Building Space Weather for Astrolabe, and a Little Holiday Planning

How a simple aurora request grew into local space weather forecasts and a little holiday automation.

It started with a simple forum question: could the aurora go on Astrolabe’s “Worth looking for” list?

Space weather was already on my list of things to add, and that seemed like a good place to begin. Get the solar activity, check your location, and tell you whether it might be worth stepping outside.

As usual, “a good place to begin” turned into a somewhat larger project.

Could I see the aurora from here?

That was the question I wanted Astrolabe to answer. A geomagnetic storm reading is interesting, but it doesn’t tell you much by itself about what you might see from your backyard.

The new Space Weather device uses data from NOAA’s Space Weather Prediction Center, combined with Astrolabe’s calculations for your location. It gives you an aurora outlook for tonight and right now, with answers such as:

• Not from here
• Low on the horizon
• Overhead

There’s also Why That Aurora Answer, which explains how Astrolabe reached its conclusion. The idea is to give you something more useful than a number and leave you wondering what to do with it.

The Sky page now has an aurora panel and a space weather summary, and the Tonight summary mentions the aurora when there’s something worth watching for.

These are estimates, of course. Clouds, local light pollution, and the storm’s actual behavior still have a say. Astrolabe can suggest a look outside; it can’t promise the Sun will cooperate.

The first surprise: latitude isn’t quite latitude

One of the interesting parts was working out what “from here” actually means.

Auroras follow Earth’s magnetic field, so ordinary map latitude isn’t the right measure. Astrolabe calculates your geomagnetic latitude using the IGRF-14 magnetic field model. Two towns at the same geographic latitude can therefore have different aurora prospects.

It then compares your location with NOAA-based estimates of how far the aurora might reach and checks whether it will be dark when the activity is expected.

That last part matters. A strong aurora forecast at lunchtime is exciting news, but a rather poor reason to turn off the backyard lights.

I also tried a broader visibility rule based on seeing an aurora from a distance. It produced some decidedly optimistic answers, so that approach didn’t make the cut. I’d rather Astrolabe give a cautious, explainable estimate than send everyone outside for an empty sky.

There’s more going on up there

Once the NOAA connection was in place, it made sense to include the rest of the picture.

The Space Weather device has 19 features, covering:

• Current geomagnetic activity and the highest forecast Kp over the next 24 hours.
• The estimated Kp needed for aurora visibility at your location.
• Current and forecast geomagnetic storm levels.
• Radio blackout and radiation storm levels.
• The Sun’s X-ray activity, major flare chances, and solar flux.
• Aurora prospects, an explanation, and NOAA’s overhead aurora probability when relevant.
• A one-line summary and the last update time.

Each feature has its own icon, and missing information is shown as Unknown, with a grey question mark. A missing reading shouldn’t quietly become a reassuring zero.

You may also see Not checked for NOAA’s overhead aurora probability when Astrolabe’s location estimate puts the aurora out of reach. In that situation, it skips downloading the map.

Space weather is optional and off by default. You’ll find Fetch space weather under Setup → Online extras.

Then came the real-world testing

Tests are useful. Live feeds have a talent for supplying the cases you didn’t think to test.

During an active flare, one NOAA feed can report the peak time as “Unk” and leave the flare class empty. My first parser interpreted that as a failed feed. It now handles the incomplete report properly.

Another early message said “Aurora from 4:00 AM,” but that was the forecast’s peak hour—not necessarily the first hour the aurora might reach your location. That distinction is now handled correctly.

There was also a date-parsing surprise, and a couple of test expectations that turned out to be wrong on my side. Building astronomy software is occasionally an exercise in discovering that the computer has answered exactly the question you asked, rather than the one you meant.

I also introduced a weather-download regression while trying to save bandwidth. Enabling an additional compression format upset the existing cloud-cover and elevation downloads in versions 1.3.3.0 and 1.3.3.1. Version 1.3.3.2 fixes that by returning to gzip only.

Around the same time, the Earth-orientation data file moved, and its backup source was timing out. Astrolabe now has updated addresses for those sources too.

The engine currently passes 834 checks, including the new space weather checks. NOAA downloads are limited to once every 15 minutes, while Astrolabe re-evaluates the available data between downloads to keep its answers current.

You can try it now

The aurora outlook and space weather summary are already live at astrolabe.cyberlogix.net.

The website uses the same engine as the plugin, so you can enter your location and see the answer Astrolabe would give you. It’s also an easy way to explore how the outlook changes between locations.

Meanwhile, back here on Earth: the holidays

With Halloween approaching and Christmas not far behind, this also seems like a good time to mention Astrolabe’s Calendar features.

They tackle a familiar HomeSeer problem: making schedules follow the calendar without revisiting a collection of dates every year.

The Calendar can tell you whether today is a holiday, whether it’s a business day, what holiday comes next, and which seasonal themes are active. Day Type provides a straightforward answer: Workday, Weekend, Holiday, or Day off.

That makes it useful for things such as skipping the weekday wake-up routine on a holiday—or giving yourself a little warning before tomorrow’s schedule needs to change.

There are ten built-in seasonal themes, including Halloween, Thanksgiving, Advent, and Christmas. You can configure the Christmas window so the lights stay on past New Year, and you can define your own seasons. Those seasons can overlap, too.

Two event triggers bring this into HomeSeer:

• The date is a holiday, with an optional number of days ahead.
• A season is running, for seasonal routines.

Pair the Christmas season with Astrolabe’s civil-dusk state, and you have Christmas lights that come on at dusk and go off at bedtime throughout the season.

No annual hunt for the event containing last year’s dates.

A calendar lesson I particularly enjoyed

You might expect more accurate Moon calculations to make every calendar more accurate. Sometimes they would make the answer wrong.

Easter uses an ecclesiastical calendar, and the Hebrew calendar follows arithmetic rules. Their dates need to follow those definitions rather than the actual Moon’s position.

The Chinese calendar, on the other hand, depends on astronomical new moons and does need the astronomy calculations.

Astrolabe supports Western and Orthodox Easter, Hebrew, Islamic and Chinese calendar calculations, Nowruz, and seasonal dates. Building those has been a good reminder that accuracy starts with choosing the right rules for the question.

For holiday and season event conditions, an unknown state evaluates as false. Restarting HomeSeer in July shouldn’t accidentally announce Christmas.

A few things you could do with it

• Aurora alert: send a phone notification when the aurora becomes potentially visible from your location, and turn off the backyard floodlights.
• An evening heads-up: have a speaker announce the aurora outlook at dinnertime.
• Radio activity: notify the ham operator in the house when the reported radio blackout level reaches a chosen threshold.
• Seasonal lighting: run Halloween or Christmas lights at dusk while the relevant season is active.
• Holiday schedules: skip the normal weekday routine or prepare tomorrow’s thermostat schedule ahead of a holiday.

Getting the update

The holiday calendar is available in the current HomeSeer store version. Space weather is coming in the next store update, which is in final testing on my own system.

Once that update is installed, enable Fetch space weather under Setup → Online extras. The new device should begin filling in within a minute or two.

Thanks to the forum member who asked about adding the aurora. That one suggestion turned into quite a bit more than another line in the Tonight summary.

If Astrolabe’s outlook doesn’t match what you see, please post your approximate location, the date and time, and what you observed. That gives me something useful to compare with the forecast.

Space weather data courtesy of NOAA’s Space Weather Prediction Center. Geomagnetic coordinates use the IGRF-14 model published by NOAA NCEI.