For most astrological observing, the image orientated doesn't matter. However, it is something an astronomy has to get use to. Refractor and Cassegrain telescopes an inverted image, or one that that is upside-down. There are some star atlases which are printed with the south at the top to compensate for this. One will find that an inverted image is also the case with a straight-through finder scope. The invert image has been an issue with telescopes ranging all the way back to the first, with Galileo, but there have been advances which provide erecting prism diagonals which right the problem.
Another issue is when a refractor or Cassegrain telescope is used with a standard 90 degree star diagonal. The image will be right-side-up but mirror-reversed. This makes using a star chart nearly impossible as one has to imagine the image right to left in order to match it up with what is printed. The erecting prism diagonals will also rectify this problem. An erecting prism is also referred to as a Porro prism. However, erecting prisms do not work with reflector telescopes.
The first problem of the simple inverted issue only happens when one is not using a diagonal, which isn't the normally the case. Most often one will run into the mirror images and therefore will likely wish to purchase a prism. Porro prisms are not typically included in standard telescope packages, and have to be purchased separately. If one wishes to try their hand with mirror images, then it shouldn't distract from the beauties of the night sky. Only when using printed materials to help navigate do the mirror images really affect an astronomer. The problems that astronomers have faced with the mirror images is what initially gave the idea for computerized telescopes which locate astrological bodies within the viewfinder. A computer is able to easier invert and flip mirror images and thus can track constellations or planets with greater ease.
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