Dougie
Visually spotting the difference between FPL-51 and 53 to us amatuers is miniscule also quality often depends on where the optics are made. The range of ED80's available is significant, personally if your budget can stretch go for a well known brand such as WO, Mergz, Borg, Stellarvue etc
or
http://www.astronomics.com/main/prod...duct_id/AT80LE
Cheers
