Why Is My Telescope Upside Down & How To Fix It (2022)

One of the most surprising discoveries of first-time telescope owners is finding their new telescope project images that appear upside down. 

This is an enigma to many people, and before you throw your telescope away, we’re here to tell you not to worry. 

So why is my telescope upside down? 

Read on as we share the answer to the query and what you can do to correct the image.

Why Telescope Projects Everything Upside Down

It’s always a wonder to gaze at celestial objects. More often than not, we like to see them the same way they’re portrayed in the media, books, and magazines. However, this rarely happens. 

Here’s the thing: All astronomical telescopes produce a non-erected or non-rectified image [1]. This means refracting telescopes produce a telescope image upside down, reversed, or rotated.

All optical components used for astronomical viewing will always produce an upside-down image. 

Why? 

This is because the light entering the objective lens converges as it travels through the tube, making us view astronomical objects upside-down from the eyepiece.

Is It Normal To See Upside-Down Images In A Telescope?

Viewing a telescope image upside down is normal, whether using a refractor or Cassegrain telescope, and a Newtonian reflector. 

Unlike telescopes used for terrestrial viewing, astronomical devices limit the number of prisms within the tube to allow more light to enter. 

Since you’re viewing images from space, you will need all the light you can get, and lenses only result in optical aberrations. The only caveat is that you won’t see images with the naked eye.

To correct the image, you will need peripheral accessories called erect image prism diagonal.

Do All Telescopes Show Upside Down Images?

Not all scopes produce images upside down. Telescopes used for terrestrial observing, like binoculars or spotting scopes, produce a correctly oriented image [2]. 

This is achieved by using a corrector to flip the image right side up, plus nobody wants to see the world upside-down. 

In other words, you need an odd number of lenses, not just two mirrors, to achieve this. 

Since there is plenty of light among terrestrial objects, light transmission is not a problem. This, however, is not the case with telescopes used in astronomy.

How To Correct An Upside-Down View On Telescopes

As mentioned above, image rectifiers involve peripheral accessories to solve the upside-down problem. 

One tool used for refractors like Cassegrain telescopes is the diagonal mirror which fixes the inverted images (up and down) but flips the view from left to right. 

To get around this problem, you can use erect image prism diagonals to perfect the image orientation. Other image rectifiers include erecting eyepiece and other prism attachments.

Corrective Telescope Accessories You Can Try

Erecting Eyepieces

A Newtonian reflector, where the viewfinder is on the side, will require an erect image eyepiece to correct the image. 

The view won’t appear upside down in Newtonian telescopes but will project the image at a weird angle. 

Moreover, the long focal length of the erecting prism negatively impacts the user’s field of view.

Star Diagonals

A Cassegrain telescope uses a star diagonal to flip the image right side up, which means the image will be in its vertically correct position. 

However, the prism flips the image from left to right. As with other accessories, additional optical elements limit the light path, dimming the image.

Prism Attachments

Roof-Style Prisms

Most telescopes for terrestrial viewing do not produce images that appear upside down thanks to prism attachments within. 

One is the roof prism, an internal attachment that bounces the light from the objectives to correct the image.

Porro-Style Prisms

Not all telescopes use roof prisms, but if you have a bulky and rugged binocular, they most likely house a Porro prism. 

This bounced the light from the objectives against two right-angle surfaces to produce an erected image. Despite the rugged feel, Porro binoculars have better-quality images.

Amici Prism 

This is the highest-quality erect image prism. They can either be housed within a 45 or right-angle degree diagonal. It is created when you put two triangle prisms in contact.

Pentaprism 

As the name suggests, pentaprism is a five-sided reflecting prism. Many telescopes don’t use this in their telescope diagonal as it is more prominent among digital cameras.

Should You Correct The Upside-Down Images?

Any type of telescope can be corrected. However, correcting an upside-down image is irrelevant when dealing with celestial bodies because of three reasons:

• The night sky limits the light your device reflects, and additional attachments will only reduce light transmission.
• While the mirror fixes the vertical orientation, it flips the image horizontally, which poses a problem when viewing star charts.
• You can easily flip star charts upside down to match the inverted image. 

When dealing with a star chart, you’ll need more than a star diagonal. You can use an attachment called erect image prism diagonal to render images right side up.

FAQs

What type of telescope flips an upside-down image?

Inverted images can be corrected using attachments like erect image prism diagonals. Both Newtonian reflectors and Cassegrain telescopes do not produce right-side-up images. 

The upside-down image results from the two mirrors used in the telescope. 

What telescope lens produces an image that is upside down?

Any telescope that only uses an objective and eyepiece will produce a telescope image that’s upside-down. 

Additional attachments like star diagonals align the vertical orientation of the image to our naked eye. 

More sophisticated tools like erect image prism diagonals are required to produce accurate image orientation.

Key Takeaways

If you’re just starting in the astronomy hobby, upside-down telescope images might surprise you. 

Astronomical telescopes are specifically designed to project images in reverse to allow better light entry. In any case, there are many attachments you can use to correct the image. 

Whether you’re dealing with a vintage Newtonian device or a more sophisticated refracting rig, your telescope definitely has a dedicated attachment. 

All you have to do is search for the one that suits your specific needs.

References:

1. https://skyandtelescope.org/astronomy-equipment/how-to-choose-a-telescope/
2. https://www.bhphotovideo.com/explora/outdoors/buying-guide/spotting-scopes-vs-telescopes-for-beginner-astronomers