Polar alignment

[dragonlord]

I've borrowed a Newtonian on an eq mount and tried polar aligning it using the polar scope built into the mount. When I use the manual slow mo control though Polaris doesn't stay in the view finder.

Ive also tried fine tuning the alignment with the scope. What am I likely to be missing/doing wrong?

[Gomtuu]

Polar alignment is about aligning the mount, not the scope. Polaris should hold position in the polarscope once aligned (providing you don't move the mount).

For observing, it's sufficient to get Polaris in the rough centre of the reticle.

When you move the scope itself, this should not change the position of Polaris in the polarscope.

[matsey]

Gomtuu is correct - it is the mount that needs to be polar aligned rather than the scope itself.

You should be able to see two sets of bolts on the mount - one set front/back parallel to where the polar scope is, the other set sort of at the front left/right - these are what you use to adjust the mount to get Polaris centred in the polar scope. It's very important when adjusting one bolt that you loosen off its corresponding pair first.

I'd suggest googling astronomy shed complete mount and scope setup polar alignment - it's part two of a set of you tube videos (apologies should have posted the link but I'm on my phone and that's proving quite a challenge this morning!!).

The video is for the eq6 but the principles are the same so it should help explain how to polar align your mount. Note though for visual you only need to worry about getting Polaris roughly centred in the polar scope - you can skip the bit about getting the little circle in the right place on the "clock" and getting Polaris exactly on that circle - that's really only important for imaging.

Might also be worth checking out a couple of the other videos in that series - I think particularly the first one covers levelling and balancing the scope on the mount which would also be useful for you.

Hope that helps and don't worry - EQ mounts do seen really confusing at first but you will get the hang of it.

Matsey

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[Stargazer33]

There is a quite comprehensive guide to polar aligning a mount here: http://www.themcdonalds.net/richard/?title=Polar_Alignment_of_your_Equatorial_Mount

Just doing a search on 'polar alignment of an equatorial mount' brings up loads of "how to" guides.

HTH

[dragonlord]

I've followed all of those, and had Polaris centered in the polar scope already. My problem was that after I'd done that when I used the right ascension on the mount with Polaris centered in the ota it didn't stay in the centre (or even in view)

[matsey]

In that case.... if the star you're looking at through the ota is drifting out of view, my conclusion would have to be it is not Polaris you're looking at....

Just to check, when looking through the polar scope after polar aligning, does that star drift in polar scope view? Probably need to watch it a bit longer to be sure as the mag will be much lower than through the scope. If that drifts then sounds like you're also polar aligning against the wrong star. First time I polar aligned I did that and had the same problem, so it's not an uncommon problem.

If the polar align is definitely on Polaris and the star in the ota is drifting then it is just the star in the ota that is the issue - just to be clear (apologies if you do already know this!) but if you can see Polaris in the polar scope you won't see it at the same time through the ota and vice versa.

Hope that makes sense - but as I said the most likely issue for the drift is that the star you're looking at is not Polaris...

Matsey

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[knobby]

Don't forget... Polar scopes need to be set up too!

Aim at something distant in the day time, turn the mount round and check if target stays centred,

or Google polar scope set up

[Gomtuu]

Don't forget... Polar scopes need to be set up too!

Aim at something distant in the day time, turn the mount round and check if target stays centred,

or Google polar scope set up

True, we've all been assuming that the polarscope reticle is aligned correctly. It may not be.

[PhobosPhil]

There is a quite comprehensive guide to polar aligning a mount here: http://www.themcdona...quatorial_Mount

Unless I missed it in that one, they never seem to mention putting the RA axis back to the center after polar alignment is done. I had always left it in the position it was in to match polaris' position. After learning that useful nugget of info from someone on the forum I did manage to find a youtube vid where it was described - can't link it at the moment though as i can't get to youtube from where i am.

[astrosathya]

Phil,

The RA axis is always pointed at the polaris. Difference is, when you need to find an object, say Orion Nebula in the UK, which is almost opposite to the North star, you rotate the RA axis, but you move the DEC axis towards the Orion nebula. The job of the RA is simple. Point to the Pole, and be able to rotate around itself, horizon to horizon. In case you have doubta, I'd highly recommend you become a member of a local astronomy club. Seeing is always better than simply reading.

[PhobosPhil]

I dont think i should have put the word "axis" in my statement. I look through the polar scope, I move RA so the diagram matches what PolarFinder is telling me and then use the adjustment bolts to get polaris in the spot indicated. I used to leave RA in that position and try to use it from there - which I believe was my mistake.

[Chuggs]

...

just to be clear (apologies if you do already know this!) but if you can see Polaris in the polar scope you won't see it at the same time through the ota and vice versa.

...

Why is this?

I'm new to this whole this polar alignment thing, and this is certainly my experience (can't see Polaris in polarscope and through OTA), but I can't work out why.

I've always made the (possibly heroic) assumption that it is just the RA and DEC angles that define what you can see through the scopes, and that the lateral shift between the polarscope and OTA's axes should make no difference to what is visible (provided that their axes are parallel, or nearabouts).

C.

[StevieDvd]

Yopu should always be able to see polaris through the polarscpoe (otherwise you are not polar aligned) but the telescope is probably not 100% parallel anyway. If you were to physically pick up your scope and could move it parallel so the polarscope was now where the telescope was would you expect to still see polaris in it?

The smallest angle difference from your mount has a much bigger effect up there in the clouds, so even if you had a perfect parallel setup betwenn polarscope and ota you'd need a very wide angle eyepiece to get polaris in the field of view.

Next time you are setup and aligned set the telescope to polaris and see what position the mount uses to achieve that.

I would guess that if you could centre polaris in your ota at a pre-defined position on the RA/DEC scales that would mean your scope was aligned. I've never heard of that as a method to align so it's most likely to be impractical and inaccurate.

The new SW firmware has a polar alignment option which means that you would not have to have a polarscope to align accurately, it sort of does what I mention above but only if you have done a 2 or more star alignment.

[Gomtuu]

just to be clear (apologies if you do already know this!) but if you can see Polaris in the polar scope you won't see it at the same time through the ota and vice versa.

What? Explain please, as I seem to be missing something.

I find that in the home position the OTA is parallel to the polarscope and thus looking at polaris when the mount is polar aligned. Obviously it's slightly off-centre if polar alignment is accurate.

[knobby]

I think if your scope is perfectly in 'parked or home position' then the view through the polar scope and the actual scope will be the same...

but the chance of them actually pointing at the same thing is pretty slim.

[dragonlord]

I think my problem was that I was fine tuning to the wrong star. As it seems to be working now.

[matsey]

Well you certainly won't be the last person to do that

Really glad you got it sorted.

Matsey

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[todd8137]

Doh.! every one as that at some point, glad every thing is up and running smooth

pat

[dragonlord]

it was the first time I'd done it and I stupidly assumed that the brightest star I could see through the finder scope after I thought I'd got polaris roughly centred in the polar scope (don't have any lenses for it) was actually polaris when it turns out it was actually a star that I can't normally see with the naked eye from my garden.

[Gomtuu]

from my garden.

Luxury!

[dragonlord]

not really, as I'm a beginner it's more a case of learning what I can see and when I run out (which I'm sure I will) start looking else where. After all I live in a suburb of london, what do you think the sky quality is like?

[Gomtuu]

not really, as I'm a beginner it's more a case of learning what I can see and when I run out (which I'm sure I will) start looking else where. After all I live in a suburb of london, what do you think the sky quality is like?

I think perhaps you didn't take my comment in the spirit I intended it (see Four Yorkshiremen sketch). No slight was intended.

I live in a city centre, but I have no garden so I have to take an entire carful of telescope gear out of the city and set it up from scratch every time. It's a real pain. In a garden you can put in an observatory, mains power etc. or even just as a bare minimum aid, you can mark the tripod feet position.

A garden? Luxury!

[dragonlord]

Sorry bout that, really bad at reading intent sometimes.

I'm figuring that once I've got better at astronomy I'm going to be in the same boat as you for the most part, if for no other reason than I'll want to see more.