Why is the image through my telescope upside down ?
One of the most surprising discoveries first-time telescope owners will find is that images may appear upside-down or backwards depending on the type of telescope.
The first thought is the telescope is broken - when in fact it is working perfectly normal. Depending on the type of telescope, images may appear correct, upside-down, rotated, or inversed from left to right. Why is this? Why would you want to see everything incorrectly? All telescopes, refractors, reflectors, and catadioptrics, as well as all cameras, have inverted images because that's the way all lenses and mirrors work. Even the lenses in your eyes invert the images of the world, and your brain erects them. Astronomers usually don't bother adding the optics needed for an erect image because extra optics reduce light throughput and introduce aberrations. Who cares what's up or down in space anyway? For astronomical viewing, it is not important whether an object is shown correctly. In space there is no up or down! The orientation of the observed image is dependent upon the type of telescope that you are using, and there are ways that you may be able to correct it for land (terrestrial) use.
Here's a brief explanation of this on the manufacturers website, click on this link: Celestron