Moon Phase Program

Need to know when the next few phases of the moon will be?

Time and Date dot com will give you an accurate and reliable moon phase data, should you, for example, be a werewolf. In this case, knowing the exact minute of your upcoming transformation, I imagine, would be incredibly useful information.

I am not a werewolf (to my knowledge), but I am interested in astronomy, ancient computers and a bit of paganism. Therefore, this post is about a different Moon Phase application I often run on my BBC microcomputer and Raspberry Pi running RISC OS.

I hope this post will be of use to amateur astronomers, pagans and lycanthropes everywhere. Following the phases of the moon not only provides great evidence that the world is not a flat plane but studying our celestial neighbour is very relaxing. The moon is more than just a heavenly calendar. Really.

I originally found this program on a disk of public domain software, and it was originally adapted by D. Ambrose from that given in Microsoft QuickBasic 4.5 in Chapter 1 of Numerical Recipes in Basic by J. C. Sprott, CUP 1991. I have adapted the code slightly so that it picks up the time from the BBC micro's inbuilt battery-backed clock, and I also included some nifty 8-bit graphics for the moon phases. I have also changed the date format so it uses the (more correct) IEEE standard (follow that link for an in-depth rant about the subject).

Moon Phases running on the Beebem BBC micro emulator (Note, that this BBC has not been adjusted for the millennium bug as to my knowledge it is NOT 1999 all over).

Moon Phases running on my desktop PC in BBC BASIC for Windows.

I am assuming that this program remains in the public domain, and so I present it here. You can download the code from my OneDrive, and the directory includes:

  • A BBC microcomputer disk image; 
  • BBC BASIC for Windows source code; 
  • a Windows executable file (totally not a virus!); 
  • RISC OS application for Raspberry Pi, 
  • and the source code in plain text for you to do whatever you want with. 


Have fun now.


Could win an award for the best comment ever?

+1 Geek experience points awarded to J. C. Sprott and D Ambrose.

This is all for today, but if you like this sort of thing, then you might like other posts about the BBC microcomputer, or Raspberry Pi. Maybe you just want something completely different, or you are feeling brave enough to click this link.