How's my collimation?

[Shure]

Just trying to get my head around the black art of collimation and have been reading AstroBabys guide along with Andy Shotts.

Here is the view through my cheshire on my 250px:

How does it look? To me it seems pretty good but I am not sure if it should be better...

EDIT: Clearer picture uploaded

[Mudskipper]

I just got my first newtonian yesterday. Yours looks a shade off but I cant tell exactly where as still learning. I will be following this thread to help me out too and will post picture of mine if I can later.

[kniclander]

it's quite a small pic so it's hard to see but to me the primary doesn't look quite round (did you check for the mirror clips) nor does the secondary and the secondary shadow doesnt look quite centred.

I would suggest using the scope before making further adjustments to give you an idea of whether adjustments actually make things noticeably better or not.

[smolloy]

...nor does the secondary and the secondary shadow doesnt look quite centred.

Please excuse my lack of knowledge, but I thought that the secondary played no part in the collimation process, and that there was no necessity for them to be centred. In fact, in fast scopes, I read that the reflection of the secondary *should* be off-centre. Am I wrong?

John Reed Home Page Collimation - Cheshire

Astro Babys Guide to Collimation

Both of these guides explicitly state that. Am I misreading something?

Steve

[Duns]

I'm pretty new to this but the secondary does play a part in collimation. If you follow Astro Baby's guide there are a number of checks/adjustments that are necessary to ensure the secondary is properly aligned with the focuser. When I checked mine it was a mile out. In my limited experience yours does not look too far off - as suggested previously try it on some stars first - do the star test - if it looks ok then your good to go.

[kniclander]

Please excuse my lack of knowledge, but I thought that the secondary played no part in the collimation process, and that there was no necessity for them to be centred. In fact, in fast scopes, I read that the reflection of the secondary *should* be off-centre. Am I wrong?

John Reed Home Page Collimation - Cheshire

Astro Babys Guide to Collimation

Both of these guides explicitly state that. Am I misreading something?

Steve

the secondary offset is apparent in the photo as the off-centre position of the silver circle within the black circle. I meant the black circle didn't look centred within the big silver circle. It's quite hard to describe

[smolloy]

I'm pretty new to this but the secondary does play a part in collimation.

Sorry. Of course you are right, and what I wrote was a little sloppy.

I was responding to kniclander's comment that the shadow of the secondary didn't look right, and my comment was supposed to say that I didn't think that the location of the shadow of the secondary was important to the process.

It is this that is stated in the two links I posted, and I'm sorry for suggesting that the location of the secondary itself isn't important, which is obviously wrong.

[Rob L]

I meant the black circle didn't look centred within the big silver circle. It's quite hard to describe

I agree with that, but would the angle the camera was at when the picture was taken effect how it looks though?

A bit like if the hole in your coli cap is slightly off centre you won't get a true idea whether the secondary is centred correctly.

EDIT: Scrubb that! You mean the innermost black circle is off-centre (I think!)

[Shure]

Here is another pic I have just taken, this time with the focuser all the way in:

I haven't attempted any collimation as yet, this is just as it is since I have had it.

I think this pic shows it is more out of line than the first. Would being out of collimation to this extent show a major impact in what I see?

[umadog]

You're close. The primary centre spot isn't quite under the cross-hairs of the sight-tube, though. It's even further out in your second photo. The primary seems to be correctly adjusted in the sense that the centre spot is correctly placed in the Cheshire. It's hard to see the edge of the secondary (to my eye, at least) so hard to judge how the primary sits within it. Perhaps the site tube is racked in too far in this photo to tell. Similarly, this makes it hard to judge if the secondary is rounded and centred under the focuser. The secondary offset is implemented automatically as it seems to be done here. For more info you can check out these links:

Rob Campbell's Home Page Find the links on adjusting the secondary to learn how far in you want the focuser to be racked. I collimate with the focuser racked to about where it would be if I had an eyepiece in there, focused at infinity. The sight-tube is positioned so that its edges appear to touch the edge of the secondary.

[sausages]

Scopes n Skies have an excellent youtube video on collimation. They use a laser collimator to sort a really messed up scope. Try this clicky:

AstronomyAndNatureTV's Channel - YouTube

[Shure]

I think I've made a pigs ear out of this:

I presume my secondary is now out of place?

One thing I am unable to do is to get the primary completely in the secondary. Not sure how important this is but it is mentioned from both Astrobaby and A.Shotts guide

[Shure]

Slightly better...