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Hi all i am still asking lots of questions, erm so the scope I am looking at is the Skywatcher Explorer 150P EQ3-2 I have been aware for a while that they have to be Collimated every now and then is this tricky? Do I need a tool to do it? I know you can buy tools for this specific task and make your own?

Its just I am on a tight budget and mistakes are costly.

Edited by punchy

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Collimation is easy with a laser collimator. If you search scope collimation on youtube you will find some excellent tutorials.

Edited by Veracocha

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Hi There,

From memory there is also a guide on SGL by astrobaby.

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I had a go at collimating mine yesterday and it ended in a dilemma. After turning one of the screws at the back of the scope it all seemed aligned nicely but, shouldn't the screws be retightened afterwards? I had to loosen one of them to collimate so to tighten it would just make it uncollimated again. *confused*

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I wouldn't bother with astro_baby's tutorial. It is over fussy and too complicated. Half the collimation questions on this board seem to be caused by using it.

The clearest guide on the web can be found by Googling Andy's Shot Glass.

TheThing

Sent from my iPhone using Tapatalk

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I've found my 150p holds collimation very well, even with transporting it to the local astro club. I bought mine from RVO and they checked collimation when I picked it up.

I use a cheshire, but that's my preference. I first used Astrobaby's guide, but I agree Andy Shotglass's guide is easier to follow.

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I had a go at collimating mine yesterday and it ended in a dilemma. After turning one of the screws at the back of the scope it all seemed aligned nicely but, shouldn't the screws be retightened afterwards? I had to loosen one of them to collimate so to tighten it would just make it uncollimated again. *confused*

You should have two sets of screws or knobs to turn. Sometimes you have to take a plate off the back of the scope to get to all of this as they hide it away for some reason. Anyway, one set of screws are actually what the mirror sits on and the other set are just to tighten things up once you've finished with the adjustment screws. So loosen one set. Adjust other set. Then retighten original set.

Hope that helps

Steve

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Thanks for the pointers but Im still confused about the screw business. I loosen some screws, its looks collimated. I tighten the screws to finish which then causes it to become uncollimated again. Bear in mind I'm not really sure what I'm doing so there is a small chance it may not even need collimating but the point remains, if Im loosening screws they then have to be retightened which puts the mirror back in exactly the same position as when I started. (??)

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are you clear which are the screws for adjusting the collimation and which are the locking screws? you loosen the locking screws, adjust the collimation screws, and then gently finger-tighten the locking screws. Apologies if I've misunderstood. good luck:)

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I would bother with AB tutorial. Andy's Shot glass is wrong and misleading in places. Avoid. You can try this if you don't like the AB tutorial: John Reed Home Page Collimation - Cheshire

Don't loosen the screws. They always need to be relatively tight. You change the tension on the screws to move the secondary.

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Umadogg, are you saying you don't need to loosen the locking screws on the primary to adjust it?:) I always thought you had to but it could just be another of the many things I'm wrong about....:)

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Sorry, the locking screws. I thought you meant the secondary screws. Just loosen the primary locking screws and never tighten them again :). You probably don't need them. I didn't with my Orion 12", and that had a heavier mirror. The locking screws are there in case the mirror causes the cell to shift across different elevations. If you find this happens then you can swap the springs for stiffer ones.

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there are two sets of screws on the primary. the large ones are the adjusters. the small ones are the 'locking screws'. you loosen the locking screws right off. then collimate the primary (assuming you have already checked / collimated the secondary) with the big ones. in truth you could effectively remove the locking bolts as they do nothing really. if you prefer to retain them, then tighten them gradually and sequentially VERY lightly with fingertip pressure only and check the collimation as you do. to my eyes they are more trouble than they are worth.

Edited by Moonshane

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seriously, unless you are rebuilding a scope that has been taken apart, collimation is a two minute easy job. I'd recommend a Cheshire personally.

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Hi collimation is practice and common sence, all the toys like cheshires and lasers will help but though practice you will get a deeper understanding and a star test is still the best check. As a side point don't trust lasers they are mostly poorly collimated themselves and even when not the ones I have had experience of need very careful insertion into the focuser to obtain meaningful , repeatable information. I have just collimated one laser yesterday (sealed at factory and was out of true by 27mm! at 10meters. After ( less than the spot width (2mm at 10m))

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There is a common impression that lasers must be the best 'cus ...well...they're lasers...rather than a couple of bits of wire in a tube??? but I get the best, most reproducible collimation using a Cheshire. A 'must have' bit of kit.

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+1 on a cheshire/sight-tube. You need the sight-tube anyway to round the secondary. A laser isn't going to help there.

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I must admit that collimation intimidated me for the longest time until I purchased a laser collimator. Now, these are not cheap but I've been told that those made "at home" are quite reliable.

Isabelle

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There are many methods on how to do a collimation and it seems to me that it is all down to what sort of palaver you want to undertake and what scope you have.

I currently own a 4.5" scope and as it is just about managable to look though the eyepiece while being able to fiddle with the colloimation screws, I actually find the star-collimation to be the easiest and quickest way to collimate the thing, due to no central mark on the primary and with the optical centre of it being slightly offset from the geometrical centre (the central mark I made then is useless, or for general reference at least).

However, my thought are currently slipping towards purchasing a 12" newtonian scope which, given the OTA's size, renders the star-collimation useless, or impractical to say the least. So I reckon that for such a hulk, laser-collimator is the most practical way to go (using a barlowed technique perhaps).

For you, as you own a short-tube fast scope, I would suggest trying a star-collimation. You might eventually find it to be rather easy, plus you do not have to purchase all the extra gubbins - a simple collimation cap is all you need for aligning the secondary. :)

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Ah! I think I can see where my confusion is coming from. Where you talk about locking screws and adjusting screws Im confusing that with the screws that hold the back plate on and the adjusting screws, I don't recall seeing any locking screws(?) Unfortunately my scope is kept at my mums and I can't check it right now.

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Hi if you need any further help, I'm only in swadlincote south derbyshire, so have sent a private message with phone number.

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I have used A.B.'s collimation guide and a collimation cap to good effect. It is quite long winded, but as a first time collimator it helped me understand what I was doing. Although she describes using a cheshire for aligning the primary, I persevered with the cap. Finally a star check and a tiny tweek. Negligible cost for those on a tight budget and good results. :)

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