This tool helps finding transits of the international space station in front of the moon and the sun. Transits are calculated taking into account atmospheric friction and relativistic effects aswell as optical refraction. ISS positions are based on Two Line Elements and the SGP4 model. As the orbital position of the ISS has an uncertainty of approximately 1km, the shown results here are about the same accuracy.
Choose a start- and end date in the form at the top of the page and click Show. Sun-transit and moon-transit tracks will be shown on the map.
Reset passes will reset to current time + 24h.
Colored areas show points where a transit can be observed with a solid line marking points of a transit through the center of the celestial body.
Click on the track for data on time, coordinates and altitude / azimut.
Click anywhere on the map to create a transit mail alert: Receive mail alerts for your region if you have transits coming up. The tool will send you 1 mail 14 days in advance and another 2 days in advance of new transits.
Data is calculated for 14 days in advance at a 60s time interval between 2 calculations. For the first four days, this interval is decreased to 10s. Data between these points is interpolated.
For more information on this project and the used algorithm or for feedback and critics, feel free to reach out to me here: Contact
Happy to announce some novelties:
- The Hubble Space Telescope (HST) joined the list of predicted satellites.
- Finally the mailalerts can be set up for all space stations, the ISS, the CSS and also the Hubble Space Telescope!
- We feature a new dark mode so that you can check our website more comfortably while outside at night!
- Our mailalerts have been tidied up and now come in a more organized format.
... and there is a lot more going on behind the scenes which we hope to present to you soon!Due to a bug, the data in the transit finder in the last 14days was unprecise. We apologize for this and we are back to normal.
Users noted that the buttons Reset and Show passes were not working properly. This problem has been fixed. Please do not hesitate to reach out to me if you notice problems. I try to fix them as quickly as possible.
The official address of this site is now https://altitudeazimuth.de. The transit calculation tool deserved a proper name for itself already a long time ago and I hope you find altitudeazimuth.de a nice replacement for the subdomain iss.vierwandfrei.de. Let me know what you think: Contact. Of course nothing else changed, and if you prefer, you will also be able to continue using the link iss.vierwandfrei.de to access this website.
Over the last two days, you may have experienced some problems using this website. Transit alerts were not sent, too. This server just migrated to a new infrastructure which caused some issues. The website should be back to normal from around 12pm UTC today. Mail-alerts for upcoming transits will be sent also for the 2 days the server did not work correctly, so you should not miss anything...
Some mail-alerts have not been delivered the last two weeks. This issue is solved and should not arise again. If you have any questions, feel free to write me an email (see above).
Currently the TLE data for ISS has not been updated since June 15th. This should not affect prediction quality on this website, since I use the (more accurate) supplemental TLE. If you compare predictions here with predictions on other websites, you currently will notice a difference, if these sites use standard TLE affected by the issue. [Update June 20th: this issue has been solved.]
As requested by some users, I experimentally included the possibility to predict passes of the chinese space module Tianhe. The predictions are for 5 days and use the same mechanism as for the ISS. However TLE data is not from supplemental TLE. For now, I did not implement the possibility to sign up for mailalerts, but this may be added if there is demand for the feature.
As I have not tested these predictions, please get back to me if you made some observations and can provide feedback.
Both the calculation algorithm and the webinterface got a small update this week. Most important, in the webinterface I added the possibility to share passes in the popups and to download .ics calendar files. Furthermore, as this caused some confusion, passes now indicate whether the ISS is visible (sunlit) or whether the ISS transit is not visible to the naked eye.
On the algorithm side, as suggested by user José, I moved to Celestrak's supplental TLE which offers higher accuracy for long term predictions. (Also see https://celestrak.com/NORAD/elements/supplemental for more on this topic). Different TLE are now used for each 6h window.