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How to Set Up an Equatorial Mount

There are two common types of telescope mount for refracting and reflecting telescopes, the altitude-azimuth mount (think camera tripods) and the equatorial mount.  This guide explains a quick and easy way to set up your equatorial mount so that celestrial objects can be tracked across the sky quickly and easily.

What is an equatorial mount?

Equatorial mounts (commonly referred to as EQ mounts) are specifically designed telescope mounting systems that are built to follow the rotation of the sky.  This is accomplished by aligning one rotational axis of the mount with the Earth's axis of rotation.  This means that as the earth rotates, the mount can be rotated in the opposite direction with fine adjustments to keep a celestial object in view.  

EQ mounts are required to easily track celestial objects, because while stars may rise in the east and set in the west, they appear to do so in a curved trajectory that is actually due to the angle of the earth.  EQ mounts follow this trajectory and make your job of tracking objects much easier.

Why do EQ mounts need to be aligned?

They don't necessarily have to, but in order to be effective according to their design, they need to be aligned with a point in the sky.  Otherwise, the purpose of the EQ mount is defeated and constant fine adjustments in declination and right ascention is required.  This makes for a frustrating night of trying to track objects instead of observing.  Using an EQ mount that is not properly aligned can be more difficult than tracking objects with an alt-azimuth mount.

Aligning an Equatorial Mount

We'll assume that you have your telescope attached to your mount, and your mount attached to your tripod.

1.  Ensure that your tripod is level and secure.  

Some tripods have bubble levels built in, but may do not.  You may want to invest in a small bubble level, but it's OK if you don't have one.  For casual observation, "close" is usually good enough.  The farther away you are from level, the more fine adjustments you'll have to make in order to keep a celestial object in your view.

2.  Set your tripod's polar axis to your latitude.

The spot where you're observing is at a specific latitude on the earth's surface.  You can usually find this on your city's Wikipedia article, or on Google Maps.  This latitude corresponds to the polar axis your mount should be set at.  For example, we here at OpticsCamp are at about 41.25 degrees northern latitude, so we would set our polar axis to about 41 degrees, or as close as we can get to 41.25 degrees.  Again, close is good enough for casual observation, but accuracy here helps track objects later.

Loosen the clutches (or set screws, if your mount does not have clutches) and raise or lower the mount to the correct position.  You don't need to use the fine adjustment knobs to do this - you should be using a clutch or adjustment screw on the base of the mount.  Set to the correct latitude, and tighten.  This step is complete!

3.  Center your mount on Polaris.

This is the quick and easy method.  Polaris, also known as the North Star, is less than one degree from the celestial north pole, so this is usually close enough for casual observation.  

Loosen the mount where it attaches to the tripod.  Spin the mount until it looks like it's pointing in the direction of Polaris.  When you think you have it aligned, step back and look from your mount up to Polaris.  You should be able to imagine a straight line going through polaris, down through the night sky, and through your mount, into the ground directly below the center of your tripod.  Your mount should appear to be pointing directly at Polaris.  When you have it properly aligned, tighten the mount on the tripod.  Again, closer is better, but casual observers will see promising results.  

We at OpticsCamp have utilized this method of aligning with Polaris with a Ceslestron CG-2 Equatorial Mount and found that we only had to do minor adjustments in declination during extended viewing to keep objects in view, even at high magnification.

Some mounts have a view port that will actually allow you to physically aim the mount at Polaris.  If you have this feature on your mount, consider yourself lucky, it makes the process of aligning your EQ mount much easier.

4. Enjoy your telescope!

At this point, your equatorial mount should be set up to track celestial objects through the night sky with minimal headache.  Since objects along the celestial equator seem to move the fastest across the night sky, try to track stars in constellations that it passes through.  If you can keep objects in view in your eyepiece just by fine adjustment on your right ascension control, you are aligned!