  We imaged the symbiotic star CH Cyg and two PSF calibration stars using the
unique 6.5m MMT deformable secondary adaptive optics system. Our
high-resolution (FWHM=0.3"), very high Strehl (98%+-2%) mid-infrared (9.8 and
11.7 um) images of CH Cyg allow us to probe finer length scales than ever
before for this object. CH Cyg is significantly extended compared to our
unresolved PSF calibration stars (Mu UMa and Alpha Her) at 9.8 and 11.7 um. We
estimated the size of the extension by convolving a number of simple Gaussian
models with the Mu UMa PSF and determining which model provided the best fit to
the data. Adopting the Hipparcos distance for this object of 270 pc, we found a
nearly Gaussian extension with a FWHM at 9.8 um of ~40.5+-2.7 AU (0.15+-0.01")
and a FWHM at 11.7 um of 45.9+-2.7 AU (0.17+-0.01"). After subtracting out the
Gaussian component of the emission (convolved with our PSF), we found a faint
\~0.7" asymmetric extension which peaks in flux ~0.5" north of the stars. This
extension is roughly coincident with the northern knotlike feature seen in HST
WFPC2 images obtained in 1999.
