Astronomy Tonight

This tool collects together, on a single page, basic information of interest to most amateur astronomers. It's most useful for residents of Canada and the US. Outside of those areas, no weather data is shown.

Below you will find a large form that lets you customize the output data. Its defaults are for Ottawa, the capital of Canada. As a convenience, here are the results for some selected locations (Canada and US only):

The information is customized for your location, and includes:

These links will help you look up the data you need when filling out the form:

If the meaning of an item in the form below is unclear to you, try and hover your mouse over the item; some items have a tooltip. Required items are marked with *.

Location name*:
Clear Sky Chart station id*
Radar Station*:
Weather Station ID*
Time scale:
Show locations
Limiting Visual Mag:
Limiting Mag Messier/Caldwell:
Limiting Mag Messier/Caldwell (planisphere):
Clouds: degrees on a side
Clouds: pixels on a side
Clouds: visible or infrared?
Star chart rotation angle:
Minimum auroral activity level:
Occultations: num days to look ahead
Occultations: min magnitude
Exclude clouds
Exclude radar
Exclude ecliptic
Exclude Sun, Moon, and Planets
Exclude sky diary
Exclude minor planets
Exclude comets
Exclude Messier objects
Exclude Caldwell objects
Exclude meteor showers
Exclude Galilean satellites
Exclude observation window
Exclude current weather
Exclude weather forecast
Exclude libration
Exclude planisphere
Exclude Clear Sky Clock
Exclude aurora
Exclude occultations
Exclude Jupiter satellite phenomena

There is a defect related to time zones. Example: if you are in Ottawa, then you can view data for Washington DC, since those two cities are in the same time zone. If you are in Ottawa and you view data for Los Angeles, however, then the times are going to be messed up. Everything works fine only if you stay in the same time zone used by your browser. Most of the time, this defect won't bother you, because you're usually concerned with nearby locations. (This problem is caused by how Javascript treats dates and times. There are ways around this problem, but I haven't done anything about it yet. If you need a work-around, then just temporarily change your computer's time zone setting.)

The satellite imagery is particularly useful, because it shows detailed cloud information. The satellite image generated by the above form centers on a given location, and has a small area. It's also interesting to see the clouds over a large area of the country. The images are especially dramatic when the Sun is low in the sky, and produces longer shadows. Here's a form for showing larger cloud images.


This site also allows you to generate a customizable, precise planisphere for your location (as two PDF files).

You can help to improve, by contributing to its github repository.

Code last updated on: 2024-01-18.