Unlike external guiding arrangements, when using an OAG, the guiding camera and the imaging camera share the field of view of main optical system. If a user’s OTA has a long focal length, and the environment is not ideal, there will often be fewer stars suitable for guiding to be found in the FOV. One way to improve the chance of finding a good guide star is to use a guide camera with a larger sensor. For example, guide cameras like the QHY5III174M or the QHY5III585C have a FOV that is 2-4 times larger than that of smaller cameras typically sold as guiders. This larger FOV naturally allows you to capture more stars, essentially solving the issue of no or few stars available to guide the image.
In order for a large-sensor guide camera to fully perform to its potential in an OAG, a prism large enough to allow illumination of the larger sensor is needed to avoid severe vignetting. The new OAGM Pro uses a new wider prism to better accommodate larger sensor guide cameras. The prism size of the standard QHYOAG series is about 8 x 8mm, while QHYOAGM Pro is 10 x 14mm.
The QHY OAG-M-Pro Model shown here is designed for use with the QHY CFW3 M-US 7 x 36mm Filter Wheel or the QHY CFW3 L 7 x 50mm Filter Wheel
