The colour setup dialogue box allows you to choose the colours which are associated with the main components of C2A’s graphical interface. The sky background colour management area allows you to specify that you want to display a sky background colour dependent of the time of day:
You can specify the colour index range. 0 corresponds to black and 511 corresponds to blue “cyan”. The default values are 0 (black) for the night-time background sky and 126 for the day-time background sky (it is an intermediate blue which always allows you to see stars and deep sky objects on the map). Note that this option does not change the magnitude limiting the display of objects. Only the standard filter based on the zoom level is applied.
Another option allows you to take the brightness of the Moon into account in determining the colour of the background sky.
To get information about one of the components of this dialogue box, left click on it in the image below:
To display the colour setup dialogue box, use the button Colour setup... in the Misc tab of the Options dialogue box. Note that background sky zone does not appear when you invoke this Colour Definition dialogue box from the Planet Positions tool.