Hello!! It's Joseph

 Both are dobsonian. Metal vs wood: Both are 16" F/4.5,typ 13 kg Left: Explore Scientific 30kg mirror box + 10 kg rocker = 40kg Right: 18-20 kg mirror box + 10-12 kg (rocker + UTA) = 28 to 32 kg est. COG is higher reference: sumerian alkaid Alan xmission DS4 JWST back plane  is made from prepreg comprising carbon fiber provided by Toray Advanced Composites and cyanate ester resin from Hexcel (Stamford, Conn., U.S.). Support payload of more than 300% its own weight.  

  the making mirror from Mike Lockwood webpage   youtube uwakina bokura other ATMers in Japan blueforest anettai  

 760mm dobsonian also from Mr. Sloboda, deltagraph 465mm f/3.2 ( zimmerald widefield ?)   with ASA 0.95x wynn corrector   reference books: written by  Leonid Sikoruk and Navashin Mikhail Sergeevich М.С.Навашин , “Телескоп Астронома Любителя,” Астрономическая Библиотека amateur telescope makers in Russia astronet  astroclub ua