Expert: Paul Wagner - 2/10/2008

Question
Hi Paul,
When setting up my telescope using hills a mile or so away, they were
inverted.
Does this mean that when I look at the moon, or any other heavenly body, it
will be inverted?. I don't understand why one cannot just view something the
right way up and the right way around!
Thanks,
Dave

Answer
HI Dave

This is normal for astronomical scopes.  To get the image turned right side up, you need a couple of extra reflections...and every one of those loses about 5% of the light, as well as adding just a bit of distortion.  So astronomical telescopes always leave things upside down--not that you can tell right side up from upside down in space!  

If you want, you can sometimes buy what is called an image erector for these scopes...it will do just that.  But the optical quality of the image will be degraded just a bit.

Paul Wagner