When sight-seeing larger nebulae (like the North America Nebula) and big star clusters (like the Double Cluster or Beehive), it’s usually best to stick with lower magnification and wider fields of view to take in the entire object. But most deep sky objects benefit from greater magnification, sometimes much greater. To demonstrate this, I prowled around in the constellation of Hercules, using my 8-inch Celestron Edge HD scope and an 8mm eyepiece, giving a magnification of 250x.
The first object on my tour was the planetary nebula NGC 6210. Like many planetaries, it has a high surface brightness that enables it to bear high magnifications well. At low powers it looks like a tiny bluish dot. 250x brings out considerable visual character in this 16 arc second object. Slightly oval, its edges are diffuse. Colorful as many planetaries are, it shows an aqua tint with hints and flashes of a fierce electric blue. I found that an 8-inch scope isn’t quite big enough to show these colors strongly in this particular object, but a 12-inch or larger instrument will make them unmistakable, and then you’re viewing an exotic object indeed. I did not consistently see the nebula’s central star, though this should not be difficult at magnitude 12.7. This may be due to the consistently rough seeing I experience in this valley of the southern Sierra Nevada range, where I’m surrounded by mountains on all sides. This tends to muddle the faint star into the bright glow of the nebula.
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