What effect do the lights in the park have in the story?

The author devotes many words to describing the lighting
of the park setting at night.

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Half the enchantment of the place was due to the
fact that it did not have the benefit of municipal lighting. The place was lit up by
shop lights. One or two had hissing gaslights, some had naked flares stuck on poles,
some were lit up by old cycle lamps, and one or two, like the astrologer's, managed
without lights of their own. It was a bewildering criss-cross of light rays and moving
shadows.

The lighting is very
poor and irregular. It is noteworthy that the astrologer doesn't even have a light of
his own. This description of the bad lighting helps the reader to imagine the scene, but
more importantly it explains why Guru Nayak doesn't recognize the astrologer as the man
he has been looking for. The lighting has become even worse by the time Guru Nayak shows
up late that night.

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The nuts vendor blew out his flare and rose to go
home. This was a signal for the astrologer to bundle up too, since it left him in
darkness except for a little shaft of green light which strayed in from somewhere and
touched the ground before
him.

Not only would Guru
Nayak be unable to recognize the astrologer in the darkness, but the astrologer would
have been unable to recognize him except for a lucky
break.

The
astrologer sent up a prayer to heaven as the other lit a cheroot. The astrologer caught
a glimpse of his face by the
matchlight.

At this point the
author does not tell the reader that the astrologer recognizes his old enemy and nemesis
Guru Nayak. So when the astrologer eventually calls the formidable man by his name, the
reader is just as astonished as Guru Nayak. Not only does the astrologer seem to possess
incredible supernatural knowledge, but he can even identify people in the dark. It never
occurs to Guru Nayak that he might be talking to the very man he has been searching for.
Even if he had been able to see the astrologer's face, he might not have recognized him
because of the passage of time, because the astrologer had grown a beard and painted his
forehead, because he was no longer an ignorant peasant but a smooth and articulate
urbanite, and no doubt because Guru Nayak wouldn't understand how his illiterate enemy
could have learned to be a "real" astrologer.

This is the
hardest test the astrologer has had to pass since he adopted his profession. He
distracts Guru Nayak by arguing about petty sums of money when his very life is in
danger. Calling his nemesis by name is taking a great risk. Either Guru Nayak will
suspect that the astrologer knows him personally, or else he will believe that the
astrologer really and truly knows all things. Fortunately, he believes the latter and
follows the astrologer's advice to return to his village and remain there for the rest
of his life.