guidecamera

A guide camera is a small, dedicated imaging device used in astrophotography to assist in maintaining precise telescope tracking during long exposures. It continuously images a portion of the sky, typically including a bright guide star, and provides real-time positional data to guiding software. The software analyzes the star’s centroid, detects drift, and issues corrective commands to the telescope mount to compensate for tracking errors.

Guide cameras are usually paired with a guide scope or mounted via an off-axis guider that shares the main telescope’s optical path. They are commonly monochrome sensors (CCD or CMOS) chosen for high sensitivity and fast readout. Many guide cameras are cooled or thermoelectrically controlled to reduce dark current, though uncooled models are common for budget setups. Typical specifications include small pixel sizes (often in the 3–6 micrometer range), high frame rates, and low read noise. Exposure times commonly range from a fraction of a second to a few seconds, balancing signal-to-noise with the need to detect short-term mount errors.

Operation involves selecting and tracking a guide star, calibrating the guiding algorithm to determine how the mount moves in right ascension and declination, and running the guiding loop. During imaging, the guide camera continuously streams frames and the guiding software sends corrections at a cadence appropriate for the mount’s response.

Guide cameras are a standard component of most long-exposure astrophotography setups and are compatible with guiding software such as PHD2. They can be used with separate guide scopes or integrated guiding solutions and support automated calibration and dithering routines.