How Ascendants (Rising Signs) Are ACTUALLY Calculated
wtf is a rising sign? and can you believe astrologers used to calculate them by hand?
I’m a 21st century astrologer... I love the internet and Astro Wiki. I consistently have at least 15 tabs of charts pulled up at any given moment. I love switching between Placidus and Whole Sign house systems, and I love tinkering with all the chart settings on astro.com.
I really cannot imagine being an astrologer in the age before technology. Not just before the Internet, where you can find the birth data of nearly every famous person or event, but before the age of computers, period. Before astrology software that can cast charts for you. Whenever you wanted to look at a chart, you had to use an EPHEMERIS and draw the chart BY HAND!
We are truly spoiled rotten nowadays.
A few years ago, when I was finding my footing as an astrologer, I became interested in learning the art of casting a chart by hand. Using an ephemeris was straight forward enough, but the concept I found the most confusing and elusive was the ascendant. The ascendant moves pretty fast, changing by the minute (this is why EXACT time in astrology is so important). How could it be calculated so precisely without using a computer?!
What is the ascendant?
When learning astrology, you often see the ascendant, or rising sign, described as “the sign that was rising over the horizon when you were born.” When I was a beginner, I only half-understood this concept, so let me break it down for you:
→ Astrology uses a geocentric POV, meaning the Earth is at the center of the universe, surrounded by the twelve constellations (or signs).
→ If you were to step outside and look East, one of those signs would be rising over the horizon.
→ Earth is always rotating, so every 2 hours or so, a new sign would be coming up over the horizon.
Take a look at this diagram, compared to a birth chart:
As an astrologer, I believe it is imperative to understand the foundations of astrology, even in today’s age when we have computers that can do it all for us. So, let’s dust off the ephemeris, crunch some numbers, and dive into our studies. I promise it’ll be interesting—I PROMISE!
How Ascendants Are Calculated
In this article, I will break down two methods for calculating the ascendant: the ~rough & dirty~ method and the more precise, ascendant tables method.
Rough & Dirty Method
As a rule of thumb, the ascendant at sunrise hour is the same as the Sun sign, as the Sun rises every day in whatever sign it is in. So, if you are Capricorn born at sunrise, your ascendant is also in Capricorn.
Astrologers can do “magic tricks” using this concept. For instance, if a client doesn’t know their exact birth time, I will cast a sunrise chart so that the Sun is exactly conjunct the chart’s ascendant. This way, I can still give them a decent reading by anchoring the chart around their Sun. Astrologers also use a similar method when writing pop horoscopes (assuming the Sun as the Ascendant when making predictions). It is also how astrologers can look at a chart and approximate the time of day without knowing the details. For example, if your Sun and Rising are in opposite signs, I know you were born at sunset, without needing to look at your exact birth time.
Normally, the ascendant changes signs every two hours. To arrive at the ascendant quickly, you can fix the sunrise hour over the eastern horizon to your Sun Sign at 6 am. So, if you are an Aries born between the sunrise hour of 4 am to 6 am, you would have an Aries ascendant. From 6 am to 8 pm, there would be a new sign rising over the horizon, clockwise this would be Taurus. Every two-hour period, the sign would shift… from 8 am to 10 am, Gemini; from 10 am to 12 pm, Cancer; and so on.
Why is this method so ~dirty~, you ask? For one, it assumes that the sunrise time is constant throughout each zodiacal season, but we know that the sunrise time shifts a little bit every day. It also doesn’t take into consideration the birth location (more on that later). It doesn’t adjust for daylight savings. Finally, it depends on sun sign astrology, and we astrologers know that there is so much more beyond the sun sign!
This is easier method to conceptualize when looking at quick ascendant tables, like this one from lunarliving.org:
Here is another example of a quick ascendant table from astrotrends.net. This one is actually worse because the hour ranges are incorrect, lol.
This quick method is best used if you are only interested in finding the rising sign, not degrees. Even then, it doesn’t always work. To be more precise, you would have to use the…
Ascendant Table Method
This is going to seem like a lot of math–but stick with me, babe!
Back in the olden days (aka before astrology software), astrologers used ascendant tables to calculate risings. These tables would be set to specific latitudes, and the astrologer had to adjust to the latitude of their (or the subject of the chart) birth by adding or subtracting to the degrees in the table.
I first learned this technique from a 1971 book, A Time For Astrology by Jess Stearn. (I strongly encourage astrology students to pick up older astrology books every once in a while, they are fascinating and deeply insightful!!)
˚ ༘♡ ⋆｡˚ I scanned the tables in the book and you can access them here to try to calculate your own ascendant! ˚ ༘♡ ⋆｡˚
Step 1: Finding Latitude & Adjusting to Ascendant Tables
For the sake of this article, I will use the Ascendant tables that are printed in this book. These specific tables are set for 41 degrees latitude, roughly a line crossing New York, Chicago, Omaha, Salt Lake City, and Eureka. Before modern technology, an astrologer would have to use a map to find the birth location coordinates; now we can use a website like latlong.net.
As a quick refresher, latitude are the vertical lines that run up and down Earth, depicting how far north or south of the equator the location is, with 0 degrees being the equator and -/+ 90 degrees being a pole. The sun rises in the East, so picture it crossing over each latitude line as it rises. This is why we use latitude rather than longitude.
To be really precise in your calculations: if you're using tables set for 41 degrees latitude, but the birth location has a different latitude, you'll need to adjust for that difference in your arithmetic.
This explains how it’s possible for babies born at the exact same moment to have different ascendants, therefore different manifestations of the same planetary alignments. For instance, a baby born in Chicago, USA and a baby born in Sydney, Australia at the same time would have different ascendants. How cool is that!
But let’s keep it simple and avoid unnecessary calculations, and assume that our birth location is right at 41 degrees (in alignment with the tables in my book).
Step 2: Using the Ascendant Tables
Now let’s take a look at the tables themselves. Here is a snippet from my book:
These tables are set specifically for dates approximately two weeks apart. Let’s say the querent was born on March 14th at exactly 4:00 pm. This would give them a Virgo Ascendant at 0 degrees. If they were born at 4:30 pm, we would take the difference between the 4 pm ASC (0 degrees Virgo) and the 5 pm ASC (12 degrees Virgo). In this case, they would have an ASC at 6 degrees Virgo.
Remember, each sign spans 30 degrees total: from 0 degrees to 29 degrees. So if they were born at 11:30 pm, we would calculate halfway between 23 degrees Scorpio and 5 degrees Sagittarius and get an ASC of 0 degrees Sagittarius.
What if the birth time isn’t on the hour or half hour, like 4:44 pm? The math is actually pretty simple, we must calculate the degrees per minute. Using our previous example of March 14th, the difference between the 4 pm ASC and the 5 pm ASC is 12 degrees. This works out to 0.2 degrees per minute (12 degrees / 60 minutes = 0.2), which means a birth time of 4:44 pm would give an ascendant of 8.8 degrees (0.2 * 44 minutes = 8.8). You can do additional math to figure out the degree minutes, or simply round up to 9 degrees.
But what if the birth date falls between the two dates listed, like on March 20th? We would use a similar calculation to determine halfway between the dates listed. If they were born at 10 am, we would look at the degrees for 10 am in each table: 14 degrees Gemini in the March 14 table and 26 degrees Gemini in the March 26 table.
The difference between the two tables is 12 degrees, averaging out at about 1 degree per day. Thus, from March 14 to March 20, six days, add 1 degree per day, and you have an ascendant at 20 degrees Gemini.
Step 3: Casting the Chart
When using this method, it’s easiest to use either Whole Sign or Equal Sign houses:
Whole sign: each house cusp begins at 0 degrees. Place the ascendant at its respective degree.
Equal sign: each house cusp begins at the Ascendant’s degree. If your ascendant is 5 degrees Capricorn, then your 2nd house would start at 5 degrees Aquarius, third house at 5 degrees Pisces, and so on.
Once the houses are created, an astrologer would use an ephemeris to locate the other planets and place them in the chart.
Casting a chart by hand is a beautiful art, as it forces you to move slowly, take in every single placement, draw the aspect lines and ponder how the planets are all communicating with each other. If you are curious about a tutorial on how to draw a chart by hand, let me know! I do have a YouTube channel now, after all ♡
Not All Ascendants Are Created Equally
While studying ascendant tables, you may notice that some signs take longer to cross the horizon than others. Because of Earth’s tilt, the twelve signs do not take the same amount of time to cross the eastern horizon. This is also relative to latitude; at the equator, there is very little difference in time, but larger and larger differences emerge as you move further north or south.
From Astro Wiki: “In the northern hemisphere, the signs of Capricorn, Aquarius, Pisces, Aries, Taurus and Gemini take much less time than the theoretical two hours to cross the eastern horizon, whilst the signs of Cancer, Leo, Virgo, Libra, Scorpio and Sagittarius take much longer than two hours to do so.”
Pisces and Aries are the fastest moving ascendants, taking only one hour to cross the horizon. Meanwhile, Virgo and Libra have an ascension of two hours and forty five minutes. At higher latitudes, the differences are even more dramatic. In the southern hemisphere, the ascension lengths are reversed.
This further makes birth charts more unique to the individual, especially when cast using a house system like Placidus. For example, take a look at the insane houses in the chart of Gordon Ramsey, who was born at a very northern latitude:
This is also why the ascendant table method is more precise than the rough & dirty method. The dirty method assumes that the ascendant changes every 2 hours, but that is dependent on one’s latitude and location of birth.
Conclusion
Hopefully now the “the sign that was rising over the horizon when you were born” definition of the ascendant makes a bit more sense! I also hope that you step away from this article with a newfound sense of gratitude for astrology software and modern technology… because could you imagine doing this for every single chart you want to cast?!
Let me know your thoughts, questions, and insights in the comment section below! And I’m curious… what is your rising sign? ♡