Currently, the QHY4040 is only available in a front illuminated version. A back-illuminated version of this sensor is rumored to be available in the future. In general, the fan-blade mechanical shutter will be broken if it is used 200,000 times or so, and in some specific cases it is easy to fail to switch on or off. The advantage of electronic shutter over mechanical shutter is high reliability and stability when the observatory shoots a large number of pictures. The electronic shutter is a relatively perfect choice for the observatory.