Sakthivel writes :

Planets and days of the week ........

The sky is our natural calendar. The year is based on Sun(365 days to come
round the zodiac) and the month is based on the moon(30days , full moon to full
moon). I do not know the need for the week and how it is originated.

But the naming is based on the naked eye objects seen in the sky other than the
stars. They are the Sun , Moon and all the five naked eye planets namely
Mercury, Venus, Mars, Jupitor and Saturn. The names of these naked eye objects
(called grahas)are chosen for the days of the week. All these seven naked eye
objects and two other points in space (Rahu and Kethu, which are intersecting
points of the moon's path and the sun's path in the sky) form the nine grahas
known in indian culture.

Uranus and Neptune were not known to civilisation before the invention of
the telescope.

Uranus can be seen with difficulty by naked eye( Bothe the sky and the eye
should be good) as its brightness is in the limit of visibility(magnitude 6)
for many of us.But it is an easy object through the binoculars.

The only other planet Neptune(magnitude 8) can be seen only using a telescope /
binoculars.