Technical term for "cityglow"

According to Wikipedia, astronomers use the term skyglow.

Edited to add synonyms

In going through the thesaurus, I found the following terms that might be what you're looking for.

• aureola, cf. areola
• lambency
• refulgence

You might be looking for loom.

Sometimes, this sky glow is called a loom and it is spelled different ways. Some people spell it l-o-o-m and others l-u-m-e. We probably get the word "loom" from looming up in the sky, or we may get the word “lume" from the word "lumen," the unit measure of light.

_{The International Association of Electrical Inspectors, 1940}

Here is a more explicit definition from the book U. S. Coast Guard Light Lists: Volume Six Pacific Coast and Pacific Islands:

The "loom" (glow) of a powerful light is often seen beyond the limit of visibility of the actual rays of the light. The loom may sometimes appear sufficiently sharp enough to obtain a bearing. At short distances, some flashing lights may show a faint continuous light between flashes.

OED mentions that it is a seaman's term that suggests the appearance of an object and the first recorded sense is from 1836:

A seaman's term for the indistinct and exaggerated appearance or outline of an object when it first comes into view, as the outline of land on the horizon, an object seen through the mist or darkness, etc.

• F. Marryat Mr. Midshipman Easy II. x. 291 We're very near the land, Captain Wilson; thick as it is, I think I can make out the loom of it.

It is also used as the loom of the light:

According to my friend, Michael Sarratt, a former U.S. Navy seaman, the loom of the light is a seafarer's phrase which refers to the sky glow of a distant lighthouse not quite rising above the horizon.

_{The Loom of the Light By Donald Young}

You also mentioned that it sounded a bit dirty when you first saw this word, and here is why it might be the case (from OED, loom, n.¹):