siebren klein Sep 18, 2001
----- Original Message -----
From: "Paul Schlyter" <pausch@...>
To: <guide-user@yahoogroups.com>
Sent: Saturday, September 15, 2001 8:22 AM
Subject: [guide-user] size or brightness?
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1)therefore, we are able only to distinguish about 20 levels of intensity
: > more or less simultaneously.
:
: Again, that depends on the intensity of each level. You here seem to
: assume that the levels increase linearly in intensity. But they
: could just as well increase logarithmically, such that each level is
: 10% brighter than the previous level - in that case we'd be able to
: distinguish all levels from one another.
----------------------------------------------------------:
2)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?
:
: Definitely not. But i think it would be quite hard to make a point on
: the video screen really shine with an apparent magnitude of 6. It's the
: same with planetariums - the artificial stars on the planetarium dome
: shine brighter than the corresponding stars in the real sky.
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3) 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!
:
: I though we were discussing representing stellar brightnesses with points
: of varying brighness but the same size, not points of varying sizes.
----------------------------------------------------
4)Now, if the faintest dots on the screen would have to be several mm
: large to be seen at all, shouldn't the same be valid for the real stars
: in the sky? I.e. wouldn't a star of magnitude 6 have to be, say, at
: least 1/10 degree or so in apparent size to be visible to our eyes?
:
:
: I was considering 1-pixel approximations.... after all, real stars are,
: to our eyes, point sources, not small squares or circles.
:
: ----------------------------------------------------------------
: Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
: Grev Turegatan 40, S-114 38 Stockholm, SWEDEN
: e-mail: pausch at saaf dot se or paul.schlyter at ausys dot se
: WWW: http://hotel04.ausys.se/pausch http://welcome.to/pausch