The most recently measured value of 225 GHz optical depth at the CSO is 0.036, at 09:09 UT. Current time is 09:29 UT.
The most recently measured value of 350 micron optical depth at the CSO is 0.86, at 08:58:06 UT on 2009-11-23. With a scaling factor of 24.75, this gives another estimate of 225GHz optical depth of 0.035.
If you'd like to see plots of tau vs. time and/or tau cumulative distribution functions by quarter and by month, click here.
For a short explanation of the tau sky monitor instrumentation click here .