Polar Alinment

Polar alignment for Astrophotography and normal viewing.

A German Equatorial mount has an adjustment, sometimes called a wedge, which tilts the mount's polar axis so that it points at the appropriate Celestial Pole (NCP or SCP). Once the mount has been polar aligned, it needs to be rotated around only the polar axis to keep an object centred. Do not reposition the mount base or change the latitude setting. The mount has already been correctly aligned for your geographical location (ie. Latitude), and all remaining telescope pointing is done by rotating the optical tube around the polar (R.A.) and declination axes. A problem for many beginners is recognizing that a polar-aligned equatorial mount acts like an alt-azimuth mount which has been aligned to a celestial pole. The wedge tilts the mount to an angle equal to the observer's Latitude, and therefore it swivels around a plane which parallels the celestial (and Earth's) equator. This is now its "horizon"; but remember that part of the new horizon is usually blocked by the Earth. This new "azimuth" motion is called Right Ascension (R.A). In addition, the mount swivels North(+) and South(-) from the Celestial Equator towards the celestial poles. This plus or minus "altitude" from the celestial equator is called Declination (Dec).

  1. Scribe a line on the ground pointing South. To do this, use a compas and add the Magnetical  Declination MD to 180deg for your area.
  2. Place your tripod over the line scribed and pointing south and level the tripod as good as possible. Prefably with a digital protractor.
  3. Now place your equatorial mount on the tripod and adjust your Latitude on the mount. Again you can use the digital protractor or otherwise the protractor on the side of the mount.
  4. Finaly add your telescope and set the balance carefully in both RA and DEC positions

If you have a computerised handpad and need better acuracy for goto functions or Astrophotography, you need to do the next steps as well.

  1.  Input all information acurately on your hanpad. Date format, position deg min sec or just deg.
  2. Do 3star alinment, but make sure that the star is properly centred.
  3. If your telescope's alinment is not sucsessfull, your mount's alinment is off or your data input is incorrect.
  4. Do star drift alinment.

PLACE

LONG

LAT

MD

Alexanderbaai

16.18

-28.67

-19

Beaufort West

22.60

-32.30

-23

Bloemfontein

26.12

-29.20

-20

Cape Town

18.48

-33.94

-23

Durban

30.93

-29.92

-23

East London

27.92

-33.00

-25

George

22.40

-33.97

-24

Harare

31.05

-17.83

-8

Johannesburg

28.00

-26.25

-17

Kimberley

24.77

-28.72

-19

Komatipoort

31.92

-25.42

-17

Kosibaai

32.87

-26.92

-20

Luanda

13.23

-8.80

-6

Lusaka

28.28

-15.42

-6

Mafikeng

25.65

-25.88

-16

Maputo

32.58

-25.97

-18

Maseru

27.50

-29.47

-21

Messina

30.00

-22.38

-13

Phalaborwa

31.22

-23.92

-15

Pietermaritzburg

30.27

-29.62

-22

Pietersburg

29.42

-23.90

-14

Port Elizabeth

25.67

-33.97

-25

Pretoria

28.17

-25.75

-17

Upington

21.25

-28.42

-19

Walvisbaai

14.52

-22.98

-15

Windhoek

17.10

-22.57

-14

eg Cape Town's Magnetic Declination 203deg

180+23= 203deg

 
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