A 'proper' way to carry out a precise polar alignment?

[choochoo_baloo]

Hello all,

I spent my first proper evening getting acquainted with my new equipment tonight, which is now mounted on a permanent pier in my garden. However I have really struggled to make any progress in polar aligning my Celestron Advanced VX mount. I followed the instruction manual - first doing a GoTo align, then using the polar align feature on the mount handset.

I carefully followed the instructions for the Polar Align feature, but after two attempts the mount was quite a bit further away from Polaris's azimuth line than at the start of the evening! To be honest the instructions aren't overly lucid.

Therefore I'd like to ask how other imagers complete accurate polar alignment. Surely there's a simpler and more effective way of carrying out this crucial step to a high degree of accuracy?

Thanks in advance.

[Thalestris24]

Hi

Drift aligning is probably the best and simplest way. If you have a guide scope and phd2 it has an easy to use drift alignment tool. I have an AVX but don't use the hand controller. Drift alignment and Astrotortilla for plate solving does everything I need.

Louise

[PeterCPC]

I use ASPA with my AVX and get a good PA after two iterations of the method described in the handbook. I use an illuminated reticule 12.5  EP to get the stars centered as accurately as possible. Try using more calibration stars. Remember to unsync after the first PA.

Peter

[jambouk]

Do you have a polar scope? A polat scope alignment (asuming a number of other issues) will give you pretty accurate polar alignment. Depends what your goals are and how accurate you need the polar alignment to be.

I gound the handset polar alignment routine on the skywatcher kit to be really good, but only after a lot of fiddling and trial and error. The bits which i found key for the handset routine were:

- physically reduce cone error

- physixally reduce backlash

- use a reticle eye piece

- only do the handset polar alignment after

- a two star alignment

- a star alignment using two stars on the same side of the meridian as each other

- using those same two stars for the handset routine

- repeating the handset polar alignment routine 2-4 times

James

[choochoo_baloo]

Hi

Drift aligning is probably the best and simplest way. If you have a guide scope and phd2 it has an easy to use drift alignment tool. I have an AVX but don't use the hand controller. Drift alignment and Astrotortilla for plate solving does everything I need.

Louise

Yes I have an Orion Short tube in piggyback as guide scope, a guide camera and laptop with phd2. Please could you outline the method I need no follow for 'drift alignment' - as I said I am a beginner.

Also how do you by pass using the hand controller?

[Thalestris24]

Yes I have an Orion Short tube in piggyback as guide scope, a guide camera and laptop with phd2. Please could you outline the method I need no follow for 'drift alignment' - as I said I am a beginner.

Also how do you by pass using the hand controller?

Hi

The drift align tool is documented in phd2. It does require that you can see east or west and south-ish but is simple to use.

Re: the hand controller: I interface to the pc via the hand controller - one has to! But what I meant was that I don't use it to do any aligning. I have the scope setup info set etc. and check the time via the real time clock (the time usually needs a little adjusting, especially if I haven't used it in a while). So basically, when I power up I just hit enter 3 times, select 'last align' and I'm ready to go .

Louise

[Steve Ward]

Found this the easiest method personally ... 

http://www.cloudynights.com/page/articles/cat/articles/darv-drift-alignment-by-robert-vice-r2760

[Joel Shepherd]

I have the same mount and have gotten better alignment results with its "All Star Polar Alignment" (ASPA) routine than I was ever able to via drift alignment. A few tips/comments:

* Plan to do it twice. Do a basic 2-star alignment, and then center your finder on a star near the meridian, follow their polar alignment routine on that star (making sure to use the manual controls, not the hand controller, for the actual polar alignment). Then start over (I return to the scope to the home position, turn it off and on again and start from scratch: will have to try "unsyncing" as someone suggested earlier). The second time do the 2-star alignment plus 2-3 calibration stars, then polar align again on a star near the meridian. You should find that much less adjustment is needed on the second pass. It sounds like a lot of work but once you get the sequence down it goes quickly.

* Make certain -- before starting the manual adjustments -- that the star in your eyepiece is really the one you've chosen to align on. Check it out through the finder first: I've found that if I'm even modestly out of alignment to begin with the star I'm aligning on won't even be in the eyepiece at the beginning (remember, the mount just pointed itself where the star *should* be), so I have to use the manual alt-az knobs to center it in the finder first and then precisely center in the eyepiece. If you accidentally align to the wrong star, well, you're not aligned to anything. :-)

* A good sign that you're trying to center on a different star than the one you've told the mount is if you feel like you're "chasing" the star during polar alignment. If it's moving much at all, it's probably not the right star.

* Don't bump anything. :-)  Since you have a pier this may not apply to you, but even a modest bump can move the mount enough to render the alignment worthless.

* Use an illuminated reticular eyepiece to ensure things are really and truly centered. My eyes are _terrible_ at judging centers and straight lines and being a little off will make a big difference.

If there are specific things about the routine that are confusing, feel encouraging to ask for clarification here.

-- Joel.

[Thalestris24]

Just to say, the phd2 drift alignment uses the guide scope, guide cam and neat software so is easy to use and as accurate as you want it to be. I think polar alignment error of ~1' of arc is fine for most guided imaging.

Louise

[choochoo_baloo]

Thanks all for the information - very helpful and much appreciated.