Guidescopes

All About Guiding Scopes: The Key to Pinpoint Astrophotography

Want to peer deep into space and capture nebulae or galaxies with long exposure times? Then you need a guidescope (guidescope) an indispensable part of your setup. Even the most accurate mount has minor deviations; a guidescope corrects these errors in real-time, ensuring your stars always remain perfect pinpricks instead of streaks.

What is a guidescope?

A guidescope is a smaller, secondary telescope mounted on top of or next to your main telescope. Instead of an eyepiece, you place a special Camera guide This camera focuses on one specific ‘guide star’ and meticulously monitors if it shifts.

When the star moves a fraction of a millimeter, the software immediately sends a signal to your mount to correct its position. This process is called autoguiding.

Why do you need a guidescope?

  • Long exposures For deep-sky photography, exposures of 5, 10, or even 20 minutes are often necessary. Without guiding, the slightest mechanical inaccuracy will result in blurry photos.

  • Correction of periodic errors Every mount has gears that are never 100% perfectly round. A guidescope picks up these fluctuations.

  • Better pool alignment: Although a good polar alignment is the foundation, autoguiding compensates for the final small deviations that can occur during a night.

What should you pay attention to when buying?

When choosing the right guidescope for your setup, three factors are crucial:

  1. Focal length: As a general rule, the focal length of your guidescope should be about 1/3 to 1/10 of that of your main telescope. For modern software, a compact 30mm or 50mm guidescope is often sufficient for most refractors.

  2. Aperture The faster (lower f-number) the viewer, the brighter the stars will appear on your guide camera. This makes it easier to find a suitable guide star in any part of the sky.

  3. Sturdiness Flexure (the bending of the guidescope relative to the main telescope) is the enemy of sharp photos. Opt for a sturdy mount with a dovetail or firm tube rings.