Discovered by Edmond Halley in 1714.

M13, also called the 'Great globular cluster in Hercules', is one of the most prominent and best known globulars of the Northern celestial hemisphere. It was discovered by Edmond Halley in 1714, who noted that "it shows itself to the naked eye when the sky is serene and the Moon absent."

At its distance of 25,100 light years, its angular diameter of 20' corresponds to a linear 145 light years - visually, it is perhaps 13' large. It contains several 100,000 stars.

Click on images for high resolution (opens new browser)

		Taken on 8/1/2008 Orion ED80 Hap Griffin modified Rebel XT 350D 30 - 90 second exposures ISO 800 Stacked with DeepSkyStacker Processed with PhotoShop CS Copyright © 2008 – Antonio Pascarella
		Taken on 7/25/2008 Orion ED80 Hap Griffin modified Rebel XT 350D 20 - 60 second exposures ISO 800 Stacked with DeepSkyStacker Processed with PhotoShop CS Copyright © 2008 – Antonio Pascarella
		Taken on 7/6/07 with an Unmodified Canon Rebel XT 20 - 30 seconds exposures ISO 800 Stacked with DeepSkyStacker Processed with Photoshop CS No darks/flats/bias images were applied Copyright © 2007 – Antonio Pascarella