Hi
I have the exact same problem. I have tested nebulosity 4, latest pre-release. same crash.
I also tested TheSkyX on mac, latest version, the software does not crash but it cannot connect the camera.
I suspect someting with El Capitan latest release. Indeed everything works fine using yosemite.
I have enabled the log on TheSkyX driver for El Capitan :
D: 56c90ca0.e608e : ++ Building driver chain ++
D: 56c90ca0.e6218 : ++ Building driver chain - 1
D: 56c90ca0.e7543 : ++ Building driver chain - 2
I: 56c90ca0.e7748 : ArtemisLinuxUSBTransport::writeBulkPipe: ** return entity not found - the device could have disconnected (LIBUSB_ERROR_NOT_FOUND) **
I: 56c90ca0.e778b : Failed to connect to camera - or camera not responding and unrecoverable during initialisation
regards
Emmanuel