Observer guides — TelescopeTo

Practical guides to telescopes, eyepieces, observing conditions and safe equipment use.

Start with your observing site, transport limits and the objects you genuinely want to see.

Magnification is telescope focal length divided by eyepiece focal length; exit pupil is aperture divided by magnification.

Apparent field describes the eyepiece viewing impression; true field is the patch of sky visible through the telescope.

Choose the Moon, planets, double stars and bright clusters before attempting very faint galaxies.

Split the list by season and by objects visible from your latitude.

Never point a telescope, binoculars or camera at the Sun without a special-purpose solar filter secured over the front of the optics.

Collimation is the correct alignment of optical elements with each other and the mechanical axis.

A temperature difference between optics and ambient air can degrade the image even with good collimation.

A dew shield reduces radiative cooling and may be enough in light humidity.

Seeing describes image stability; transparency describes absorption and scattering in the atmosphere.

Limit bright screens and direct light before observing faint objects.

Record date, object, instrument, eyepiece, magnification, conditions and one concrete detail.

Sketching encourages longer inspection and comparison of detail without requiring photography.

Do not clean optics merely because a few dust particles are visible; frequent touching can cause more harm.

Image scale combines pixel size and effective focal length to show arcseconds per pixel.

Protect optics from impact, but do not seal damp equipment in a case.