Tuesday, May 31, 2022

High Sun, Solargraphy, and Location of the Tyr Region


I wanted to do this post near the same time as the summer solstice in the northern hemisphere, June 21, the longest day of the year, but decided to do it a little early. I previously posted on solstices and equinoxes here.  On Athas, the summer solstice is also the first day of the year according to the most common calendar throughout the Tablelands. This day is Dominary the 1st and is referred to as the Highest Sun. It is the day the sun is in the sky longest and it is also the day the sun reaches its highest point of the year.  Learn more about the solstice here

Athas revolves around its sun once every 375 days. The sun is highest in the sky on Dominary first and then after that day the sun will be lower and lower in the sky each day until it reaches the winter solstice, or Lowest Sun, which occurs on Morrow the 3rd, exactly half way through the 375 day cycle. Or 187.5 days later. After that day the sun will gradually begin to climb in the sky reaching higher and higher at its zenith at noon until it hits Highest Sun again. (Please do not think that Low Sun will be hotter because “the sun is lower and thus closer to the planet’s surface, like if I get closer to a fire I get warmer” That is WRONG! It has to do with the angle of incidence - a topic for another day. 

I recently learned about a method of filming the path of the sun on a daily basis to plot the movement of the sun against the sky through the year.  This is called solargraphy. It’s typically done over several weeks or months with a pinhole camera pointed toward the direction of the sun. The result will plot the course of the sun in the sky. If started on the summer solstice and ended on the winter solstice you will get a neat plot of each day with the sun’s position clearly marked. Different latitudes will provide different arcs in the image. This short news clip video here explains it pretty well in just two minutes.  




All in all there are some amazing images that are captured using this method. I recommend you google “solargraphy” and check out some more.  There is still time to get your pinhole camera build and in place before the solstice so you can get six months worth of images.  You will want to start it by June 21st to get the full effect.

You can imagine what this would look like if done on Athas and it gives you a better idea of what Athasians would understand as High Sun and Low Sun. 

There are some pretty simple equations to calculate the position of the sun at varying latitudes for the solstices and equinoxes.  You just need two pieces of information: your latitude and your planet's tilt.



For example: I live on about 40 degree north latitude.  So, per the equation: 90-40 = 50.
Which means that when I look to the south at noon on the day of the equinox, around March 20 or September 22 the sun will be at about 50 degrees above the horizon. (Where 0 degrees is looking directly to the horizon and 90 degrees is looking directly up.) The tilt of the Earth is 23.5 degrees.

And for the next part of the equation, for the summer solstice, I just add the tilt of the Earth to that number to get 50 + 23.5 = 73.5 degrees.  And then for the winter solstice I just subtract the 23.5 from 50 and get 26.5 degrees.  Which means the sun will have a total of 47 degrees difference between the solstices (23.5 + 23.5 = 47)

You can see what happens if I live at the Tropic of Cancer. The sun will be 90 degrees above the horizon, directly above me at noon on the Summer solstice.  At the equator on the Summer solstice the Sun is now in the north sky (an answer above 90 means you have to now face the opposite direction to see the sun) It will just oscillate between the south sky and the north sky. It will stay above the 66.5 degrees above the horizon to both the south and north and on the equinox it will be directly overhead.  

Angle of the Sun on Earth

We can do a similar thing for Athas. We don't know the tilt, but for argument's sake let's assume it is roughly half of Earth's tilt, or 12 degrees.  Which contributes to its hotter climate.  This places the Tropic of Balamarash at 12 degrees North and again for argument's sake let's say the Tyr region is at the 20 parallel to the north.  This will keep the High Sun and Low Sun still discernable, but just not as extreme as what we have on Earth.  

Angle of the Sun on Athas


 If we assume Athas is approximately the same size as Earth (I believe there is plenty of good reasons to assume this: here and here). Then 1 degree latitude is equal to 69 miles (traveling north-south mind you). That would place the Tyr Region some 20*69 miles away from the equator or about 1380 miles north of the Equator. Of course you could place it in the south as well or change the tilt or latitude of Tyr.  

Here are some things to think about:

If Athas didn’t have a tilt of any kind there would not be multiple curves of varying height throughout the year  but just one curve the sun travels along each day that matches the equinox curve.  

If the tilt of the planet Athas was less than Earth’s ~23.5 degrees the distance between the highest and lowest arcs would be tighter. (For comparison Mars’ tilt is ~25 degrees and Venus’ is ~3 degrees.)

Imagine that pattern of curves permanently fixed in the sky to the south from where you live. (Assuming you live north of the equator). If you were to continuously travel south along the globe (because Athas, like Earth is roughly a sphere, not a disk) that pattern would get higher and higher in the sky, the curves would start to straighten out and go more directly from east to west to where the high sun point is directly overhead at noon on the summer solstice at the Tropic of Cancer  (The 23.5th degree north latitude) As you continue south towards the equator the entire pattern moves overhead to where the “high sun” curve is now in the north sky, and the ”low sun” curve is in the south sky. Then at the equator during the equinox, the sun is directly overhead at noon. 

If the events of Athas happened at the equator the sun would be directly overhead at noon on the equinoxes. This means that the solstices would fall equal distance to the North or South from directly overhead. There would be little ability to discern which was “summer” and which was ”winter”,  implying that instead of having a High Sun and Low Sun you would have "North Sun" and "South Sun" that corresponded to the solstices. 

If the events happened between the equivalent of the Tropic of Cancer and the equator you would have to look slightly North of directly overhead at noon to see “high sun”.  Then Sun starts to lower slightly to the north. it wouldn’t necessarily be the on Dominary 1 that the sun is directly overhead.  

If the events happen too far north or south you could get a day that the sun would not set completely on the summer solstice or a day it would not rise completely on the winter solstice. 

Based in this information I make the following conclusions. 

Athas is a planet roughly the shape of a sphere, Similar to Earth.

Athas has a tilt. It’s unknown how much, but it’s enough that it’s noticeable to distinguish between summer and winter solstices and create a a discernable "Lowest Sun" and "Highest Sun" in the skies.

The Tyr Region does not lie at the equator. 

The Tyr Region most likely lies north of the equivalent of the Tropic of Cancer.  - Tropic of Balamarash we’ll call it. Or possibly south of the equivalent of the Tropic of Capricorn - Tropic of Tasker we’ll call that one. This is strictly based on the observation of Highest Sun and Lowest Sun.

Personally, I like to believe it lies to the north, I may be persuaded otherwise if something were to turn up to convince me. But you can put your Tyr Region anywhere you like. I don't think the original authors deliberately put the Tyr Region in the north there, but unintentionally placed it there based on writings and art from their own biases and familiarity with Earth and living in the northern hemisphere. However, I cannot find any canonical references that indicates one way or another. A simple “Rikus looked south of Tyr toward the oncoming horde. He lifted his hand to shield his eyes from the sun before him” would be enough. 

Ask your players if their character is facing south at noon if the sun is in their eyes or at their back or directly overhead. They probably have their own biases based on where on the globe they live. 

And finally, some questions for all my fellow Athasians mapping the surface of Athas. 

Where is the Tyr region? 

Where is the equator? 

Where is the Tropic of Balamarash? 

And where is the Tropic of Tasker?

Hopefully this provides some insight into Athas, its sun, and the location of Tyr.


Friday, May 20, 2022

Flat Athas Society

Occasionally I see a comment or speculation about Athas not being an Earth-like planet.  Comments range from Athas being a Mars-size planet to a flat disk. Both of which I disagree with.  I subscribe to an Earth-size Athas for all the reasons it makes sense from a physics standpoint.  I do not subscribe to a flat Athas for all the same reasons I do not subscribe to a flat Earth.  Those who do believe in a flat Athas are sometimes referred to as (Flat-Athers, Flat-Ath, etc.)  However, it should be noted that Athas does have a history of belief in a flat-Athas. Read about it in Dragon Kings page 5 under the story Uncle Tontor: A Wyrm's Tale. This story and the whole flat Earth idea inspired me to create the following graphics:




Friday, May 13, 2022

Athasian Star Map and Planisphere

 Athasian Star Map



  Beautiful stars! in other days
The prophet's eye might read your rays;
And tell of many a strange event,
Of warfare, and of warning sent.
I would not wish to know the fate
Of purple crown or royal state.
The stars might show to other eyes
Their deep and mighty mysteries—
Enough for me to know them fair,
And read my lover's safety there.
L. E. L.

I was inspired to create this star map partly because I had recently purchased a planisphere for viewing constellations in the night sky. And I recently had been playing around with the calendar.  I have also been aware of a star map of Athas created by Geneome a few years ago.  

I really liked the idea of mapping out the heavens of Athas and have felt this is an area that is lacking in Dark Sun. Especially after reading several Pathfinder products; particularly People of the Stars and Distant Worlds. I tried to add in more detail than just the known zodiac constellations from the 2e Ivory Triangle supplement and I tried to make something actually useable in some manner.  So I figured I would combine a star map with the calendar information I have recently worked.  The result is a Star Map above and working planisphere below.  I used some of the methods and programs that Geneome recommended for the artwork I am not an artist by any means.  I did not follow his layout exactly, but I did try to follow it fairly closely in case other people were using his layout.  I tried to keep the orientation of the constellations similar and I tried to keep the location of large stars in a given constellation as well. I did add a few stars where I felt it was needed.

I went ahead and populated the map with a bunch of more constellations, images, and names; several of them came from what legends I could find in the DS material.  Dragon Kings had several.  I pulled art from 2e and 4e sources. I aligned the map with the corresponding months and day along the outer edge so that a front cover with a viewing hole could serve as a planisphere. If you know how one works. Great.  If not, they are pretty straight forward. Turn the date on the outer circle to the hour of the night and in the viewing screen are the visible constellations. East and West are reversed.  So be aware of that.  One way to think of it is to face north and point it north and hold it against the night sky. 

Another thing to not get tripped up on is that the month that corresponds to a particular zodiac constellation IS NOT the one that is visible at night. The zodiac sign corresponding to a date is where the position of the SUN is at daytime.  The zodiac sign sits behind the sun, but it cannot be seen because of the brightness of the sun, atmosphere, and daylight. A given zodiac constellation is most prominent at night a half a year later. For example on the year or Ral there is a lunar conjunction (eclipse of Ral crossing Guthay) at midnight on Dominary 1; the first day of the year, on the star map, directly opposite of that date you will find the constellation of Tasker the Scorpion at its zenith at midnight. This is where the moons would be visible in the sky in that constellation.

I also included the breakout of the constellations to also include the three cusps (five day festival weeks) as designated in the Ivory Triangle supplement.  I lined these up with the corresponding dates. I also added a few names to important stars and objects.  

I decided to omit the planets that Geneome had included because planets do not show up on a standard planisphere. And if you were tracking them on one somehow, they would show up along the ecliptic anyway. However, I have decided to include a few names of stars, particularly the brighter ones and also I included a few named after the seven names in the Seofean cycle, which are spaced out about 51.4 degrees apart (360/7) I am assuming that the Seofean cycle is based on a planet in the Athasian system named "Seofea" that has a seven year orbit around the sun and passes one of these these seven named stars every year in the standard Seofean cycle: Fury, Contemplation,  Vengeance, Slumber, etc.  

So here I have the image of white stars on a black background.  For the planisphere I have black stars on white background printer friendly pdf version you can print out and assemble yourself. 

Linkified Planisphere PDF

When assembled it will look like this:




Moon Calendar Update Oct 2023