Any reflector “experts” in England?

[Astrobits]

For years a lot of collimation was done with a simple pinhole eyepiece. I have done this with my own 16" (f/4.5 ish ) reflector and had satisfactory views. I suggest that the OP uses this method first and then uses the telescope for a while before deciding to go into cheshire's, catseye's lasers etc.

Nigel

[Spile]

V blocks mean that I’d need to remove the laser. The rotation method in situ means I don’t. That works for me.

[John]

11 hours ago, Spile said:

V blocks mean that I’d need to remove the laser. The rotation method in situ means I don’t. That works for me.

No, the laser collimator as a whole goes on the V-block, provided that it is a symmetrical unit such as the one I posted a link to earlier in this thread.

@steppenwolf / Steve Richards shows a simple approach here:

 

[CraigT82]

Interestingly Lego bricks also makes for very good V blocks, they’re made to a high precision dimensionally (0.005mm I think)

[Mandy D]

1 hour ago, CraigT82 said:

Interestingly Lego bricks also makes for very good V blocks, they’re made to a high precision dimensionally (0.005mm I think)

When I read the tight  tolerance you gave for Lego bricks, I had my doubts, so naturally, I had to look it up and it turns out you are wrong ...

It's actually 0.002 mm. Who would have guessed! 😃

[a6400]

22 hours ago, CraigT82 said:

Yes I'd agree that V blocks would be more precise, however I'd counter that by saying that precision is not necessarily required, as any collimation method that involves clamping a device in your focuser will only get you close as there are too many uncontrolled variables. e.g. is the geometric centre of your mirror coincident with the optical centre, does your focuser clamp your eyepieces in the exact same way as your collimation device and is that repeatable and consistent etc etc...

For a true collimation the only method that eliminate those variables is to do it on a star, but granted that has it's own issues

That’s why I am going to use this:

https://www.firstlightoptics.com/adapters/william-optics-2-to-125-rotolock-visual-back-adapter.html
 

As for star collimation some people already told me you can’t fully trust it.

[John]

18 minutes ago, a6400 said:

That’s why I am going to use this:

https://www.firstlightoptics.com/adapters/william-optics-2-to-125-rotolock-visual-back-adapter.html
 

As for star collimation some people already told me you can’t fully trust it.

When you have your primary mirror out for cleaning you can check that the centre spot really is in the centre. Sometimes they are not and that is another source of collimation error of course.

 

Edited October 4, 2023 by John

[John]

The star test is the ultimate test of collimation in my opinion. It shows whether our efforts with lasers, cheshires etc, etc have had the desired result.

My routine with my 12 inch dob was to check the collimation with a cheshire eyepiece once the scope was setup, tweak it if needed, then do a quick star test (often using polaris) to check things were OK before starting to observe.

[CraigT82]

5 hours ago, a6400 said:

As for star collimation some people already told me you can’t fully trust it.

I’m not sure who would have told you that and why, but it really is the only method you can trust. It does take more time and can be difficult or impossible to do in rough seeing but then again in those conditions a slight miss-collimation isn’t going to ruin your views any more than the seeing is.  Also as John mentions above you could even just do it once in order to validate your other methods so you know they produce good results and can trust them. 

[Spile]

11 hours ago, John said:

No, the laser collimator as a whole goes on the V-block, provided that it is a symmetrical unit such as the one I posted a link to earlier in this thread.

@steppenwolf / Steve Richards shows a simple approach here:

 

Sorry but you have misunderstood my point. I don’t need to to remove my laser collimator from the focuser to find out if it’s no collimated or it’s nots correctly registered.

[John]

35 minutes ago, Spile said:

Sorry but you have misunderstood my point. I don’t need to to remove my laser collimator from the focuser to find out if it’s no collimated or it’s nots correctly registered.

OK, I understand now.

We have different ways to check that our laser collimators are collimated thats all 🙂