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Saturday, 15 February 2014

Why do I see stars only as points of light even when using my highest power eyepiece?

The ability to see details on an object ultimately depends on how far away it is and how big it is. Stars are so very far away that they will never show a real disk or ball shape in a telescope.

Planets, the Moon, and the Sun are much closer and will show discernible disks and details even at low or medium powers in most telescopes. Nebulae and galaxies are also very far away, but are so enormous they will also show details in many telescopes.

What you will see looking at stars at high magnifications (assuming a steady atmosphere that will allow this) is an optical pattern known as the diffraction pattern. It’s a bull’s-eye with a bright central area or disk surrounded by one or more concentric rings. It is not the actual disk of the star you are seeing. The diffraction pattern is due to the way the telescope’s circular lens or mirror acts on light from a pinpoint source like a star.

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