[time-nuts] A real world project need for timing accuracy...
jimlux at earthlink.net
Wed Nov 3 14:12:02 UTC 2010
Bob Camp wrote:
> I have indeed seen people try to do this with 18 ~ 24" aperture optics. They don't seem to do a lot better than the smaller stuff spotting holes at distance. They do get a nice bright image though.
Yeah, at that size, the atmospheric propagation issues are probably the
limiting aspect. For astronomical use, you tend to be looking closer to
straight up, which helps (same for looking down).
Clearly (a pun) it is possible to get this kind of performance from
reasonable sized optics e.g. the proverbial reading license plates from
orbit... 10cm resolution at 300 km range.. .1/3E5 -- .3 microrad (I do
calculations in my head MUCH better in metric)... even 1 meter
resolution (which is widely published) from orbit is 3 microradian.
the KH series satellites are rumored to have 2.4 meter optics. Whether
they have 10 cm resolution in use is uncertain.
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