Contributions

If you like the website and want to contribute to the running costs then please do so below. All contributions are most welcome.

PayPal - The safer, easier way to pay online.

In a reflecting telescope the secondary mirror prevents or obstructs a portion of the incoming light from reaching the primary mirror. The central obstruction is the proportion of obstructed light expressed as a percentage of the incoming light.

For example, an 8" f/6 Newtonian reflection has a central obstruction of 18%. A 10" Schmidt-Cassegrain (f10) scope has a much larger obstruction of 37% due to its shorter and more compact optical tube.

Schmidt-Cassegrain telescopes generally have quite large central obstructions

Glossary A B C D E F G H I J K L M N O P Q R S T U V W X Y Z