GeographicLocation

   54°12.0' N; 4°25' W

                                    Polar Alignment

                                                   The Drift Method

                                                                      Why Do You Need Accurate Polar Alignment

Every object in the Universe is moving including our own planet Earth. Objects move in an arc shape across the sky from the East setting in the West. The Earth is tilted at  23.45° from perpendicular, and Polaris (the North Star) sits directly above the North Pole. Polaris is circumpolar which means that it does not rise and set at all, however this is unique due to its position in the sky, all other objects have field rotation. In long exposure photography of celestial objects field rotation has to be eliminated to prevent star trailing. Star trailing occurs when photographing celestial objects as they move across the sky. Photos showing star trailing produce star images as streaks of light rather than as tight star images.

A Motorised Equatorial Mount can eliminate field rotation by tilting the telescope at the same rate and angle as celestial objects move across the sky. To achieve this you need to obtain accurate Polar Alignment, which can  be accomplished using the Drift Alignment Technique.

                                                                Achieving Accurate Polar Alignment using Drift Alignment

1. Roughly Polar Align by centring Polaris in the eyepiece

2. Point the telescope at a SOUTHERN star above the celestial equator

3. Centre the star using a cross hair eyepiece

4. Wait and let the star naturally drift across the eyepiece field of view

5. If the star drifts NORTH in the eyepiece the axis is too far EAST, to correct rotate the mount axis RIGHT

6. If the star drifts SOUTH in the eyepiece the axis is too far WEST, to correct rotate the mount axis LEFT

7. Rotate the mount polar axis left or right accordingly

8. Point the telescope at an EASTERN star near the celestial equator

9. Centre the star using a cross hair eyepiece

10. Wait and let the star naturally drift across the eyepiece field of view

11. If the star drifts NORTH in the eyepiece the axis is too LOW, to correct move the declination mount axis up; RAISE IT

12. If the star drifts SOUTH in the eyepiece the axis is too HIGH, to correct move the declination mount axis down; LOWER IT

13. Repeat stages 2-12 until all noticeable drift is eliminated. Usually two or three times are required.

14. You are now ready for long exposure Astrophotography showing tight star images.

Messier 37, showing hundreds of tightly imaged stars.