Help needed - Collimating a Skywatcher 200p

[Phil73805]

It has been a very long time since I posted on the forum and frankly, a very long time since I got out the old Skyliner 200p and had a look at the stars. It was a friend's interest in astronomy that got me to take it out of the storage shed, dust it off and point it skyward. I was able to show him the Andromeda galaxy, the ring nebula and, after it rose to an observable height, the moon. He was appropriately blown away.

However, I was troubled by my inability to properly collimate the telescope. I used the laser collimator today and thought I had, at last, done it but the views were worse than they had ever been. I put in a visual collimator piece and the setup is all over the place. I have attached a picture taken down the collimator to show you the problem. This has been a problem since day one with this telescope and despite hours spent trying to sort it out I have failed. I bought the telescope seven years ago and in all that time it has never been properly collimated. Apparently the laser collimator is only useful after having properly aligned the secondary which I obviously haven't done and every attempt has resulted in hours spent chasing a red dot to no avail.

I looked through the forum to find similar threads figuring that I was probably not the first person to struggle with this and the theme of the responses was along the lines of 'you'll figure it out'. Well, I haven't. And I have really tried. (Youtube videos, written descriptions etc.)

And so it comes down to this, is there anyone in the North West London (UK) area who can spare me some face to face time to help and show me the ropes so that I can do it in the future? I really would be eternally grateful.

(One other weird point, there's a little spider in the tube, don't know how it got there as the tube was sealed in storage. How the hell do you remove it?!)

[Charic]

Hi there, I favour this guide for collimation http://www.astro-baby.com/collimation/astro babys collimation guide.htm

Another useful guide here,  relating to using a Laser with a Barlow? http://garyseronik.com/collimation-tools-what-you-need-what-you-dont/

Just a pity this request for help was not submitted in August during my last visit to London, it would have been a pleasure helping someone setup their scope.

[Tim]

1 hour ago, Phil73805 said:

 

(One other weird point, there's a little spider in the tube, don't know how it got there as the tube was sealed in storage. How the hell do you remove it?!)

 

Welcome back

The answer is, carefully, with a hoover. I found an earwig inside my refractor the other day, again, it seems to be sealed.......

[Jason D]

To OP,

Laser collimators can't be used to center/round the secondary mirror under the focuser. You need to use your sight-tube to center/round the secondary mirror under the focuser first then use the laser collimators as you did. You might need to re-iterate.

Check out the following old post for your reference:

 

Jason

[Phil73805]

Thank you all for your replies. Charic, I too regret that I missed your visit. Please let me know when you're next in London and let's see if we can hunt some grey fuzzies together

I'm not going to lie, the Astro Baby guide to collimation is daunting to say the least. I am fairly mechanically apt but this seems like the thirteenth labour of Hercules! I have, as I mentioned, spent many a frustrating hour trying to collimate the beast and based on what's happening now I think I must have got fairly close before using the laser collimator and making a total mess of everything.

If there is any other member of this forum in North West London who has the time and experience to help me, just once, I would be very grateful (honestly, I am happy to pay you for your time). If you can show me the ropes I'm fairly confident I will be able to do it myself in the future.

Oh, one other thing, I have invested in a set of Bob's Knobs (primary and secondary) to make the process a little easier.

[Ricochet]

Where in north west London? That still seems quite a large area for someone to commit to. 

As for the Astro baby guide being daunting, it is actually a lot simpler than it initially seems. Judging by the picture you posted your main problem is not having the secondary aligned with the focuser. Once that is centred the primary should be easy. 

[Phil73805]

1 hour ago, Ricochet said:

Where in north west London? That still seems quite a large area for someone to commit to.

Apologies, I was perhaps being overly cautious in putting details of my location in the public domain. I live in Golders Green in NW London.

[Charic]

Leave the scope aside and just read and re-read the guide, use coloured card to help 'see' what your doing with reference to the images.
You will at some stage collimate the scope without issue, and once you have collimated your scope, you'll wonder what all the fuss was about, honestly.

Why not just try popping a small 1mm hole in the focusers blanking cap, using this alone  to align your eye to the axis of the scope. The most important part is to get the secondary  mirror central to the edge of the focuser tube when you look into the focuser (without eyepiece) do the best you can with just the guide and your eye. Don't use the Laser for now.

[Phil73805]

Okay, I replaced all the Allen screws on the secondary mirror holder with Bob’s Knobs (one at a time as instructed) and I thought I’d aligned the secondary mirror. I then thought it would be worth replacing the primary mirror screws (lock screw and adjustment) with Bob’s knobs (once again, one at a time). 

I cannot for the life of me get things lined up! I’ve read through the guidance a few times already. 

I don’t have a collimation cap. I do have a Cheshire eyepiece and a (rather inaccurate) laser collimator that I’ve quickly realised causes more harm than good. I can’t look through the Cheshire eyepiece while I’m adjusting the primary so I can’t see what my adjustments are achieving, if anything. I also can’t get the secondary set correctly. 

It doesn’t help that my knees are buggered (technical term)  so kneeling down and getting up is painful and a frequent requirement. 

[Singlin]

1.  Measure the distance from the middle of your secondary mirror bolt to the inside edge of the scope tube (along the spider vane).

Make sure that  the measurments are the same for the opposite spider vane; Insuring that the Bolt is central.

2. Place a piece of  coloured thin cardboard or paper behind your spider vanes in order to obstruct the view of the primary mirror.

3.  Place a piece of white paper or thin card opposite your focuser on the inside of your tube. Make sure that it is long and wide enough .

4. Use an old lid from a roll of camera film or take your polascope cap and drill a 2 or 3 mm hole in the middle.

5.Place the cap in your focuser (you might have to put the extension tube on).

6. You will see a white background with your secondary mirror in front of it.

7. Loosen  the secondary mirror bolt just slightly, Enought to be able to twist the secondary mirror and still keep it in place.

8. Twist the secondary mirro one way and then the other ever so slowly untill you see the shape of the secondary mirror as round as you can get it.

9- The outside edge of the secondary mirror needs to be concentric to the outside edge of your focuser tube.

10. Once you think that the secondary mirror is as round as you can get it tighten or loosen ever so slowly the secondary mirror bolt in order to move the secondary circle left or right untill it is dead center with regards to the focuser.

11. Using your bobs knobs gently adjust the mirror so that it is centered up and down when looking through your collomation cap.

 

Once you have managed this get back to us.

 

[AdeKing]

You're not the only one that struggles with this, I absolutely hate having to adjust the secondary and struggle with it every single time, but I do get there eventually.

Keep at it, you will get there in the end.

Ade 

[Phil73805]

Okay people, I think I've got it...or as close to gotten it as I can get without killing anyone. With the help of a cheshire collimator, a laser collimator and a homemade collimator cap I've squared and rounded the secondary and aligned it with the primary. The laser dot is three quarters of an inch off the centre black ring but it was as close as I could get without...well, you know. I attach some photos of my efforts for your entertainment; though if I'm honest watching me sweat and swear trying to get it done was probably more entertaining.

Thanks all for the encouragement and links to helpful articles.

Incidentally, the reason the centre circle is black is because the collimation cap was homemade and did not have a reflective inner surface and my phone camera couldn't handle different light level in the same shot.