Why are the refractor telescopes offered in the market all so heavy?
Here is a great example:
140mm F/7 Doublet Lens Cell, weight = 2kg
140mm F/7 Doublet Telescope + Tube rings = 9.8kg
I don't understand why no one would make and market the telescope near 6-7kg.
Tube: 2mm x 165mm x 900mm = 933 cm3
=>1.5 g/cc Carbon Fiber = 1.4kg
=>2.7 g/cc Aluminum = 2.5kg
Baffles: 0.1 - 0.2 kg
Focuser & Adapter: 0.6kg Starlight 2.5"
Dew Cap 1/5 Tube: 0.2-0.5 kg
Mount Support: 0.5-1 kg
Total weight = 4.8 - 5.9kg + 1kg (if you want extra supports)
I know some older Borg scopes were very light. The current Borg 107 (with 4 elements no less) weighs 3.5kg. So what gives? Why does no one want to manufacture really light weight refractors? I am practically ready to just design my own refractors because I don't see what is so difficult. But, maybe there are some finer points I don't understand. Please enlighten me or I am going to run off and make lightened refractors.