Terry - This may not be the most accurate advise available but here goes... The main differences between the Celestron G5/C5 and the new ETX-125 are the optical setups. The g5/c5 series are Schmidt cassegrains, and lend themselves combining fairly good optics with portabilty and reliability. The ETX is a Maksutav Cassegrain which is a little more delicate instrument, and has a bit more resolution for the money. The ETX also has a longer focal length which will produce more contrast in the image then the Celestrons. The ETX will outperform the Celestrons on planetary views, but is not as "Bright" when it comes to deep sky. The Celestron and Meade instruments go through very similar coating processes, so this should not be a factor in your desicion. Hope this helps...