The Program Icon

Clicking SELECT on the program icon on the icon bar causes the Draw a Map menu to be displayed. You use this to plot a map and also to vary the settings that will be used for the next map to be drawn.

Clicking MENU on the program icon displays the icon bar menu. This is your route to other aspects of NightSky such as processing the catalogue in memory, operations on files of places and generating files of predictions for lunar occultations of stars and planets.

Various kinds of file can be loaded into NightSky, as a rule by dragging the item to this same program icon:

• Files of places : these are text files. A places file is limited to 255 locations. Each record is a single line of the file in CSV format, so they can be edited in a text editor such as Edit as well as within NightSky.
  
• Configuration files of choices that tell Nightsky how to plot a map. These too are text files and can be edited by Edit or another text editor. It is preferable to save such files from NightSky itself. If a badly-formed choices file is loaded, no error will occur, but NightSky will reinitialise itself using the default choices file specified in NightSky's own !Run file.
  
• Map instructions. These are also text files, but are stamped with file type &DFE (CSV file). They are produced by Nightsky but again can be edited in a text editor if you know what you are doing. The files in the Demos directory discussed in the tutorial are of this type.
  
• Star catalogues are contained in subdirectories of the NightSky program directory, with the largest one on the resources disc NightSky_2. Load a new catalogue by dragging the directory icon to the program icon.
  

The StarsZ directory contains all the stars down to magnitude 7.55 that can be occulted by the moon at epochs close to the present, plus a few bright stars for orientation purposes. When it is loaded constellation joins are not selectable. By excluding 90% of stars that cannot possibly be occulted by the moon, it permits those calculations to be much faster (if not fast).

The Palette Icon

When you use this icon to change display mode, or when another application imposes a new mode on the desktop display, NightSky responds as follows:

• If a map is on-screen NightSky does nothing. The Window manager will do its best to display the previously created map as faithfully as possible in the new mode. If a map has been created in a high resolution mode you can therefore select say mode 0 before printing it: this will free memory that will allow the printer driver to do its work much more quickly.
  
• With no map on-screen NightSky reorganises its memory to use the new mode for future plots. This may involve claiming or releasing memory.
  

Note that if you change mode with a map on-screen and close the map window, NightSky is still organised to use the previously selected mode. To use the current one for the next map you must select the new mode after closing NightSky's map window. Select the new mode again if you forget to follow this sequence of actions.

Remember that if you choose a mode, NightSky will try to use that mode even if it has to reduce the size of the star catalogue in memory; however if you try to increase the catalogue size (more stars), NightSky will not reduce resolution or sacrifice Drawfile saving unless the catalogue is at minimum size.

Interactive Help

NightSky provides a degree of interactive help which may be accessed by loading the !Help application supplied with your computer. The help messages generated by NightSky cover both the computing and the astronomical features of the application.

Iconised ('minimized') windows

If you Shift-click on the close icon of a map window, or other NightSky window, it is reduced to the size of an icon bar icon; that is the window disappears and a small icon is left of the desktop background, labelled with the first word of its title bar. The window remains active, and anything you could do before can still be done. In particular, in RealTime mode the window will still be refreshed at regular intervals, a process which deprives other applications of processor time for a few seconds whilst it is updating, (the hourglass will appear during this time). Double click on the iconised window to restore it to full size, or Shift-click with MENU to get the menu associated with the window, if any.

High resolution icons

If NightSky is started up in a high resolution mode, such as a multiscan mode, a VGA mode or an SVGA mode, it will use a different set of icons for its files and on the icon bar.

The Territory Manager

NightSky does NOT use the RISC OS territory manager due to problems with the current system. In the meantime it is suggested that you operate NightSky as follows.

First, ignore daylight saving time for all locations other than those in your own country. If you are in U.K. you probably neither know nor care when New South Wales goes onto or off summer time: so leave Sydney as zone +10 in the places file. If you are in Sydney, then leave London as zone 0 for the same reason.

Star maps will be correct, provided the next point is followed. When the time setting of your computer is varied to reflect the change in civil time, you need to edit the places file. In the U.K. for example, after BST comes into force you need to change all UK (and Irish) records from zone 0 to zone +1, and back again when GMT comes into use, leaving all others as they are. This actually has been done for you already, the resulting file in your NightSky directory being placesDST. All that is necessary 's to ensure that the correct file is loaded for the time of year. Follow the procedure in the box below in order to do this.

In other countries, follow the same procedure, but you also need to edit (once only) the file placesDST so that (a) places in the UK and Ireland are changed back to zone 0; (b) places in your own country are labelled with their correct daylight saving zone. This will usually be 1 hour ahead of the standard value. If you live in a place where daylight saving is not used (or in one like Singapore where it is permanent), you need do nothing: the files are correctly set up as supplied.

At the start and finish of Daylight Saving Time:

• Once, after daylight saving comes into force:
  Open the NightSky directory, with !Edit installed and double click on the file ChoicesD to load it into the text editor. A window opens. In this window, look for the line "#3 Places file...", and in it change Places to PlacesDST
  Press F3 and click OK to save the amended file.
• Once, after daylight saving ends
  Follow the above procedure, but edit PlacesDST back to Places