Help needed collimating

[starryMcStarface]

Help! I have my first Newtonian and can't get it collimated. I've followed along with countless videos and blog posts but never end up with what I'm supposed to have.

Is there anyone in the Lisburn/Craigavon area of Northern Ireland that is willing to give me a hand? 

[JOC]

Have you got astrobaby's guide?  I followed it literally to the letter and even I succeeded. https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=241871 - note do absolutely everything it says, do not miss a step and do everything even if you think it sounds daft.   When you do the secondary be aware that you might have to use a little trial and error as sometimes a final screw tightening shifts is a fraction and you have to allow for this movement when you position it.

[Trikeflyer]

Can you post a picture of what you have? We might be able to advise? Can you be more specific about which bit you seem to be struggling with?

steve 

[wookie1965]

And which scope you have as some have a whats called a birds-jones corrector in. 

[Sunshine]

Been down that road a lot with Dob's, follow the guide and be careful not to become obsessed with it, you don't want to fall into a downward spiral seeking perfect collimation.

get a collimation cap, easiest little device ever and once you have a fairly good collimation with that, do a star test, remember the ultimate test of collimation is a star test period! a star test is the be all end all of collimation verification (what a mouthful!) regarding the secondary,  i would not mess with it too much unless it really is needed.

 

[Red Dwarfer]

Is it a 130P ? In which case you need to unscrew the back panel to get at the adjusters 

PM sent 

[Red Dwarfer]

1 hour ago, JOC said:

Have you got astrobaby's guide?  I followed it literally to the letter and even I succeeded. https://stargazerslounge.com/applications/core/interface/file/attachment.php?id=241871 - note do absolutely everything it says, do not miss a step and do everything even if you think it sounds daft.   When you do the secondary be aware that you might have to use a little trial and error as sometimes a final screw tightening shifts is a fraction and you have to allow for this movement when you position it.

That’s the same guide / link I used to collimate mine too ?

[Redscouse]

I joined SGL around Christmas when I got my new scope of Santa (the wife ) anyhow, I remember asking the same question and at one point I thought I'd broken my scope beyond repair! Take a look here, it is me asking and receiving good advice. 

I took photo's during the process and added them here so anyone reading after me could see it may look bad but it's not really. Just hang in there and you'll soon get to grips with it. As a side note; the best bit of advice I was given is to isolate the secondary by using a piece of paper behind it so you can't see the primary when looking down the tube.
Please note; You really must have your scope in the horizontal position when doing this as you do not want to drop anything down the tube. 

Here is the link. It should take you straight to my photo's in the thread.

 

Hope this helps.
Pete.

[starryMcStarface]

Thanks for the quick replies!

My telescope is a Skywatcher 200P and I have a cheshire collimator.

Can't post a picture right now, sorry, but the main issue is with aligning the secondary. I got a perfect circle behind with a piece of paper between the two mirrors and when I took it away the reflection of the primary was all over the place.

Once I got everything as well aligned as I could (which wasn't that well) the thickish black ring around the doughnut was off-centre, and the crosshairs of the collimator were not in the centre of the struts that hold the secondary in place or the little spot right in the middle.

I haven't read that guide you mentioned @JOC, will check it out, thanks.

[Redscouse]

That threw me too. The 'thickish black ring' I believe you are referring to is actually the thing holding the secondary mirror in place. If you look at my pictures in the thread I posted above, you'll see when I removed the paper I could only see just over half the primary, needless to say it was at that point I began to panic. 
On the 130P I have, the rear cover comes off with 3 or 4 screws. This will allow you to access the collimation screws for the primary so you can adjust it. I assume the 200P is the same.

Honestly, follow astro babys guide. Do one thing at a time. You'll have it sorted before you know it.
(now as a beginner, I can tell you it will probably take a good hour or three! I remember it well; I was almost too scared to touch anything! )

[starryMcStarface]

@Redscouse the thread you linked to is super useful, thank you! I might not be as far off as I thought.

[Buzzard75]

Follow that guide. After you mess with it a few times you'll get it figured out. I use a combination of collimation cap, cheshire, and laser when fine tuning my collimation from time to time. In the field, I typically just go with a laser as it's quicker and I don't have to fuss with it as much. Assembling, disassembling, and toting it around can throw the collimation off, but not usually by much. The hardest part for me is getting the rotation of the secondary just right. Every time I adjust the secondary set screws it introduces some rotation. It's a pain, but it gets to the point where it's good enough and not worth the effort to get it perfect because it usually just throws something else off.

[JOC]

If you read astrobaby's guide you will see that in the finish a 200P (which is the example in the guide) does finish very slightly off centre - mine was also slightly apparently off centre, but looked exactly like astobaby's pictures.  Depending on which Cheshire you have bought when it comes to looking for the clamps which surround the primary (and which you try to get central) you might find you can only just see them and they might be just disappearing out of view, but I found I could see mine if I estimated their locations to know where they were for that part.  

16 minutes ago, Redscouse said:

I can tell you it will probably take a good hour or three! I remember it well; I was almost too scared to touch anything! )

This ^^^^ was me too and you will need that extra time.  Once you start reading the guide and comparing it to what you have it is really easy then to see what you are trying tp achieve.  Watching the videos will give you confidence to make the screws loose in the first place, but don't watch them for any more than that IME.  The Astrobaby guide is the way to go.

[wookie1965]

I used astrobaby`s and this one to do my 200p.

http://www.schlatter.org/Dad/Astronomy/collimate.htm