Is it worth staying up tonight, or will clouds mar your view? Any would-be stargazer needs to know if they'll have clear skies. Below, you'll find the online resources that provide astronomy forecasts.
Astronomy Stargazing Forecast
The Clear Sky Charts are the first place that most North American stargazers look when they're trying to figure out whether observing conditions will be good for the next night or the one after.
The underlying data for the Clear Sky Charts comes from the Canadian Meteorological Centre (CMC) astronomy forecast. Each Clear Sky Chart gathers all the information for one location into a single view, while the Canadian Astronomy stargazing forecast has maps showing how conditions evolve over the entire continent.
Weather Underground is another excellent source, with a separate section for the astronomy forecast under any local forecast.
Skippy Sky has astronomy and stargazing forecasts for Europe and other parts of the world, including North America. This is based on the Global Forecast System, which covers the entire planet and stretches more than a week into the future, but is less detailed and reliable than the CMC model.
General Weather Forecast for Stargazing
It's always worth checking a general weather forecast as well, both as a cross-check for the astronomy-specific stargazing forecast and to include conditions such as wind speed that are important to astronomers but not included in the CMC astronomy forecasts.
By all means consult the forecasts from your local news media, too. AccuWeather is one particularly handy source for private weather forecasts. But be aware that all other forecasters routinely consult the ones from the various national weather services, such as the following:
To see what the weather is actually doing, check the U.S. Geostationary Satellite Server.
Computer Weather Models
All modern weather forecasts are based on models running inside supercomputers at the various national weather centers. The two most important models for North America are the Global Forecast System (GFS) and the North American Mesoscale (NAM).
The GFS covers the entire planet and runs two weeks in advance, but its model is fairly crude. The NAM is much more precise, but runs only four days in advance. Data from both models can be accessed at the U.S. National Weather Service Model Analyses and Guidance website.
What if you're planning a vacation, or looking for a retirement home with good astronomy conditions? Then you will want to check the long-term climatic conditions.
The U.S. National Climate Data center displays a huge amount of data in tabular form. For data on nighttime cloud cover, which can be see only in infrared, consult the historical data from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite instruments.
Alphabetical List of Forecasts:
- Canadian Meteorological Centre Astronomy Forecasts
- Canadian Meteorological Centre General Forecasts
- Clear Sky Charts
- IPS MeteoStar, Inc.
- Penn State University Electronic Map Wall
- Skippy Sky astronomy forecasts
- UK Met Office Climate Summaries
- UK Met Office Forecasts
- U.S. Geostationary Satellite Server
- U.S. MODIS Historical Data
- U.S. National Climatic Data Cente (NCDC)
- U.S. NCDC Climate Tables
- U.S. National Weather Service (NWS)
- U.S. NWS Model Analyses and Forecasts
- Weather Underground
This article accompanies an article that ran in the February 2010 issue of Sky & Telescope. See this article to find out how to interpret the information on these websites and how to get your own stargazing forecast.