Finally got time to try out this combo, here are the photo of full moon on mid-autumn day
Tokina 400mm f5.6 at f22 + Takumar A 2x TC + Vivitar 2x TC = 1600mm (equiv 2400mm on Pentax Kx)
Tokina 400mm f5.6 at f16 + Vivitar 2x TC = 800mm (equiv 1200mm on Pentax Kx)
the tripod with IR remote
Tokina 400mm f5.6 at f22 + Takumar A 2x TC + Vivitar 2x TC = 1600mm (equiv 2400mm on Pentax Kx)
Tokina 400mm f5.6 at f16 + Vivitar 2x TC = 800mm (equiv 1200mm on Pentax Kx)
the tripod with IR remote