by Chris Peterson » Tue Jun 08, 2010 5:28 pm
All of these images have much in common. They are all made with dynamically unstable instruments: cameras on tripods, telescopes on piers, all are basically inverted pendulums. All have resonances, and those resonances are typically in the area of 10 Hz, which is consistent with the wiggle seen in the meteor trails. And all are long exposures- on the order of a minute or more- which are recording a briefly moving point of light much brighter than the background stars. So the apparent shape of the meteor trails in these images is not at all unexpected. Satellites and airplanes caught in astroimages also tend to show trails that wiggle this way.
This resonance does show up in the star images as well, but it's almost impossible to see. All it does is to slightly alter the shape of the star profiles, from what is approximately Gaussian to a slightly broadened Gaussian with elevated wings. For some of my work, I use a special camera that simultaneously records the positions of many stars over a wide field, with very high accuracy and a rate of 400 measurements per second. This instrument clearly shows the sort of vibration seen in the meteor trail images if I have it mounted on any sort of ordinary tracking telescope mount or simple tripod.
From my allsky camera network, I have recorded about 75,000 meteor trails. These cameras are small, light, and very rigidly mounted. I've never recorded any meteor trail that wiggled.
[quote="owlice"]And yet another twisted meteor trail can be seen here: http://asterisk.apod.com/viewtopic.php?f=29&t=19725[/quote]
All of these images have much in common. They are all made with dynamically unstable instruments: cameras on tripods, telescopes on piers, all are basically inverted pendulums. All have resonances, and those resonances are typically in the area of 10 Hz, which is consistent with the wiggle seen in the meteor trails. And all are long exposures- on the order of a minute or more- which are recording a briefly moving point of light much brighter than the background stars. So the apparent shape of the meteor trails in these images is not at all unexpected. Satellites and airplanes caught in astroimages also tend to show trails that wiggle this way.
This resonance does show up in the star images as well, but it's almost impossible to see. All it does is to slightly alter the shape of the star profiles, from what is approximately Gaussian to a slightly broadened Gaussian with elevated wings. For some of my work, I use a special camera that simultaneously records the positions of many stars over a wide field, with very high accuracy and a rate of 400 measurements per second. This instrument clearly shows the sort of vibration seen in the meteor trail images if I have it mounted on any sort of ordinary tracking telescope mount or simple tripod.
From my allsky camera network, I have recorded about 75,000 meteor trails. These cameras are small, light, and very rigidly mounted. I've never recorded any meteor trail that wiggled.