I was looking through my telescope for the first time and came across this weird star. I think its a celestial donut but im not sure.

enter image description here


This is because your image is not in focus. So you’re seeing the shadow of the secondary mirror.

You should have a knob near the eyepiece, that you can turn to adjust focus. You need to turn it, one way or another, until the image is as small as possible and as bright as possible.

Good luck!

  • $\begingroup$ I am attempting to look at Jupiter and I am running into the issue that this individual was experiencing. You said to turn the focus knob until the image is as small and bright as possible. If I'm using a 10mm eye piece would this tiny spec of white light be Jupiter? $\endgroup$
    – Keegan
    Jan 9 at 5:48
  • $\begingroup$ It could be—if it’s really bright, then it most likely is, as there’s nothing as bright around Jupiter. Do you know the focal length of your telescope? Divide it by 10 (from your eyepiece) and you’ll get the magnification. If it’s under ~100× then it’s normal that it’s small and that you can’t see much detail. You should still see two darker stripes (called “bands”), though, with at least 20×–30×… $\endgroup$ Jan 9 at 8:05

This is a heavily de-focused image (possibly taken through cloud looking at the orangeish "glow" to the right). The dark center of the "donut" is the shadow of the secondary mirror centered within the image/pupil coming from the primary mirror. The focus needs to be adjusted until the "donut" shrinks down to sharper points of light or a disc (depending on whether you are looking at a star or an extended object such as the Moon or a planet)


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