I'd suggest that a refractor is not the best option. With LP and restricted sky he needs aperture and a big aperture Refractor costs !! A SCT or Mak Cas in the size he is talking about would be a minimum IMHO. A short Newt or any of the folded optics options will give aperture and not be too big\long in a restricted space like a balcony and for storage as well. Apartments in Singapore are not big in my experience.
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