Visibility Index

Visibility Index is a short coded description of the appearance of the object. How easy it is too see, and is there any details visible with unaided eye?

There are three groups on codes:

1234 npsm fc

• visibility class:
  • 1 easy
  • 2 moderate
  • 3 difficult, possible with average eyesight in good conditions
  • 4 very difficult, possible with good eyesight in good conditions, or suspect visibility
• appearance:
  • n nebulous or glow
  • p starlike (with nebulae)
  • s one star
  • m multiple stars
• details, shape, color:
  • f recognizable shape or details, "features"
  • c color visible
  • none no shape or details

Examples

• 1 m f = easy, multiple stars, details or shape
• 2 nm f = moderate easy, nebulous with multiple stars, details or shape