Unfortunately, manufacturers seem to publish everything in their specifications except resolution in Arc Seconds
, contrast index, diffraction limitation, and which aberrations might be present and to what extent.
For 3- to 5-axis machining centers, Hamar's L-743 Ultra-Precision Triple Scan laser has three rotating laser planes that are perpendicular to 1 arc second
and flat to 1/2 arc second
in a 360 degree sweep and 1/4 arc second
in a 90 degree sweep.
Rotary (A, B) axes feature accuracy of [+ or -]30 arc seconds
and repeatability of 15 arc seconds
In contrast, natural stars can serve as adaptive-optics beacons in visible light only for targets less than a couple of arc seconds
For tracking down the natural satellites of the outer planets, a program by the Bureau des Longitudes in Paris gives accurate north-south and east-west offsets, measured in arc seconds
from the parent planet, for any date and time in 1994.
It was first spotted between 4:00 and 5:00 Universal Time (UT) on April 2nd, shining near visual magnitude 13 1/2 about 18 arc seconds
southeast of the spiral's nucleus.
For a telescope with perfectly smooth optics and no design aberrations, the theoretical angular resolution is 252,000[lambda]/D arc seconds
, where [lambda] is the wavelength of the light and D is the telescope's diameter (aperture) in the same units.
Furthermore, the angle over which light from astronomical bodies encounters essentially the same atmospheric turbulence is only about 2 arc seconds
at visible wavelengths.
This is because the field here shows only the galaxy's nuclear region, about 20 arc seconds
The programmers -- former employees of the Soviet space program working in Kaliningrad, Russia -- claim that planets are plotted with a positional error no greater than 2 arc seconds
from 1411 B.
After subtracting a model of the smoothly varying starlight, Zaritsky's team found that the galaxy's two spiral arms wind to within 10 arc seconds
(1,300 light-years) of the nucleus.
One is a low-resolution survey covering the whole sky north of declination -42 |degrees~ with a resolution of 54 arc seconds
-- about the sharpness of a very keen-eyed person's eyesight.
When I returned the star was less than 30 arc seconds
from the eyepiece crosshair, which was inside the limits set by the drive's periodic error