SIMBAD references

Individual distances of 50 nearby planetary nebulae are determined using a variety of methods, but excluding statistical methods or distance scales. These distances, together with a discussion of the sample completeness, are used to determine local PN formation rate. Together with the brightness of the nebula, its ionized mass is derived. The evolution of the ionized mass is discussed. As a by-product, the Zanstra temperature of the central stars of the optically thick nebulae is found. Interestingly this temperature indicates that the DA white dwarfs in the sample are considerably hotter than previously thought. Finally, with the help of the galactic bulge PN, a luminosity function for PN in the galaxy is derived.