This review contains a brief survey of the issues that have been the concern of optical and ultraviolet studies of planetary nebulae since the last IAU Symposium on this subject in 1982.

The nature of this review is such that it is not possible to do justice to the wealth of work that has taken place in this period, I will just point out some characteristic examples of the different aspects of the work done.

Five months after the 1982 Symposium in London the InfraRed Astronomical Satellite (IRAS) was launched. Undoubtedly this has been the major event of the last five years in the infrared world, with a great impact in the field of Planetary Nebulae (PN) research (^).

The continuum radio spectra of planetary nebulae are discussed, and the structure of these objects is examined from the observed aperture synthesis brightness distributions determined with the Very Large Array. The use of radio observations in determining distances to planetary nebulae is examined. The detection of atomic neutral hydrogen at λ21 cm associated with planetary nebulae, as well as the associated CO and OH components are discussed. An upper limit, of the nebular magnetic field associated with the neutral material, of 1mG is reported for NGC 6302.

75 objects have been classified as new planetary nebulae since 1982. They are summarized in Table 1 which gives the designations, names, coordinates and references to the discovery. In the list of misclassified PN (Table 2) 41 objects have been included; Table 3 presents objects with incorrect identification in CGPN. The main properties of a PN and of its nucleus are given in a summary which can be useful for a correct classification of planetaries.

Firstly, the general requirements concerning catalogues are studied for planetary nebulae, in particular concerning the objects to be included in a catalogue of PN, their denominations, followed by reflexions about the afterlife and computerized versions of a catalogue. Then, the basic elements constituting a catalogue of PN are analyzed, and the available data are looked at each time.

This paper is based upon observations carried out at the Observatorio Astronómico Nacional, San Pedro Mártir, B.C.N. México. They are of two types: (1) α(16)Λ(9)-photometry, obtained with the 1.5-m Johnson telescope, and (2) maps at the wavelengths of Hα and λ7751 A [Ar III] emission lines secured with the 2.1-m telescope.

Spectral and monochromatic observations of two thin-filamentary nebulae S22 and YM29 have been carried out in the lines [O III] 5007A, [N II] 6584A and [S II] 6717+6732A. Radial stratification of the emission typical for photoionization excitation has been found: displacement between [O III] - bright regions and [S II] - and [N II] -bright regions is equal ΔR ∼ 0.1R (about 0.01 to 0.2 pc), the first ones being closer to the nuclei. Both nebulae are characterized by more diffuse morphology in the [O III] line and by thin-filamentary one in the [N II] and [S II] lines.

Within a spectroscopic study of some southern planetary nebulae, we have observed 32 objects. Some of them are symbiotic or suspected symbiotic stars, and one (He 2-61) is evidently not an emission object.

Since 1984, we have undertaken a spectroscopic survey of planetary nebulae, both at La Silla (E.S.O.)., and at the Observatoire de Haute Provence (France), Up to now, the spectra of about 900 PN have been obtained; all 723 spectra observed at La Silla have been reduced and the line intensities have been measured for 250 of them; about one fourth of the 182 OHP spectra have been reduced.

The Hα emission object M3-44 was observed photographically and spectroscopically. Photographs were obtained in the visual region, in [0 III] λ5007, and in Hα. The visual image is faint and has almost stellar aspect; the object is not visible in [0 III], but the Hα image is very intense, with a diameter of the order of 5″.

Infrared observations of He2-442 carried out at Crimean Station of Sternberg Institute during 1984–1986 revealed that in the past ten years the 1–10 μm flux has decreased by factor ∼ 2.4, the colour temperature determined from (K-L) index has decreased by ∼ 300 K, and the infrared energy distribution has been changed also essentially. However, the definite cool star features, for example, Mira-like variability was not yet recorded.

The photoelectric UBV-observations of planetary nebulae variability, begun in 1968 at Crimean Station of Sternberg State Astronomical Institute (USSR) and Skalnate Pleso Observatory (Czechoslovakia), were carried out during 20 years, 1987 inclusive.

Among the planetary nebulae showing noticeable long-time variations of brightness (see our foregoing contributed paper; Astron. Circ. USSR, No. 1430, 3, 1986, and earlier publications) the young stellar planetary IC 4997 is the most prominent. Our photoelectric observations revealed its rather surprising behaviour. During 1968–85 its total UBV-brightness was monotonously decreasing, especially in filter V: the reduction of the value Δv amounted ∼ 0m.5–0m.6. The colour indices of the planetary showed that during the observation period the object as a whole, became definitely bluer. In 1985–86 our observations revealed an unexpected stop of mentioned brightness decrease, but in 1987 the object appeared to start brightening.

By means of broad and narrow-band photometry in UBV spectral diapason the variability of the object He 2-467 earlier classified as peculiar central star of planetary nebula has been revealed. The light amplitude significantly decreases with the wavelength, from 1m.7 in U-band to 0m.3 in V. The brightness variations were found to be periodic, with P ≈ 500 days. The observations of He 2-467 have been interpreted using the model of binary consisting of very hot subdwarf and G5 II giant. The parameters of both components have been derived. The hot star is probably the evolved low mass nucleus of planetary nebula already dissipated. The periodic variations in U-band may be the result of the reflection effect due to the presence of hot extended region on the side of cold star facing the subdwarf. The subdwarf UV-flux can heat and ionize the upper atmosphere of the giant giving birth to the emission lines and Balmer continuum. The yellow symbiotics to which He 2-467 belongs may be predecessors of red symbiotics with M-giants.

Using the IRAS and near-IR photometry obtained at the 1-m, 3.6-m ESO telescopes, and 1.5-m TIRGO telescope, we will discuss the 1 - 100 microns energy distribution of selected PNe.

The study of young planetary nebulae can provide information about the ejection process of the nebular material as well as on nebular evolution and the enrichment of the interstellar medium. The youngest PN are expected to be compact and very dense, they usually show signs of variability and IR excess due to the presence of warm dust which, in some cases, seems to be mixed with the ionized gas.