  One of the challenges of X-ray astronomy is how to both collect large numbers
of photons yet attain high angular resolution. Because X-ray telescopes utilize
grazing optics, to collect more photons requires a larger acceptance angle
which in turn compromises the angular resolution. All X-ray telescopes thus
have angular resolution far poorer than their diffraction limit. Although
collecting more photons is a desirable goal, sometimes selective collecting
fewer photons may yield more information. Natural (such as lunar) occultations
have long been used to study sources on small angular scales. But natural
occulters are of limited utility because of their large angular velocities
relative to the telescope, and because of the serendipity of their transits. We
describe here how one can make use of an X-ray Big Occulting Steerable
Satellite (X-BOSS) to achieve very-high resolution of X-ray sources. An X-BOSS
could significantly improve the resolution of existing X-ray facilities such as
the Chandra telescope, or X-ray Multiple Mirror (XMM) satellite, and could
vastly improve the resolution of some future X-ray telescopes, particularly
Constellation X where sub-milliarcsecond resolution is possible for a wide
range of sources. Similar occulting satellites could also be deployed in
conjunction with planned space observatories for other wavebands.
