(meteorobs) Determining meteor speeds with all-sky cam?

[Chris Peterson]

Hi Esko-

Have you had much success doing this with relatively low resolution 
allsky video, or mainly with narrower field data? I've tried doing this 
with single station data using a second station to check, and haven't 
gotten consistent results at all.

Chris

*******************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On 6/3/2011 12:02 PM, Esko Lyytinen wrote:
>
> If one gets measured good individual directions for each video frame,
> then the change of the apparent angular velocity tells the true
> direction of entry. And with reasonable begining height one can "scale"
> the whole entry path with velocities also. The beginning height depends
> also on the velocity but with an iteration a reasonable value can be
> obtained. The atmospheric deceleration also affects the apparent angular
> velocity, but this mainly affects the end part of the track and less so
> the beginning part (which, because of this, is more important for this
> derivation). Only if a relatively long apparent (angular) track on the
> sky is visible, can you expect to get a good result.
>
> I have derived like this, a good number of meteor entry tracks including
> velocities. Some of these could later be determined from multistation data.
> In good instances the accuracy of the entry direction may be around two
> degrees or better. And the accuracy of the velocity about or better than
> 10%.
> The latest such derivation was the 2011 May 13/14 in British Columbia
> http://lunarmeteoritehunters.blogspot.com/2011/05/montana-washington-idaho-alberta.html
> In this case the original direction (by means of the Cranbrook video)
> from az. 17 altitude 39 degrees, did not change (by good luck) even a
> degree after two other videos came available. ( now 17.0 , +39.4 )
> The beginning height and consequently the velocity did increase a
> little. The veloctiy is now 24.5 km/s, as compared to that 22 km/s what
> is mentioned at that lunarmeteoritehunters blog.
> ( This entry is still not especially well determined, because of non
> good mutal situation of the camera stations relative to the meteoroid
> track (and the two others at bigger distance), but probabaly within
> about a degree accuracy, as to the direction.)
>
> High velocity meteors are less affected by atmospheric deceleration and
> because of this (if of enough apparent angular length) are more suitable
> for this, but this can be applied also for meteorite droppers, as for
> example that British Columbia example shows. Then a deceleration model
> also for the beginning part is very valuable. The end may tell something
> of the deceleration, and a physical ablation model can continue from
> this. And some iteration between these can be further applied.
>
> In some instances, a rough one station value of velocity can be got even
> without accurate frame data. For example if it is apparently close to a
> point meteor and so coming towards the observer, then (considering also
> the apparent visible altitude angle (of the point meteor) and reasonable
> beginning height) the path length must be limited (between the beginning
> and the camera station (decreased from this because of reasonable end
> height)) and the total duration will give some upper limit of the velocity.
>
> Esko