Telescope Image Orientation
by: OZScopes - The Australian Telescope Experts
So you've bought a telescope, set it up, put your eye right up against the eyepiece - to a resounding "huh"?
Many amateur astronomers get confused with their first telescope.
"Why are my telescope's images upside down? Or backwards?" - these are common questions. Your first thought might be that your telescope's broken, but rest assured that you're telescope's perfectly fine. Depending on your telescope type, images often appear correctly, upside down, rotated, or inverted from left to right.
So why is this so? Typically, astronomers using astronomy scopes aren't bothered if an object in space is shown right-way-up or not. In space, there is no up or down. If, however, you elected to use an astronomy scope for terrestrial (land) viewing - you should instead be using a spotting scope, by the way - you'll find that people, building and cars are those things which you should ideally be able to see right-way-up.
(Read our guide to Choosing Between Spotting Scopes and Telescopes to work out which is right for you!)
Hence, the important question - how do you choose the telescope that is right for your viewing needs?
To answer this, we will discuss the different types of telescopes and the orientation of the image observed through each type, and what you can do to correct them in order to suit your needs.
Refractor and Cassegrain
telescopes available on OzScopes:
Images produced with our refractor and Cassesgrain telescopes are fitted with a diagonal so it is already corrected to the right side up. Refractors are by far the easiest dual-purpose (astronomy and terrestrial) telescope to use out of the box, but Cassegrains are much more powerful than they are. Cassegrains are also more expensive, so be aware of your needs and your budget before you make your purchase! Note that Cassegrains should come fitted with an Erecting Image Prism diagonal if you want to use them for land use. Otherwise, images will appear inverted.
Cassegrains are generally also too powerful to work well for anything within a 500m radius. Such close targets are likely to fill the entire eyepiece.
Reflector telescopes available on OzScopes:
Images produced with our telescopes are upside-down. Although an erecting eyepiece will correct it to be right-side-up, your resulting image will now be inverted. Reflector telescopes are generally not recommended for land viewing due to its design.