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North Pole Orientation to locate stars


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Hi all,

I have just started out in astronomy and have been doing some simple observations. In the equatorial coordinate system is the North Pole the true North? if I am using a compass to find the North Pole do I need to factor in the earth's declination to arrive at the North pole (a declination of 90degrees)?

Any help would be appreciated.

Thanks beforehand,

Regards,

Joseph

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In the coordunate system the North Pole should be true North.

If you use a compass then you need to factor in the Magnetic Declination for Malta - this appears to be 2 deg 32 min, so 2.5 deg East.

Your Lat/Long is about 35.9 and 14.5, so for an EQ mount you be setting it to 35.9 deg inclination, say 36.

If you are aiming directly at the pole star then you can be up to about 1 degree out, lot better then a compass. No real problem for visual, unacceptable for imaging.

Not sure where you get the valie of earths declination of 90 degree from?

What mount is it that you are aligning, useful to know, is this for visual or imaging.

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You want the celestial north pole, not the Earth's north pole. The celestial north pole is defined by the axis of Earth's rotation, i.e. it's the point in the sky around which all the stars appear to rotate. Polaris is very close to that point - close enough for rough alignment of an equatorial mount.

For astronomy, the only cardinal point on the Earth that really matters much is south, which is where objects rise to their highest elevation (i.e. when they're on the meridian). I sometimes use a compass when observing at a site that's new to me, but only so that I can check where south is. Celestial north is easy - I just look for Polaris.

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You do want earth's North Pole, it's the axis around which the celestial sphere revolves. It's Polaris that is not the true celestial pole.

Only twice daily does Polaris lie in a True North position from your local meridian. The Celestial Pole is therefore midway between those two positions.

If you have a permanently mounted telescope on a pier for example, you can use a star drift method to determine True North,

.

You can also you a software programme called Alignmaster to do the job, or alternatively, you could buy a Polar telescope for your mount if there is provision for one.

If you are an Observer only, then rough polar alignment will be quite adequate for you., but If you intend to Image via long exposures, the perfect polar alignment should be carried out, and although modern guide systems will cope with alignment anomalies to a certain extent, accurate polar alignment will ensure only minor corrections will be made as and when necessary.

Ron.

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