Hello Paul,
First, the human eye is only able with many precautions and much effort to
distinguish intensity differences of more than 5 %. Although our displays
have 256 levels, therefore, we are able only to distinguish about 20 levels
of intensity more or less simultaneously. Divided evenly among 10
magnitudes, this would be about 0.5 mag steps.
Then, do you really want to be 6th mag stars in GUIDE output to be as
difficult to see as in the real world? To be visible at all, the lowest
brightness of that 20 level scale would have to be rather large, at least
several mm across, and that is exactly the problem we meet when representing
Sirius in the diameter scale. Not very attractive, I think!
There is one thing we might try, however, that is to use the intensity
handle as well as the radius handle to represent star brightness. When we
would represent the weaker stars in say, 4 brightness levels, the radius
requirement could be a little relaxed.
I am asking myself if I want to try and find the weakest stars in that
representation, but on my display anyhow, a dim 1.5 mm dot might be a better
approximation to what I see than a lopsided four-bright-pixel approximation.
I wonder if Bill could find ways to try this out...
Siebren Klein
s.s.klein@...
http://www.geocities.com/siebren2001/index.html
----- Original Message -----
From: "Paul Schlyter" <pausch@...>
To: <guide-user@yahoogroups.com>
Sent: Wednesday, September 12, 2001 8:42 AM
Subject: Re: [guide-user] size
: If you divide those 256 brightness levels evenly across a 10
: magnitude range, you'll get one brightness level for every 0.04
: magnitudes! Skilled visual observers are able to distinguish
: brightness differences of 0.1 magnitudes....
:
: Therefore, those 256 brightness levels are in themselves no obstacle
: against reproducing a magnitude range of 10 magnitudes.
:
: Finally: many modern graphics cards have more than 256 brightness
: levels. And most computer displays today are analog devices, i.e.
: they have no limit of 256 brightness levels.