Visibility

Object visibility is measured on 0-5 scale,where 0 is invisible and 5 bright. Visibility depends on object brightness and dimensions, sky condition (its limiting magnitude - the magnitude of the faintest star one could see at zenith), telescope aperture, its passthrough and magnification (that is an eyepiece used with the telescope). Blackwell model is used for visibility calculations.

Visibility is not calculated for comets and objects with absent magnitude or dimension. For such objects visibility is considered a missing parameter. Set Empty field treatment as you need to include / exclude such objects when filtering them in the Object Selection module.

As an exception if dimension is missing in planetary nebula, minor planet, or double star its visibility is calculated as that of a star (point-like lighting source).

Detection limit is a minimum visibility threshold: when using visibility filter to look for objects only objects with visibility above or equal to the detection limit are found.