What is telescope collimation?
Steve says: "Collimation describes how accurately the optical elements in a telescope are aligned with one another and to the optical tube that contains them.
Irrespective of whether the telescope is a refractor or reflector, it is necessary for all the optical elements to be accurately aligned to achieve the best views or images from the scope’s design.
A badly collimated telescope will display poor star shapes and other aberrations that will spoil the view.
It is also important that the optical elements are aligned with the tube assembly, otherwise there can be problems with aligning the focuser, which is a purely mechanical part of the instrument."
For more on this, read our guide on how to collimate a Newtonian telescope.
Email your astronomy queries to Steve atscopedoctor@skyatnightmagazine.com and they could get answered in a future issue of BBC Sky at Night Magazine.
