35185 How does it keep stars from being recorded  in the image?  Maybe the shutter speed is fast enough not to record stars? Most stars are very faint.  With some stacking stars down to magnitude 4 and 5 become visible.  I need some stars in the image so I can keep the cameras calibrated.  The tric...

35194 How long after take off did the Concorde take to become supersonic?  I don't think it was allowed to do that over land? 35194 About the asteroid, I heard that no one knew about it because it approached us from the "blind side" (the sun side) and so it was in the sun's glare and that...

35186 Will you venture out to look for fragments, Mid? No, only from my desk.  There are people out in the field.  It's hard to find the time, besides there are quarantine restrictions in effect. 35186 About Chelyabinsk if I remember correctly, wasn't our attention fixed on a different (predicted) ...

I made another visualisation where the meteor fragments into three pieces: a few grams, a few kilos and above 100 kilos.  Of course, the smalles fragment wont make much sound, but it's interesting to see the differences in deceleration.

35165 It might be very important for meteor entries, as they pass through a very wide range of temperatures. Yes, the speed of sound is lower at higher altitudes.  And the winds are higher also, which can alter the propagation significantly.  I did not attempt to model that in any way, just assumin...

I edited the post above with a visualisation of a more realistic deceleration.  Units on the axes are in km and the animation is in real time.

There is one thing these visualisations tell us, which I didn't realise.  The delay between the sonic transition and the initial sound can not trivially be used to calculate the distance, as indicated by the waves emitted before the transition (red) and the waves emitted after (blue), unless you're ...

Wow.  You beat me to it.  

35153 I plotted its spectrogram Nicely visualised.  Same thing visible in the spectrogram of the meteor sound. Now thinking aloud: The object is decelerating.  Before the sonic transition it leaves a  trail of ripples moving slower than the object, so the object is outside  the ripples.  As it appr...

There is a similar sound heard in the Mythbuster cement truck explosion, which I'm not sure how to explain.  The guy referred explicitly to the sound of that explosion saying that it was exactly like that.  The pitch drop in the Mythbuster explosion sounds faster, but in the Swedish videos I suspect...

I've posted about the Swedish bolide in the "show off" forum.  Here are two videos that are not mine in any way. They are simply too amazing not to be shared.  Listen carefully, the first sonic boom arrives less than 30 seconds after the flash (the exact timing is still a bit uncertain, as...

This is a 5 megapixel video camera recording at 10 fps using a semi-fisheye lens covering roughly 1/3 of the sky.  Meteors are automatically detected and an image centered on the meteor and reprojected to gnomonic projection.

35131 No chance this and the other stuff that has been seen over the past couple of weeks was related to the Leonids right? No chance whatsoever that the bolide is related to the Leonids.  The Leonids enter the atmosphere at 71 km/s.  Whatever crashes with Earth at that speed either instantly gets ...

The Leonids are here.  One of the better meteor showers peaking around 17th November.  They are very fast, zipping across the sky in half a second, but can be quite bright, sometimes leaving a glowing mark in the sky.  Best seen shortly after the radiant rises (check when Regulus rises at your locat...

Still working on this meteor event.  We now have good reasons to believe that the entry mass was in the 5 - 10 tonne range, still bright when passing aircraft cruising altitude, and not going subsonic until 3 - 7 km above ground.  Wow.  It means that terminal velocity was probably not reached, thoug...