Bobby1970

I think this may be of some use to you:-

http://astronomy.tools/calculators/field_of_view/

You can select your scope, eyepiece combination and target. 

It should then show you approximately what the view will be like of the selected target.

Hope this helps

Well I am not to impressed, the moon looks like I am lookin through a cheap pair of binoculars, not very good at all. It looks like I wont be getting the ST 120mm. the moon looks very small, I cant see anything like any detail. Have I done some thing wrong. I put all the right info in , it auto detects focal length and such, and with the Celestron 6 or 7mm x-cel lx eyepiece it looks rubbish. I am glad you pointed me to this tool. I am very disappointed at a telescope with that lens and getting near the £400 mark giving that kind of image. Thanks for sharing it with me

                                   Regards. Dave

if you desperately want high magnification, then a Mak would be a better choice

But

they aren't as good on some DSO's because of their narrower and darker field of view. 

High Mag planets/moon = Get 127 Mak

Low to medium, star clusters DSO, nebula = ST120

This is basically what i use my two scopes for

Try the tool again, but with the 127mm Mak

Believe me, the view of the moon, even in an ST120 is far superior to any pair of binoculars i have ever looked through.