Does a digital (GPS/compass) polar alignment scope exist?

[g__day (Matthew)]

You know what I’d like?
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comhttp://www.iceinspace.com.au/forum/ ...<P><FONT face=A digital polar alignment scope that works from GPS and compass bearings to allow you to very precisely polar align your scope on a German equatorial mount, without having to look for any stars.

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Something that you insert where a polar alignment scope would normally go, that when you switch it on and it simply GPS and magnetically aligns then gives you a red dot or arrows pointing to how you have to move your mount left or right, up or down until your alignment is pretty perfect.
<o:p></o:p>

Does something like this exist?


PS


I'm not so much lazy, but I don't have views South or straight up where my scope is mounted, so drift alignment is alot tougher and I'd like a (rentable) digital technology solution!

[Vermin (Tom)]

Flux gate compasses are only accurate to within +/- 0.5° unless you pay really big $.

GPS is not very accurate either especially with a limited horizon. Averaging your position over an hour or so can be quite accurate if you have a full horizon view, however you could probably have drift aligned in this time.

[allan gould]

For what you want the cost would be equivalent to a Losmandy G8/11 with gemini which has 2 polar alignment routines which get very close to the pole.

[g__day (Matthew)]

But I'd love a rental version. I'd pay $50 for a piece of equipment (or a person) I could borrow over night to do this!

[gary]

Originally Posted by g__day

You know what I’d like?
<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comhttp://www.iceinspace.com.au/forum/ ...<P><FONT face=A digital polar alignment scope that works from GPS and compass bearings to allow you to very precisely polar align your scope on a German equatorial mount, without having to look for any stars.


I'm not so much lazy, but I don't have views South or straight up where my scope is mounted, so drift alignment is alot tougher and I'd like a (rentable) digital technology solution!

Gary Kopff here from Wildcard Innovations.

As has been noted by "Vermin", magnetic compass technology, whether
electronic or otherwise, is not terriby accurate for these purposes.
As you are also probably aware, a stationary GPS reading will determine
your location but not establish a bearing.

Furthermore, such a hypothetical system, even if it were possinble, is
far from the ideal as it does not take into account the geometric and
flexure errors within your mount/OTA.

What many of the professional observatories do is after having pointed
the telescope through surveying techniques, then perform a star pointing
test and error analysis to determine the polar alignment corrections
necessary. The polar misalignment in azimuth and elevation for the
mount are just two "errors" out of a whole range of possible
errors that impact upon the scope's pointing performance.

Our Argo Navis system employs a similar approach. You devote one
evening and perform a star pointing test on perhaps 50 bright stars
scattered over the whole sky. The system helps you locate them.
You then fit use a feature within the system that alows you to compute
a pointing 'model'. This model consists of the various geometric and
flexure terms within the mount/OTA as well as the two polar
misalignment terms. You then tell the computer to apply
all the terms within the model except the two polar misalignment
terms. You then use the computer to guide you to a familiar bright star.
The star may not be centered in the eypiece but the pointing residual
will be in fact just the polar mis-alignment. You then adjust the scope
in Az and Alt until the star is centered. You mount is now polar aligned.

If your mount is on a pier, you are done.

If the mount is portable, on subsequent nights, you simply set the mount
down and perform a short pointing run on perhaps 4 to 6 stars and have the
system re-compute your polar mis-alignment. You guide to a star and adjust
the mount as before to center the star and you are polar aligned.

As a rule of thumb, the resolution of the fitted encoders dicates the
ultimate resolution by which the mount can be polar aligned.

The beauty of this approach is that it is faster than a drift test, it allows
you to use any bright stars you can observe and unlike a drift test, takes
the other geometric, harmonic and flexure errors into account.

I hope you found the above an interesting insight into the state-of-the-art
in polar alignment assistance. As I mentioned, most large professional
observatories with equatorial mounts employ a similar technique. Howver,
it is also possible to do this within your own back-yard.

Best Regards

Gary Kopff
Managing Director
Wildcard Innovations Pty. Ltd.
20 Kilmory Place
Mount Kuring-Gai NSW 2080
Australia
Phone +61-2-9457-9049
Fax +61-2-9457-9593
sales@wildcard-innovations.com.au
http://www.wildcard-innovations.com.au

[g__day (Matthew)]

I very much did find this interesting and rational. Also thinking about it for a simple eq3-2 on a pier, probably easier to offer someone in North Ryde a case of beer to do it for me!

Low tech, high touch!

[gary]

Originally Posted by g__day

I very much did find this interesting and rational. ALso thinking about it for a simple eq3-2 on a pier, probably easier to offer someone in North Ryde a case of beer to do it for me!

Low tech, high touch!

Way to go!

If you have the space, you might want to consider a permanent
pier. A Google search will uncover numerous design plans.


Best Regards

Gary

[g__day (Matthew)]

Like this you mean?

http://members.optushome.com.au/mowg...e/DSC00001.jpg

[gary]

Originally Posted by g__day

Like this you mean?

http://members.optushome.com.au/mowg...e/DSC00001.jpg

Looks like a nice set-up!

If it's yours, you must be a good part of the way there to it being aligned.
If you have a CCD camera, it can also be a powerful tool to help refine
the alignment if your views of the south and zenith are obscured.

Best regards

Gary

[g__day (Matthew)]

It's my second scope, basically a learner rig, coupled with 20 * 80 binoculars on a tripod and two swivelling bar stools (with back support!) on a deck 5 * 1.5 metre deck with four adjestable panels (5 * 4 foot oregeon frames of toughened black plastic) to shut out the lights of playing fields and street lights, but dissappear during the day as there nice views from my deck!

Interesting the scope + mount and tripod + motors was around $1,500. The lens and binoviewer have probably cost about the same.

Deck modifications and tools and materials to build the pier probably came to $1,400.

So this is simply set up and preparation to have a permanent site that I step out of my lounge room and in 20 seconds I'm star gazing in comfort (but missing the best views directly over my head of the milky way.

Close but no cigar yet on drift aligning the mount on the pier with an illuminated reticle. But I have plenty of patience an am learning.

My goal is to set up a bigger scope on a firmer (concrete and steel) permament mount in my backyard which does have protection from all the streelights and good fields of view. I figure get the basics under your belt before spending $6 - $9K on a bigger scope plus goto mount. Then add CCD and your looking at a total spend of $9 - $15K. So don't rush things and learn lots before choosing your equipment!