I am having a lot of trouble getting the guideer image to focus on my FW8G-STXL. Presumably, the backfocus distance to the guide chip should be the same as for the main imaging sensor in the camera (which is 2.557" from the dovetail nose piece to the main imaging chip). The guide chip focus knob on the FW8G-STXL has a total adjustment range of about 14 revolutions. Can you tell me what range of backfocus distance (min. / max.) corresponds to this number of turns ?
The FW8G is designed so that the backfocus distance for the main camera is within the range of focus adjustment. This assumes that the wheel is installed normally on the front of an STXL camera. I don't have the exact number handy. My usual technique if I'm having trouble setting it up is to use the moon. It's very easy to find the moon - you certainly know for sure when you've found it! Plus you can find rough focus very quickly by looking at the limb of the moon and using very short exposures.
