When does your target clear the roof?

SkyWindow shows when stars, galaxies, nebulae, the Moon and planets are really visible from your spot, with your houses, trees and balcony walls taken into account. Tonight or on any date.

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Free · no ads · no account · works offline · Android phones and tablets

AR view: the Moon's path over the rooftops with hour ticks

See the path over your own sky

Point your phone at the sky: the camera shows your real surroundings, and SkyWindow draws the target's position and its whole path for the night on top, with hour ticks. You see straight away where it disappears behind the neighbour's roof and when it comes out again.

Green where the target is usable, red where your blocked sky hides it
Scrub through the night with the time slider
Gyro-stabilised heading, with a warning when metal nearby disturbs the compass

AR view: the California Nebula's path across the evening sky

AR view: red where the path runs behind blocked sky

Plan with your real horizon

Mark the directions that are blocked in seconds: tap the compass, drag the edges, or point the camera at the edge of a roof and tap Set start here. SkyWindow then works out the usable windows for every target: "M31: usable 5 h 50 m, 21:21–03:12", and why it isn't usable the rest of the night.

Altitude chart against your blocked sky, and a 360° sky map with the path
Several locations (home, allotment, holiday cabin), compared side by side
Messier, Caldwell, bright NGC/IC objects, famous stars, the Galactic Center, the Moon and planets

Andromeda Galaxy: usable 5 h 50 m with altitude chart and timeline

360° sky map with blocked directions and the target's path

Made for smart telescopes

Choose your ZWO Seestar S30, S30 Pro, S50, S50 Pro or DWARFLAB DWARF mini, DWARF 3 or DRACO. SkyWindow checks how each target fits the camera frame, in alt-az mode (the field slowly rotates during the night) or EQ mode, and suggests tonight's best targets for your setup.

Only targets that fit your frame, with a little room to spare
LP filter advice per target: on for emission nebulae, off for galaxies and clusters
Moon phase and distance, minimum altitude for your telescope
Warning when a target passes near the zenith, where alt-az mounts struggle
Red night mode to protect your dark adaptation

Framing for a Seestar S50 Pro and time lost to forecast clouds

Altitude chart against the blocked sky, with the path on the sky map

Pick the right night

Switch on the optional cloud forecast and SkyWindow rates the coming week on dark hours, moonlight and clouds, so you see at a glance which night is worth setting up for.

Clear hours per night, counted inside the dark hours only
Warnings for rain, snow, thunder and stormy wind: cover the telescope in time
Hour by hour: low, mid and high cloud, rain, wind gusts and a dew warning, each hour marked good, thin high cloud, cloudy, rain or storm (also in red mode)
Metric or imperial units

Nights: the coming week rated on darkness, moonlight and clouds, with a rain warning

Hourly weather: cloud layers, rain, wind and dew for the night

Finish a target over several nights

Add the targets you want to image with the hours you want on them. SkyWindow spreads them over the next two weeks, inside each target's usable window and around clouds and bright Moon, and tracks your progress.

Advice on total hours and mosaics for your sky brightness
Free time slot tonight? Find the target that fits it best and book it in your plan
Log your capture time, with the share of rejected frames
Session reminders, with quiet hours when you'd rather sleep
Share a plan with friends, optionally with your progress
Home-screen widget: tonight's clear hours, best targets and the cloud curve
Clear-night alert for the locations you choose

Plans: targets with their progress and the nights they are scheduled on

Home-screen widget: tonight's dark hours, clear sky, best targets and the night's cloud curve

Clear-night notification: dark and clear from 23:34 to 01:34

Test SkyWindow

SkyWindow is not in the Play Store for everyone yet. Help test it in one of two ways; updates arrive through Google Play like any other app.

Open beta Stable builds that are nearly ready for release. Best for using SkyWindow on real nights. Anyone can join. Closed alphaThe newest features first, but they may still contain bugs. Via the tester group.

Join the open beta

Beta builds should be as good as the release version: new features arrive here once they have been tested in the alpha. Use the same Google account as on your Android phone.

1
Become a tester
Open the test page and tap Become a tester. This works on your phone or on a computer.
Become a beta tester
2
Install on your phone
On your Android phone, open SkyWindow in the Play Store and install it. Updates arrive like any other app.
Open in Google Play

Leaving is easy: tap Leave the program on the test page.

Join the closed alpha

The alpha gets new features first, often several builds a week, but they may still contain bugs. Join it if you like trying things early and reporting what goes wrong. It is open to members of the tester group. Use the same Google account as on your Android phone.

1
Join the tester group
Open the SkyWindow tester group and click Join group. You won't receive any spam; you can set emails to "No email".
Join the tester group
2
Become a tester
Open the Google Play test page and tap Become a tester. It is the same page as for the beta: because you are in the group, Google Play gives you the alpha builds. Already a beta tester? Then joining the group is enough. If it says the app isn't available, wait a few minutes after joining the group.
Become an alpha tester
3
Install or update on your phone
Open SkyWindow in the Play Store; the newest build you have access to is offered.
Open in Google Play

Back to the beta only: leave the group. Leaving testing completely: Leave the program on the test page.

Your sky, your data

No account, no ads, no tracking. Your locations stay on your phone. Only if you switch on the optional cloud forecast are rounded coordinates (about 1 km) sent to the weather service Open-Meteo. Read the privacy policy.

Become a tester