I need your help here boys...

[Chubster]

Is your primary center marked? If not, that's first thing to do.

Yes, its marked....

And is this something you did, or is it already marked, cant say Ive noticed anything on mine

[Caz]

Hi Chubster,

I see you have the same scope as me, so I'm guessing your primary mirror has a mark in the centre, makes for easier collimation, well so they tell me..

[Ant]

Usually you have to mark the mirror yourself.

Use one of the hole re-enforcers... to find the centre of your mirror, get a sheet of paper and cut it to the same size as your mirror, fold in half and then half again. This gives a fold in the centre of the circle.

Cut a small piece out at the point, open back out to a full circle and there's your centre.

Ant

[Kaptain Klevtsov]

Mine's the 200mm f/5 Skywatcher Newt. and its definitely marked with a ring in the centre of the mirror.

Captain Chaos

[Chubster]

Know what i doing in the morning............

[daz]

Good stuff Caz

[Caz]

Sorry chaps, back again with yet more collimation troubles!!

I've done a rough drawing in PS, to give you an idea of what I'm seeing through the collimation ep. Imaging last night highlighted the fact, that its not 100% by any means.

As you can see from the drawing, the central part is slightly over to the left. I can visibly see the 3 troublesome clips, and the centre dot, is well, centre. Now, it doesn't matter how much I adjust the secondary, I can't get it bang on centre... Or, am I adjusting in the wrong place, do I need to twiddle the 3 allen screws on the secondary more....????

Owning a scope is the best thing in the world, but as for their maintenance, troublesome...

Would like this sorted for tonight, got a feeling it might be clear...

So has anyone got any suggestions?

Caz

Ps... Nothing to edit this time Jamie...

[geppetto]

Could be wrong but the bit that's slightly over to the left might be OK

as it could be the slight offset that you need on the secondary..

But then there are two "could be's" and one "might be" in that statement

[Caz]

Could be wrong but the bit that's slightly over to the left might be OK

as it could be the slight offset that you need on the secondary..

But then there are two "could be's" and one "might be" in that statement

Thanks for that Phil...

[Ambermile]

Looks suspiciously like the focuser is out there Caz, do you have a laser and if so, can you make sure the laser fires in the exact centre of the secondary?

Arthur

[Caz]

I don't have a laser, what do you mean by the 'focusser being out' ?

Caz

[MartinB]

Hey Caz, missed this thread.

Have you tried Andy's Shotglass :roll:

[Caz]

Hey Caz, missed this thread.

Have you tried Andy's Shotglass :roll:

[MartinB]

:shock:What???

[Andrew]

I'm coming to this a bit late, but if anyone can take it I have a few more collimation questions

Before last night I'd only ever collimated a scope using a collimation cap.

Last night I decided that I should have a go at my new scope with a laser.

Before starting I made sure the laser was properly aligned.

After spending an age trying to minimise the effects of the slight wobble of the laser in the focuser drawtube I started with the secondary and altered the tilt of this to get the laser in the centre of the 'polo mint' on the primary. So far so good I think. However, when I look through the collimation cap I see that I can no longer see the whole primary mirror.

Checking a set of collimation instructions that I downloaded I see that the way to rectify this problem is to tilt the secondary so that the reflection of the primary becomes fully visible (you can see where this is going). :roll: So, I move the secondary slightly further down the tube and rotate it until it is centred in the focuser drawtube. Of course I now have to change the tilt of the secondary again to get the laser in the polo mint. When I've done that, what do you know - I can no longer see the whole of the primary! :x This goes on for some time.

It was a bit like one of those films where you head out into the mist to escape the haunted house and two hours later roll up outside the front gate again.

Two requirements - primary fully visible + laser in the centre of the polo mint, both achieved by adusting the secondary (according to my instructions) but they seemed to be mutually exclusive goals.

I'd be interested to know if anyone has an explanation for this.

Also, when you rack out the focuser the reflection of the primary gets closer to the edge of the secondary (no surprise there) - hence it's harder to see the whole primary when the focuser is racked fully out. I've been assuming that you need to see the whole primary when the focuser is in the position where your eps come to focus (for me that's almost fully out ). It's easier to make sure the whole primary is visible with the focuser racked in, but presumably if you do this you may be wasting light when your eps are at focus if that is further out so you start to lose the edge of the primary?

After much swearing I finally sorted this out - i.e. laser in the polo mint + I can now see the whole primary even with the focuser fully out - However, the reflection of the primary is not exactly in the middle of the secondary, even though I can see all of it. Does that matter?

Having done that I barlowed the laser and adjusted the primary to get the image of the polo mint centred around the middle of the laser in the drawtube. It's amazing to see the polo stay fixed even when you wobble the laser, and by comparison with using the unbarlowed laser and/or fiddling with the secondary this part was a piece of cake.

All in all in only took me 3 hours

Anyway, the good news was that when I finally managed to get out last night stars were definately sharper than with my previous efforts with the collimation cap alone.

[geppetto]

Caz

Had any luck with the tweaking?

[Caz]

Hi Phil,

I had another tweak this afternoon, its slightly better. When I get the chance, I'll try again with the camera, it clearly showed up when taking pics

Thanks for asking..