colamination

[todd8137]

hi every one just a few quick ones ,as ya can see from my pic a made when i look down the cheshire this is the view i have the circle on the main mirror seems to be just under the cross but down and to the right of it see pic,

it does not seem to cause any probs with the 12" dob i have should i tinker with it?

am i be in to Concerned about this ?

would this be better to just leave it or to turn a few screws i no i must take the plunge at some point,but like the heart of a little tremberling bird caught in a trap a dare not touch it the only other answer would be to join the local astro group and ask a member to of set it more than this and then show me how to corect this a bet am just be in over cautious and not wanting to do this and to be honnest not really sure what to do any comments would be great

which screws moves the miror so i can align them together

screw1 or screw2 ?

you all must think i am so thick

pat

[John]

Hi Pat,

Have you read Astro Baby's guide to collimation ? - it explains what you should see down the cheshire, what you might see and what you can do about it:

Astro Babys Guide to Collimation

[todd8137]

yes did that ,now round the back there is 3 big round headed ones and three skinny ones which one`s do i turn to move the main mirror ?

[jwallis]

Hi there. The largest screws, with the big round head are the ones you need to move to align the mirror. Before you do that though,loosen the smaller 3 screws. Once you have collimated your scope, tighten the smaller 3 screws to hold it all in place. Once you have done this a few times, it does come a lot easier. By the way, if your secondary mirror is ok, leave it ,because that is the one that takes a bit of time to get used to aligning. Hope this helps, Jon.

[todd8137]

yes thanks for ya help there jon

[todd8137]

so just to get this straight i am try in to get the black dot has a look down the cheshire in the centre of tHe eye piece because if ya look pic drawing" no 3", B is what a see at the minute the dot is just under and to the right a bit.the A is were it should be a think in the centre of the cross

the ring binder is just hidden in the black ring ya can just see a bit of white were a drew a circle to show were this is HELP

just as a quick one the big black circle is not the donut/ ring binder ,thats the outer edge of the view of the cheshire where it says ring binder follow the line and the ring binder can just be seen on the inside of this black ring through the cheshire so it must be out by miles

[umadog]

If I correctly understand where you are in the process, then it's the secondary mirror which you want to be adjusting, not the primary:

John Reed Home Page Collimation - Cheshire

Just keep playing with it, you can't break it.

[xboxdevil]

Hi Pat

Before you adjust these screws on the primary mirror you should check out that your secondary mirror is correctly aligned and rotated. When you are happy with that you then move on to the primary mirror.

You may know this but by now, but just to make it clear you need to turn the thinner (You've labelled number 2) thumb screws a few turns anti-clockwise to release the tension, then turn the larger thumb screws (You've labelled number 1) clockwise until you hit a stop when the mirror is right back in the tube. Then turn the large one's back anticlockwise by one full turn before finally adjusting two of them clockwise until you get alignment.

Good luck and don’t let the collimation spoil your views if you can get tight focus on a star to a pin point then you are ok. I’ve used my scopes visually when they were way out and in the main it didn’t bother me that much.

[keef_uk]

Is there any truth in the 'tale' that refractors dont require collimation? I have never had to do anything to my Celestron 102SLT but im worried that I may someday!!

[todd8137]

thanks xboxdevil done that will wait to test it on a star now ,thanks all pat

[tomw28]

Is there any truth in the 'tale' that refractors dont require collimation? I have never had to do anything to my Celestron 102SLT but im worried that I may someday!!

I don't think refractors need collimating but no doubt someone more experienced will correct me if I'm wrong.

Tom

[xboxdevil]

thanks xboxdevil done that will wait to test it on a star now ,thanks all pat

Cool, when I mentioned focusing on a star it was more just as simple test to see if things look ok, when my collimation was way out the focus would not come to a central point and the Moons around Jupiter were oval, towards the end of this article it explains a proper star test in more detail: SkyandTelescope.com - Do It Yourself - How To Collimate Your Newtonian Reflector

[Doc]

I don't think refractors need collimating but no doubt someone more experienced will correct me if I'm wrong.

Tom

Quite a few of the larger APO refractors come with collimatable mirror cells so I suppose the answer to your question is Yes, if they get knocked out of collimation then it's fixable.

[John]

Refractors do need to be collimated occasionally and some are fitted with collimatable objective lens cells for that purpose. They generally hold their collimation very well and it rarely needs adjusting once done. I've done a few and frankly they are easier to do than other scope types, in my opinion.

[LukeSkywatcher]

Just keep playing with it, you can't break it

Famous last words those.

Its true though. Just keep turning the collimation knobs a bit until everything is nice and centred.

I think i'll check mine tomorrow. Just in case.

[jordanclarke]

can anyone recommend what equipment i will need to collimate when my 8inch dob arrives, like any specific brand?? cheers

[todd8137]

now the donut is in the centre and not high and to the right i fully understand the thing now(hahahahi hope and think) and have re done the pic to show how it now is

[todd8137]

yes a think a have done it

[todd8137]

got it done now thanks donut over the centre and not high and to the left

[John]

got it done now thanks donut over the centre and not high and to the left

That sounds good

Hopefully it will more or less stay put now and you will only need to fine tune things before a session.

[Bigdaddyjeff]

I'm about to order myself a collimator to make sure my scopes set up as well as possible so i'll be coming back to these posts real soon

[todd8137]

yeah hope so johninee checkedit wenfi got itbuwill have no probs do in it now thankds to every ones help

[sixela]

Is there any truth in the 'tale' that refractors dont require collimation?

Yes and no. They keep collimation a lot better, so it's often true that if factory collimation is correct you won't have to adjust it.

But I've collimated enough Synta refractors to know that the factory collimation isn't always correct . I even saw one where the objective cell was cross-threaded in the tube, and more where the focuser wasn't exactly pointing the right way.

[todd8137]

bigdaddyjeff hi the paper work was double dutch to me astrobabys guide sorted me out take a look,hope things go well when you get round to it

[Bigdaddyjeff]

thanks todd...have just ordered me a relevation collimator so hopefully get myself sorted and i'll be taking a look at astrobabys instructions too...happy viewing