Back spacing, in the context of astrophotography, refers to the distance between the camera’s imaging sensor and the telescope’s focal plane. It is an important parameter to consider when setting up a camera and telescope for astrophotography, as it affects the focus and image quality.

In order to achieve optimal focus, the back spacing needs to be carefully adjusted so that the imaging sensor is positioned at the correct distance from the telescope’s focal plane. This distance is determined by the optical design of the telescope and the camera being used. If the back spacing is too short or too long, the image may appear out of focus or distorted.

To adjust the back spacing, various adapters and spacers may be used between the camera and the telescope. Some telescopes have a built-in focuser that allows for back spacing adjustments, while others may require external accessories. The optimal back spacing can be determined through trial and error or by using specialized software that analyzes the image quality.

Back spacing is also important to consider when using accessories such as field flatteners or reducers, as these can affect the distance between the camera’s sensor and the telescope’s focal plane. Proper adjustment of the back spacing is crucial for obtaining sharp, high-quality astrophotographs.