Nightmare Collimating SW Skyliner 200p Dob

[aurochs]

I am in desperate need of some information. Skywatcher arrived today and I have looked at it and it needs collimating (for starters I can only see two pegs of the primary mirror). BUT none of my allen keys will fit it to adjust the secondary (at least I am pretty sure that's what I need, anyone with the exact same scope?). Literally tried all I could find and they don't do anything.

What tools, being as specific as possible, do I need to get?

Thank you so much for any help.

[JamesF]

I've not owned a newt from new, but they don't supply any suitably allen keys with it?

James

[Spec-Chum]

IIRC the Allen key for the secondary was in a random bag with some (unrelated) bolts on mine.

However, I didn't get a 2.5mm for the primary locking screws.

[SamAndrew]

Not sure what size allen key you need without checking mine, but I think it's 2mm

I think I found mine a bit tight to get the key in the first couple of times

[aurochs]

Oh god false alarm We were setting it up in the living room and one the plastic bags fell down the side of a seat - containing the allen key that does fit... I have manged to get all the pegs in view, just - is that enough?

thanks for the advice anyway though..

[Spec-Chum]

If you're sure the secondary is central and showing a nice round circle in the focuser, you just need to ensure the primary is collimated now. That's the easy bit.

Follow this guide: http://www.astro-bab...ation guide.htm

Or if you need a bit more detail read this: http://www.propermotion.com/jwreed/ATM/Collimate/Chesire.htm

Good luck

[John]

Don't rush collimation. It's something that needs some tools (eg: a cheshire eyepiece) to perform accurately and something that you will need to tweak each time you use the scope, if you want to be sure it's performing well that is.

Viewing slightly out of focus star images through the scope is the real test of collimation in my opinion. That will soon tell you if there is further adjustment needed.

[TheThing]

Oh no, collimation myths again!

Unless you're using a really big scope - 14"+ - you shouldn't need to.touch collimation all that often.

My 6" newt was last collimated after SGL5. When I had an 8" newt that only needed collimating once a year.

If you're careful when moving and transporting the scope you will not need to collimate it very often at all.

I met a bloke once who confessed to collimating every 30 mins during an observing session. True, he had it down to a fine art, but what a waste of time! It was probably all that fiddling that was causing problems in the first place.

The very best guide you can find on the web is Andy's Shot Glass. Nothing over fussy about it at all. Just good advice from someone in the know. None of this nonsense about clips, just a straight forward, talk thru guide.

He also dies brilliant guides for drift aligning and a host of other topics, but that is by the by.

Don't fear collimation and don't let anyone try to make it more complicated then it needs to be (which is not very!)

TheThing

[Tinker1947]

I think when you viewed the primary clips they won't be all in view, there lined up when the secondary mirror is aligned central to the focus tube with all the clips in view, then when the 3 adjusting screws are altered to line up the secondary with the paper circle they will move out of alignment, ....well that's what i think happeneds...its very rare for the secondary to need any attention mostly the primary mirror.

[Naemeth]

Oh no, collimation myths again!

Unless you're using a really big scope - 14"+ - you shouldn't need to.touch collimation all that often.

My 6" newt was last collimated after SGL5. When I had an 8" newt that only needed collimating once a year.

If you're careful when moving and transporting the scope you will not need to collimate it very often at all.

I met a bloke once who confessed to collimating every 30 mins during an observing session. True, he had it down to a fine art, but what a waste of time! It was probably all that fiddling that was causing problems in the first place.

The very best guide you can find on the web is Andy's Shot Glass. Nothing over fussy about it at all. Just good advice from someone in the know. None of this nonsense about clips, just a straight forward, talk thru guide.

He also dies brilliant guides for drift aligning and a host of other topics, but that is by the by.

Don't fear collimation and don't let anyone try to make it more complicated then it needs to be (which is not very!)

TheThing

Unless you've made the telescope vibrate on a table or chair (yes I've done this accidentally), that will knock collimation right out.

[John]

With respect, I think I differ a little from The Thing on this issue. It's not a complex operation and the tools / techniques are simple enough to master but keeping a newtonian in decent collimation is rather like tuning a guitar - part and parcel of owning the thing and something that you should check regularly if you you want to be confident that you are getting good performance.

The collimation "sweet spot" for an F/5 newtonian (regardless of aperture) is quite small (a little over 2mm at the focal plane) and if the alignment of the optical system falls outside this it impacts contrast and resolution - the scope is simply not able to provide "diffraction limited" performance, ie: it can't deliver as well as it's aperture ( and the seeing conditions !) should allow.

The "myth" is that it's complex. With the right (simple) tools and some straightforward guidance it's soon mastered and you will wonder what all the fuss was about. A quick check and tweak each time you use the scope takes just a minute and becomes a normal part of setting up the scope.

[Spec-Chum]

I'm with john on this one in that it should at least be checked every outing but interestingly my collimation hasn't budged since I installed Bob's knobs on my primary I used to have to give the primary a small tweak every time before.

I would agree with thething if we're talking about collimating the secondary tho. Mine hasn't moved a mm since I set it up ages ago.

[Naemeth]

With respect, I think I differ a little from The Thing on this issue. It's not a complex operation and the tools / techniques are simple enough to master but keeping a newtonian in decent collimation is rather like tuning a guitar - part and parcel of owning the thing and something that you should check regularly if you you want to be confident that you are getting good performance.

The collimation "sweet spot" for an F/5 newtonian (regardless of aperture) is quite small (a little over 2mm at the focal plane) and if the alignment of the optical system falls outside this it impacts contrast and resolution - the scope is simply not able to provide "diffraction limited" performance, ie: it can't deliver as well as it's aperture ( and the seeing conditions !) should allow.

The "myth" is that it's complex. With the right (simple) tools and some straightforward guidance it's soon mastered and you will wonder what all the fuss was about. A quick check and tweak each time you use the scope takes just a minute and becomes a normal part of setting up the scope.

I have to agree with John here. I initially thought when I started at the Primary that I was getting nowhere (and to be honest, I wasn't), because my secondary was slightly out of alignment. When it's done just before a session, the views look that bit clearer and better, you get the best not only out of your aperture, but the best out of your eyepieces.

It may be a good idea once you've got everything aligned to adjust slightly until it's out (random turns of each screw), and then adjust it back. It's all about practice .

[Mr Flibble]

Just a quick check at the start of each session is all I do, it's just become part of my routine. The secondary hardly ever needs tweaking once its been set correctly and the primary if needed can be tweaked within seconds. Job done.

[TheThing]

We'll have to agree to disagree then.

My experience shows it's not necessary to check it so often. If your scope goes out of collemation due to slight vibrations then I would be very worried. That is not right at all.

Scope are more robust then people warrant them. You can't chuck them around, but nevertheless you don't need to wrap them in cotton wool.

A quick check is fine, but if it is regularly out you have other issues to worry about - worn bolts/screws, probably from over adjustment.

TheThing

[Naemeth]

We'll have to agree to disagree then.

My experience shows it's not necessary to check it so often. If your scope goes out of collemation due to slight vibrations then I would be very worried. That is not right at all.

Scope are more robust then people warrant them. You can't chuck them around, but nevertheless you don't need to wrap them in cotton wool.

A quick check is fine, but if it is regularly out you have other issues to worry about - worn bolts/screws, probably from over adjustment.

TheThing

Quite loud vibrations I must say, and my outside chairs of often wobbly! It's alright though, everything is fine now.

[S1m0n]

I'm surprised you need to adjust anything out of the box, other than the finder scope.

When I got mine I just needed the base fixed up and aligned the finder scope and everything was crystal clear looking at the moon for the first time was amazing and Jupiter !!! Well that was gobsmackingly amazing.

[WaveSoarer]

I posted on this thread () about issues seeing the three primary clips with a Cheshire eyepiece with the 200p. You can't get your eye close enough to view them all, even with the focuser all the way in, unless you use a collimator cap. The clips aren't necessarily symmetrically protruding onto the primary either so the cross-hairs on the Cheshire is likely to be more reliable than the colly cap - though it can be reassuring as a double check (bearing in mind the clips aren't completely reliable).

I found out that my 200p only needed the tilts of the secondary and the primary adjusted and the positioning of the secondary was spot on (as far as I could tell). I measured the centring of the secondary in the tube by using dividers (school compass) on the spider vanes but this was spot on too and, to be honest, there is precious little adjustment available. The positioning of the secondary along the length of the telescope tube, and its rotation, also looked good as the secondary was centred and nice and round in the colly cap and the Cheshire. It's easy to get hung up on collimaiton and don't let this get in the way of you enjoying your telescope. Get out there and use it and tweak and optimise the collimation when you are ready to do so to get the best possible performance from your scope. It's actually very easy and once the secondary is aligned (and this is probably only the tilts) then any subsequent tweaks will be mainly confined to the much heavier primary - this is very easy to align with a Cheshire.

[Scott]

i'm kinda lazy in almost everything i do so i probably only check my collimation every 4th or 5th outing. usually only minor tweaks of the primary are required and i haven't touched the secondary since it was collimated when i got it 6-7 mth ago (although i do check it). what i do know however is that when i make adjustments to the primary i almost always "think" the views are better. whether or not they are i don't know but if i believe they are then in my minds eye i am seeing better views so thats good enough for me. i also don't see a problem with being obcessive with collimation providing it doesn't detract from the pleasure of actually using the scope. it's not like we don't get plenty of time to fiddle with our toys when the weather isn't what it should be. i guess what i'm saying is that collimation or the frequency of collimation is a personal thing that we all have to work out for ourselves. (except of course that my way is the right way )

just my opinion so ignore it if you see fit

Scott

[aurochs]

Tonight I went out and the sky was clear, and there was near enough a full moon. But I had problems and I would like a bit of advice please. Bearing in mind the time of this was roughly between 11:00 and 11:40 pm, so I suspect it could have been darker than it was.

1. The finder scope seemed to be out of line or something. I got the moon dead centre within the crosshairs of the finder scope, however the moon was not visible through the focuser. At this point I was using the 25mm EP as opposed to the 10mm. I had to move the scope at least 1 "field of view" to get the moon into sight.

2. Once in sight it would not come into focus, no matter how careful I was with the focusing wheels. It was just blurred really. I tried the 10mm and couldn't see the moon at all.

Is poor collimation probably to blame for these things?

After looking through the Astro Baby guide I know I've not done a number of the steps. I guess I am somewhat afraid of altering too much and putting the telescope into an irreparable state or breaking one of the mirrors or vanes (I just have a paranoid/nervous disposition like that). But anyway one other thing I noticed while collimating after this observing session (not correctly), I noticed that there was a slight deformation at the top of circle of the secondary mirror.

When I look through the Cheshire the top of the circle which is the secondary mirror is deformed slightly:

The deformation was not present, as far as I could tell, when viewed without the Cheshire.

Could this also be caused because of bad collimation?

I don't mean to be a bother but I just want to enjoy my new telescope and I haven't been doing so thus far. I realise that I haven't really done the whole collimation process (I can see that now) BUT I am mainly asking so I can rule out faulty optics, etc. I almost forgot to mention but it could be important, on the first night I used the telescope (yesterday), the finder scope did accurately show what was viewed through the focuser.

Thanks very much.

[umadog]

Collimation is not to blame for either of those things. The first is your finder not being aligned. You probably knocked it so that's why it worked well the first time but not now. The second could be any number of things, including the focuser tube not moving when you turn the knob (is it a rack and pinion or a crayford?).

Do not be afraid of messing around with the optics. You can't really mess it up so just experiment. The one thing to be careful about is not dropping tools down the tube. So keep the scope horizontal when doing stuff.

[Scott]

_{with regards to the finderscope, i'd say that it's probably been bumped (no big deal) what you need to do is:-}

_{1. make sure that you have put the o-ring on the finderscope (sorry i'm asumming its the same as the skywatcher)}

_{2.once you have put the finder in the bracket in daylight find an object in the distance with your telescope with your lowest power ep (highest number)}

_{3. once this is centred swap to your highest power ep (lowest number)}

_{4. once this is centred look through your finderscope and using its adjusting screws centre your target in the crosshairs.}

_{5. job done}

_{if you know all this i'm sorry for pratling on. hope this helps.}

_{as for the collimation issues, all i can really suggest is going through the astrobaby's guide one step at a time. be patient and if you start to get frustrated go inside, have a brew and continue when youve calmed down. it is daunting when you first do it but pretty soon you'll wonder what the drama was all about.}

_{most of all don't worry, we've all been there.}

_Scott

[Scott]

hmmm, umadogs explanation for focus issues sounds better. make sure the focuser locking screw is not locked. still need to make sure collimation is right though

[dweller25]

Don't panic - everything is OK.....

The finder needs to be manually aligned to the optics - you will need to do this AFTER you adjust the collimation.

Your scope is not in collimation from the supplied picture.

The guide written by Astro Baby is very good and you should follow it in exactly the order it is written in.

Your scope is the F/6 version - like mine - and I can see all three mirror clips when collimation is correct.

Don't worry you will not break anything (as long as you don't force anything) and once you have practiced collimation a few times it becomes easy.......

Do follow AB's guide.

Regards,

David.

[umadog]

And there are other links to guides here: http://www.physiol.ox.ac.uk/~raac/collimationLinks.shtml (should you need them, the AB guide covers most things)