Abstract
III.
WE know that both with object-glasses and reflectors a certain amount of light is lost by imperfect reflection in the one case, and by reflection from the surfaces and absorption in the other; and in reflectors we have generally two reflections instead of one. This loss is to the distinct disadvantage of the reflector, and it has been stated by authorities on the subject, that, light for light, if we use a reflector, we must make the aperture twice as large as that of a refractor in order to make up for the loss of light due to reflection. But Dr. Robinson thinks that this is an extreme estimate; and with reference to the four-foot reflector now in operation at Melbourne, and of which mention has already been made, he considers that a refractor of 33.73 inches aperture would be probably something like its equivalent if the glass were perfectly transparent, which is not the case.
Article PDF
Rights and permissions
About this article
Cite this article
LOCKVER, J. The Modern Telescope 1 . Nature 17, 188–189 (1878). https://doi.org/10.1038/017188a0
Issue Date:
DOI: https://doi.org/10.1038/017188a0