Astronomy for Beginners
Here’s where you’ll find observing guides, how-to articles and great astronomy hints and tips. Don’t forget to also check out our comprehensive astronomy dictionary.
'How To' Guides
Astronomy Dictionary
Secondary obstruction
The secondary obstruction in a reflecting or catadioptric telescope is a result of the necessary placement of a secondary mirror in the optical path. A large secondary obstruction will generally lower the brightness and contrast of images through the eyepiece at high magnifications.
Tachocline
A thin boundary that separates the Sun’s outermost layer, called the convective zone, from the denser internal regions. These layers rotate at different speeds to create the Sun’s magnetic activity.
