I would like to know how fast a subframe of 256x256 pixels, cleverly positioned towards the serial register and output, can be read from an STX-16803. The camera's spec sheet states a pixel digitization rate of 1.8m pixel/s, and a download time of 11.5s for a full frame. Digitizing 4kx4k pixels takes 9.32s and apparently there is a 2 s download time (due to USB speed?), i.e. 9.32 + 2 = 11.32 ~ 11.5 s. However, 256x256 pixels should be digitized in only 36.4 ms. Does this camera allow windowing, and if so, how much overhead is added? I would love to know what image cadence this camera can achieve with a small subframe, thinking towards applications in time domain astronomy. Thanks, Karsten
The USB interface is faster than the CCD clock rate, and doesn't add any significant latency. There is other overhead, such as a finite time that is required to clock the CCD vertically, and the fact that the whole array needs to be flushed prior to the next exposure. I just measured the repeat rate of a 256x256 subframe at the upper left corner of the array at 2 seconds. This is on my somewhat slow observatory PC so the number is conservative.
