The Cartoni Focus 18 comes in two versions, one with +90 to -70 degree, the other other with +90 to -90 degree, the latter with a sliding base plate, which is more expensive. How are the angles defined? For the night sky 0- 90 degree is sufficent, the sign plays no role, or do I miss something?
I can only speak for Manfrotto video heads but when they spec "Vertical Tilt +90° to -70°", they mean the head will point downward 90° and upward 70°. That's why for binocular use we need to turn them around 180° to orient them so they point our binoculars to zenith.