Palantirium

Notes on optics, small telescopes and night-sky observing.

Collimating a Newtonian in ten minutes

A cheap collimation cap and a bright wall are enough to get a reflector close to perfect. Centre the secondary under the focuser first, then tilt it until the primary is round and centred, and finish with the primary adjustment screws until the reflection of the cap sits in the donut.

Why the Moon looks best at first quarter

Shadows along the terminator give craters and mountain ranges real relief. At full Moon the light is flat, so detail disappears even though the disc is brighter.

Dew is the real enemy

A simple dew shield made of camping foam doubles the time a corrector plate stays clear. Let the telescope cool outside for half an hour before judging the seeing.