Never Enough Spacetime

Tales of an astronomer trapped in a programmer's body.

NexStar GPS, a Telescope App for Android

Every clear evening I get a chance I take my telescope outside, plug it in, go through the location and date/time setup, then align my scope. Repetitive manual tasks annoy me! After about 20 iterations of this, I decided it was time to automate the location and date/time configuration. I tried using Celestron's SkySync GPS accessory, but to no avail. At $200, I expect a bit more than GPS synchronization! I wondered, "Why isn't there an Android app for this?" Hence the birth of NexStar GPS...


NexStar GPS is a native Android app which can communicate via WiFi to synchronize the current date, time, and GPS location with a telescope using the NexStar protocol.


In order to run this app, you must have some way to connect to your telescope via WiFi. I posted my hardware configuration I'm using to connect, but you also may have another method. Here are the basic requirements:

  • NexStar compatible telescope
  • WiFi-enabled telescope via
  • Android Phone (reasonably modern)

Syncing GPS to Your Telescope

Once you install the app, go ahead and open it. After a brief stay on the splash screen, your phone should show you your exact position (or complain that GPS isn't enabled, at which point you'll need to enable it).
GPS Location

If this is the first time you've run the app, you'll need to configure the IP address and port your WiFi telescope server is running on. Find the Settings option in the application menu, and you'll see that the host and port are blank. Enter the hostname or IP address and the port on this screen. When you are finished, it will look like this:
WiFi Telescope Settings

Go back to the map screen, and you'll see the Connect button in the top left corner. Once you click the button, it will attempt to make a connection with your telescope. If it can't connect, you'll be prompted to check your settings. If all is well, you'll see this:
Connect to Telescope

At this point the Connect button will transform into an Update GPS button. I did this to preserve real estate. Once you're connected, make sure you like your GPS position shown, and click Update GPS. You will see a nag screen to make sure you want to do this (I had to make at least one nag prompt!); as soon as you click OK the data will be sent.
GPS Update Prompt

If all went well, you will see the following. Otherwise, you will be prompted with an error. Feel free to Update GPS as many times as you like!
GPS Update Success

I personally find this saves me a lot of hassle, and helps me focus on the fun stuff like observing. In the next month or so, I'll be posting some pics now that the humidity is coming down.