Authentic Science Fiction Monthly, No. 66 — page 46: what you’re looking at

Machine-transcribed from the original scan — historical spelling and the odd misread are preserved.

AUTHENTIC SCIENCE FICTION one year in seven seconds. This meant that the bulky Moon projector whipped around in about half a second, or over 25,000 times in the trip backwards through time which actually consumed about four hours of continual operation. The design of a planetarium dome of some 80 feet in diameter involves problems in optics, acoustics and ventila- tion. If the dome is of painted steel or aluminium the surface is perforated with small holes to prevent echoes. As these holes are so small they do not interfere with the projected star images. The silhouette of 45 the local horizon is a cut-out at the base of the dome. The light passes beyond the dome to strike an inclined black screen and the illusion is complete. In a planetarium the arti- ficial firmament, shines out with unusual brilliance. The sky appears blue-black and gives the impression of in- finite space. The image of Mars is red, Jupiter appears with belts and Saturn with rings. Mercury and Venus are clearly distinguishable. It is most interesting to see the stars by day, to follow the course of the Sun among the stars and to see at any desired point comicloooks.com