Night sky planning
Night sky planning in Parks Manager works out, for each night of a trip, when it is dark enough to see the Milky Way core from the parks on that itinerary, how high the core climbs, which direction to face, and how much the moon will wash it out.
People drive to a dark-sky park and then spend the one clear night looking the wrong way at the wrong hour. The geometry is knowable weeks ahead, so Parks Manager works it out ahead.
- −12°sun altitude that counts as dark
- 8°minimum core altitude
- 0.35moon fraction that washes it out
- 8meteor showers tracked
What counts as a night worth staying up for
Three conditions have to hold at once, and Parks Manager reports the window where all three do rather than a single verdict for the night.
The sun has to be more than 12 degrees below the horizon, which is the end of nautical twilight and the point where the core stops competing with skyglow. The galactic core has to be at least 8 degrees above the horizon, because below that you are looking through too much atmosphere and usually through a ridgeline. And the moon has to be either down or less than 35 percent illuminated.
Each night is graded on the result: excellent, good, washed out by the moon, or core below the horizon. A washed-out night is still reported rather than hidden, because a bright moon is fine for landscapes and it is worth knowing which night to spend on what.
Which way to look
For the best moment of each night, Parks Manager gives the core’s altitude and its compass bearing to eight points. That is the part a chart of rise and set times leaves out, and the part that decides whether the ridge behind the campground is in the way.
An orient view lines the bearing up against a map of the park, so the direction can be checked before dark rather than worked out in a field at midnight.
Meteor showers
Eight annual showers are tracked, each with a peak date and a window of two or three nights on either side. A trip overlapping one of those windows says so alongside the moon phase, which is what decides whether the peak is worth anything.
| Shower | Peak | Window |
|---|---|---|
| Quadrantids | January 4 | 2 nights |
| Lyrids | April 22 | 2 nights |
| Eta Aquariids | May 6 | 3 nights |
| Perseids | August 12 | 3 nights |
| Orionids | October 21 | 3 nights |
| Leonids | November 17 | 2 nights |
| Geminids | December 14 | 3 nights |
| Ursids | December 22 | 2 nights |
It runs on the device, with no network
Sun, moon, and galactic core positions are computed in the browser from an astronomical routine bundled with the app. No request is made to any sky service.
That is not an optimisation, it is the requirement. The place you need this is a campground with no signal, several hours after you last had any, and a feature that needs an API call is a feature that fails exactly then.
It also arrives the night before
The night-before trip email carries the sky schedule next to the forecast and the current park conditions. Clouds and the core are the same decision, and splitting them across two places makes it a worse one.
What it does not do
This is geometry, not a forecast, and the distinction matters.
- Cloud cover is not part of it. A perfect geometric window under an overcast sky is still an overcast sky, which is what the weather feed is for.
- There is no light-pollution model. A park near a city is treated the same as one in the middle of Nevada.
- Shower peak dates are the long-run averages, not a maximum computed for the year you are planning, and outburst years are not predicted.
- Terrain is ignored. An 8-degree core altitude clears a flat horizon and not a canyon wall.
- A trip is planned for up to 3 parks and 16 nights at a time.
Common questions
When can I see the Milky Way on my park trip?
Parks Manager reports the window on each night of a trip when the sun is more than 12 degrees below the horizon, the galactic core is at least 8 degrees up, and the moon is either down or less than 35 percent lit.
Does Parks Manager say which direction to face?
Yes. For the best moment of each night it gives the core’s altitude and its compass bearing to eight points, and an orient view lines that bearing up against a map of the park.
Which meteor showers does Parks Manager track?
Eight: the Quadrantids, Lyrids, Eta Aquariids, Perseids, Orionids, Leonids, Geminids, and Ursids, each with a two or three night window around the peak.
Does the night sky planner need a signal?
No. Sun, moon, and galactic core positions are computed on the device from a bundled astronomical routine, so the schedule works in a campground with no coverage.
All Parks Manager features are indexed in one place.