RE: ATM Active Optics

[GregJ888@aol.com]

Well, depends.  There is a difference between "Active" and "Adaptive" optics. 
 The first being rather slow to correct for figure, the second being fast and 
correcting for atmospherics.  Adaptive is of greater interest, to me anyway.

Without getting to long, there are several tip/tilt (2 orders) systems 
working with the AO-7 being the most visible.  These systems are probably 
more correctly called fast steering systems due to bandwidth, but they are 
all we currently have.  I'm playing with a 5 order system but it's a long way 
from working, though all the parts seem to work.

Here is a short list of the issues, 3 orders and above-
  1) only helps below 1 arc-second (.5 really) so image scale is large
  2) only good across an area of about 1 arc-minute**2 with lots of caveats
  3) works best in the IR; I'm planning to use I-band (CCD) but really need 
K-band. 
  4) need to be able to read the wavefront sensor at 100 FPS or better
  5) due to #4 and #1 guide stars for a small system need to be fairly bright 
       (10 mag? maybe 12 but wow) or big bucks for sensors ($20k- $150k).
  6) due to #5, #1, #2 anything less the a 16" mirror is likely a waste
  7) still requires a very good site-  how good I don't know...

I haven't updated my web site in quite a while but here is what I'm doing.
   http://hometown.aol.com/gregj888/DAC/DAC.htm

The 20" primary is almost done, I hope.  I have a copy of QNX (realtime Unix) 
to write the control code in/on.  Have built a new WFS camera based on the 
TI-211 (I know but $$$$) which is wired but I need to write the driver.

Hope that helps.

Greg Jones


<< 
 Date: Wed, 25 Apr 2001 21:18:15 +0200
 From: "Ugarte" <ugarte@retemail.es>

 Hello all,
     Has anybody challenged the idea of buildin an active optics
 system. It's been going round my head for some time and I don't
 know if this would be a too ambitious project. Does anybody=20
 have information? >>