Xasteria for iOS


MARCH 24th Notice:

Unfortunately the 7Timer! service that powers Xasteria is down for technical reasons, and the maintainers tell me it will take a while to restore. I will prepare a Xasteria version with a proper warning and some alternative weather data until the 7Timer! service is restored.

Xasteria brings the Astronomical-oriented ASTRO world weather forecast of the service 7Timer! to any iOS 6.0 or later device. You can use your device GPS for a forecast of your location, enter manual coordinates or search of a location online.

7Timer! is mainly derived from the NOAA/NCEP-based numeric weather model, the Global Forecast System (GFS) and gives you a forecast for the entire globe with a resolution of about 20km at 3-hour intervals.

Xasteria is available iPhone/iPod/iPad with iOS 6.0 or higher.

Download on the App Store


Graphic/Visualization Modes

Xasteria provides you with a choice of 3 visualization modes for the data: the new 7Timer! ASTRO graphics, which tries to be quick to read by using different visuals per category and not overwhelming with data that is not useful (e.g. if humidity is low, you don’t need to know the exact percentage), the color-stripe graphics similar to some other astro-forecast services and a raw text mode.

7Timer! Mode

Stripe Mode

Text Mode


Available Data

A list of available data categories, along with the graphics that are used by the 7Timer! graphic mode and the stripe graphic mode.

  • Moon phase.
  • Cloud cover. Will give you the cloud cover forecast from 0% to 100% (worst).


  • Astronomical seeing. Turbulence and temperature differences in the atmosphere can reduce the amount of detail visible through a telescope, especially with high magnification on planets.


  • Atmospheric transparency. Water vapor can reduce the transparency of the atmosphere. Good transparency is required for low contrast targets like galaxies and nebulae.


  • Temperature. Apart from your comfort level, a low temperature can affect the cool-down time of your equipment.

  • Humidity. High humidity can, depending temperature, telescope type etc, lead to quicker dew formation on optics.


  • Rain/Snow.rain
  • Atmospheric instability. Indicates when there is a high chance of a thunderstorm (based on a calculation of the lifted index).


  • Wind. The app will either warn you about high wind (in graphic modes), or show the wind strength in the beaufort scale (text mode). Strong winds apart from comfort affect the stability of your telescope and can be crucial for astrophotography.


Language Support

Xasteria is available in English and Greek. If you’d like to translate it to your language, contact me about it!

Meaning of The Name “Xasteria”

Xasteria is a Greek word (Ξαστεριά) which means a night without clouds where you can see the stars.

Polar Scope Align Pro

There is a special version of Xasteria in the Polar Scope Align Pro app, which adds the ability to switch to night-mode (and access to that app’s quick-dim function) and also can take advantage of the app’s location manager.


      • What does “Xasteria” mean?

Xasteria is a Greek word (Ξαστεριά) which means a cloudless sky with all the stars visible.

      • What is the altitude correction?

This is something you should normally leave “off”. However, if you are on the top of a steep mountain, it is likely that the resolution of the forecast system (about 20km) is not enough to give you readings specifically for the peak you are on. This will become obvious if you notice the Xasteria temperature reading being much higher than the actual temperature at your location. In that case you can try the +2 km correction (or the +7 km in a couple of places in the world).


If you have any questions or problems with your app, the quickest solution is to use the Contact page to write directly to the developer. Or you can post your suggestions, questions in the comments below

Share this Page:
Share on FacebookShare on Google+Tweet about this on TwitterShare on LinkedInEmail this to someone

2 thoughts on “Xasteria for iOS

  1. Ari Siqueira says:

    I downloaded Xasteria for iOS but could not yet figure out how to use it for a polar alignment. Have you published detailed instructions or perhaps a tutorial?
    Thank you.

    • ecuador says:

      Hi. I am not sure I understand what you are trying to do. The Polar Scope Align app is for polar alignment. There are general instructions (button on top left on the main screen) and also specific instructions for your polar scope (Reticle Help button in Settings screen after you select your Polar Scope Reticle).
      Xasteria is a different app that gives you a weather forecast.
      The connection between the two apps is that the Pro version of Polar Scope Align includes a night-vision enabled version of Xasteria.
      Hope this clears it up.

Leave a Reply

Your email address will not be published. Required fields are marked *