CelestronESPWifi
ESP8266 based wifi adapter for Celestron telescopes
The official Celestron Skyportal WiFi module is €190~. (aka SkyQ Link, aka Skylink)
CelestronESPWifi parts list:
- ESP8266 Module: €1.25c
- Buck Converter: €0.75c
- Cable: €3.00
- Jellybeans: €2.00
Total = less than €10 anyway.
Notes and Features
- Confirmed working with Celestron SkyPortal App and Skysafari 6 Pro (Select scope type: "Celestron Wi-Fi").
- Works with keypad (Tested on Celestron 4SE), not tested with other peripherals.
- ESP firmware can be updated remotely over webpage via http.
Example Build
Minimum Parts List
- ESP8266 Module (Example 12F)*
- ESP8266 Programmer*
- 2 Diodes
- 1 10K Resistor*
- Buck Converter (Example: LM2596)
- RJ12 Cable
*Alternatively you can use something like a NodeMCU and set the buck converter to 5v instead of 3.3v needed for a bare ESP.
Firmware Notes
ESP firmware will host a wifi access point, default named Celestron. The ESPs IP is 1.2.3.4 and opens a tcp listen port on port 2000. Don't change these as it's a requirement for the SkyPortal app to work. Port 80 can be accessed to update firmware over HTTP if required - please make sure to flash it before you embed it in a project :)
Because SoftwareSerial is used - we can choose what pins to TX and RX on, so if it needs changing afterwards this can be updated in the sketch and uploaded over HTTP. Just make sure the diodes are in the correct direction for the TX and RX data flow. Similarly the RST pin can be changed. If you plan to use a bare ESP, I recommend not to use GPIO15 as it will be shorted to ground.
Hardware Notes
If you use a bare ESP; set the buck converter voltage to 3.3v, any other module such as a NodeMCU will take 5v. The scope uses a UART system over one wire. Multiple devices can communicate on this same bus by pulling RST low, then sending data. Source and Destination IDs are sent in the packets so devices know what data is for them. There have been varying reports from other smarter people on pull up/down resistor anomalies so if you deviate from this design you may come into those issues, see reading material below. If using a NodeMCU or other similar premade board, the pullup resistor and short on the EN pin and GPIO 15 are not needed. Be aware there are RJ12 cables with reversed colour layout, use a multimeter to find the 12v pin if you are unsure if you have a reversed version.
Similar projects
This project would be much more difficult without the help of these posts:
https://sebastianfoerster86.wordpress.com/2020/08/10/celestron-teleskop-skyq-link-wi-fi-hack/
https://sites.google.com/site/wayneholder/nexstar-direct-telescope-mount-control
Simply having this info meant that I could confirm my setup worked and my logic analyser was reading expected data.
Additional Notes
On AA battery power, when the batteries are low at some point the motors will stop working. In this situation the ESP will probably still have power and the ability to communicate and link to the Skyportal app successfully. Input commands to the motor will not work, there is no indication of low power. It seems this behaviour is normal and even the official keypad gives you no low-power warning. Don't panic, simply get new batteries.
CelestronESPWifi was developed and confirmed working on a Celestron Nexstar 4SE.