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The surface brightnesses of objects are difficult to estimate because of plate-to-plate variations of sky, and emulsion conditions. Occasionally, however, the surface brightness of an object is so high that it burns out an area of the image. Such a compact object can be detected if its burned-out diameter is larger than that of a star, if it is bright but lacks diffraction spikes, or if there is slight fuzz around the image. One must be careful to view such objects on two plates because emulsion defects often fit this description. In the illustrations we present only a few members of this Category as examples, and as interesting individual objects. Some compact galaxies found on the U.K. Schmidt plates have been investigated spectroscopically by Allen et al. (1978) and Martin, Penfold and Glass (1978).

On page 13.1 the compact object, IC 2913, south-east of the spiral NGC 3717, was also shown as part of the system AM 1129-300 in Category 8: Galaxies with Apparent Companions; short exposure plates show the compact to be composed of a ring and nucleus. The spiral on page 13.3 was also shown in Category 8 and Category 11.

Page 13.4 reproduces a photograph taken with the CTIO 4m telescope; the compact galaxy, AM 0215-504, is south-east of a bright star and it is striking how well the image of the galaxy resembles that of the star, except that it lacks diffraction spikes. On the following page there are examples of groups of compacts: AM 1932-532 and AM 0029-663.

On page 13.6 another 4m CTIO photograph (4403A) is shown; the compact galaxy is seen to the north-west of the large spiral. In very good seeing the compact resolves into a triple: two very compact objects on either side of a compact nucleus.