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 OAG-L  Pro uses a new wider prism to better accommodate larger sensor guide cameras. The prism size of the  standard QHYOAGL is about 8 x 8mm. The new QHYOAGL Pro prism is 10 x 14mm.   

When the QHY5III174M is connected to the older version of QHYOAGL for actual shooting, there is  severe vignetting (Image 1, below). In contrast, when QHY5III174M is connected to the new QHYOAGL  Pro in the same optical system, there’s only a small amount of darkening occurs at the edges, which  won’t affect guiding at night (Image 2, below).  

The QHYOAG Series directly attaches to the camera or filter wheel with six screws, ensuring a solid,  parallel and reliable mechanical connection. At the same time, various standard and optional QHY  accessories can be used to realize a variety of structural combinations. 

The QHYOAGL Pro has the same aperture as the front plate of the QHYCFW3XL (62mm) and they can be  directly mated. QHY also provides compatible adapters for QHYCFW3L and QHYCFW3M as standard  accessories, making the OAG-L Pro compatible with more filter wheels. At the same time, solutions to  achieve a back focal length of 55mm are also provided, see below: 

The QHYOAGL Pro is designed to support cameras with larger sensors like the QHY461PH, QHY600, and  their corresponding large optical systems. Therefore, it only provides M62 and M54 thread outputs. For  smaller systems needing M48 threads, a new QHYOAGM Pro with larger pick off prism is under  development and will be available soon. 

  www.QHYCCD.com