Focus Your Telescope

Your telescope's focus knob is for focusing, not zooming. You're in focus when the target is as small and sharp as possible. Scroll down for more tips.

Focusing tips and tricks

  • Focus is achieved when the eyepiece focal plane, or the camera sensor, meets the telescope's focal plane. This is what the focuser's job is.
  • If you turn the focus knob but nothing seems to change, make sure the drawtube moves in and out when you turn the knob.
  • If the drawtube is not moving, look under the body for a tension thumbscrew you can adjust to add some friction to help it engage.
  • If the drawtube is moving but the view isn't improving, you may be very out of focus. Keep turning the knob until it comes to focus.
  • If you run out of outward focuser travel before the view comes to focus, you may need to use an extension tube.
  • If you run out of inward focuser travel, it means the focal plane is too close to the telescope and the focuser cannot reach it.
  • A star will always look like a small dot. Stars are too far away to resolve as disks. If you see a disk or donut instead, you are out of focus.
  • Planets should show visible surface features unless the atmosphere is too turbulent or there are other issues. See this article.
  • Telescopes are designed for astronomy and may not focus on a nearby target correctly.
  • If you want to make the view bigger, use a shorter focal length eyepiece to get more magnification. The focuser knob is not for zooming.
  • When you change eyepieces, you will likely have to re-focus the telescope.
  • Focused doesn't always mean sharp. Too much magnification, too much atmospheric turbulence, or bad collimation can make the view blurry.
  • Don't observe the Moon when full. It can be hard to get good focus because lighting is flat. Observe it during gibbous or crescent phases.
  • A DSLR likely won't focus in a Newt. You will run out of inward focuser travel. Use a barlow or remove extension tubes as needed.

Annotated comparison of out-of-focus stars showing the expanding disc and diffraction rings

More out-of-focus examples

Each of these are examples of targets that are out-of-focus. If the view through your telescope looks similar, it means you need to turn the focus knob to bring the view into focus.