Telescope Reviews: ETX Issues

Jacob,

You have a bunch of questions there but let's sort through them.

Based on your description you most likely have an original ETX, later known as the ETX-90RA. You also most likely have the Deluxe Field Tripod which allowed for polar mounting.

Assuming this, here is an acceptable polar alignment procedure that will be sufficiently precise for visual observing.

--> Set the angle of the mounting plate on the tripod to your approximate latitude using the scale on the side. The angle of the plate to the horizontal should then be (90-latitude) degrees.

--> Set the north tripod leg to true north. This may not be easy in the daytime but with a compass and the magnetic declination of your location it can be done.

--> Mount the scope onto the plate using the proper bolts. Be sure the bolts are not overly long and do not tighten excessively. The base of this ETX model is plastic and could crack with excessive force.

--> Loosen the lever in the center of the scope base. Rotate the telescope counterclockwise until you hit the hard stop. Then, rotate clockwise 1/4 turn and tighten the lever. Again, a firm feel is sufficient.

--> Loosen the top knob on the right fork (as seen from the back) and rotate the tube - not the base! - such that the objective points directly away from the base. Tighten the knob to keep the tube in that position.

You are now at the "home" position. The tube is pointing to the north celestial pole, close to but not directly at Polaris. Now when you loosen both axes, point to an object in the sky and re-tighten the locks, the tracking motor will move the scope to keep the object in the field of view.

Now, a few other notes about this ETX model. The tracking in this ETX is Right Ascension (RA) only. there is no motorized correction for Declination (DEC) in this scope; adjustments are made by either round knob on the lower half of the forks. However, if any telescope is reasonably well polar aligned there will be minimal if any necessity to change the DEC. This is the primary reason for polar aligning a scope; it allows for tracking adjusting only one axis (the RA). If a telescope is altitude/azimuth aligned - such as setting the ETX on a table - then both axes would need to be adjusted to compensate for the Earth's motion.

I would suggest you try it on the Moon first; it's easy to find and would allow for quicker verification of the tracking.

Good luck and have fun. And don't forget to enjoy the views which, after all, is why we obtain telescopes!

Regards, Marc

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Goseck Observatory
Kunming 152 f/5.9 & Baader Wedge
Orion ED80 & LS75FHa2/B1200
Meade 102ED & LS18CaKMDd2