Once a year: what has quietly worked loose

Do this in daylight, indoors, with the equipment on a table. None of it should cost an observing night.

Collimation and the tool that checks it

Collimate the telescope, and first check the tool: rotate a laser collimator in the focuser and watch the dot. If it traces a circle, the tool is out of true and has been aiming your telescope wrong.

Every screw that holds something to something

Finder bracket, dovetail bolts, tube ring screws, tripod leg fastenings, the retaining bolt at the end of a counterweight shaft. All of them loosen with handling and temperature cycling, and the last one prevents a predictable accident.

Batteries and cells

The coin cell in a red dot finder, the cells in a handset, the pack that runs a dew heater. Replace the coin cell whether or not it still works, and keep the old one as the spare.

Optics, inspected rather than cleaned

Look at them under a torch and resist the urge. Clean only what is actually scattering light — a dried dew film, a fingerprint, sap — and follow the maker’s guidance for that coating.

Focuser and mount movement

Run the focuser through its travel feeling for roughness, and check for sideways play in the draw tube. Move each mount axis through its range with the clutches loose, feeling for tight spots. Both are adjustable on most equipment and both get worse if ignored.