Pixel and chip sizes
Depending on which telescope has been chosen for object viewing, a matching camera must be selected in order to achieve an optimal interaction with its pixel size and the focal length of the telescope (see menu item 'Basics' - 'Telescope-camera-combination'). Which camera could fit with which telescope can be determined under the menu item 'Tools'.
The chip size in connection with the focal length defines the image field width, i.e. the area that can be displayed with this sensor. If capturing large deep sky objects, the moon or the sun is planned, a larger chip size should be chosen (e.g. APS-C). For planetary images or small planetary nebulae a smaller chip can be used, considering the telescope focal length.
This relation is also shown in the menu item 'Tools'. After setting the camera and telescope specifications, it can be checked there directly whether a selected object fits on the chip.
Хрюша, CC BY-SA 3.0, via Wikimedia Commons