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How to Know If a Telescope Mirror Needs to Be Replaced

Star gazing is a popular hobby. Since the dawn of the 20th century, telescopes have become affordable, reliable and accurate, making star gazing easier. Unfortunately, even though they have become reasonably priced, they still require repair at times. This may include replacing the telescope's mirror when dirt, dust or other foreign objects get on your mirror, or if your mirror cracks. Knowing when to replace your mirror is the key; this isn't always easy to tell. If you are having problems with seeing through your telescope, it may be time for a change of mirror.

Things You'll Need

Reflecting telescope
Screwdriver

Instructions

- 1
  Gaze into your telescope as you normally would on a starry night. If you see dark spots, or you see nothing at all, your telescope mirror is in bad shape and probably needs to be replaced.
- 2
  Look down into the telescope tube in direct sunlight. You will see your mirror directly below. Carefully examine it from this point, and check for dirt, cracks or foreign objects blocking your view.
- 3
  Take the telescope mirror out of the telescope by removing the screws on the bottom of the tube. Once the mirror is off of the telescope, look for anything that may cause it to function incorrectly. For example, your mirror may need to be replaced if the protective aluminum coating is gone: check this by wiping your finger slightly across the mirror; if it leaves a streak, you will need to get your mirror replaced.

Astronomy