest guide anywhere.

TheThing

Sent from my iPhone using Tapatalk

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Adz

Adz

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Hi,

Not sure if its the right thing to do but I had the same with flexing spider vanes on my Omni XLT 150.

I loosened them off slightly which worked for me. It was only a very small amount, but enough to allow me to adjust the secondary.

Not the right thing to do buddy, keep the spider vanes nice and tight, with equal distances to the middle centre screw.

Then use the centre screw to loosen off and get position along the OTA perfect for the adjustment screws to finish the appearance into a circle.

HTH

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Nova

Nova

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Adjust by loosening and tightening. Doesn't matter which way you do it but I normally loosen one and tighten the other 2. Just keep playing until you get the mirror moving in the right direction. You will need to make sure all the screrws are tightend when your finished

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Leigh

Leigh

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Not the right thing to do buddy, keep the spider vanes nice and tight, with equal distances to the middle centre screw.

Then use the centre screw to loosen off and get position along the OTA perfect for the adjustment screws to finish the appearance into a circle.

HTH

Sorry didn't mean to confuse matters!

I didn't mean loosen the spider vanes by the screws on the outside of the OTA but the 3 adjuster screws. :D

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umadog

umadog

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It's unwise to suggest binning atrobaby's guide. It is pretty complete and not over-complicated: it presents all the steps you need to accurately collimate a telescope and nothing more. There is a lot of good information in there and the eyepiece views are shown correctly. It should at least be used alongside the shot-glass video.

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Grunthos

Grunthos

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It's unwise to suggest binning atrobaby's guide. It is pretty complete and not over-complicated...

+1

I just finished reading through it yesterday Found it very useful.

However, now find myself wanting more.

Signs of incipient collimation OCD! :D

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TheThing

TheThing

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A_B's guide just causes more confusion than it cures. 95% of the post on this board about collimation problems have been caused by that guide. Bin it and save the heartache.

Collimation is not a dark art, nor is it complicated, as Andy's Shot Glass shows. It's just a simple job of lining your mirrors up. Daunting at first, granted, but with a simple guide - dead easy. A_B's guide is not simple or good, I'm afraid.

TheThing

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Jason D

Jason D

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A_B's guide just causes more confusion than it cures. 95% of the post on this board about collimation problems have been caused by that guide. Bin it and save the heartache.

Really???

Can you share some of these 95% posts? Please provide links.

Jason

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kniclander

kniclander

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I am no expert but it's clear to me that Andy's shot glass misses out a couple of stages in the process, ie ensuring that the 2ndary mirror holder is centred and ensuring that the secondary is not too far up/down the tube. I suspect that often those steps won't actually be necessary so Andy's shot glass will work well enough.

A-B also provides a great tip about shoving a sheet of paper down the tube when working on the secondary which takes away all the confusing reflections.

there are actually lots of posts thanking A-B for her collimation guide and I can't remember any (except the one above) suggesting that it's been confusing.

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Duns

Duns

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Being new to this and about to undertake collimation of my first scope -aaagh! I have looked at both resources AB's and Andy's and from a newbie perspective I found them both very helpful in their own way. Andy's overview was easy to understand and the real detail of AB's gave a good detailed run through of the whole process. Taken in conjunction with each other - perfect (from a Newbie perspective) :D

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umadog

umadog

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The shot-glass guide is simple because it over-simplifies. The only concern I've repeatedly seen from AB's guide is this one about the mirror clips. If your secondary is too small then you will never be able to see all three clips. Advising beginners to ditch a more complete guide does them a disservice. If you don't like the writing style in that guide then there are other sources of information which cover everything: http://www.physiol.ox.ac.uk/~raac/collimationLinks.shtml The second link on that page is simple and covers most things using a combo tool. As you will see from those links, there is plenty of material out there more complicated than the AB guide .

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TheThing

TheThing

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Really???

Can you share some of these 95% posts? Please provide links.

Jason

No. If you want them, you search for them. I'm not doing it for you! There is a search facility at the top of the board which I'm sure you can get to grips with.

Experience (and I've been around this board a while, both as a member and as a moderator) has shown that A_B's guide causes no end of problems.

There's no point in beginner's referring to a 'guide' which causes more questions than it answers! It's not a guide then, it is a hiderance.

Don't get at me about it though - I didn't write it. I'm just pointing out it is unhelpful and providing an alternative which is much more user friendly.

I'm not associated with either A_B or Andy's Shot Glass. You don't want my advice? Don't take it! It's no skin off my nose if you struggle with collimation becuase you insist on following a so called 'guide' which is over complicated and fussy.

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Jason D

Jason D

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No. If you want them, you search for them. I'm not doing it for you! There is a search facility at the top of the board which I'm sure you can get to grips with.

Experience (and I've been around this board a while, both as a member and as a moderator) has shown that A_B's guide causes no end of problems.

There's no point in beginner's referring to a 'guide' which causes more questions than it answers! It's not a guide then, it is a hiderance.

Don't get at me about it though - I didn't write it. I'm just pointing out it is unhelpful and providing an alternative which is much more user friendly.

I'm not associated with either A_B or Andy's Shot Glass. You don't want my advice? Don't take it! It's no skin off my nose if you struggle with collimation becuase you insist on following a so called 'guide' which is over complicated and fussy.

I just happened to closely track collimation related threads in this website and other astro websites for a long time. I am quite familiar with all the popular collimation guides and videos. It is clear to me that AB’s collimation guide is well-perceived by those who struggle with collimation.

I did try to find negative posts about AB’s guide and I did manage to find a single post – yes, a single post:

http://stargazerslounge.com/beginners-help-advice/161591-collimation.html#6

But the above post belongs to you in which you stated that 50% of collimation related posts in this forum were written by confused readers of AB’s guide. Your percentage seems to have jumped to 95% in this thread.

Jason

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Macavity

Macavity

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I think I'll stay (relatively) out of this one. <G> Though I do note one omission or error, often made, re. leaving (/creating) a lateral offset for the secondary of a FAST Newt. Though only ~0.25" even then... Aside: I'm not convinced my TS/GSO provides sufficient flexibility (as yet)! :icon_salut:

I found a good thing - With CAVEATS (if in doubt don't!) was to strip down the scope completely. For secondary adjustment, I filed off any burs (smoothed) the end of (Bob's knobs) screws etc., applied a light greasing to threads etc. Then spent a while turning things back and forth until adjustment became a lot smoother and reproducible. Also, I was able to reassure myself re. "adjustment limits" - The innate fears that something might "fall off" and smash stuff! Also managed to extract (judicious / gentle taps) the whole primary cell, and repeated the general "tidying" and "loosening" process. Gave mirror a much needed clean too. It had gathered quite a lot of wood-dust and fluff, from (observatory) "commissioning" etc. :confused:

But it all works a lot more smoothly now. As I learn my own(?) technique, I find I do a lot more of the initial adjustments "by eye" now - Common sense dictating, rather than (as before!) stressing over identifying WHICH "circle" is which etc. <G> The result seems to agree quite well with a final laser check too. :p

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TheThing

TheThing

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I just happened to closely track collimation related threads in this website and other astro websites for a long time.

Sounds like you need to get out more.

I'd hate to get stuck talking to you at a party, but possibly, you don't go to any as you're too busy 'tracking posts'? :p

Like I say, take it or leave it. I don't 'track posts' but I do try the advice out and, in my experience, A_B's guide is over complicated and fussy.

Can't argue with experience I'm afraid.

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