I am going the other way , I owned and really loved a good ED80 for years . It was an awesome scope for what it was , and here lies its weakness , only 600mm focal length and if you want higher powers >200x ( which it is capable of
) I found I had to start stacking barlows and use <3mm eyepieces , a huge pain as the jump from say a 10mm eyepiece ( in average Joe Blog eyepieces , not exotics worth more than the scope
) down to 2-5mm eyepieces was an exercise in frustration , trust me at midnight in the middle of winter juggling eyepieces is a pain .
Whereas the C5 with its 1250mm fl is just cruzing at 200x , planets , double stars , globulars , smaller open clusters and the moon take on another scale , trust me it does make a huge difference ,, image scale is an often forgotten aspect of observing and an ED80 wont give the views a well columinated C5 can , jump to a C8 and the perspective really shows , especially at the 200x mark .
If AP is your thing then a good FR will work well with the C5 and it is easiler to mount than the longish ED80 tube .
My 5c as a visual guy
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Brian.