Meteors

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A Clear Night

 

This time lapse shows a clear night, with only a thin veil of very high cloud, which can be seen more clearly while there is some light in the sky after sunset and before dawn.

The movement of the sky reflects the rotation of the earth. The summer constellations, Lyra and Cygnus are prominent on the right half of the video, with the great square of Pegasus beginning to appear from the bottom towards the end of the sequence, with the W share of Cassiopeia towards the left. The camera is pointed just north of East with an 88 degree wide field (so showing from NE to SE) and pointed up at about 45 degrees. This camera sees stars down to about magnitude 6, which is about the same as an average human eye would see in perfectly dark conditions. This location has reasonably dark skies by southern England standards, but is really quite severely light polluted. Without light pollution, most of us would see clear night skies quite similar to this time lapse.

The camera is considerably more sensitive than the human eye, which helps it to overcome the effects of light pollution. On this night, at this location, I could see stars down to about magnitude 4.5-5, so the camera can see many more stars than I can. (There are 2,822 stars in the sky >= magnitude 5 and 8,786 >= mag 6 so the camera can see roughly 3 times the number of stars that my eye can see)

There are lots of satellites, some aircraft and about a dozen meteors visible in this sequence, but the time lapse makes them flash across the sky very much more quickly than in reality. Each meteor event is captured separately as video and still images and is calibrated and processed to define its precise visible track across the sky. This information is uploaded to the uk meteor network and to the global meteor network. The uk meteor network attempts to match the same events from more than one camera, which allows the orbit of the object that caused the meteor (the shooting star) to be calculated. An archive with these events is publicly available.

Satellites

 

This is an extract from a whole-night timelapse which shows a "constellation" of internet-providing satellites (starlink or oneweb) passing overhead. As a timelapse, this is much faster than real time. These satellites are placed in orbit one after another, gradually spreading along the same orbit until they are spaced out, so that a ground station (even a house) always has several of them above the horizon able to send and receive data by radio to have an internet connection. Seeing them close together in a train like this, means that the satellites have probably been launched fairly recently (These might be from the starlink launch on 15 May 2021). There is an animation here that gives some idea of the large number of satellites involved in starlink.

For obvious reasons, astronomers and others who love the night sky see these systems as a form of light pollution: they certainly interfere with any attempt to photograph or make video of a natural night sky.

The camera is slightly out of focus. I have re-focused in the day time and will test and refine the focus when we next have clear weather.

 


Timelapse

 

This is an automatically produced time-lapse of what my meteor camera sees in a fairly typical night. There are four meteors in among the dozens of aircraft, satellites and clouds passing in front of the stars. The system detects meteors (and is quite good at ignoring other moving objects) and captures video of the event, from which accurate positions and times are derived. Meteor events are uploaded and where possible matched to events from other meteor cameras, allowing a precise 3d trajectory to be calculated, which can tell us the orbit the object had before it hit the atmosphere (where it came from) and rarely, with very bright meteors called "fireballs", can be used to calculate where any meteorite would have fallen to earth.