Guiding is a technique used in astrophotography to improve the accuracy of tracking celestial objects during long-exposure photography. It involves using a separate guiding camera to track a reference star and make small corrections to the mount’s position to keep the object being photographed centered in the camera’s field of view.

When taking long-exposure images of celestial objects, even small tracking errors or vibrations in the telescope mount can cause the object to appear blurry or distorted in the final image. Guiding compensates for these errors by constantly monitoring the position of a reference star and sending corrections to the mount’s position in real-time.

To guide, a separate guiding camera is attached to the telescope, typically pointing towards a region of the sky near the object being photographed. The camera captures a live view of the stars and selects a reference star that is close to the object being photographed. The guiding software then analyzes the position of the reference star and sends small corrections to the telescope mount to keep the object centered in the camera’s field of view.

The guiding camera can be controlled manually or using specialized software, such as PHD2 or N.I.N.A. The software typically provides tools for calibrating the guiding camera, selecting a reference star, and adjusting the guiding settings to achieve optimal performance.

Guiding is an essential technique for capturing high-quality images of celestial objects, particularly for objects with small apparent sizes, such as galaxies or nebulae. By using guiding to compensate for tracking errors, astrophotographers can capture longer exposures and produce clearer, more detailed images.

Guiding can be communicated to your equipment through two different mechanisms - Pulse Guiding and ST4

ST4 (also known as ST-4) guiding is a method of autoguiding that uses a direct physical connection between the guide camera and the mount’s hand controller. The ST4 cable connects the guide camera to the mount’s autoguider port, and the guiding commands are sent as electrical signals over this cable. The ST4 interface provides a simple and reliable way to send guiding corrections to the mount, and it is widely supported by guiding software and mounts.

Pulse guiding, on the other hand, is a method of autoguiding that uses the mount’s pulse guiding capabilities to send guiding commands to the mount. Pulse guiding uses software to translate the guiding corrections from the guide camera into a series of pulses that are sent to the mount through the mount’s computerized control system. Pulse guiding is a more flexible approach than ST4 guiding, as it does not require a physical connection between the guide camera and the mount. However, pulse guiding can be more complex to set up and may require specific software and mount compatibility.

In summary, ST4 guiding is a simple and reliable method that uses a direct physical connection between the guide camera and the mount’s hand controller, while pulse guiding is a more flexible method that uses the mount’s computerized control system to send guiding commands. Both methods can provide accurate guiding corrections and improve the quality of astrophotography.