  Developed right at the beginning of the space age in the 1940s, the
proportional counter was the first detector used in X-ray astronomy and stayed
its workhorse for almost four decades. Although the principle of such a
detector seems to be rather simple, over time it underwent considerable
performance improvements and the lifetime under orbital conditions was extended
tremendously. Particularly the invention of position-sensitive proportional
counters provided new and sophisticated methods to discriminate background and
thus enabled observations of much weaker sources.
  A leap forward in position resolution was achieved with the advent of
microchannel plate (MCP) detectors in the 1970s. In contrary to gas filled
detectors, they provide no considerable energy resolution but feature spatial
resolutions reaching down to a few tens of micrometers, fitting ideally the
angular resolution of the novel grazing incidence imaging X-ray telescopes
upcoming at that time.
  Even today, both types of detectors are still relevant in space-based
astronomy. However, in case of MCPs new developments focus on the far and
extreme ultraviolet wavelength range, while the Chandra X-ray observatory is
most likely the last mission applying this technology for X-rays. In contrast,
compact detectors with gas electron multiplier (GEM) foils and micropattern
readout are currently under heavy development for the soft X-ray range, since
they allow for the first time to measure polarization in X-rays over a broad
energy range.
  This chapter presents the principles of proportional counters and MCP
detectors, highlights the respective performance characteristics, and
summarizes their most important applications in X-ray astronomy.
