How to Align a German Equatorial Mount for Visual Observing
- OR -
Quick and Dirty Polar Alignment

By Chuck Hawks


Celestron Omni XLT 102 Telescope
EQ mount with telescope pointing north. Courtesy of Celestron International.

Equatorial (EQ) mounts, and particularly German equatorial mounts, are the best way to mount a portable telescope. These mounts allow easy tracking of objects as the rotation of the earth makes them appear to move across the sky in an arc. EQ mounts are designed to allow correction for the earth's rotation by adjustment in one plane, called "right ascension." Right ascension is the arc through which celestial objects appear to travel across the night sky. (Alt-azimuth mounts must be adjusted in two planes, azimuth and altitude, to counter the earth's rotation.) Motorized EQ mounts do this automatically, slowly turning the mount to cancel the earth's rotation. The operator of an EQ mount without a motor drive achieves the same thing by manual adjustment of the right ascension slow motion control to keep objects in the telescope's field of view.

Any German EQ mount worth its salt incorporates either manual or motor driven slow motion controls in both the right ascension and declination (essentially up and down) planes, very important for both finding and keeping an object centered in the field of view. The use of Vixen, Losmandy or similar dovetail rails on the telescope allows it to be quickly attached and detached from the mount for transport. This is a precise, convenient way to mount an astronomical telescope.

However, to accomplish this miracle of convenient tracking, EQ mounts must be at least approximately aligned with the north celestial pole. For Northern Hemisphere observers, this is located within about degree of Polaris, the North Star. Thus, for visual use, the EQ mount can simply be pointed at Polaris. How to do that is the subject of this article. Or, as I sometimes call it, quick and dirty polar alignment.

The system I am about to describe works for visual use. It is not accurate enough for long exposure astrophotography. That is fine with me, as I don't do astrophotography. A precisely aligned EQ mount will keep an object centered in the eyepiece for the entire night. Achieving a truly accurate alignment is a subject for another article. My quick alignment system is not that precise. However, it will usually keep an object in the field of view for at least 15 to 30 minutes before a declination adjustment must be made, which is ordinarily more than long enough for visual observation. Here is how I align a German EQ mount. (The same concept works for fork mounts on an equatorial wedge.)

  1. Set-up your mount's tripod so that the north leg (usually marked with an "N") is facing north.
  2. Attach the mount to the tripod (if you removed it for transport--I generally don't) and the telescope to the mount. Make sure the mount's opposing azimuth adjustment screws have the mount centered on the tripod, not slewed to the right or left. Now, verify that the altitude of the mount is set for the latitude of your observing position (44-degrees in my case). There are adjustment screws and a latitude scale on the side of German equatorial mounts for this purpose. The scale is small and not perfectly precise, but it is close enough.
  3. Adjust the tripod's legs to a convenient observing height with the tripod approximately level. Try to avoid having the legs fully extended or fully retracted; give yourself at least a couple of inches of final leg adjustment to play with, so you can more accurately level the tripod when the time comes. If you are setting-up on a smooth, hard, reasonably level surface, you can go ahead and level the tripod now, as described in step 6. You can then skip steps 6 and 7. If you are setting-up on an irregular surface, wait until you reach step 6 for final leveling.
  4. If you have set-up at dusk, while there is still enough light to see what you are doing (highly recommended), wait for it to get dark enough for the North Star (Polaris) to become clearly visible. Make sure it is really Polaris.
  5. Stand at least 10 feet (farther is fine) behind your tripod/mount and directly behind the two rear (southerly) legs. Position yourself so that, visually, the north leg is centered between the two rear legs. Imagine a line extending straight up into the sky from the north leg. This imaginary line will probably pass to the right or left of Polaris. Turn the whole tripod to the right or left until your imaginary line intersects Polaris when the north leg appears centered between the two back legs.
  6. Now, level the tripod as well as you can by adjusting the length of the legs. Use the bubble level provided on most EQ mount tripods. If your mount did not come with a bubble level, buy a small, stick-on level at the hardware store. The kind used to level a travel trailer usually works.
  7. Step back after final leveling and re-check that your imaginary line extending up from the north leg still intersects Polaris. If it does, good. If it is a little off after leveling the tripod, readjust the position of the tripod slightly until it does.

Your visual alignment is now completed! This is all you need to do to align a German equatorial mount to minimize declination adjustments for enjoyable viewing. You may have to make a minor adjustment with the declination slow motion control once every 15 minutes or so, which is no big deal. If you do not have a right ascension motor drive you will, of course, have to use the right ascension slow motion control to counter the rotation of the earth.




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