However, more seasoned globular hunters know this is definitely not the case.<\/p>
The classic Northern Hemisphere globular known as M13, the Great Globular in Hercules<\/a>, is a case in point.<\/p> Core concentration, brightness, size, shape and the ability to be partly resolved all help to create distinctions between globulars.<\/p> There are other features too, and a good challenge is to view M13 and try to find its most characteristic feature: the propeller.\u00a0<\/p> The propeller is a pattern offset to the southeast side of the core of M13 that appears as three dark dust lanes converging to a common point.<\/p> The lanes are offset from one another by 120\u00b0 and it\u2019s this regularity that produces the pattern reminiscent of a propeller.<\/p> The feature was originally reported by Bindon Stoney around 1850, an astronomer assisting William Parsons, the 3rd Earl of Rosse at Birr Castle in Parsonstown, Ireland.<\/p> His initial drawing of the propeller greatly exaggerated its contrast, making it look like an easy-to-see, stand-out part of the globular.\u00a0<\/p> In reality, the M13 propeller is easy to miss unless you know it\u2019s there and where it\u2019s located.<\/p> It helps if you have a bit of aperture to hand to pull in as much light as possible, but if not it\u2019s still worth giving it a go.<\/p> Magnification is key here and the strategy we\u2019d recommend is to locate M13 at low power, then keep swapping for higher-power eyepieces until you reach the best, high-powered view possible.<\/p> For the best chance of spotting the propeller, wait until M13 is high in the sky.<\/p> M13 is an easy Messier object to find using the faint but distinctive Keystone asterism in Hercules<\/a>.<\/p> Once you\u2019ve found that, M13 is located at a point one-third of the way along the line from the northwest corner towards the southwest corner, that\u2019s from Eta (\u03b7) towards Zeta (\u03b6) Herculis.<\/p> It\u2019s bright enough to just about be visible to the naked eye from a dark-sky site.<\/p> Being big and bright, M13 is a commonly photographed globular.<\/p> As such you\u2019d think the propeller was well covered in images, but this isn\u2019t the case.<\/p> Over-exposure of the core of M13 will hide it very well, so special consideration needs to be made to avoid doing this.<\/p> Be aware, though, that under-exposing M13 may not capture enough of the object to show the propeller at all!<\/p>What is the M13 propeller?<\/strong><\/h2>
![\"M13](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2019\/02\/m13_5hr_10min-bd78d3b.jpg\")
How to observe the propeller in M13<\/strong><\/h2>
Locating and photographing M13<\/strong><\/h2>
![\"A](\"https:\/\/c02.purpledshub.com\/uploads\/sites\/48\/2022\/06\/hercules-constellation-50f84ac.jpg\")