Collimation - That Old Chestnut...

[Guest]

How about this? 🤔

[Pixies]

I think you can get the secondary alignment better (stage 1). 

It still looks rotated to me. IE: not a perfect circle. I think the top of the secondary (in the image) can be rotated towards you a bit.

It's a pain, I know. But once you get this sorted, the rest is a breeze. And you won't have to do it again unless you take the secondary out, or drop the scope!

[Guest]

Any better? 

[Pixies]

Just get the Cheshire tighter and tighter towards the secondary. You should end up with the circles almost touching - then you'll know they are completely concentric. Like this:

(There is a gap between them)

Yours still looks the same to me:

It can be frustrating. The first time I did it, I gave up and came back the next day - then got it straight away. Get the Cheshire a little bit closer, then try loosening the secondary a bit and watch down the Cheshire as you manipulate the holder and see how it looks as you rotate and tilt it.

 

[Guest]

2 minutes ago, Pixies said:

Just get the Cheshire tighter and tighter towards the secondary. You should end up with the circles almost touching - then you'll know they are completely concentric. Like this:

(There is a gap between them)

Yours still looks the same to me:

It can be frustrating. The first time I did it, I gave up and came back the next day - then got it straight away. Get the Cheshire a little bit closer, then try loosening the secondary a bit and watch down the Cheshire as you manipulate the holder and see how it looks as you rotate and tilt it.

 

I'm hoping this is it... 

[Pixies]

get the Cheshire closer. Is still looks very slightly oval, with the bits marked in blue wider:

You just need to rotate the top (in the picture) away from you just a wee bit. Does that make sense?

If you get the Cheshire closer, it will be more obvious. But you are nearly there.

 

[Guest]

10 minutes ago, Pixies said:

get the Cheshire closer. Is still looks very slightly oval, with the bits marked in blue wider:

You just need to rotate the top (in the picture) away from you just a wee bit. Does that make sense?

If you get the Cheshire closer, it will be more obvious. But you are nearly there.

 

The focuser and Cheshire are as close as they can go, I'm afraid. 

[Guest]

Hopefully, that's made some improvement. 

[Pixies]

That's perfectly circular. just slightly off-centre, but we're being fussy now. You can either fine-tune it or head back to the next stage.

[Guest]

I moved it back and lost it... What the circle generation programme that you use? 

[Pixies]

That looks pretty good.

The reticle program is called "Mire De Collimation". Google it for the link. 

[Pixies]

http://sweiller.free.fr/collimation.html#chapter5