Collimating problem (I think)

[Steve_meg]

Sorry for another collimating post but I'm a bit confused. Scope arrived today:) I didn't get home from work till late so by the time I set it up it was dark. I have tried collimating it indoors. Is that ok instead of in daylight? And then when I thought I'd done it clouds filled the sky. The only issue I had was getting the clips in the secondary mirror. By the time ones visible the others ate miles out of view. Everything else seems to be ok though. Confused and can't do the star test, so what's going wrong if anything. Just to add I'm using a Cheshire on a sw250px

[david o]

Hi Steve,

I can't offer much help beyond pointing you to Astro Baby's collimation guide.

HTH and sorry if you've already found it.

Edit : PS That 'scope got to you quickly, you lucky chap.

[John]

The best test of whether or not a scope is in collimation is a star test - it becomes clear very soon if things are not quite aligned correctly.

At the end of Astro Baby's guide to collimation she explains a bit about star testing and how to interpret the results:

Astro Babys Guide to Collimation

You will probably find it's not too far off and a couple of tweaks will put it back where it needs to be - the dark shadow of the secondary mirror in the centre of the "Polo mint" which is the slightly out of focus star.

Use Polaris for star testing is it stays more or less put which saves having to track at the same time as trying to interpret the star image !.

[Steve_meg]

I was using astro babys guide which was brilliant as de instructions weren't great, just confused as everything seemed good apart from the clips. Can't wait to try it on the stars, fingers crossed for clear skies

[Shibby]

I think if you put the focuser in a bit, you'll see more of the primary visible in the secondary. This should make it easier to align the secondary using the clips...

[Rob L]

Are you trying to use the Cheshire to align the primary clips? It's much easier to use a film canister as described in AB's guide for aligning the secondary.

Also make very small adjustments and check each time to see what it does, small changes can make big differences, take your time.

One other thing, the 250px (if it's the same as mine) has 6 mirror clips not 3 as described in most guides.

[solarwallace]

FYI: I can't see the primary clips in my flextube 250. Well I can see one at a time if I want to which isn't much use that's using a Cheshire.

[Steve_meg]

well i'll try the film cap see if that helps. just weird as i can only get 2 clips in view but then others are miles off then, guess ill play around some more and hope the sky clears up for later.

[kniclander]

if you can see two only, it aint right. if the focuer is racked too far out, you won't see any; then, as you rack in, they should all come into view at the same time. if they come into view at dfferent points then you need to adjust the secondary. as has been said before, read the famous a-b guide or google "andy's shot glass" which imho is not quite as good but very easy to follow.

[tipftop]

hi steve

if you cant find a film cannister,use the cap that came in the focuser and drill a hole ABSOLUTELY dead centre in that(1/8" drill bit)

hth

dave

[Si W]

I think this thread needs to be made a sticky, more and more the question of Collimation of a Newtonian keeps popping up on the forum on a regular basis, and is a very popular question asked by people who have just purchased or are having issues with there scope's.

[Ursa Major]

I really like andy's shot glass collimation video. I was finding astro babies one a little difficult to follow because of all of the infomation but it is still very useful. Thankyou kniclander for the recommendation

[Steve_meg]

Ok bit more progress on collimating my new scope and a clear sky so firstly a big error my way, I didnt put the cheshire in fully yesterday so that helped a lot. having said that i agrre with AB's guide that the cheshire doesnt let me see the edge of the mirror well and i found it hard to get on with. So i used mainly my eye only, then the cheshire on the primary.

I took it out for the star test which I'm unsure about. When focused the star seemed clear to see and the defocused like a polo, white band with black centre, perfectly round. is this right?

Enjoyable first view, although need to find out what i'm looking at better and new eyepieces and barlow. just a question, with the supplied eyepiece what should you be able to see? saturn?

[Bazzaar]

Hi Steve,

Just want to chip in some encouragement, yes from what you say in you last post the star test sounds good. The "doughnut" or "polo" or what ever you want to call it should round with the black hole dead center. actually the white bit should be a series of circles, one inside the the other, all evenly spaced. You dont always see this if the star is disrupted by poor seeing, atmospheric conditions or if the scope hasnt cooled to outdoor temperature.

Saturn? yes you should see Saturn really well with that scope, the question is how big it will appear, that depends on the eyepiece focal length, you didnt mention that.

Good luck with the scope now!

Barry

[Steve_meg]

I couldnt see and cirles in the with band, but it was nice and circular. I'm using the standard 25mm and 10mm eyepiece that came with my sw 250