Polar Alignment Using The Star Drift Method

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Polar Alignment Using The Star Drift Method - an Astronomy Net Article

Polar Alignment Using The Star Drift Method
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Polar Alignment using the Star Drift Method

by
Blaine Korcel
October 1, 1985

Abstract

Here is good method to align your telescope to the pole using the star drift method. This is a classic method from the 1980s when electronics for telescopes was just a drive corrector. Each step is explained and a table of suitable stars is shown.

Several members have asked me how to get the best and fastest polar alignment. I have decided to share with everyone my methods of obtaining proper polar alignement taught to me by our own Richard Lawson. This method with, a little practice, can give you reasonable polar alignment within one half hour. I have been lucky and have once obtained near perfect alignment in only 15 minutes.

First, you need an illuminated crosshair eyepiece and a lot of magnification, 200x or more, most easily achieved by using a 2X or 3X barlow lens. Next, balance the scope perfectly and roughly align your R.A. axis towards Polaris. Choose a bright star within 10 to 20 degrees of the equator lying near the meridian. Now align your crosshairs west and east. More accurately, shut the drive off and align the crosshairs so that the star drifts parallel to one of the hairs. Next, turn on the drive and adjust the R.A. tracking speed, if your able to, so that the star does not drift east or west. Allow the scope to sit until you can perceive that the star is drifting north or south. If the star drifts northward, your scope is west of the pole. Move your scope slightly in azimuth towards the east . Remember that as your adjustments get you closer to the pole, the star will drift slower and you must wait longer to detect a north-south drift. If the star drifts south, you are east of the pole and you must turn the mount towards the west. Repeat this until no drift can be seen.

After you have passed this test, you must choose a star 20 degrees above the east or west horizon. Now again adjust your crosshairs east-west as you did before so that the star drifts parallel when the drive is turned off.

Suppose you choose a star in the west. If it drifts northward, you are now below the pole. Adjust your scopes altitide upward making sure you do not change the azimuth and repeat until no star drift is perceived. If it drifts southward, you are above the pole. Lower the scope's altitude and again repeat this test until no drift is seen.

If you choose the eastern horizon, reverse the directions, i.e. southward drift means you are below the pole and you must raise the scope's altitude. Northward drift means you are above the pole.

If your telescope uses an even number of mirrors, such as a Newtonian, the star will appear to drift in the opposite direction than given above, due to the inverted image formed by such. Therefore, where you would be looking at a northward drift, you would actually be seeing a southward drift because of the inverted image.

After you have finished, you will then be ready for photography. Good luck and remember, "Practice makes perfect." Happy hunting!

LIST OF BRIGHT STARS
Name	RA	Dec.	Mag.
Hamal	2h 10.2m	+23 28m	2.0
Aldebaran	4h 35.9m	+16 31m	0.9
Rigel	5h 14.5m	-8 12m	0.1
Sirius	6h 45.1m	-16 43m	-1.5
Regulus	10h 8.4m	+11 58m	1.4
Vega	18h 37.0m	+38 47m	0.0
Altair	19h 50.8m	+8 52m	0.8
Markab	23h 4.8m	+15 12m	2.5

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