  We examined the maximum bolometric peak luminosities during type I X-ray
bursts from the persistent or transient luminous X-ray sources in globular
clusters. We show that for about two thirds of the sources the maximum peak
luminosities during photospheric radius expansion X-ray bursts extend to a
critical value of (3.79+/-0.15)x10^{38} erg/s, assuming the total X-ray burst
emission is entirely due to black-body radiation and the recorded maximum
luminosity is the actual peak luminosity. This empirical critical luminosity is
consistent with the Eddington luminosity limit for hydrogen poor material.
Since the critical luminosity is more or less always reached during
photospheric radius expansion X-ray bursts (except for one source), such bursts
may be regarded as empirical standard candles. However, because significant
deviations do occur, our standard candle is only accurate to within 15%. We
re-evaluated the distances to the twelve globular clusters in which the X-ray
bursters reside.
