Perseid Meteor Shower 2021
The Perseid meteor shower is one of the meteor showers that boasts the best condition for observation this year, and the estimated peak would be at around 3 to 6 am on August 13. It is estimated that the zenithal hourly rate (ZHR) of the meteor shower can reach 100 during the peak period. The neglectable influence of the moonlight also provides an excellent observation condition. However, due to other factors such as light pollution from the city, observers in remote areas of Hong Kong might only see 20-30 meteors during the peak even in fine weather.
In mid-August, the radiant of the Perseid meteor shower will rise in the northeast at about 10 pm. More meteors should be seen when the radiant is higher above the horizon. The best observation time would be at around 4 to 5 am on 13 August. It is recommended to observe the meteor shower from 10 pm on 12 August until the dawn of 13 August.
The parent body of the Perseid meteor shower is a comet called 109P/Swift–Tuttle. When it travels through the Solar System, a large amount of debris is left. When the Earth passes through these debris in space as it orbits around the Sun, a large amount of debris falls into the Earth's atmosphere, forming a meteor shower. Since these debris are from the same origin, all meteors emanate from the same point called the radiant. When the radiant of the meteor shower is in the constellation Perseus, we call this meteor shower as the Perseid meteor shower.
Information about the peak of Perseid meteor shower 2021:
|Date and time||Zenithal Hourly Rate*|
|3am to 6am, 13August||100|
* The zenithal hourly rate (ZHR) is the extrapolation hourly rate of meteors observable in an extremely dark and wide sky with the radiant located at the zenith. As some meteor showers have very short peak periods, observers sometimes extrapolate the number of meteors observed in ten and a few minutes to an hourly number in proportion. Therefore, the zenithal hourly rate cannot be regarded as the actual number of meteors visible in one hour. Yet, it can be used as a meaningful comparison between the activity of different meteor showers. Some meteor showers can be as inactive as having single digit zenithal hourly rates. There are "three major meteor showers" (Quadrantid meteor shower, Perseid meteor shower, and Geminid meteor shower), which have the ZHRs reaching 100 or even higher values, and hence worth watching.
(Source: International Meteor Organisation)
|Best local observation time||Expected maximum number of meteors within one hour|
|4 am - 5 am, 13 August||City outskirts1||Nearby countryside2||Remote area3|
1Region where stars brighter than magnitude 3 are visible (about 100 stars) and with an unobstructed view of about 60% of the entire sky.
2Region where stars brighter than magnitude 4 are visible (about 300 stars) and with an unobstructed view of about 70% of the entire sky.
3Region where stars brighter than magnitude 5 are visible (about 1,000 stars) and with an unobstructed view of about 80% of the entire sky.
For information about star magnitude, please check the online education resources of the Space Museum.
The Hong Kong Space Museum will livecast the Perseid meteor shower from 10 pm on 12 August to 12 am on 13 August through its YouTube channel:
Here are some tips for watching the Perseid meteor shower:
- There are still a certain number of meteors around the peak period. 1-2 days before and after the peak period is also suitable for observation as long as the weather is fine.
- Meteors do not necessarily appear near the radiant, and most of the meteors are dim. Observers should choose a site with a large unobstructed view and low light pollution. Staying away from other light sources can help your pupils dilate and increase their sensitivity to light.
- Basically, a telescope is not required as meteors are better observed by naked eyes. You may bring along with you a star-map, a red torch, a deck chair and a sleeping bag or blanket. Please observe stargazing manner and refrain from using excessive light as this will affect other stargazers.
- To photograph meteors, a camera with long-exposure function and a wider angle lens are essential. After focusing on starlight, point the camera to the zenith or the darkest area on the sky and set an appropriate aperture and ISO value (such as F2.8 or lower, ISO 800 or higher, depending on the design of the lens and camera, as well as the nearby environment). Then select the time of exposure based on whether a star tracker is used. In general, a longer exposure gives you a higher chance of capturing unexpected meteors. For long exposure you may consider stepping down the aperture to say, F4 or F8 and ISO value to 400 for better image quality. The star image distortion due to camera shaking can be solved by using a remote control or the self-timer function on the camera.