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All astronomical information is calculated for mean sea level at latitude 22°18'7.3", longitude 114°10'27.6", which is the location of the Hong Kong Observatory, based on astronomical data provided by the HM Nautical Almanac Office, United Kingdom and the United States Naval Observatory.
The night sky brightness (NSB) is measured by the SQM-LE Night Sky Brightness monitors at the monitoring station on the Hong Kong Night Sky Brightness Monitoring Network (NSN); smaller value represents brighter sky while larger value represents darker sky. Detailed information can be found at http://nightsky.physics.hku.hk/hk-light-pollution-map.php
"The latest star map information" is updated every 5 minutes automatically.
"The daily rise and set times of the celestial bodies" shows the times of rise and set of the celestial bodies on the current day.
"The information of special astronomical phenomena" shows the special astronomical events in the coming 30 days but not all events can be observed in Hong Kong. The information will be updated whenever there are any other ad hoc events or events of public interests.
The air temperature and relative humidity of each astronomical observation hot sport is using observation of the nearest automatic weather station(s) close to sea level operated by the Hong Kong Observatory.
From sunset every day to sunrise the next day, the night sky brightness provided by the Department of Physics of the University of Hong Kong is updated once every 5 minutes by the median value of the night sky brightness of the past 15 minutes. The night sky brightness data is only available at night time.
The information of the "Astronomical Observation Weather Information" website is jointly provided by the Hong Kong Observatory, the Hong Kong Space Museum, the Department of Physics of the University of Hong Kong and and Ho Koon Nature Education cum Astronomical Centre. The information is for general only.
This webpage is jointly organized by the Hong Kong Observatory, Hong Kong Space Museum, Department of Physics of the University of Hong Kong and Ho Koon Nature Education cum Astronomical Centre.
For enquiries on astronomical service, please contact Scientific Officer (Geophysics Services) at 2926 8433
Monday to Friday 8:30am to 5:45pm
Closed on Saturday, Sunday and public holidays
< 0.5 mm
≥ 0.5 mm
Wind Speed / Wind Direction
The information of rainfall forecast is updated every 12 minutes automatically. In reality, heavy rain can develop very rapidly. Significant intensification or weakening, or even changes in the direction and speed of storm movement may occur within the forecast period. Should such development happen, large forecast errors are likely to result. This is a limitation that existing weather forecasting science and technology cannot lift yet. Rainfall forecast is generated automatically by computer without any manual adjustment. The main purpose is to provide the first instance the latest available information for users preliminary reference. From the Observatory's forecast verification result, the accuracy of the rain forecast in the first half hour would be about 75 %, depreciating to lower values as the forecast range increases through one to two hours. It may be different from the other weather information disseminated by the Observatory for the general public of Hong Kong. The user should not assess the likelihood of rainstorm or other warnings based on the rain forecast information directly. For taking precautionary actions against inclement weather, the public is reminded to refer to the latest local weather forecasts, special weather tips and severe weather warnings issued by the Hong Kong Observatory.
The information of temperature, humidity, wind speed and wind direction in the Automatic Regional Weather Forecast is updated twice a day at about 0400H and 1600H local time (the 1st day). The former provides hourly forecasts from 0500H the same day to 0500H of the 3rd day. The latter provides hourly forecasts from 1700H the same day to 1700H of the 3rd day.
In the time series chart for wind speed/wind direction, the black arrow represents the hourly forecast wind direction. "←" and "↓" indicate easterly and northerly winds respectively.
The Automatic Regional Weather Forecast shows the general weather situation over the stargazing hot spots as forecast by the model. The weather conditions described by the products may be different from those recorded at individual weather stations within the grid box and the weather forecasts issued by the Observatory.
Minimal quality control and screening of the computer model generated forecast products are carried out by the Observatory's staff to ensure that the forecasts are within acceptable range. No manual adjustment is made during the whole process. Details of the computer model can be found at the following website (http://www.hko.gov.hk/nhm/mesomodel_e.htm)