You're describing an occultation, which is an astronomical event where one celestial object passes in front of another. This can be seen in various forms:

* Lunar Eclipse: The Moon passes through the Earth's shadow, causing it to dim.

* Solar Eclipse: The Moon passes between the Sun and the Earth, blocking the Sun's light and creating a shadow on Earth.

* Stellar Occultation: A star, planet, or other celestial body passes in front of another star, causing it to temporarily dim.

The "dimming" effect occurs because the light from the farther object is blocked by the closer object. The extent of the dimming depends on the size and brightness of the objects involved.

Let me know if you'd like to explore any of these specific events in more detail!