This meniscus lens could be an alternative, but if possible I would like to find a lens that would be a bit soft when wide open and pretty sharp when stopped down. In the 1000 - 1200 mm range what could be possible ? Of course if it could be mounted in a shutter it would be very nice. Perhaps I want too much ? Any idea of that dreamed lens that could cover 20x24 also at infinity ?

Hope that what I said is correct ?

Thank you for your answers. Thierry M.L.