II. Spectroscopic observations of the nebula of Orion, and of Jupiter, made with the great Melbourne telescope

Abstract

In one particular the spectroscopic observations of the nebula of Orion are not void of interest; they show distinctly that considerable nebulosity exists within and about the trapezium. The image at the slit is sufficiently large to well separate the stars of the trapezium, so that when two of these are* as it were, threaded on the slit, a clear space lies between them ; this in the spectroscope gives the well-known lines with little, if at all, less brilliancy than the general bright nebula. The small comparison-mirror being removed, the available slit is *4 inch high, equivalent in the case of the Cassegrain image to about 43" arc; with an image condensed about three times (which is the usual arrangement and still allows sufficient separation), the slit may, therefore, be made to considerably overlap the trapezium contour, and thereby, at the same time as the trapezium, light from the brightest part of the nebula is under in-: spection; it is curious to see that the spectral lines run with almost continuous brightness throughout the height of the slit.