Why does my NexStar SLT hand control say Transmit Data

It appears that your hand control is stuck in programming mode. Fortunately, the fix is easy.

First, try cycling the power of your scope. This will often clear the condition.

If you have an RS-232 cable (the cable that attaches between your computer's serial port and the port on the bottom of the hand control) you will be able to download the HCUpdate program that will allow you to reprogram the hand control. This is available for free download off of our web site
celestron.com/downloads.
Complete instructions on how to do the reflashing are elsewhere in the Knowledgebase.

Complete instructions on how to do the reflashing are elsewhere in the Knowledgebase, “How to Flash Update your Hand Control and Motor Control Firmware“.


If you are unable to program the hand control or this problem continues after attempting to program it, your hand control needs to be replaced. Contact Celestron Support for help.

Updated 12/27/13