ISS tracking

For astronomer wanting to track the ISS (or any other earth satellite) in the sky with their ASCOM compatible telescope mount. This python program will pilot the telescope mount. It was originally written in Python 2 then futurized to Python 3 and should work with both versions. I programmed this in 2018, it works fine but I need to get back to this when time allows and build a complete doc, and use numpy arrays. It could be easily ported to Indi, as the compute and command are fully decoupled, and ASCOM and Indi commands are very similar.


  • Start with a low focal length. Really! Like 200mm so you have something in the frame, then work you way up.
  • Drift align.
  • Build a sky model if you can.
  • Have your computer clock synchronized with a time server.
  • Use the simulation mode first, it is easy to have a pier collision if you are not careful.
  • Just track close to the zenith.


  • Install ascom platform 6.3
  • Install Ascom driver for mount
  • Install Ascom dev components (devlopper components)

Install the following python modules:

  • ephem

The other modules should be standard:

  • import win32com.client #needed to load COM objects
  • import ephem
  • import datetime
  • import time
  • import winsound
  • import sys
  • import urllib2
  • import re
  • import numpy as np


The Ephem part download the satellite 2 line elements and compute the track for the location. The second part use the precomputed track (editable) and commands the mount via ascom to follow the satellite.