Hello Gumbatman

Welcome to Cloudy Nights and the ETX forum in particular

The eyepieces that you need are 1 1/4 inch.

As far as magnification goes the standard eyepiece is 26mm.

You'll need an eyepiece around 15mm and one around 10mm, possibly also one around 35mm.

Before buying loads of eyepieces, I'd consider a Barlow lens (which effectively doubles the maginification = halves the focal length of the eyepiece). So a 2x Barlow when used with the 26mm would behave like a 13mm.

The ETX-80 has an internal Barlow, but it isn't too good from what I hear.

A suitable selection of eyepieces and a Barlow would cover most eventualities.

The rear port is indeed for photography, although you can use it for eyepieces if you purchase a suitable adapter.

Hope this helps

Art