Guiding, Centering & Adaptive Optics
Guiding can be a daunting task for the new astrophotographer, but it doesn’t have to be. An equatorial mount is a must-have for anyone interested in imaging celestial objects. An equatorial mount compensates for the Earth’s rotation to help your setup stay fixed on a guide star. However, there are many more accessories that can help you guide easily and hassle-free. The three basic tools that astrophotographers use are an off-axis guider, auto-guider, and a guidescope.
An off-axis guider (OAG) connects to your main optical train and typically uses a prism to redirect a small pathway of light to a separate guiding camera. This way, you can do short exposures, detect stars, and calculate guiding errors. This setup is a lightweight option and, in most cases, will not add flexure to your imaging setup. Also, an OAG is typically a cost-effective option: all you need is an OAG and a guiding camera. However, an OAG will add extra length to your imaging train, so it may be cumbersome to obtain focus. We recommend OAGs for new amateur astrophotographers because it is a straightforward and inexpensive guiding system.
If you are looking for a more advanced guiding system, then a guidescope is the way to go. These scopes are typically small refractors that you mount on top of your main imaging system. This is a great option for astrophotographers who prefer to image through a smaller aperture and slower telescope because this is when stars are more difficult to see through an OAG. However, piggybacking a guidescope adds significant weight to your setup and can cause flexure or extra strain on the mount.
An autoguider is an excellent choice for astrophotographers looking to take long exposures. This high-tech camera sits on the back of your guidescope or OAG. The autoguider is then connected to your mount to keep your setup continuously tracking the guide star throughout your imaging session. This dramatically reduces tracking errors and eliminates drift, which can cause oblong stars to appear in your image. Autoguiding is perfect for deep-space imaging, where it is crucial to be precise when guiding.