Alternatively, the encoder can sometimes be re-mounted so that it turns the opposite direction.

Bad encoder/cable. While the probability of an encoder or cable being bad is extremely small, it is a possibility. If the problem is isolated to either the cable or encoder, there are a few simple tests which can quickly determine the exact culprit. Follow each point as outlined below, checking the operation of the encoders after each until the problem disappears.

1.Confirm that all three ends of the encoder cable are securely connected. If visible, inspect each of the four wires at the encoder pins to check for a loose or intermittent connection (it is normal for one of the second-to-outside pins to have no connection).

2.Swap the two encoder ends of the encoder cable so that the Right Ascension/Azimuth cable is plugged into the Declination/Altitude encoder and vice-versa.

3.If the symptom is still present on the same displayed axis after step 2, then the problem is in the encoder cable. Remove the cable from the problem axis and check the wire for damage and the cable's plug to see that all four golden metal plates have been pressed down evenly. If necessary, compare it with the other encoder plug. If one or more of these plates is high, you may try to press it down carefully with a small flat-head screwdriver or similar tool. If this cannot be done, the cable should be replaced.

4.If the symptom switches axes after step 2, then the problem is at the encoder. Remove the encoder cable connector and visually inspect the jack on the encoder. The four golden wires inside should be roughly even, although they might be staggered high-low-high-low. If any of the wires appears to be bent at an odd angle or pressed down too much, this could be the problem. The jack may need to be replaced.

"Hung" German mount. (German equatorial mount users only). Because of the design of these mounts, it is possible to point the telescope at the same location from two quite different positions. To visualize this, point the telescope at 0° Declination. Now rotate the telescope 180° in each axis, avoiding the base as necessary. The telescope is on the opposite side of the mount head, yet pointing in the same direction.

This feature of the German mount is nice when an object is located in a normally hard-to-view position, but it has the added affect of changing the polarity of the Declination encoder. For this reason, a unique stipulation is placed on users of German mounts — when performing the encoder test or an initial star alignment, the telescope tube must be on the West side of the mount. (Southern Hemisphere users should place the tube on the East side of their mount.) Refer to the addendum titled Star Alignments with a German Equatorial Mount for a complete description.

Swapped encoder cables. The Encoder Installation sheet included with the encoder mountings should detail exactly which encoder cable is for each axis. As a general rule, on equatorial mounts the Declination encoder cable is the longer of the two, and on Altitude/Azimuth mounts the Azimuth cable is longer.

Not polar aligned. This is not a true problem as the MAX computer works very well even if the mount is 90° from polar aligned. However, there are symptoms of which the user should be aware.

First, do not use the EP or GP mount setting unless your mount is accurately polar aligned, or you intend to use the POLAR mode to assist in polar alignment. Please note that the EP/GP settings assume a perfectly polar aligned mount

—most pointing errors when using these settings are due to an inaccurate polar alignment.

Second, a clock drive (Right Ascension motor) cannot properly track the stars if the telescope mount is not polar aligned — stars and other objects will appear to drift out of the eyepiece, requiring regular re-positioning. In other words, the closer your mount is to polar alignment the longer an object will stay in view without manual adjustments.

Third (and the cause of misplaced concern among some new users of units such as the MAX computer), is the simultaneous change of both Right Ascension and Declination as seen under the RA DEC display when moving only one axis of the telescope. This is not an error as the MAX computer is simply reporting the telescope's true Right Ascension and Declination. What is commonly overlooked is the fact that a non-polar aligned mount is always moving through both Right Ascension and Declination when either of its two axes is rotated.

Incorrect initialization. A common problem is that of ignoring or misunderstanding the initial pointing instruction from the MAX computer at power up (e.g. SET DEC=0, LEVEL ME, and VERTICAL). If you have set up the MAX computer for a polar aligned telescope (EP or GP), then you do not need to concern yourself with this aspect, although it might be a good idea to be familiar with it. See SETUP on page 11 for more information.

Slew rate exceeded. The MAX computer has a maximum rate at which the encoders can be rotated. Due to the frequency at which the computer samples the encoders, they can be rotated faster than the computer can accept the data. The maximum speed depends on the number of tics per telescope axis rotation and the sampling rate. While it is unlikely that you will spin your telescope through a large arc fast enough to exceed this speed, it can be jolted a small amount in a very short interval causing a loss of alignment. With smaller telescopes and higher total encoder resolutions you will be more susceptible, but under normal operation you should never exceed the limit.

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