Barlow Lenses and Reducers

A telescope has a certain focal length which means that it has a certain field of view. My scope, the Celestron Edge HD 8", kind of sees through a drinking straw. That results in quite a small part of the sky which comes in handy for planets and very small objects. Very small if you think of planets being nothing more than 'just another star'. So... if you want to zoom in on a planet or zoom out to be able to get a large(er) nebula you have to adapt the scope.

Zooming in you do with Barlow lenses. Zooming in means less light to be captured by the camera sensor. That means either more or longer exposures and a more critical polar alignment.

Zooming out requires a reducer or a Hyperstar. Reducers lessen the focal length a bit, there are several types but they are limited in capability, but have the advantage of making your telescopes Focal Ratio faster as more light is captured. However a Hyperstar does this far more drastically sinking your Focal Ratio down to f2 speeding up exposure times enormously. The Hyperstar comes with a 'but' though: you have to collimate your scope after replacing the 2nd mirror when you're done because the Hyperstar comes in the place of the 2nd mirror. Also at first placement (I'm not yet sure if this goes for every time you place it) you have to do a collimation. Bear in mind that the cabling for the camera on the Hyperstar will produce spikes on the bright stars. Look here for more information on this topic.

Alternative: Celestron Rasa Telescope

Dylan O'Donnel on the choice between Hyperstar and RASA.