cheshire

[cristian abarca]

Hi guys, I just bought a cheshire from Andrews, now what do I do with it. I am still having trouble collimating and I have read many sites on the subject and it's still clear as mud.

Regards Cristian :doh:

[asimov]

Is it the one with the cross-hairs in it..?

Is your primary centre-spotted..?

There's plenty of info on that subject in this site. Go through the archives.

[cristian abarca]

The answer is yes to both. I have also made sure the primary is inside the view of the secondary and I use a laser to make sure the secondary is centered in the primary. After that I'm supposed to move the primary to make sure it's centered. I have a sight tube(Which I made with cross hairs). I then try to align the cross hairs of the sight tube with the reflected cross hairs. is this right? I find that when I do a star test the rings are not quite circular they are skewed. I try to tweak the primary and that's when I stuff it up. I have one of those cheap crappy scopes soldent was talking about in another thread. Also how far am I supposed to have the focuser, I try to have it where I focus with an eyepiece.

Regards Cristian :doh:

[asimov]

Do you mean in the star-test, the star looks elongated or the concentric rings are not 'concentric' with one another. Damn internet! It takes so long to work out whats trying to be conveyed!

[asimov]

correct on the focuser distance

[elusiver]

u should see the reflection of the cheshire when you look down it. Then you want it and the centre spot to line up, and everything else to be concentric.

have u seen this http://www.andysshotglass.com/Collimating.html

el :)

[cristian abarca]

What I men is that the rings are not concentric but slightly like a cone. The first one is round and they become slightly more elongated as they go. This is at the centre of field of view. As I move away from the centre they become worse. I have done it before where the rings were concentric at the centre but not as moved away from the centre. This time I'm not that close. Last time it was just a fluke and I only did it with a laser. I know I'm out because the stars don't look simmetrical (if you know what I mean). I have been trying to avoid this subject for a while but I can become a bit obsesive at times and when I have an itch I cant't stop scratching till it's gone.

Regards Cristian

[Starkler]

If they are concentric at the centre of the field, thats what you're looking for.

[cristian abarca]

The reflection of my primary in the secondary is not in the centre. It's off to the side but the centre spot ligns up with the cheshirre.

Regards cristian

[asimov]

Then your secondary needs tweaking slightly till the primary looks central. Then repeat the primary collimation again.

[Starkler]

Yep what asimov said :thumbsup:

My suggestion is to put the laser away and just do these three steps.

1:Secondary centred under the focuser.
2:Reflection of the primary centred in the secondary.
3: Primaries centre spot centred in the cheshire.

[asimov]

IMHO the sight-tube would be better than the cheshire for #1

[cristian abarca]

Thanks for your help guys. I think I just about have it. I have all the parts almost concentric. I'll try again tonight and then wait for clear skies to try it.

Regards Cristian

[cristian abarca]

Eureka shouted cristian as he ran around the back yard. After 6 months of trying to collimate my telescope I have finally succeeded. Now I know what stars are supposed to look like. the only down side was that seeing last night was not great , but it didn't matter I have finally done it. Now I can focus on figuring my 10 inch mirror.

Regards Cristian:cool: