But some DSLR cameras have a 30-second exposure limit, which requires an external shutter release cable to ASIAIR PRO.

ZWO Shutter Release Cable is of the soft, curled type that can extend the usable length. There are two types of Shutter Release Cables:

N1 (MC-30, 10PIN)
D300/ D300s/ D700 / D3/ D3s /D3x

N3 (MC-DC2, 8PIN)
D90/ D3200/ D3300/ D5000/ D5100/ D7000 Cable

Length: 1 meter