Perhaps we can get someone from Lowell Observatory or Stewart observatories,
the former in Flagstaff and the latter in Tucson, to answer this, although I
wonder how definitive the answer would be. It seems to me that this is
another area of human knowledge where DEFINING what you mean by adaptive and
active would clarify what the situation is immensely.

As for my two cents . . .

I don't know what is meant by "active." Is tracking an object automatically
active? Is changing the optics to "correct" for something active?

Adaptive to me means a method by which the optics can be changed to reduce
or eliminate seeing effects. By this definition, and by the fact that
SBIG's tilt-mirror system reduces low frequency "waves" seeing, it is an
adaptive system.
--
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There is a fifth dimension beyond that which is known to Man.
It is a dimension as vast as space and as timeless as infinity.
It is the middle ground between light and shadow,
Between Science and superstition
And it lies between the pit of Man's fears
and the Sunlight of his knowledge.
It is the dimension of imagination.
It is an area that might be called. . . The Twilight Zone.


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"Mike Simmons" wrote in message
...
Hi Don,

I'd just like to double-check something. It seems that you would then
agree that the SBIG AO-7 "adaptive optics" unit -- a tip-tilt mirror --
is truly "adaptive" optics. Is that right? I've asked this of others
working in the field -- astronomers and optical engineers -- and get
varied responses. Some say tip-tilt is "adaptive", others (a minority,
I think) say it's not. Most, however, give me a quizzical look and say
something like "Well, you could say..." (fill in the blank). So I'm
very interested in the view of someone not just building a particular
unit or using AO but having spent many years in the business.

Best regards,

Mike Simmons

Don Bruns wrote:

Ante Perkovic wrote:
Hi,

Can someone explain me the difference between active and adaptive
optics?

"Active optics" usually refers to optics that can be slowly moved, while
"adaptive optics" usually refers to optics that can compensate
atmospheric turbulence. Active optics can range from a
temperature-programmed focuser to automatic primary recollimation to
compensate tube sag as the telescope is pointed at different altitudes.
Flexing a spherical primary to a parabolic shape as the temperature
changes can be considered active optics. "Adaptive optics" usually uses
light from the target area to determine the effects of atmospheric
turbulence, then moves the optics rapidly to compensate. These optics
may be a tip-tilt mirror or a deformable mirror.

Don Bruns