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SW Quattro Collimation - not sure what i'm seeing


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Hi All,

I recently bought a SW Quattro  and in the process of setting it up.  So far i'm seeing some strange things during the setup process.  I've used a 2" concentric  tool to setup the secondary and in the tool the secondary appears perfectly central and presenting a perfect circle but the inner circles appears oval shaped as per Image A below.

looking down a cheshire sight tube - The black shadow which appears oval is more obvious as per Image B.   So not sure what is causing this - i.e.is it tilt in the focuser or maybe rotation or tilt error on the secondary.

Any help would be greatly appreciated.

Cheers,

Rich.

 

Image A

Secondary_Mirror.JPG

 

Image B

Secondary_Mirror_2.JPG

Edited by Northernlight
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  • 3 weeks later...

Hi Rich,

I owned a SW 10-inch Quattro and found it a challenge to collimate accurately. I used various lasers and Cheshire sight-tubes but could never get them to quite agree. Eventually, I used a Catseye  autocollimator kit and only then did I get good, consistent collimation.

Looking at your pictures I find it difficult to work out what is going on. One comment is that in image B, you cannot see uniform reflections of all of the mirror clips or secondary mirror supports in the primary. So something is amiss.

I found that I had to start the collimation process by first removing the secondary mirror and collimating the focuser to ensure it was square to the tube. The Quattro focuser has adjustment screws to enable this. To collimate the focuser, you need an accurate laser and then after removing the focuser itself, carefully measure the position of the centre of the focuser cut-out on the tube and calculate where that centre will be projected onto the inside of the tube opposite the focuser. Now mark a spot on the inside of the tube opposite the calculated centre of the focuser; I used a label stuck on the inside of the tube and marked it with a cross using a micrometer. Now reassemble the focuser and use the laser to project a mark on the opposite side of the tube and adjust the focuser to hit the cross.

It's very easy to get confused by the view into the focuser with the primary mirror in place. So as a first step, block the tube with some screwed up paper so you can't see the primary. Now put some coloured paper on the inside of the tube opposite the focuser so you can see the ring of coloured paper around the secondary as you adjust it. Getting the secondary centred in the focuser and at exactly 45 deg is the challenge. The Catseye kit includes an adjustable 2" sight tube with an accurate crosswire. It is excellent for getting that rim of coloured paper to show uniformly around the secondary.  

Now remove the paper to enable you to see the primary mirror and adjust that.

In 2017, I rebuilt a 10-inch Newt for a friend and collimated it. that proved an interesting experience and I set out my experiences as a talk. I've put the slides here (lots of photos), so you can have a look:

 

https://www.dropbox.com/s/vsgwk7rvie32vu9/Collimating a Newtonian.pdf?dl=0

 Good luck,

David

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Hi David,

Thanks for the reply  - I took the leap and bought a set of CatsEye collimation tools and boy what a difference having a 2" Cheshire makes. The combination of the Blackcat XLS 2" cheshire  and the Blackcat Xl for the primary make thing so much easier. Now the Catseye XKLP auto collimator - i'm not a fan of that - as i really struggled with it.

The good news is that i sorted my collimation and it looks so much better now.

Cheers,

Rich.

gallery_12874_13865_570708.jpg

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