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Don't drive yourself mad.


vlebo
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I recently bought an Orion precision eyepiece centering adapter Orion Precision Eyepiece Centering Adaptor

to eliminate any focuser slop and help me collimate my scope more accurately.

Using it with my Baader laser collimator I found the secondary mirror was out so I went ahead and centered that then tweeked the primary and everything looked fine ( much joy ).

I was just about to pack it all away when I thought I would check it again being the ocd person that I am.

After checking collimation again I found that it was out by a good couple of centimeters so again I tweeked everything and got it right .

This happened a few more times and I was beginning to get quite frustrated especially since I had not even moved the scope from its position but just moved it about on its mount to emulate a viewing session.

Finally rang a very helpful chap at Harrison Telescopes to find out if I had a faulty item and he told me that even by eliminating any focuser slop and centering collimaters etc there are still many variable that can affect collimation such as even tilting the scope to horizontal and back again can move it by a few mill especially with one as big as the 300 and mass produced machining tolerences do not guarantee accurate fit and finishes etc. I tried one test he mentioned where I have the laser on the donut and just by moving my focuser out a little the red dot moves out of the donut proving innacurate tolerances.

So I have come to the conclusion you can never get collimation 100 % all of the time with mass produced scopes so roughly right and just enjoying viewing will be the order of the day. I know much is written about how important collimation is especially for astrophotography but for viewing I will be spending more time under the stars than driving myself mad about getting collimation perfect.

There you go , feel better already.

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Hi Viebo - if you were doing this on the flextube - check the locking nuts to the side of the T-bolts on each truss. They need to stay in the same place once collimated as they help to maintain the accuracy.

They come factory set and taped in place - but like most people I thought it was just to do with packing - took the tapes off and adjusted them d'ohhh.

Once you reset them on an accurate collimation it should hold for several sessions and only need tweaking once in a while. :D

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Thanks Deneb and Brantuk

I did the same and took the tapes off but I thought they were just for tensioning up the trusses so it does not come crashing down if they were too loose so I have them set pretty firm but never adjust them.

Edited by vlebo
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You're welcome Viebo - I can only echo Denebs advice then - my hotech is on it's way as we speak - apparently it does self center'ing so I'm looking forward to that. :D

Edited by brantuk
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You're welcome Viebo - I can only echo Denebs advice then - my hotech is on it's way as we speak - apparently it does self center'ing so I'm looking forward to that. :D

That was the idea with the Orion adapter but you could also use it with eyepieces etc. Should I spend another 100 odd pounds for a Hotech ? Am I slowly going insane ? Stay tuned.

Edited by vlebo
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Hi there Vlebo. Don't worry, you are not going mad. Collimation is easy...

If I were you, I'd be ensuring that my primary mirror is tensioned tight enough against the springs. To do this, loosen all the locking screws, then tighten all the 3 adjusters to the max. then loosen all three of them by 1turn.

Then you adjust the primary (when it comes to this) on 2 of the 3.

This little trick ensures that when you tilt the optical tube assembly from upright to horizontal, the primary mirror is held as firm as it can be. Personally, I never use the 3 locking screws and rely only on the mirror cell springs to keep the mirror held firm

Coming to the change in collimation, to avoid any possible focuser errors, ensure all the screws holding the draw tube are correctly tensioned.

Finally, it is not at all rare for people to discover that the Baader laser is itself, out of collimation. This means that if you remove and inadvertatly rotate the orientation of the laser in the focuser, then the beam will now point to a different place, thus fooling you into re-collimating.

since the baader is a wierd shape, the process of checking the collimation of the laser itself is not easy.

Get yourself a collicap and a mechanical cheshire and you will not have these problems. Sure, it will not be as convenient when it's dark, but you will have a fighting chance of getting your collimation right every time.

Hope this helps

BR's

Edited by albedo0.39
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....but for viewing I will be spending more time under the stars than driving myself mad about getting collimation perfect.

There you go , feel better already.

I with you on this - I use a cheap laser to get the tilt of the secondary correct and an old plastic cheshire to do the primary tilt then a quick final tweak of the primary under the stars - most times it's only the final tweak required.

From my observing experiences with it, my Orion Optics 10" newtonian seems to be performing pretty much as well as a 10" can with the observing conditions being the most significant limiting factor. So I'm happy :D

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Thanks everyone for your help , Albedo , I will check everything as you advise to make sure everything is ok and see how it goes from there and tonight (weather permitting ) I want to get some viewing in and do a star test .

Thanks again.

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Hi.

I have a flextube with an Orion adaptor, and one thing I read was to tighten the locking screws in the same order each time to minimise the effects of assembling the scope on your existing collimation. This works surprisingly well for me and you soon get in the habit of working your way around the scope in the same way each time.

Alex

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I've build and used newtonians from a 6" f4 through to a 29" f5......

All I used was a Cheshire and star test to collimate! You CAN use a Cheshire in the dark; you just need a torch to illuminate the side mirror.

Lasers CAN work very well but they must be checked to ensure they are infact collimated themselves. If the laser spot is smack in the middle of the central doughnut ring on the main mirror and the reflected spot on the secondary mirror lies on top of the initial spot on the secondary mirror - you're not far away from collimation.

A quick star test should verify this.

( Nowadays I rely on the laser collimator to align the optics in my spectroscopes and it works 100%)

ken

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