Hey Gang, I'm hoping I can contact someone with SBIG software development experience. I've been developing software for an STX-16803 based on the sample C++ code supplied by SBIG. I have no problem taking images from either the tracking or the imaging CCDs individually. The sequence of events is: 1. CC_OPEN_DEVICE 2. CC_ESTABLISH_LINK 3. CC_GET_CCD_INFO 4. CC_QUERY_TEMPERATURE_STATUS 5. CC_END_EXPOSURE (in case an exposure is already in progress) 6. CC_START_EXPOSURE 7. CC_QUERY_COMMAND_STATUS (until exposure is completed) 8. CC_END_EXPOSURE 9. CC_READOUT_LINE (repeat for all CCD lines) Where I am confused is in the case of imaging while tracking. This requires both CCDs to be operated simultaneously, with the tracking CCD being read repeatedly until the imaging CCD exposure is completed. I've attempted this in several different ways, but the result from the imaging CCD is always degraded. Could someone please sketch the calling sequence? Should I be calling StartExposure and EndExposure for every tracking CCD image? Are there any special flags or parameters that need to be set specifically for imaging while tracking? Thank you!