This means that, looking directly through a Newtonian reflector, or most commercial catadioptric or refracting telescopes without a stellar diagonal, the image is upside down. To correct the upside down view, equipment known as a diagonal can correct the image and turn it upside down.
When a diagonal is used the image will be corrected right side up, but upside down from left to right. If you prefer a video to understand why the image is upside down, this one explains the concept quite well in relation to telescopes.
Telescope image upside down? Here’s why
A simple refractor produces an upside down view. Refractors and cassegrain telescopes produce an upside down image when used without a diagonal. On the other hand, some telescopes will display images upside down, others will display them rotated or inverted.
Generally, if your telescope has an even number of optical elements – such as a Newtonian reflector with its two mirrors – your object will appear upside down. This is the same for Dobs too – even if you have the best Dobsonian telescope, you can still sometimes get telescope images that appear upside down.
Generally, if your telescope has an even number of optical elements – such as a Newtonian reflector with its two mirrors – your object will appear inverted. There are special diagonals called erect-image prism diagonals that can correct the image upside down for terrestrial use. However, this will flip (reflect) your image from left to right. There are special diagonals called erect image prism diagonals that can correct the image backwards for earth use.
There are special diagonals, to correct the image as to how it would actually look called Erect-Image Prism diagonals and they are used in the same way as regular diagonals. There are special diagonals called Erect-Image Prism diagonals that can correct the image upside down for ground use. Depending on the type of telescope the images can appear correct, upside down, rotated or inverted from left to right. There are special diagonals called Upright Prism diagonals that can correct the image upside down for ground use.
If you have just purchased and are using your telescope for the first time, and notice that the images appear upside down, don’t panic or worry. If you are using a Refractor or Cassegrain Telescope and want to invert the image, you can purchase a Telescope Diagonal to correct the upside down and inverted orientation to the correct position.
If you are using a Refractor or Cassegrain Telescope and want to invert the image, you can purchase a Telescope Diagonal to correct the orientation upside down and inverted to the correct position. One of the most surprising discoveries that first time telescope owners will find is that images can appear upside down or inverted depending on the type of telescope.
A finder with a correct or inverted image will match the star charts, as will a zero-power finder, so there is no need to worry about the inconvenience of orientation when pointing the telescope. Your finder is not upside down, but the image you see through the finder is the opposite of what you see with the naked eye. If you have an odd number, like a Nasmyth-Coudé with its three mirrors, the image is reversed from left to right. It will be like trying to read a sign in a mirror.
The truth is that not all telescopes will display the image upside down – it depends on the type of telescope you have purchased and are using.
How to fix the telescope image being upside down
Generally, if your telescope has an even number of optical elements – such as a Newtonian reflector with its two mirrors – your object will appear upside down. Find a right-angle right image finder that fits your brand of telescope and you’ll solve your telescope’s upside-down image problem.
One of the biggest surprises beginner astronomers get is when they discover that the view they are seeing through their telescope is upside down or right side up. If you’ve just bought a new telescope, set it up and looked through the lens, you may have been surprised to find that objects in space appear upside down.
Although you can rightly argue that there is no “up” in space – what’s right-side up in the northern hemisphere appears upside down from the southern hemisphere, after all – it’s still useful to know why some telescopes show things one way and others show them another, and how to “correct” things for your convenience.
Other image rectifiers involve an erector lens or a diagonal mirror (star diagonal) that solves the upside-down problem. It can be a surprise the first time you look through a telescope or finder to realize that the image is upside down (inverted). In general, the image on most telescopes will be inverted, mirrored, or a combination of both, depending on the accessories and telescope design.
Conclusion
The image is inverted in all directions (left to right and right to top), while the mirror fixes the right side up – the image of the telescope copied upside down – but not the inverted left to right. There are special diagonals called erect-image prism diagonals that can correct the upside-down image for terrestrial use.
The truth is that not all telescopes will display the image upside down – it depends on the type of Telescope you have purchased and are using. One of the most surprising discoveries that first time telescope owners will find is that images can appear upside down or right side up depending on the type of telescope.
