Path: newsfd02.forthnet.gr!jussieu.fr!ciril.fr!fr.ip.ndsoftware.net!proxad.net!postnews2.google.com!not-for-mail From: canopus56@yahoo.com (Canopus) Newsgroups: sci.astro.amateur Subject: Re: Image Luminosity vs magnification (long explanation) Date: 30 Aug 2004 09:33:55 -0700 Organization: http://groups.google.com Lines: 35 Message-ID: References: <1093598175.922815@athnrd02> <1093633886.990864@athnrd02> <1093641120.500668@athnrd02> <1093642681.105451@athnrd02> <1093849144.886794@athnrd02> NNTP-Posting-Host: 168.179.186.155 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1093883635 5362 127.0.0.1 (30 Aug 2004 16:33:55 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: Mon, 30 Aug 2004 16:33:55 +0000 (UTC) Xref: newsfd02.forthnet.gr sci.astro.amateur:518728 Ioannis wrote in message news:<1093849144.886794@athnrd02>... > Canopus wrote: A correction to the long explanation: > For example, in Table 6, an 8-power 25mm binocular, a NexStar 4 at 40 > power, might be expected to produce images of comparable brightness as > an 8" telescope used at 120 power. > > > My personal test was to compare the _unit brightness_ of image > produced by a 10x50 binocular, a 20x70 binocular, a 6" newtonian at > 40x and 100x and the 6" newt's primary mirror. The ordering of > brightness generally followed that suggested by Table 6. Should read: For example, in Table 6, the following telescopes roughly might produce an image of the same unit brightness: 1) a NexStar 4 at 20x (relative brightness 0.33% in Table 6), 2) an 8" telescope used at 60 power (relative brightness 0.3% in Table 6), 3) a 10" telescope used at 80 power (relative brightness 0.33% in Table 6), and maybe a 4) a 10-power 50mm binocular (relative brightness somewhere between 0.02% and 0.56% in Table 6). My personal test was to compare the _unit brightness_ of image produced by a 10x50 binocular (not on Table 6), a 20x70 binocular (RB=0.14%), a 6" newtonian at 40x (RB=0.28%) and 100x (RB=0.05%) and the 6" newt's primary mirror. The ordering of unit brightness generally followed that suggested by Table 6. - Canopus