On 21/11/2019 17:36, Dave Liquorice wrote:
On Thu, 21 Nov 2019 08:37:27 -0800 (PST), whisky-dave wrote:


Aslo mots can;t tell the colour of a star from just veiwing with the
naked eye. but they aren't all white. I can just make out that Mars has
a sort of orange colour.

Mostly down to the light level from the point source of a star not
being high enough for the cones to work. You can tell the colour of
the really bright stars. Mars isn't a star. B-) and looks like a
red/orange dot to me, Jupiter is a definate disc.

Jupiter might seem like a disk to you but it is more likely to be from
scattering in your eye. A tiny handful of young children with better
than 40:20 vision can sometimes see the Galilean satellites of Jupiter
in the most favourable conditions (and also split epsilon Lyra).

Mars is very obviously red/orange. Saturn is yellowish.
Venus is pure white very bright. Visible in daylight at maximum
elongation if you know exactly where and how to look.

Arcturus and Betelgeuse are also orange. Rigel is bluish white.

First and second magnitude stars do show some colour to the naked eye
but it is hard to judge unless you compare one with another. The human
eye is rather good at doing an automatic white balance.

The brightest stars Sirius and Canopus when they are low in the sky
appear to flicker between quite saturated colours due to wavelength
dependent differential refraction.

--
Regards,
Martin Brown