A laser collimator makes it possible, which is most of its appeal. A star test confirms the result without any tool at all, and the two together are a five-minute routine rather than an evening.
The procedure is the same in the dark as in daylight; only the tool changes.
Why a laser suits the field
It projects a visible mark, it works with no ambient light, and it needs one person. That is the whole case for it, and it is a good one.
Check the tool first
Rotate it in the focuser and watch the dot. If it traces a circle, the laser is out of true and will confidently aim the telescope wrong. Look for one that can be adjusted in its own body, and test it once in daylight.
Then the star test
Defocus a bright star a little and look at the rings. This is the confirmation, and it costs nothing. If the rings are concentric, the job is done whatever the tool said.
What to do about focuser slop
Any play between the tool and the drawtube tilts the tool, and the tilt goes straight into the result. Tighten the compression ring gently and consistently, and use the same orientation each time.
The questions that keep arriving
What is a star test?
Defocus a bright star slightly and look at the pattern. Concentric rings mean the mirrors are aimed at each other; rings offset to one side mean they are not. It needs steady air and a tracking mount to be comfortable.
Should I collimate before or after cool-down?
After, if the tube has moved temperature significantly — some designs shift slightly as they settle. For a quick check on arrival, before is fine.
Last reviewed 17 September 2026