Three Fathoms Observatory
Stewart Yeung

 Current Special Feature



Doomsday for My CCD ?



Sample : 10 sec light frame binned 2x2 with autodark (bias set at 167) taken with MaxIm DL5 Suite


Click to download the original FITS :

Light Frame in FITS

30 sec Dark

Bias Unbinned


It seems that the UNBINNED image indicates light reception problem by the CCD:

5min Unbinned FITS

The same FOV when binned 2x2 : same b/w vertical stripes

5sec Binned 2x2 FITS


One night when I turned off the chiller and imaged with the camera's built-in cooler and fan only, the image became normal. This made me suspect that condensation was the culprit (I always worry about the susceptibility of CCD to chilled water cooling). But this turned out to be a coincidence only.The next day the image became faulty again, even without chilled water cooling.

Then I followed JoeMize's "crazy" suggestion and overhauled the camera drivers. After disabling the camera's USB composite device (device manager in Windows), I deleted all the SBIG drivers in the "Driver Checker" directory. Then I ran the SBIGDriverChecker, where the current drivers all showed up as "?", downloaded and installed all the new drivers. Bingo! It's all normal images when I enabled the camera's USB composite device and took images with either CCDSoft or MaxIm DL. ( so it seems that MaxIm DL shared at least some of the SBIG drivers.)

Afterall JoeMize's idea is not crazy at all as he had similar experiences with his STL11K.

Once again it also turns out that the CCD is not as vulnerable to condensation by chilled water cooling as I have always feared.


Acknowledgement :

Thanks for advice by members of the SBIG forum :

JoeMize (deserving the credit)

Rick Yandrick

Stan (deserving the credit re USB extender)

Steve Reilly


William R. Mattil




It happened the very next night that the same problem resurfaced. So it could not be attributed to only the drivers. I repeated the procedure of disabling the camera's generic USB hub in device manager in Windows, rebooted the PC, then enabled the camera's USB composite device. Normal images came back again.

I realized that the generic USB hub in device manager actually was the USB extender which required re-initialization for the camera to work normally.

The USB extender has been replaced by a more robust one. However, for normal images, the generic USB hub has to be disabled while the camera is off, and re-enabled while the camera is switched on again.