Tuesday, April 10, 2012

here's a thing I made

Click for a bigger if not necessarily clearer version.

I call this thing the Orrery of Sarpedon.  Sarpedon is a Saturn-like ringed gas giant in the center of the concentric circles.  The concentric circles are the orbits of Sarpedon's moons, with the partial arc showing the closest approach of a rogue moon in a particularly eccentric orbit.

Let's say that Sarpedon is in the habitable zone of its star so we can posit a science-fantasy/planetary romance style D&D campaign set on moon E, the next-to-outermost of the regular circles.  That orbit corresponds vaguely to Titan's orbit around Saturn.

In lieu of keeping strict time records and tracking orbits at the beginning of each session you can roll d4, d6, d8, d12, d16, d24 and d100 to place the moons in position around Sarpedon.  If two or more moons are placed in orbit segments that line up, like say a4 and b6, then you have a Conjunction of those two moons.  This allows for all sorts of astrologically based magical effects, like the moons in the Dragonlance books.  If the Conjunction is with moon E, the campaign homeworld, then the other moon(s) involved loom extra large in the sky and it's called a Close Approach.  Moon G becomes involved in these celestial shenanigans only when the d100 roll comes up between 37 and 68.  The rest of the time that moon is just a distant point of light.

If you feel like doing the extra work, you can advance each moon on a daily basis as time passes during the session.  Personally, I'm liable to forget to do so and would probably just reroll whenever I remembered that time had passed.

I've been thinking about this concept for a long time.  I finally made a draft of the chart in the wake of the recent death of Moebius, who would be one of the inspirational artists for a campaign set on Sarpedon E.


  1. That's quite brilliant.

  2. I like this. My preferred approach is to roll at the start of the campaign and track it from there, and using straight lines only. The straight helps keep the system to the edge of a sheet, and running from the campaign beginning gives the players more chance to plan their moves. That said, the chart looks very cool and could be something the players are allowed to see if they know the system, or glimpse in arcane locations if they don't, and the rolling every session keeps things lively for everyone.

  3. This thing you made reminds me of Spelljammer orbit charts. It is thus - references to Dragonlance aside - good and righteous.

  4. I am now imagining a campaign where you can't move through physical space at all--like every session you;r ein the same 2 block radius. But you can go anywhere you want through time. Hook up the right conjunction of Vlothurn Sporreus-3 and your enemy...

  5. The first thing I thought of was having a point where one of the other moons gets close enough to the campaign home moon that there is some way to travel between the two. I guess Anne McAffery already thought of that, but I'm not imagining it in the same way really.

    Maybe some weirdo sect of philosopher priests has constructed a ginormous trebuchet, set to hurl an iron capsule of explorers to the neighbouring moon when it comes to its closest point.

  6. For Michael Moscrip - Edward Everett Hale: The Brick Moon. Available free on Lulu. As mid 19th c sf it's gloriously free of most of the later genre conventions, and the method of launching the moon in flywheels is anti-physics genius.

  7. I did something similar but used hex paper instead. It's sitting next to my bed somewhere under my pile of books. Once I finish my Kids, Zombies, UFOs and a town losing its mind writeup, I'll finish that project.

  8. Love it! It would be an awesome prop to construct out of thin rings of copper or brass with engraved numbers for the spacing.

    As one who spends probably FAR too much time on background material of my worlds, primarily for my own joy, I'd want a quick way to run time backward and forward so I could plot a few major historical events that corresponded to the conjunctions of the various moons. If you use Excel (or any spreadsheet program) it's fairly easy to set up.

    Label Columns A through H as "Day", "Orbit A", "Orbit B", "Orbit C", "Orbit D", "Orbit E", "Orbit F", "Orbit G". (Better yet, name the moons, and use the names instead!)
    In the first row under the labels, type the following: 0, =mod(a2,4)+1, =mod(a2,6)+1, =mod(a2,8)+1, =mod(a2,12)+1, =mod(a2,16)+1, =mod(a2,24)+1, =mod(a2,100)+1.

    In this case, I decided that on Day 0, the moons would all line up in space 1.
    On Day 1, they line up in space 2. On Day 2 they line up in space 3. On Day 3 they all line up in space 4. On Day 4, Orbit A has completed, so it's back to space 1, but the rest are in space 5.

    In each column, the location will go from 1 to x over and over again.

    If you decide the actual game will start on the 1st day of the 1200th (365 day) year, that would be day (1199*365+1) or 437636, and the positions would be (A thru G): 1, 3, 5, 9, 5, 21, 37.

    Of course, it's easier to build the spreadsheet than explain it coherently... and it wouldn't be worth it without having the chart to set up for each game as a cool visual.

  9. Awesome, just awesome.

    Have you considered adding a final ring surrounding all the others to represent the sun? You could divide it into twelve large sections labeled for the months to show it's relative position throughout the year. Or just write a season along the margin on each side of the page I guess.

    Then you'd be able to track possible eclipses, like when the Saturn planet passes between the PC's moon and the sun.

    1. On second thought... instead of dividing the sun's ring into months it might be cooler to divide it into constellations. Having "a conjunction of three moons during August" is cool, but having "a conjunction of three moons while the sun is in Schleevak the Hydra" is awesome.

  10. This is fucking beautiful.

    I wouldn't have read past the first line, though, were it not for the word ORRERY, which -- as a Little, Big fan like every right-thinking lover of books -- has a place in my, y'know, my heart.

    I'd want the moons to have really severe effects on e.g. the efficacy of magic spells though. Or the thickness of Moon-G-sensitive creatures' hides, or don't tell the PCs but when three moons align all gold pieces turn to silver for a day (or vice versa, bad luck for werewolf-slayers and mom'n'pop shopkeepers); or some creatures abominate one moon and are in aching lust with another (and turn violent when they are thwarted in their randy doings/humpings).

  11. Very nice.
    Since my Weird Opera campaign takes place on the moon of a gas giant, I have been thinking of doing something like this myself. However, the planet has 72 moons, so an orbit chart would be a bit impractical. I still need to figure out some other way to figure out conjunctions.