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Bob's knobs.


RonC
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Guest Tweedledum

Without doubt the easiest way to collimate an sct is using Bobs Knobs. As Doc says replace one at a time else there will be a nasty tinkling of glass as the secondary hits the primary, check on the website which are needed for your Newt!!

Hi Catman,

They are a replacement for the fiddly collimating screws that you find on most SCT's and newts.

Check out :---http://www.bobsknobs.com/

Cheers

Edited by Tweedledum
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Let me explain what they are.

You know the little allen key adjustment screws on secondary mirrors, well they are a pain in the rear to adjust especially at night, so Bobs knobs replace these with hand turnable knurled knobs that are easy to adjust, they also do primary collimation knobs at the other end of your scope.

A worthwhile investment.

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Let me explain what they are.

You know the little allen key adjustment screws on secondary mirrors, well they are a pain in the rear to adjust especially at night, so Bobs knobs replace these with hand turnable knurled knobs that are easy to adjust, they also do primary collimation knobs at the other end of your scope.

A worthwhile investment.

Cool thanks doc. I might look into getting some. Need a laser collimating tool first.

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Guest Kheldar

Cool thanks doc. I might look into getting some. Need a laser collimating tool first.

No you don't, use a Cheshire. Learn it properly :)

Also yes, Bobs Knobs need to be fitted to every scope as standard. Also his springs for scopes with nasty o-rings or lesser spec springs holding the cells up.

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Oh man, you've opened a can of questions Stephen-what's a Cheshire and how does it differ from the laser collimating tool? I presume it doesn't have a laser?

Felix

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Guest David Pugh

If you haven't checked your collimation. I would give it a go, mine was quite far out. Wasn't a bad as I thought it was going to be, bit of searching on the internet to find what you are looking for. It took me a couple of sessions, first was a trial run, just to see the patterns and to determine whether it was out or not. Had difficulty seeing the patterns on the stars I choosing and TBH I was over de-focusing, then I think I read on here to use Polaris. After choosing that, didn't have much of a problem.

After adjusting I really could see the difference in the viewing, much crisper. Maybe that's what I wanted to see, definitely thought I saw a difference. Probably still not quite right, so will give it another go next session.

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If you haven't checked your collimation. I would give it a go, mine was quite far out. Wasn't a bad as I thought it was going to be, bit of searching on the internet to find what you are looking for. It took me a couple of sessions, first was a trial run, just to see the patterns and to determine whether it was out or not. Had difficulty seeing the patterns on the stars I choosing and TBH I was over de-focusing, then I think I read on here to use Polaris. After choosing that, didn't have much of a problem.

After adjusting I really could see the difference in the viewing, much crisper. Maybe that's what I wanted to see, definitely thought I saw a difference. Probably still not quite right, so will give it another go next session.

Thanks david. Kim very kindly collimated my 200p recently so think it is ok. Just wondered why Stephen was recommending a Cheshire over a laser collimating tool.

Felix

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As I beleive it (please correct me if wrong), a Chesire will allow you to collimate the secondary, where the laser will allow you to collimate the primary. You can barlow the laser collimator to collimate the secondary but I`m, not 100% how you would do that. Martyn did mine when I first got it, but I need another lesson.

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Hmmm I am confused a when Kim collimated mine with a Hotech laser collimator we did both the primary and secondary? Well there's another question added to the list for tomorrow :)

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I've tried both methods, and a colli cap, hut there wasn't a lot in it, so I went for personal choice and bought a laser one, eas, y to use what I would do is use a colli cap to do the secondary mirror and a laser for the primery

Edited by red dwalf
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IMO you can't beat the Hotech laser Collimator.

Undo the centre screw on the secondary mirror and insert a collicap this moves the secondary mirror, the idea here is to get the mirror looking as circular as possible, and to see as much of the primary mirror clips as possible, if done right precious light would not be lost and the image will be brighter.

Insert the laser collimator and turn the three secondary screws to adjust the tilt of the secondary until the laser dot is in the middle of the paper ring on the primary, this means the tilt of the secondary is correct.

Then go round the back and adjust the primary until the laser dot moves across the etched part of the collimator and through the centre hole, when this occurs the mirrors are aligned.

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Guest Kheldar

If you're prepared to pay £100 for a Hotech, I retract my comment.

However relatively new starters : that money would buy you two EPs at least :)

Now considering this you may say, well I can buy a cheap laser?

Problem is if you don't appreciate collimation, and what you are buying, you are going to get poor results and moan about it.

If you buy a Cheshire, apart from that fact it's foolproof (no lasers, fidding, fettling required) you also understand what it is you are trying to do.

Just my 2p ;)

Oh and before I forget, the best collimation in the world is still inaccurate if your centre spot is not correctly centred ;)

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Stephen I'm not knocking the cheshire I just found it awkward to use, Accuracy depended on where you placed your eye and it was impossible to use in the dark.

The good thing about the hotech is the self centering adapter so you know it's exactly centered in your focuser so as long as your centre marker on your primary is exact so your mirrors should be exactly in line.

What lets it down then is you place your eyepiece into the focuser tighten your grubscrews and it pushes it to one side so now you are not exactly aligned.

To combat this buy a self centering adapter from orion and insert this into your focuser then your eyepiece into the self centering adapter and all will be perfectly aligned.

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Guest Kheldar

Stephen I'm not knocking the cheshire I just found it awkward to use, Accuracy depended on where you placed your eye and it was impossible to use in the dark.

The good thing about the hotech is the self centering adapter so you know it's exactly centered in your focuser so as long as your centre marker on your primary is exact so your mirrors should be exactly in line.

What lets it down then is you place your eyepiece into the focuser tighten your grubscrews and it pushes it to one side so now you are not exactly aligned.

To combat this buy a self centering adapter from orion and insert this into your focuser then your eyepiece into the self centering adapter and all will be perfectly aligned.

Sorry mate my post was not in reply to you, it was for Daz and catman

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