(meteorobs) Deficit of southern meteor streams apparently confirmed
clp at alumni.caltech.edu
Thu Apr 3 10:04:45 EDT 2014
Stacking video frames reduces sensitivity to meteors. That's because
meteors are not static phenomena. With most video meteor cameras, the
motion of the meteor image means that it's only present on any single
pixel for about one frame exposure interval (obviously this varies
somewhat depending on the apparent velocity of the meteor). Increasing
the exposure time (whether by stacking, or simply directly, which
digital video cameras are capable of) results in a loss of sensitivity
because for all the time that the meteor isn't on a pixel, that pixel is
receiving photons from the sky background, lowering the S/N (where the
only signal we're interest in is that of the meteor).
As it happens, the optimal exposure time for meteors is right around
1/30 second. Shorter than that and readout noise reduces sensitivity,
longer than that and sky background reduces sensitivity. So you
definitely don't want to stack frames when you're analyzing meteors.
I'm not sure what you have in mind when you discuss recorders. Virtually
all of the thousands of meteor cameras in operation utilize computers to
detect motion and digitally record the video from a ring buffer,
capturing the entire sequence from slightly before it begins to slightly
after it ends.
It is true that most systems still use analog composite video cameras,
which are not quite as good as digital interface cameras with internal
capture hardware. But that's a consequence of the fact that digital
video cameras designed for maximum sensitivity have only come on the
market recently. Newer meteor detection software supports them, and
you'll see a shift away from analog cameras over the next few years.
That will provide an incremental improvement in data quality, but
Basically, there's only limited opportunity for improvements in the
hardware associated with video meteor capture (outside of some very
expensive things, like active mechanical tracking). And the software is
already very good; I don't see major changes happening there, either.
Hardware will become cheaper, which means we'll probably see more
cameras. I'm already running an experimental meteor camera on a
Raspberry Pi ($35), as are others. But the computer has never been the
primary cost- that's the camera and the lens, and for the most part,
those prices haven't changed much, and probably won't).
Chris L Peterson
On 4/3/2014 12:28 AM, Jay Salsburg wrote:
> Hello Chris
> As a matter of fact, Stacking video frames increases sensitivity while
> sacrificing motion sensitivity. What is needed is real time stacking to
> detect motion, clip the sequential frame buffer to a file and send the file
> to a server. What is not realized by those with expensive and cumbersome SD
> Composite Video - PC Recorders is that Technology has passed them by. It is
> time to adapt current and future technology to capture Meteor activity and
> abandon OLD-School SD Video technology. Inevitably, as better cameras become
> available, adaptable Apps that run on small footprint machines (Cell Phones,
> Tablets, single board computers) will provide a market opportunity. Markets
> open when costs come down and technology improves. Let us not get our
> perceptions stuck in the past. Tradition is only applicable to the
> Scientific Technique, not the Technology of the Instrumentation to use in
> the Scientific Method.
> Capturing subtle details with better instruments and Apps will eventually
> happen, but you have to start somewhere, I do not accept "the way things
> are." What is needed is open source code that is adaptable to many different
> technologies, but is standardized in its "Method" of capture. Look to the
> SDR community for this. Much development is underway by many thousands of
> Users to adapt and apply Open Source Software to Software Defined Radios.
> This same Mind Set should be applied to Instrumentation for Meteor
More information about the meteorobs