On Jun 22, 11:59 pm, Fred J. McCall <fjmcc...@gmail.com
> bob haller <hall...@aol.com
> >dime sized resolution by military spy sats has been common knowledge
> >for many years........
> 'Common knowledge' among the ignorant, perhaps. The military doesn't
> get its own laws of physics, Bobbert. They have to use the same ones
> the rest of us get. Even a dolt can follow the math, so perhaps
> someone can explain it to you.
> Let's examine what it would take to get 'dime sized resolution' one
> more time, just for Bobbert.
> Ignoring blurring of the image by turbulence in the atmosphere
> (atmospheric seeing) and optical imperfections of the telescope, the
> angular resolution of an optical telescope is determined by the
> diameter of the primary mirror or lens gathering the light (also
> termed its "aperture")
> The Rayleigh criterion for the resolution limit (in radians) is given
> by sin(resolution angle) = 1.22*lambda/aperture where lambda is the
> wavelength (550 nm is the middle of the visible light spectrum). Note
> that this is the BEST that can be done by a theoretically perfect
> telescope viewing through a perfect vacuum.
> So let's see how big the aperture of the telescope would have to be,
> given other things that are known, to have "dime sized resolution".
> A dime is 17.91 mm across. Those 'military spy satellites' are
> typically in sun synchronous orbits with perigees no lower than 250 km
> (amateur observers can spot and track them with relatively modest
> telescopes, so their general orbits are not secret). Note that the
> atmosphere extends well above this altitude, so these satellites have
> to use on board fuel to reboost periodically, even if they never have
> to actually change orbital plane for observational reasons.
> We now know enough to start doing the arithmetic. The angle subtended
> by a dime from a distance of 250 km is given by:
> tan(angle) = .01791/250000
> That gives a required resolution of 7.164e-8 radians in order to have
> 'dime sized resolution'. Now that we have that, we can calculate the
> Ralleigh criterion and see how big the aperture must be to get that
> sin(7.164e-8) = 1.22 * 4.5e-007 / Aperture in meters
> That gives us a required aperture of around 7.66 meters to get "dime
> sized resolution by military spy sats". That makes it around half
> again as big as the absolute largest cargo diameter we have ever been
> able to launch on anything other than a Saturn V.
> Now take into account that mirrors are NOT perfect and there IS an
> atmosphere and the numbers only get worse...
> Bottom line, the idea that "dime sized resolution by military spy
> sats" exists is obvious bullshit unless you assume there are secret
> laws of physics that only the military can use.
> No doubt you'll continue to repeat the same stupid shite, but everyone
> else will know it for what it is.
> "Ordinarily he is insane. But he has lucid moments when he is
> only stupid."
> -- Heinrich Heine
A dime is roughly 18 mm, and that's technically doable with good
optics and tightly populated CCDs. The size of the primary and
secondary mirrors are for the gathering of light, and not just
required for resolution. Extremely powerful magnification microscopes
do not use large mirrors.
BTW; our crack DoD and the dozen some odd other official government
and/or contracted agencies also use PhotoShop or something better in
order to resample and enlarge images by another ten fold. This
doesn't improve the resolution, but it does help us to better
interpret those otherwise fuzzy or distorted images.