Almanac update

[roe-dl]

As you certainly know WeeWX uses PyEphem for almanac, and PyEphem is deprecated. I asked about that in WeeWX issues, and in the end I was pushed to do some development. The almanac will be extensible from the coming WeeWX 5.2 on. And the first available extension is about using Skyfield for almanac computations. So the user can then choose between PyEphem and Skyfield. Existing skins will use whatever is installed without change.

But the Skyfield almanac has some additional attributes that you can display on the almanac page of the skin. First of all there is a max_altitude attribute, that shows the maximum altitude of the heavenly body at the day. This is not the same as the altitude at meridian transit.

Other additional attributes are the time of the maximum altitude, the distance of the heavenly body from earth, the hour angle, and the solar time or sundial time. Solar altitude, azimuth, and time can be included in live updates.

To distinguish between PyEphem and Skyfield capabilities you can use $varExists like this:

#if $varExists("almanac.sun.max_altitude")
... $almanac.sun.max_altitude.format("%.1f") ...
#end if

A heavily configurable sky map will also be included. Sun, moon, planets, stars, and earth satellites can be displayed with their actual position in the sky. Tooltips provide additional information about the heavenly objects. All this happens with simple $almanac.skymap in the skin.

• Skyfield almanac extension
• Skymap extension