QString SkyObjItem::getSurfaceBrightness() const { /** Surface Brightness is applicable only for extended light sources like * Deep-Sky Objects. Here we use the formula SB = m + log10(a*b/4) * where m is the magnitude of the sky-object. a and b are the major and minor * axis lengths of the objects respectively in arcminutes. SB is the surface * brightness obtained in mag * arcminutes^-2 */ DeepSkyObject *dso = (DeepSkyObject *)m_So; float SB = m_So->mag() + 2.5 * log10(dso->a() * dso->b() / 4); switch(getType()) { case Galaxy: case Nebula: return KGlobal::locale()->formatNumber(SB, 2) + " mag/arcmin^2"; default: return QString(" --"); // Not applicable for other sky-objects } }