What Is the Power for a 12 Inch Reflector Telescope?

A Newtonian reflector telescope uses a two-mirror optical system to capture light and direct it to a magnifying eyepiece. The magnifying power of a 12-inch reflector depends on the focal length of the telescope and the eyepieces used with it.

Magnification

Divide the telescope's focal length by the focal length of the eyepiece to calculate the current magnification of the telescope. A 12-inch reflector with a 1,500mm focal length, for example, provides 150x magnification when used with a 10mm eyepiece. Focal lengths vary from model to model. Manufacturers typically publish the focal length in a telescope's user manual.

Usage

A 12-inch reflector will provide low-power views of large objects, such as galaxies and nebula, when used with an eyepiece in the 20mm to 40mm focal-length range. When used with shorter focal lengths, it will produce high magnification views of the moon and planets.

Limitations

Although a typical 12-inch reflector can provide magnifications upwards of 400x, atmospheric conditions often limit the maximum usable magnification to less than 200x. A turbulent atmosphere produces unsteady images at the eyepiece, which only worsen with increased magnification.

References

• Astronomy Notes: Reflector Telescopes
• Space References: Magnification (Power) and Using Eyepieces
• Sky and Telescope: Beating the Seeing