John E. Bortle is an American amateur astronomer. He is best known for creating the Bortle scale to quantify the darkness of the night sky. Bortle has made a special study of comets. He has recorded thousands of observations relating to more than 300 comets. From 1977 until 1994 he authored the monthly '"Comet Digest" in Sky and Telescope magazine. He also had a special interest in variable stars, recording more than 200,000 observations. From 1970 until 2000 he edited the monthly AAVSO circular for the American Association of Variable Star Observers.