long double FocalLength=750.0; // in mm long double PixelHeight=9.0/1000.0; // in mm = 9 um long double pi=3.14159265; long double ArcSecPerPixel = ( ( atan((PixelHeight/2.0)/FocalLength)*2.0*180.0/pi )*3600.0 ); // 2.475 long double RotationEarth = (360.0*3600.0)/(23.0*3600.0 + 56.0*60.0 + 4.0); // Rotation of the earth in arc seconds per second // 15.04108444 long double Shiftime0 =ArcSecPerPixel/RotationEarth; // seconds to read one line at 0 dec // 0.164561 long double Declination=20.0; long double Shiftime = Shiftime0 / cos (Declination*pi/180.0); // seconds to read one line at Declination // 0.175122