Hi Ian.
I concur with David.
I 3x barlowed a 17.3 Delos with one of these on the Moon (high up) and got
unbelievable clarity and resolution with one of these, ( cooled 1 hour) 127 Maks. Saturn also great.
But only the brightest clusters and planetaries are not too dim.
Though I've easily spotted galaxy M77 with one.
If you intend to purchase, ensure any object observed is well above the horizon. Viz.35 deg.
Ps: A cheap 6"-8" dob is a better purchase imho.
Hope this helps!
Cheers bigjoe