Integrated off axis guiding camera

maropapa

A small chip placed along the longer side of the main chip (e. g. in a full frame camera like 6200) can serve as an off axis guider to the main without any extra optical part. The real advantage will be using it with RASA telescopes, where OAG can not be applied because it could block the incoming light.

w7ay

maropapa A small chip placed along the longer side of the main chip

This (patented by SBIG, and released many years ago as the ST-7 camera) has been suggested and investigated by ZWO. Execution is probably an order of magnitude more difficult than a single sensor, though. Not all sensor chips have the same thickness -- the sensor planes need to be within a couple of microns from one another from the incoming light.

http://www.company7.com/sbig/products/st7.html

There is also one disadvantage with a secondary guiding sensor: it is not useful for doing narrow band work since the guide camera would receive very little light.

Chen