  Multi-wavelength study of extended astronomical objects requires combining
images from instruments with differing point spread functions (PSFs). We
describe the construction of convolution kernels that allow one to generate
(multi-wavelength) images with a common PSF, thus preserving the colors of the
astronomical sources. We generate convolution kernels for the cameras of the
Spitzer Space Telescope, Herschel Space Observatory, Galaxy Evolution Explorer
(GALEX), Wide-field Infrared Survey Explorer (WISE), ground-based optical
telescopes (Moffat functions and sum of Gaussians), and Gaussian PSFs. These
kernels allow the study of the Spectral Energy Distribution (SED) of extended
objects, preserving the characteristic SED in each pixel. The convolution
kernels and the IDL packages used to construct and use them are made publicly
available.
