NexStar Resource Site

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No Response Errors

Please read this entire article before you start troubleshooting.

This error indicates that the hand control is unable to communicate with another system component, for example, 16 and 17 are the motor control processors located inside the mount.  One source for this error is faulty power, either low voltage (weak batteries) or a loose connector.  Read this for suggestions regarding power.

If you receive a "No Response 1" error when checking version, read this.

One recently appearing problem is for those with an older NexStar GPS.  The newest versions of the hand control - version 4 or higher - require motor control firmware version 4 or higher.  If you have older motor control firmware, the hand control will display the no response error.  See this article for details on GPS firmware versions and upgrading when necessary.

On rare occasions, the motor control may be stuck in "boot mode".  Fixing the problem requires you reload the latest motor control firmware - follow these instructions.

Many times the problem is the connector that the hand control plugs in to.  Try connecting the hand control to one of the AUX jacks (for mounts with an AUX jack), rather than the normal hand control jack.  Also, the pins on the jack or the plug can accumulate slight amounts of corrosion that can interrupt the low voltage signals.  These can be easily cleaned with contact cleaner available at electronics parts stores. Do not over do it, you do not want excess cleaner to short out the electrical connections.  Be sure the power is off and use a cotton swab dampened with contact cleaner to rub any contaminants from the connectors. Also, take a good look at the pins and insure they are not bent or misaligned.

Another potential problem area is that the plastic RJ-12 connector (phone-type connector) on the end of the coiled cable might need to be re-crimped or replaced.  Or, occasionally the connection of the coiled cable inside the hand control has worked loose and causes No Response errors.  This can be fixed by carefully removing the back of the hand control (6 screws hold it on) and reseating the connector. 

If power or the hand control connectors are not the problem, there may be a faulty connection inside the base.

For the NexStar 8/9.25/11 GPS, start by disconnecting the power from the telescope.  Using a 3/16 inch hex wrench, remove the two bolts securing the handle to the left fork arm.  Using a 9/64 inch or 3.5mm hex wrench, remove the plastic covering on the left fork arm.  Remove and reseat all connector cables attached to the small motor control circuit board - this usually wipes off any accumulated corrosion or re-establishes lost connections.  Be very careful not to misalign the pins and the connectors or damage may result.  Replace the cover and the handle and test the telescope.

If you still experience problems, there may be a connector loose under the panel on the base of the scope. Using a 9/64 inch or 3.5mm hex wrench, remove the five bolts on the top of the base panel. In a well-lit space, slowly raise the panel, being careful not to pull any of the cables loose. With the panel raised about 2 inches (rolled-up socks are a good way to prop it up), reseat all connector cables you can easily reach. Reseat the panel and secure the five bolts.

For the NexStar 5i/8i/8i Special Edition and the SE series, open the battery cover and remove the four screws securing the base cover.  Carefully lift the base cover, noting there is a cable running from the battery holder to the base.  You may find on your scope that you also need to loosen or remove the two lower screws on the plastic cover on the inside of the fork arm.  On some scopes it may even be necessary to remove the optical tube and then completely remove the cover on the inside of the fork arm.  This is not a terribly difficult task - but I won't describe it here.  You will find details in the instructions for Ray's Brackets at www.buyastrostuff.com or in the Maintenance chapter of the NexStar User's Guide.   After removing the base cover, remove and reseat all connector cables attached to the circuit boards.  Be very careful not to misalign the pins and the connectors or damage may result.  Replace the cover and test the telescope.

For the NexStar GT, NexStar SLT and Celestron StarGuide, open the fork arm (remove the plastic outer cover) and remove and reseat all connector cables attached to the circuit boards.  Be very careful not to misalign the pins and the connectors or permanent damage to the circuitry may result.  Replace the cover and test the telescope.

Similar procedures might fix this problem on the CPC, LCM, CGE, CGE Pro, CGEM and Advanced Series with GoTo (AS-GT) models as well.  Also, there is a problem on some AS-GT mounts regarding insulation between the bottom of the motor control board and the mount.  Peter Bruce has written an article describing the problem and the fix.  Click here to download the article in Adobe Acrobat format (reader available from www.adobe.com).

If none of these suggestions helps, it is time to call Celestron.


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