What to look for in a clear sky forecast
An evening can look promising on a weather forecast and still leave you with very little to shoot. The cloud clears after the target sets, or a thin veil takes the faint detail out of every sub. The best astronomy weather app for your site, in the UK or anywhere else, is one that helps you spot those nights before you spend an hour setting up. Start with the hours you can use and the direction the telescope will point.
Follow the target across the sky
A forecast for the grid square over your garden is a starting point. A low target takes you through cloud some distance away, and that cloud need not match what is overhead. The Quiet Sky goes beyond the overhead view: with an account, its sightline checks the forecast where the direction to your target crosses the low, mid and high cloud layers.
The distinction matters when one side of the sky looks open and the other is closing in. Without a target, the hourly figure is labelled “Cloud overhead”; with one, it is “Cloud on target”. Hours without sightline data fall back to overhead cover and are marked. Read that label before treating the number as a forecast for the object itself.
Open the cloud layers
Low cloud can end a run outright. High thin cloud may let bright stars through while taking away the faint outer parts of a galaxy. A single total cannot tell you which sort of night to expect, so look for the low, mid and high layers before deciding that a large cloud percentage means packing away.
The Quiet Sky puts that split in each hour's details. Its score gives high cloud less weight than low or mid cloud, using an assumed thickness for each layer. That is a scoring choice, not a measurement of the cloud's thickness tonight. The cloud cover guide explains how to read it; seeing and transparency matter even when little cloud is forecast.
Count hours you can actually shoot
Clear sky before darkness is little help for faint detail. Nor is a clear spell after the target has dropped behind a neighbour's roof. Check where the object will be through the night, then look for a continuous stretch that leaves room to get on target and begin collecting light. Several isolated gaps can be less useful than a shorter uninterrupted run.
In The Quiet Sky, only dark hours count towards the night dial. With a target, those hours must also be above your skyline and your rig's minimum altitude. The dial shows the median score across those hours; the usable window is the longest unbroken run at or above your go threshold. Saving sites and rigs needs an account. Keep the window beside the dial when deciding how much time to set aside, then plan the imaging session with capture overheads included.
Read the second model before making plans
A weather model can bring a cloud front through too early or hold it over you too long. If the models disagree about tonight, look at when each would let you start and when each would make you stop. That tells you how much of the evening depends on the timing being right.
The Quiet Sky reads the same hours with a second model from Environment Canada. When the difference is large, it shows a score range and fills the dial to the pessimistic end. If that second model keeps the sky clear for longer, the chart shows the extra hours, while the verdict stays with the main forecast. Treat them as possible extra time. The forecast and nowcast guide covers the checks to make closer to dusk.
Know where the forecast comes from
The Quiet Sky's weather forecast comes through Open-Meteo from national weather services; the models available vary by location. Knowing the source helps you read a changed forecast as a revised calculation. It does not make the next clear spell a booking you can rely on. Keep some room to change your target or shorten the run.
Each night, The Quiet Sky compares recent model cloud forecasts with airport weather reports near saved sites, region by region. It can serve a region the model or blend that has done better there recently, keeping that choice unless another improves on it by a margin. Saved sites need an account. This describes how a model is chosen, not a promise about tonight. Read how models are chosen for the checks behind that choice.
Look ahead, then return near dusk
The Quiet Sky shows 7 nights ahead. Use that view to set aside a likely evening, then return to the forecast before carrying out the rig. “Remind me” adds a calendar event; with an account, push alerts can tell you when an alert rule matches. A reminder makes time to look again. It does not settle what the weather will do.
The forecast and scores can be read without an account. The night planner needs one. If a number still seems at odds with the sky outside, the other forecast guides explain what it measures and what to check alongside it.
For current access, the FAQ explains what is available.