[time-nuts] A real world project need for timing accuracy...

[William H. Fite]

If I may disagree without being disagreeable, it is entirely possible to use
a scope with sufficient resolving power to see target holes at 800m.  I
didn't promise it would be cheap.  [?]

You're right about the atmospheric instability, of course.  And that
instability, in addition to a number of other indeterminate variables is
what will put pay to attempts at exceedingly precise measurements.





On Mon, Nov 1, 2010 at 10:08 PM, Bob Camp <lists at rtty.us> wrote:

> Hi
>
> Two gotchas, one minor, the other a bit bigger.
>
> At 800 yards, even a *very* good optical setup can't / won't see holes in a
> target. The atmosphere is just to unstable. You would have to mount the
> camera down range (minor issue).
>
> The larger one is that you really don't want to truck down a half mile of
> path to put up a new piece of paper. After a while the "target" gets pretty
> ragged. There's not much for the optics to pick up, especially if you have
> good groups.
>
> Cool idea though ....
>
> Bob
>
>
> On Nov 1, 2010, at 10:04 PM, Predrag Dukic wrote:
>
> >
> > Why not using optical methods for shot grouping?
> >
> > A cheap web camera with equally cheap telescopic lense can resolve 1mm.
> > Some image processing software can find shot positions within the 1kx1k
> pixel bitmap.... etc..
> >
> >
> >
> >
> > At 01:03 2.11.2010, you wrote:
> >>   Timenutters--
> >>   I appreciate the feedback for implementing my
> >>   ballistic field measurement project but I think
> >>   there is some misunderstanding of what the goal is.
> >>   For instance, it is not practical to find 800 meters
> >>   of coax and trench it in out to the downrange target.
> >>   This system needs to be relatively portable so it
> >>   can be set up at any given shooting range.
> >>   I need to determine: A) down-range velocity of the
> >>   still super-sonic projectile, B) time of flight and
> >>   C) shot-group size.
> >>   Measuring down-range shot-group size with an array of
> >>   ultrasonic sensors is pretty straightforward. I can
> >>   do all the computation with a $6 microprocessor and
> >>   send the X/Y coordinates back to the laptop at the
> >>   shooting bench with a simple RF link.  Down-range
> >>   velocity is easily determined with a set of sky-screens
> >>   and the results also sent back via an RF link.
> >>   Time-of-flight is much more problematic to determine
> >>   but the plan is to determine the elapsed time between
> >>   the moment the projectile passes over the muzzle skyscreen
> >>   and the moment of passing over the downrange skyscreen.
> >>   This means syncing the 10 MHz clocks at both ends together.
> >>   I guess the crux of my question to the time-nuts gang
> >>   is what is the easiest (cheapest!!) way to do this.
> >>   For a number of years I have been using an ultrasonic
> >>   shot-group size measurement system made by Oehler
> >>   Research.  It can resolve individual shot placement
> >>   to within 1 cm.  Some less expensive systems that
> >>   use fewer sensors can only resolve to +/- 2 cm. The
> >>   Oehler Research system also determines time of flight.
> >>   The problem is that these systems all use a cable
> >>   to connect back to the equipment at the shooting bench.
> >>   I am trying to find a way to synchronize/coordinate
> >>   a downrange 10 MHz clock to the "master" 10 MHz system
> >>   clock at the shooting bench without spending hundreds
> >>   of $$ doing it.  It is not too big a problem to process
> >>   all of the signals from the downrange skyscreens and the
> >>   ultrasonic shot-group sensors and telemeter the results
> >>   back to the shooting bench.
> >>   However, time-of-flight info (via an RF link requires
> >>   that I sync the 10MHz clocks at both ends together.
> >>   Use of GPS receivers seems to be the most likely way
> >>   to do this but how do I keep the cost and complexity
> >>   down?
> >>   Thanks in advance for any feedback on the matter!
> >>   Mike Baker
> >>   ---------------------
> >> _______________________________________________
> >> time-nuts mailing list -- time-nuts at febo.com
> >> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> >> and follow the instructions there.
> >
> >
> > _______________________________________________
> > time-nuts mailing list -- time-nuts at febo.com
> > To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> > and follow the instructions there.
>
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 360.gif
Type: image/gif
Size: 453 bytes
Desc: not available
URL: <http://febo.com/pipermail/time-nuts_lists.febo.com/attachments/20101101/b9841d60/attachment.gif>