The 2 images below were taken from the observatory deck. Dim celestial objects that could normally be seen in a completely dark area might be undetectable with the nearby lights. We can see how much difference a simple shade can make in the 3 following pictures of a sodium vapor lamp. The first picture shows the lamp with no shade. The amount of light scattered towards the camera and up into the sky is significant.
Glare is also very noticeable.
Here you can see that a partial shade has been added. This directs the majority of light downwards but glare is still a problem. With a complete shade added glare and scattered light is almost completely eliminated. This next picture shows a walkway near the tennis courts. The lamp in the foreground does not have a proper shade and you can see how much light is being scattered upwards into the sky.