The Planetary Hours is one of the most ancient astrological techniques as far as I’m aware. The entire art of traditional astrology is based off of the visible Planets and Stars. Neptune, Pluto and Uranus are not visible to the eye when looking at the sky, so they were not used.
We should keep in mind that astrology traditionally is not a material science. It does not hold that there is a material link between us and at the Planets and Stars. Modern Science agrees with this, as the gravitational force the Moon exerts on us is not nearly enough to cause any kind of effect on us. Far less so of the Planets.
Traditionally, the link between us and the Planets and Stars are spiritual, not material. So, because a Planet is material does not mean it needs to be considered necessarily. In my view, I consider the visible Planets and Stars to be more perfect indicators of the higher spiritual worlds from which everything descends. So, I personally do not look at either Neptune, Pluto, or Uranus.
Here is an interesting post from another traditional astrologer on here regarding light:
And here is also my post: