This is OpenSCAD design of a specialized piggyback. With it you can mount a photocamera (typically Pentax DSLR) with "SMC Pentax-F* 300mm F4.5 ED [IF]" lense on top of Celestron SCT 8i telescope (possiibly also other, with little mdification). Design is parametrized so it can be easily adapted to other telescope, and different lens. Here is english translation of parameters from the file: d1=234; //diameter of larger cylinder of a base mount d1a=228; //diameter of smaller cylinder of a base mount d2=64; //diameter of lens tripod mount ring h2=13; //thickness of lens tripod mount ring szer=100; //base width h1=50; //base depth h1a=10; //szerokość węższego pierścienia podstawy h1b=21; //width of smaller part of base kat-sr=17.5; //angle of tripod mount screws (may wary!!!), please experiment kat-pod=0; //vertical angle between main scope and leans - 0 means parallel