Introduction to Guide Cameras
What is autoguiding? Autoguiding is using a separate camera from your main imaging camera to make your tracking more accurate during long exposures for deep sky astrophotography. When done properly, autoguiding can increase your exposure length by roughly 5x longer before star trails begin to occur. Autoguiding works by using the guide camera to watch a star, and if that star begins to drift by even a pixel, it can communicate with your tracking mount to make the necessary corrections. It makes these tiny corrections while your main camera is exposing, so you end up with a sharp image without any star trails. There are two main ways to do autoguiding: with a guide scope, which is like a mini telescope that sits on top of your main telescope, or with an off-axis guider. For anyone who's a beginner, we recommend starting off with a simple guide scope and guide camera setup. Only if you're an experienced astrophotographer and are using a long focal length telescope do we recommend an off-axis guider. Check out our blog post Guide Scope vs. Off-Axis Guider for a more thorough comparison between the two!
When choosing a camera for autoguiding, you'll want to make sure it is sensitive enough to pick up stars in your field of view. This is especially true if you're using an off-axis guider at long focal lengths. The worst thing is trying to autoguide but your camera isn't sensitive enough to see any stars in your field of view! For that reason, we always recommend using a monochrome camera for guiding as they are inherently more sensitive than color cameras. Guide cameras are almost always monochrome for this reason. If you're just using a guide scope, most beginners can get away with inexpensive guide cameras like the ASI120MM Mini. For more advanced users or those who want to "future-proof" their setup, guide cameras like the ASI290MM Mini and the ASI174MM Mini are some of the most sensitive guide cameras currently available. These are best when using a long focal length guide scope or off-axis guider.
Can you use other cameras for autoguiding? Yes, absolutely! In fact, you can use just about any type of camera for autoguiding, as long as it's sensitive enough to pick up stars. However, we don't normally recommend using large sensor cameras for autoguiding because they can introduce flexure and unnecessary weight when paired with a guide scope. You can, however, use just about any monochrome planetary camera as a guide camera successfully. Can you use a guide camera as a planetary camera? You can, but due to the limited frame rates on most guide cameras, it won't be as good as using a proper planetary camera.