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Use Polaris to collimate?

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#1 cloe

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Posted 31 March 2005 - 01:35 AM

Since the North Star is stationary,is this a good star to collimate my scope?

#2 matt

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Posted 31 March 2005 - 01:57 AM

yes!
And it's also not too bright, not to faint...

But Polaris is also a double star (which most scopes resolve anyway) so don't let the companion puzzle you.

#3 tjensen

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Posted 31 March 2005 - 10:33 AM

one caution... it depends on your latitude. You can look through a lot of atmosphere if you are in a southern locale. And that could play havoc with your seeing.

#4 John Kocijanski

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Posted 31 March 2005 - 01:12 PM

It works well for collimation. Use it.

#5 garyc11

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Posted 31 March 2005 - 01:48 PM

it's a lot cheaper than an artifical star.

#6 Starman1

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Posted 31 March 2005 - 01:55 PM

one caution... it depends on your latitude. You can look through a lot of atmosphere if you are in a southern locale. And that could play havoc with your seeing.


He's in Canada. Almost by definition he isn't too far south.

When you collimate on Polaris, just remember to always bring the star back to the center of the field after turning a screw.

If you're collimating a scope with 2 movable mirrors, I don't recommend using a star to collimate. I recommend "passive" collimation tools (sight tube/cheshire/autocollimator) instead because they tell you exactly which mirror to change and by how much. Star collimation in a newt is a very "iffy" proposition--which mirror do you move, and by how much? Plus, how do you compensate for poor seeing?

It's hard enough on an SCT, where only the secondary is movable.

#7 sixela

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Posted 31 March 2005 - 04:36 PM

I recommend "passive" collimation tools (sight tube/cheshire/autocollimator) instead because they tell you exactly which mirror to change and by how much.

So do I.

Star collimation in a newt is a very "iffy" proposition--which mirror do you move, and by how much?

I'd have to disagree, if it's used wisely, i.e. to merely check your collimation. Given any choice, I think I'd simply move the primary until there was no more coma in the middle of the field.

Yes, you may end up with some angular error between the focuser axis and the optical axis of the mirror set if it was the secondary you should have moved, but at least you'll be looking at the optical axis at high power (which is more important, at least if the angular error is really small - if your collimation with the tools was no good at all, then no star testing is going to save you).

You point about seeing is correct, though: if you can't see things reliably, then you shouldn't be star testing, as you'll only succeed in messing up the collimation you should have done with the tools.

Even if you do star test, it's probably wise to get a set of tools you can use to check whether what you've done agrees with a set of tools (if you want to use them in the dark, a well collimated laser plus a barlowed laser, or the Catseye collimation tools).

#8 LivingNDixie

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Posted 03 April 2005 - 03:05 PM

Regarding the collimateing tools, there is a set made by Tectron that has the three tools and a great book that tells you how to use them heres a link tectron tools at Astronomics you can also buy them from High Point Scientfic and Tectron directly. Not sure if they can ship to Canada, I know Tectron could not sure about the dealers though... Good luck with getting your scope collimated :) It makes all the difference

#9 GaryB

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Posted 04 April 2005 - 01:57 PM

one caution... it depends on your latitude. You can look through a lot of atmosphere if you are in a southern locale. And that could play havoc with your seeing.


How far south is too far south?


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