This chart shows the phases of the two moons orbiting my D&D world, and how my race of werewoles called the Wolvega respond to them. The blue moon controls how easy it is for the Wolvega to transform into their wolf shape. They can transform at will, but their power is strongest (and transformation easiest) when the moon is full. The red moon controls their alignment. They are net-neutral creatures, connected intimately with nature. They are not truly good or evil, but wax and wane between the two. They have their own rule of law, but also think about this very differently than the humans do. The profiles at the bottom correspond to the visible area of the disc of each moon throughout the cycle, and the purple profile (blue+red) shows the combined area, representing the times that humans would consider the Wolvega most or least dangerous to interact with.

Download the chart as an image.

I had decided a while back that my D&D world has two moons. I thought it would make the world more interesting, and provide for some unique lore, ritual, and tradition. So of course, I had to decide what lycanthropes (werewolves and other were-creatures) would be like, and how they would react to the phases of two different moons. I thought it would be much easier to think about and plan for the moon phases if they could be mapped out in a consistent pattern over a consistent period of time. That creatures might evolve to respond to the moon phases is a much more compelling idea if they are in an orbital resonance than if they had no regular pattern at all. Read more about orbital resonances over at the Planetary Music Box, but basically it’s when the moons each orbit the planet at a set ratio of time relative to each other. So for two moons with a resonance factor of 2:1, Moon A would orbit the planet twice for each one orbit of Moon B. This also means that the two moons would pass each other in the sky at the same time each lunar cycle.

So, first I had to figure out how to create a small terrestrial planet with two moons. See, many planets (especially the larger ones) have captured moons- objects from the asteroid and the Kuiper belts that just kind of passed by in their orbit around the sun, and the planet’s gravity captured them into orbit around themselves. It’s easy to get these kinds of moons into resonances, but it’s hard for small planets (with low gravity) to capture things. This has to do with the speed the moons are moving and other factors- this is really not my area of expertise, so I talked to my colleagues Dr.’s Kat Volk and Christa van Laerhoven who are dynamicists. They told me that you could probably have a terrestrial planet like Earth that had two moons formed by a giant impact, like how our own moon formed. Earth was hit by a large, planet-sized object that caused a bunch of material to break off and the upper layers of the earth to melt. The impactor also broke apart, and all that material swirled around in a debris disc around what remained of Earth. Eventually, gravity caused the debris in the disc to coalesce into our Moon, and whatever wasn’t collected into the Moon was either ejected from the area entirely or rained down onto the Earth. There’s a whole bunch of cool simulations of giant impacts on youtube.

So anyways, all this to say that we think you could create a terrestrial planet with two moons that formed this way. In order to get the moons into a resonance, there has to be an exchange of momentum. The moons gravitationally interact with each other- pushing and pulling and nudging. If the inner moon is moving faster than the outer moon, then the outer moon’s gravity will pull on it, slowing it down little by little each time it passes by. Eventually it will balance out into a stable resonance. The moons also interact gravitationally with the planet, raising tides on the surface. This sucks away some of the planet’s angular momentum, which causes it to slowly despin and the moons to slowly retreat outward. Next on my list is to do a tide chart, but I haven’t gotten to it yet. Moons can get captured into resonances with different resonance factors. The simplest and easiest to develop are a 2:1 or 3:2 resonance, but some truly wacky things can happen. I tried mapping out the moon phases for each case, so see what they would look like:

It turns out that in both cases, you can never get a double full moon AND a double new moon. You only ever get one or the other. Interesting! I opted for the double full moon, since it would have a more dramatic appeal in the context of werewolves. I went with the 3:2 resonance, so the outer moon orbits twice for each time the inner moon orbits three times. I made the lunar cycle of the outer moon the sane length as a month on earth so it would be familiar to the players. So each full moon cycle is two months long. One of the moons orbits slightly at an angle to the other, so you don’t get an eclipse each month when they pass each other in orbit, but it does occur occasionally.

The werewolves in my world are called the Wolvega. They aren’t monsters, they’re a minority race of humanoids that are persecuted by the dominant human presence in the region. They developed a strong connection with the moon in their early evolution. Their lore goes that the moon’s magic is beamed down upon the planet along with the moonlight. This is then taken up by the Moon Trees, sacred trees that spread the magic out throughout the forest through their roots. It is said that on rare occasions (such as eclipses, when no moonlight is present), the trees are unable to pull the magic from the air and it hangs in the woods like a mist. They have an ancient spell, a song, a lulluby really, which they sing to their children that distilled the moonlight out of the air during these times, and drew it into their children’s bodies. This is what gave them their Wolf’s Blood, their ability to transform, and their magical connection to the moons. One of the moons controls how easy it is for the Wolvega to transform into their wolf shape. They can transform at will, but their power is strongest (and transformation easiest) when the moon is full. Wolvega that are younger or have less control over their powers may voluntarily be locked up during full moons, but most adults can control when they want to transform. The other moon controls the Wolvega’s alignment. The idea is that they are net-neutral creatures, connected intimately with nature. They are not truly good or evil, but wax and wane between the two. They have their own rule of law, but also think about this differently than the humans do. Their customs and traditions are also foreign, and the clerics of the nearby city believe them unnatural. This has caused conflict between the peoples, which lead to war and their persecution. Anyways, I won’t get into the whole history here but they are a very interesting people!

The profiles at the bottom of the chart correspond to the visible area of the disc of each moon throughout the cycle, and the purple profile (blue+red) shows the combined area, representing the times that humans would consider the Wolvega most or least dangerous to interact with. I wanted to do this based on the actual brightness of each moon, but moon brightness does not increase linearly with visible area. The moon actually gets bright extremely rapidly as its visible disc increases because of the way that light scatters off the extremely fine grained dusty material which covers its surface. There is not a trivial way to calculate this, and it proved more complicated than I had time for. I’ll leave this upgrade to the chart for future astronomers in my D&D world to discover. There’s a good discussion of other factors that go into how bright the moon appears here.

Ok, on the crafting part of this! I thought it would be really cool to make an embroidered tapestry of the chart. I recently bought an embroidery machine, and it has been a grid learning how to use it. The machine itself is easy, but let me tell you the available software is BADLY LACKING in features and usability. It’s all a giant mess. I do most of my image processing and preparation in Illustrator, and then I import the vector images into Embird (which I have to run on a virtual machine) to convert them into the special embroidery format the machine can read. I have to use two different Embird programs, which both have astonishingly terrible UI’s and inexplicably do maddening things that only create more work for you. There is apparently some nicer software, but it costs like $6k which is ridiculous. Ultimately I think these machines and their software are made for a market that doesn’t necessarily embrace technology- these companies could be making products for modern makers like me, but they aren’t. It’s a shame, really. There’s a market in people like me, like you, dear readers.

One of the most annoying things about the machine is that you have to load (temporarily, I might add) every pattern you want to stitch onto it using a flash drive. With my Silhouette, I’m used to interfacing directly with the machine through the software. This option wasn’t available that I could find- there was one brand new Singer machine that did it, but I couldn’t try out the software first to see if the higher price tag would be worth it. With a computer interface, you can do things to manipulate the designs and send them directly to the machine to try- then tweak and send again. The thumb drive adds so many extra steps to the whole process. Also, the features for splitting a design into multiple panels (my hoop size is only 5×7″) are useless, so I had to come up with my own method for this. Here is how the stitching went. First, I split the design into 10 5×7″ panels.

The moons and other parts of my tapestry didn’t split easily into multiple panels, they actually had to overlap each other. So I overlapped the panels by a couple centimeters at their tops/bottoms. To be able to line them all up properly, I added a 5×7″ bounding box inside my actual design. That way, the machine would automatically fit the box to the largest stitchable area, which is now the same size as the 5×7″ hoop, and then I know all the pieces inside the box are where they are supposed to be. The clear grid ruler that comes with the hoop has helpful holes in it, and I used white colored pencil to mark a grid onto my fabric. This way, when I loaded up a panel in the machine, I could align the fabric using the rule and the grid dots I’d drawn:

So far so good! The first panel came out great! The way it works is that it stitches the parts in whatever order you put them in in the digital file, and it stops and asks you to change the thread between colors. I made the 5×7″ bounding box in my design file a seperate color and put it at the end, so when it got to that point I could just cancel the rest and skip the stitches. Sometimes it put it at the beginning, but there are buttons to move forward/back in the pattern which enables you to skip stitches. Once it stitches, you can just snip away the extra threads it leaves between regions. Oh, and I used a cut-away stabalizer on the back of the fabric since it was kind of thin.

A video of the machine at work:

Then I went to line up the second panel to its right and somehow everything seemed off by about a centimeter. I realized with angry horror that stitchable area inside the hoop is not symmetrical, and in fact the clear grid ruler has a marking on it to make sure it’s in the right orientation. But I had had it upside down when I put the fabric in the hoop and hadn’t noticed, because it’s clear and because who in the hell would design a machine with an asymmetrical stitch area inside the damn hoop!!!!!! I almost threw my chair at this point. But it’s ok, it just means I have to line up the left panels with the ruler upside down, and then when I do the right panels turn it right side up again  😡 But I made I made it through a few panels without incident – great! Then I stitched panel six…and somehow this was off by 1.5 cm. But wwhhhhyyyyy? I had the ruler upside down the way I was supposed to—OHHHH. I had it rotated 180 degrees but not also flipped upside down, so there was more than one way to put the ruler on wrong. I ended up having to take all these stitches out (which takes hours, btw) and redo it. Uggh. But lesson learned about the ruler, I’ll never make that mistake again. Shots below show the progress up until panel six, which is offset to the right.

Went through the rest of the panels ok. When I got to the tree in the middle, it told me it was going to take 71 minutes to stitch so I left it alone. This proved a bad idea, as I hadn’t realized that it made my bounding box the same color as the tree. This means it didn’t stop and wait so I could skip the bounding box, so I had more stitches I had to painstakingly remove. The other lesson I learned was not to be lazy about editing where different parts of the stitch pattern begin and end. It really helps when you want to make sure something is lined up correctly that the place where the needle starts is a part of the pattern you can measure needs to be x cm to the left of the embroidery already there. Really, 90% of machine embroidery is making the files properly, and if you do that right then lining up and stitching it is simple. A few more in-progress shots:

So here it is, my finished tapestry! In the end, it turns out a bunch of stitching and stabalizer don’t iron into a flat tapestry very well. But once I got it hanging up it doesn’t look bad! I used a poster hangar I found on amazon comprised of a couple slats of wood with magnets between them to frame the piece a bit and make it easier to hang. Wall space in the game room is limited, but I hung it on the side of the book case. Really this is just something I made for the fun of it. The players didn’t actually need the chart for anything. I could have designed the sessions with the werewolves so they did, but it wasn’t ready yet. So instead it just serves as a beautiful, tactile prop that adds some richness to game play and to my D&D world.