Starship Asterisk*

And yet another twisted meteor trail can be seen here: http://asterisk.apod.com/vie ... 29&t=19725

Hmmm, Is it not a Vortex then?

http://en.wikipedia.org/wiki/Vortex

Mark

owlice wrote:And yet another twisted meteor trail can be seen here: http://asterisk.apod.com/vie ... 29&t=19725

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.

There are clearly oval-shaped "streaks" on either side of bright stars (download the full-res image and turn up your monitor brightness if necessary).
The key question is - are these lens aberrations? Or are these camera-shake?
The simple way to answer the question - look at other star pictures with the same camera, lens, & settings.

If the shake is coming from the reflex mirror in the camera, it would also show up in all images - use mirror lockup or hold a cap in front of the lens for the first two seconds of the exposure (for such a wide-ange lens it would have to be more of a bucket than a cap)

Can't we just say "wow that looks nice"? Nah I guess it is more fun to debate random things we can't prove. (YET)

I think we've got final evidence from good photo of a debris trail last night. The direction of the debris trail itself is twisted. Areas that move towards you, the observer, will not move. Areas moving perpendicular to you will.

Look at this picture captured within a few days, posted by Spaceweather.com.

http://www.spaceweather.com/meteors/per ... p8u5p2i4l0

The shutter apparently was opened after the meteor passed. Note the trail afterwards is not constant. The area with no trail is either dissipating towards or away from the camera. The areas with the longest trail "ghosting" are moving perpendicular.

So, there's your answer. The meteor is throwing off debris asymmetrically. The trail plasma retains some of the initial velocity vector, and therefore a spiral develops.

Thank you!

desertengineer wrote:I think we've got final evidence from good photo of a debris trail last night. The direction of the debris trail itself is twisted. Areas that move towards you, the observer, will not move. Areas moving perpendicular to you will.

Look at this picture captured within a few days, posted by Spaceweather.com.

http://www.spaceweather.com/meteors/per ... p8u5p2i4l0

The shutter apparently was opened after the meteor passed. Note the trail afterwards is not constant. The area with no trail is either dissipating towards or away from the camera. The areas with the longest trail "ghosting" are moving perpendicular.

So, there's your answer. The meteor is throwing off debris asymmetrically. The trail plasma retains some of the initial velocity vector, and therefore a spiral develops.

I see no evidence of debris thrown of in any particular direction. Meteor trails are straight- they can't be anything but. They do throw off material asymmetrically, but that can only be seen in high speed imagery at high magnification- never in ordinary trail images. What is seen in the Spaceweather image isn't a meteor trail at all, it is a meteor train, the residual dust and ionized gas left behind. It remains for minutes, and is blown around by upper atmosphere winds.

There is nothing in common between the original APOD image. which shows a meteor trail distorted by camera vibration, and the Spaceweather image, which shows a meteor train blown about by the wind.