Skywatcher 200P....What collimation tools?

[SandyC8]

Hi all,

I just acquired a Sky Watcher 200P newt and have a few questions about collimation. First, I have no idea what I am doing, I also have a RASA 8  which I have never collimated and probably won't.

I read Astro Baby's collimation article and found it very informative. The article says that I need a collimation cap and a cheshire collimator. My question is which one...what brand? I have looked at several of the supplier websites and they all seem to offer something different, not just a simple cap and Cheshire?

I also have a Hotech laser collimator which seems to fit my moonlite focuser perfectly and says my scope is pretty well aligned.  However after reading the article, it seems there is more to it than just using the laser.

I would appreciate any tool advice anyone has.

 

Thanks

[Carbon Brush]

How is the view on a star test?

Is the scope new or used?

To quote whoever said ... if it ain't broke and all that.

[knobby]

If you're Hotech says it's collimated then just try defocusing slightly with a high power eyepiece you'll be able to see from the rings if it's near ok.

Just to double check ... Turn the Hotech 180 degrees in the focuser to check if it's still looking collimated, sometimes the laser isn't actually collimated 😁

[SandyC8]

The scope is used. 

next clear night I'll try a star test.

here are a couple of images. one is the set up, the others are from CCD Inspector after evaluating 30/1 minute subs.

[Spile]

23 hours ago, SandyC8 said:

Hi all,

I just acquired a Sky Watcher 200P newt and have a few questions about collimation. First, I have no idea what I am doing, I also have a RASA 8  which I have never collimated and probably won't.

I read Astro Baby's collimation article and found it very informative. The article says that I need a collimation cap and a cheshire collimator. My question is which one...what brand? I have looked at several of the supplier websites and they all seem to offer something different, not just a simple cap and Cheshire?

I also have a Hotech laser collimator which seems to fit my moonlite focuser perfectly and says my scope is pretty well aligned.  However after reading the article, it seems there is more to it than just using the laser.

I would appreciate any tool advice anyone has.

 

Thanks

I have the 200P and I use a homemade cap and a Celestron Cheshire Sight tube combination tool. To confirm that everything is OK, I take a photo through the sight tube and overlay the image with concentric circles using the same colour scheme used by Vic Menard and Jason Khadder...

 

[wookie1965]

All I ever used was a cheshire/sight tube

[johninderby]

Best way to get the secondary set up properly is with a Concenter. Not a cheap tool but the only way to get the secondary perfectly positioned. No other method is as accurate. Available from Telescope Express or APM.

Now when setting up a newt I use the Concenter to set up the secondary, level the primary mirror setting each adjustment screw to the same length using a ruler. Then the laser can be used for final collimation but should only need a very minor adjustment. I then tighten down the locking screws and recheck collimation which again usually needs minor adjustment just using the locking screws. 

Done this way the scope stays in collimation for ages.

BTW the Hotech is one of the very rare laser collimators that is actually properly collimated right out of the box.

 

Edited June 20, 2021 by johninderby

[CraigT82]

47 minutes ago, johninderby said:

Available from Telescope Express or APM.

And FLO

[johninderby]

10 hours ago, CraigT82 said:

And FLO

I wasn’t aware that FLO had started stocking them. Good news. 👍🏻

Edited June 21, 2021 by johninderby

[malc-c]

I'm sure if you type "collimation" into the search function on the forum you'll see the hundreds of previous posts on the tools and methods people use to collimate their scopes.  From basic hole in a cover, through to sophisticated laser grid devices.

One word of caution, whichever device you use, ensure it either has a self-centring fitting into the focuser.  If it uses the normal eyepiece thumbscrews then its no point using one as the offset caused will affect the collimation.    I personally use a combination of a cap, Cheshire and Hotech laser to calibrate and then perform the star test on my 200P.  Depending on your skill, luck, and ability collimation can be achieved quite easily with either or all of them.

[Spile]

On 20/06/2021 at 18:42, johninderby said:

Best way to get the secondary set up properly is with a Concenter. Not a cheap tool but the only way to get the secondary perfectly positioned. No other method is as accurate. 

That is quite a definitive statement. Why do you believe that to be true and what evidence do you have for that claim?

[johninderby]

Use a Concenter and you will find out why I consider it to be the best way to set up a secondary. Have tried all the other methods and while some were good still not as accurate as the Concenter. It is the sheer degree of accuracy that is obtainable using the Concenter that makes it so good. Simply the perfect tool for the job.

There are some far more expensive tools that perform the same function and work in a similar way but the Concenter is a somple tool that can’t be beaten for accuracy.

Edited June 21, 2021 by johninderby

[Clarkey]

Interesting that I have just come across this post having been replying to a similar post regarding collimation.

Newton f5 - photo needed - Discussions - Scopes / Whole setups - Stargazers Lounge

I have a 200p which I always thought was quite well collimated. The cheshire and the laser (which was collimated) both gave good results and so I assumed everything was OK. Anyway, someone was asking about Reego collimators which I also have for collimating my RC8. When I used the Reego the result was not so good, showing the secondary was offset. So I decided to move the secondary away from the primary to give better results with the Reego. When I returned to the Laser and Cheshire they were a long way out. So I left the mirrors where they were and adjusted the focuser tilt. This (after a bit more tweaking) gave perfect collimation on all three methods.

So interestingly, the reego highlighted the focuser tilt which would not normally be easy to identify. Having done these tests I now have the 200p collimated better than it has ever been.

My question would be 'How do you know whether the focuser is tilted or not?' using a cheshire or laser?

[johninderby]

One other point. The basic focusers that some newts come with can cause collimation problems due to their poor quality and can cause a laser collimator to give poor results which may explain why simpler methods may work better.

[Mr Spock]

I find using a laser is easy and gets the scope collimated near enough. I then fine tune with a star test. 

Keeping it as simple as possible is usually the most satisfying and productive solution.

[malc-c]

The process I followed for my 200P after I replaced the stock secondary with a larger one from Orion Optics to resolve an issue of un-silvered edges on the stock mirror went something like this

• Place the OTA horizontal with the focuser level
• Place a piece of paper on the inside of the OTA opposite the focuser
• Using callipers, measure the distance between the end of the OTA, and the inside of the focuser, then measure the diameter of the focuser and then ad half that diameter to the other measurement to get the centre distance for the focuser
• Mark this distance on the paper inside the OTA 
• Using a set of digital callipers to measure the spider legs, set the boss centrally in the OTA
• Place a length of threaded bar through the centre hole and secure with a set washers and nuts.
• Use the callipers and or tape measure to set the bar, and thus the spider squarely to the OTA.  Thus effectively the bar becomes the centre axis. 
• Place the self centring adapter and self centring Hotech into the focuser, and adjust the vertical adjustment grub screw until the laser hits the centre of the bar
• Carefully remove the bar and then adjust the horizontal grub screw of the focuser until the laser sits on the line made on the paper.  
• Fit the secondary flat to the boss on the spider.
• With a small hole drilled centrally in an eyepiece cap, place this centrally in the self-centring adapter, adjust the secondary and primary to get a good visual collimation
• Insert the Hotech and make the small adjustments to the secondary to centre the dot in the ring of the primary, and then adjust the primary to get the reflection centred and cancelled out by itself.
• Perform a star test, by taking images of a bright star at both extremes  of focus and comparing them.  Ideally the diffraction pattern around the spider etc are even and concentric

 

Now there may be newer tools to aid this, such as using a laser pen inserted into the boss rather than a threaded bar.... but  using the above method the results were nice sharp round stars.

There are more than one way to set up a scopes optics, and my way is not infallible,   but it worked for me

 

 

Edited June 22, 2021 by malc-c

[Spile]

18 hours ago, johninderby said:

Use a Concenter and you will find out why I consider it to be the best way to set up a secondary. Have tried all the other methods and while some were good still not as accurate as the Concenter. It is the sheer degree of accuracy that is obtainable using the Concenter that makes it so good. Simply the perfect tool for the job.

There are some far more expensive tools that perform the same function and work in a similar way but the Concenter is a somple tool that can’t be beaten for accuracy.

That is interesting but does not answer my question.

What do you believe the concentre does that makes it "better" than other collimation methods? I totally get that for you it might be easier to use, but I think that if you are going to make such a bold claim it would be useful to back it up and least provide at least a little more information on the why.