Why Won’t My Erect Image Eyepiece Or Diagonal Always Give Right Side Up Images With My Scope

Why won’t my erect image eyepiece or diagonal always give right side up images with my scope?

When you look at the sky from the very zenith, the eyepiece is always directed downwards. If you were to investigate the eyepiece in this position, your neck would be aligned at a wrong angle.

Moreover, the telescope turns an image. The resultant image is then aligned upside down.

This is not a frustration while viewing astronomical objects. But it can get a bit annoying when you are making terrestrial observations.

There are visual aids for both these puzzles in astronomy. To know more about these aids and to troubleshoot some issues, follow along.

Why is everything always upside down – the image orientation of a telescope

The image orientation of your telescope would be the most surprising aspect. This is especially true if you are starting with your brand-new scope.

With the image upside-down or backward, your first conclusion is that your telescope is broken or defected. But your telescope is perfectly normal conditions.

Depending on the type of scope you are using, the image would be inversed or rotated or upside down. The real question is, why does this keep happening?

This a pure attribute of the mirror of the telescopes. All refractors, reflectors, catadioptric, all telescopes give an inverted image.

Even the lenses of your scope contribute to the inversion. It is your optical biology that erects the image back.

For a certain astronomer, this not much of a quandary. This can be purely concentrated on the fact that in space is there is no orientation.

Moreover, introducing extra optics in your scope will reduce the incoming light. This slightly affects the quality of the image.

The choice is solely dependent on the observer. While some prefer orientation, others do not wish to introduce any hindrance in their image quality.

There is a middle ground where you can have the best of both worlds. This largely depends on the type of scope you are using.

Troubleshooting the telescope image orientation

Reflector and Schmidt- Cassegrain telescopes

These telescopes will produce an upside-down image. The inversion occurs when you are not using a diagonal.

The diagonal is a mirror at 45 degrees called the star diagonal. When you employ the star diagonal, your image will be corrected right-side up.

However, it is essential to note that the image is still backward in the left to the right direction. For a better perspective, the image will appear when you view it in a standard looking mirror.

Once you have the image erect from the upside-down inversion, there is a way to correct the backward direction. You can use another optical aid called the straight image prism diagonals.

These diagonals are designed to correct the backward orientation of the image. These aids are especially useful for terrestrial imaging and viewing.

The Newtonian telescopes

The Newtonian telescope is notorious if you are using it for viewing terrestrial objects. We do not recommend using the Newtonian scope for this endeavour.

The image always appears upside-down in such a scope. The methods to correct the inconsistencies in the orientation are quite limited.

If you are using a chart for tracking the stars, you can turn them upside down. You are achieving the same orientation as it is true for your telescope’s eyepiece.

More about image erector for your telescope’s image orientation.

Most image erectors have usage. They are not designed to offer universal aid in all circumstances.

The orientation of the image in astronomy largely depends on two factors. The design of your optical telescope and the way it is oriented are the two factors under question.

The erect image in all situations is caused due to multiple prism alignment. When the prism series is aligned with the scope’s eyepiece, it will rotate the image.

The image rotation occurs up to 180 degrees. This is a commonly used correction for Newtonian reflector telescopes.

The prisms act as a replacement for the eyepiece that you should be using. The combination in the reflector telescope gives a right side up the image rather than an upside side down portrayal.

Several markers are used to define an optical image that erects your astronomical image. The star diagonal, for instance, is at an angle of 45 degrees.

The regular prism in such a case is replaced with a roof prism or an amici prism. As we mentioned before, star diagonals correct the upside-down problem.

The images are still in a backward orientation. From the argument, we can derive a common opinion; the erect image has many limitations.

There are several ways of correcting this orientation. But to get an ultimate optical aid, that tackles all the issues with the direction is a long-term goal.

Recommended Reading:


  1. Celestron
  2. howstuffworks.com
  3. Astro Asheville