How does this collimation look?

[nitram100]

I'ver never truely mastered collimation on my newt, so I decided to try and reposition the secondary and primary myself.

How does this collimation look? The image was taken through the pinhole on the red collimation cap. I used a cheshire to adjust the centre circle.

Should the secondary be sticking out like that to the bottom left? Should it be uniform? I'm not sure i have the secondary correct.

Star images are generally nice and sharp, just can't help feeling that jupiter and saturn could be a bit better in the scope.

 

Thanks for any advice!

[malc-c]

Collimation is one of those topics that everyone has opinions on, and can be hard to document as sometimes taking a picture of what you see with your eyes are two different things.  But taking your image  and comparing it to one I took when I was resurrecting my scope (hence the cobweb which was the reason for the image !) your collimation looks off.  There seems to be a slight twist in one vane and the secondary doesn't seem central as you'll see by the yellow lines in the images below

Laying the line straight and in line with the left vane, the one on the right is slightly out.  I also feel the reflection of the focuser tube is not centralised  in the secondary

 

 

This was how my collimation was before I cleaned and overvalued my 200P having been sat in the observatory unused for 3 years.  The secondary needed a little tweek, but you can see how the vanes are true and square.

The goal of collimation is to get nice round stars.  If you locate a bright star and then rack the focus all the way in and all the way out and get nice airy rings than that's all that matters

 

[nitram100]

Thank you so much Malcom for that post, really appreciate it.

 

I had thought about the spider vanes before and that they may not be straight! I did the 4 vane installtion myself a long time ago, replaced the thick 2 vane spider from OO.

Will definitely go back to the drawing board now and try and get things lined up perfectly

Thanks again! Mart

[malc-c]

There are guys on here that are far more experienced in the dark art of collimation than I, but having spend a long time in the past resolving an issue I had with my 200P I got quite good at collimating.  But I use a Hotech laser collimation tool, with the self centring adapter.  This, plus the hole in the cap method, and the string method for centring the secondary and squaring up the vanes (basically pull a length of white cotton between the anchor points along the vanes (like the lines in the images above), then checking with a set of callipers all helped get the optics aligned.

If you type in "collimation" into the search bar above and read up on all the previous discussions I'm sure you'll get it tighter

[nitram100]

Thank you so much Malcom, really appreciate the help. 😀

[Spile]

It would be helpful to see the view through a Cheshire sight tube combination tool. The secondary is offset at 7.30 whereas It should be 5.30. To me this indicates a tilt/rotation error.

[AstroMuni]

On 13/10/2021 at 10:12, nitram100 said:

Star images are generally nice and sharp, just can't help feeling that jupiter and saturn could be a bit better in the scope.

In order to get an airy disk you will need a high magnification and the image will be quite small due to reduced FOV. There are other posts on this forum by @vlaiv that explain in clear detail (as usual )

Edited October 14, 2021 by AstroMuni

[Alan64]

Your telescope is at f/5(f/4.8, close enough), therefore use a 5mm(240x) eyepiece, or the equivalent with a barlow, for collimation/star-testing.

Edited October 14, 2021 by Alan64