Select Page

Tropical vs Sidereal Astrology

UPDATE February 23, 2021 ➡️ Since publishing this blog post, I’ve learned that vedic sidereal astrology and how it’s used to calculate human design charts is different from what’s being called “true sidereal” astrology, which meant to be more accurate based on where everything actually was at the time and place of your birth. See Richard Mason (“Cosmic Human Design”) for more information on this.

UPDATE 2 February 23, 2021 ➡️ MOST of my comments below about the differences in my chart are from the perspective of “Do I see myself in my chart? Human design is actually about EXPERIMENTING. It’s not abut whether you see yourself in your chart or not – validating your chart can only be done through experimentation. SO, keep that in mind when reading my comments 😆

As a result of these updates, I will be further updating the below post once I receive my true sidereal human design chart, so the post will become a comparison of all three.

Here’s the post as it was published on February 17, 2021:

So…I’m not an astrologer, I’m just sharing what I’m learning as I’m learning it.

I first heard about sidereal (vedic) astrology through Tiffani Purdy (@newparadigmbizbestie) who started sharing her perspective on discussions happening in the human design community. I’m not “in” the HD community, so this was all new to me.

Tiffani has shared her thoughts on HD being treated as dogma, or an infallible belief system (it’s not), as well as about the “founder,” Ra Uru Hu (Robert Krakower).

I’m not going to get into all that, because it’s a conversation I’m not really part of, nor do I know much about it; however, reading Tiffani’s recent posts and listening to this IGTV got me very curious about the whole tropical vs sidereal astrology situation.

Apparently (again, not an astrologer), tropical astrology is not very accurate in terms of the actual placements of the stars and planets.

As per a very informative Wiki article:

Sidereal astrology uses corrective systems known as ayanamsas (Sanskrit: ‘ayana’ “movement” + ‘aṃśa’ “component”) to account for the precession of equinoxes, whereas tropical astrology does not use such measures. This has caused the two systems, which were identical around 2,000 years ago, to drift apart over the centuries.Wikipedia + various cited sources within said Wikipedia article

SO, 2000 years of drifting apart could result in some major differences in how a human design chart is calculated, no?

I was extremely curious, so I upgraded my Genetic Matrix* account to pro just so I could calculate my HD chart using sidereal astrology (*affiliate link).

Some people’s charts are completely different. For example, Tiffani Purdy shared on her IG account that tropical astrology said she was a manifesting generator, but with sidereal, she’s a projector. Those are two extremely different things.

BIG LESSON: No chart can define you. Trust yourself, your body, and your intuition.

Below are two charts – both mine – according to the two types of astrology. First, tropical, which is the chart I’ve been working with for over a year. (Find my thoughts on the differences at the end.)

My Human Design Chart: Tropical vs Sidereal Astrology


Tropical Astro HD Chart Sidereal Astro HD Chart
Type Splenic Projector Splenic Projector
Profile 4/6 – Opportunist / Role Model 2/4 – Hermit / Opportunist
Definition Single Single
Incarnation Cross RAX Rulership 4 RAX Contagion 4
Channels 26-44 Surrender
28-38 Struggle
18-58 Judgement
Determination High (sound) Cold (thirst)
Cognition Smell Inner Vision
Brain Active Passive
Environment Markets (External/Observer) Caves (Selective/Observed)
Motivation Need Hope
Trajectory Master Anti-Theist

(There are more elements in a chart, but I’m only looking at aspects I’ve explored/understand at this time.)

My human design chart based on tropical astrology

My human design chart based on sidereal (Vedic) astrology

My Thoughts

The similarities

In both charts, my type comes out as a projector with splenic authority, and single definition

This has always felt true for me. I don’t make “projector” my identity, but I do identify with the projector type.

All of my previous open centres have remained open.

That pretty much sums up everything that’s stayed the same. Type itself is maybe the biggest part of the chart, so overall, things feel pretty familiar.

The differences

While my open centres remained open, this new chart shows that I have one new open centre: the heart/will centre. This actually makes a lot of sense, because so much of my journey (and the things I talk about now on social media), have to do with worthiness, which is a big theme of an open heart centre.

My gates are pretty much all different, and I won’t go through each one, but I will say that after reading about each one, some of them feel SO true and totally me.

I used to have two channels through the spleen centre (26-44 – Surrender and 28-38 – Struggle) and now I have one: the 18-58 channel – “Judgement.”

The Channel of Judgment is purely projected, meaning it serves best when others ask for it. It contains the intuitive and energetic ability to make things correct in order to create a perfect expression of the Joy of

I’m very into joy, and creating and living a joyful life, so that checks out. Further:

This energy is also exceptionally difficult for Projectors. The bottom line of this channel is that in order to be heard and for you to have the platform to correct in a “correct” way, you MUST wait for recognition if you have this channel. If you do not wait, then you run the risk of being perceived as critical by others and no one likes to be criticized. The beauty of this channel is that the correction in the 18 leads to the 58, the Joy of Life. When the 18 waits to be recognized, they clear the path for the perfected expression of the Joy of Life…

So, doubling down on the “waiting for the invitation” projector strategy it seems.

Going back to the two channels in my tropical chart for a second…

26-44 – Surrender:

  • This channel is about improving upon old concepts and replacing the old with the new. It’s also called the “channel of the entrepreneur” (LOL because I quit my business 😂) for its ability to recognize what will appeal to others.

28-38 – Struggle

  • This channel is about the struggle to find purpose, and the deep sense of searching for that. I generally “struggle” with the concept of “purpose” because I think our current use of it in society doesn’t quite make sense, but I don’t know if as a person, I really feel the need to have my own individual purpose (beyond truly enjoying life), ALTHOUGH I have thought I needed one in the past, which is a whole discussion we could get into.

So far, in terms of channels, the “new” 18-58 Joy of Life channel feels more relevant to me.

Let’s move onto profile.

My tropical astro HD profile was 4/6 – Opportunistic / Role Model.

My sidereal profile is 2/4 – Hermit / Opportunist.

So, I guess technically part of my profile also stayed the same.

The 4/Opportunist part has always felt true for me. This line is less about being greedy and manipulative (though I guess it could show up that way), and more about realizing opportunities through your network.

Looking back at various opportunities I’ve had, many of them have come through my network and relationships in some way.

Whenever I read about the 6 line, it always seemed like it didn’t really come into play until the last third of your life, when you emerged as a role model from your life experiences. Because of that, I always just kind of ignored it because it didn’t have relevance “today” 🤷.

Now, the 2 line (as per my “new” chart) – this is someone who needs their alone time to cultivate their skills and interests (which also sounds very projector-y). As you can imagine with the archetype of “hermit”, someone with this line likes to be comfy and cozy and is a bit of a homebody. But not JUST a homebody – more like an introvert/extrovert combo. 2/4’s have a natural talent that comes so easily to them, that they probably have a blindspot for it, but friends/family could probably pick it out immediately (Emma Eklund).

I often feel like I don’t really know what I’m good at (apart from everything, duh 😜), so I’ll probably need to ask around as part of my ongoing HD experiment.

Moving onto determination, my tropical astro HD chart shows high (sound), and my sidereal astro HD chart shows cold (thirst).

I just shared in my IG stories about how I’m experimenting with my determination and having sound whenever I eat. My tropical chart also showed an active (left-facing) digestion arrow (top left), which suggests regular, consistent meals.

Now, I actually have found that my digestion has improved by being more conscious of my “high sound” determination; however, hold that thought, because I have a theory.

My sidereal determination is cold (thirst) with a passive (right-facing) digestion arrow. This means I would benefit from eating things cold and/or raw (i.e lots of uncooked veggies and fruits), and from having (cold) liquids with me – and always staying hydrated (but, hey, we all could benefit from that!).

So, first, I literally always have multiple liquids around me. I usually have tea, my water, maybe a shake or smoothie, etc.

The tea starts hot, of course, but I always, always drink it slowly. This means that for most of my tea-drinking experience, the tea is luke-warm or on the cooler side.

Passive digestion means eating more intuitively – when you feel like it – rather than regular, consistent meal times. 

During my experimentation, I tried to eat more regularly and consistently, with a bunch of smaller snacks and meals throughout the day. But, honestly, I find that exhausting. It’s like, constantly thinking about food.

Thinking back to my high school, university, and office life days, I would always have loads of snacks packed/with me in case I got hungry. I was naturally planning to eat intuitively. Sometimes I’d eat all my snacks, sometimes not. The thing is, I didn’t know how much I would want, so I’d pack for “just in case.” Without realizing it, I was catering to intuitive, passive eating.

“But wait, didn’t you say that eating based on a high sound determination and active digestion helped?”

Yes, I did say that. Here’s why I think it worked:

While I was “trying” to be more regular and consistent with meals, I wasn’t actually that consistent. It was more intuitive.

ALSO, mixing in cognition (because it’s all interconnected), my chart went from a smell cognition to an inner vision cognition.

Smell cognition is like literally being able to “sniff out a rat” or “smell something fishy,” but it’s also needing to enjoy the actual smells around you. And, when living “correctly” this is the sense that would become strengthened. It’s like a super sense – the ability to sniff out hidden, energetic frequencies (Vaness Henry’s blog).

Inner vision cognition is more about mindfulness and the actual vision you have for yourself and your life – like visualization in manifestation lingo. Plus, one of your highest potentials with this cognition is “the gift of sight” (Vaness Henry’s blog).

Vaness Henry uses the example of mindfully eating a single raisin, and really savouring it, to explain inner vision (Vaness Henry’s subscriber content) and the idea that you need time away to really clarify your big vision (Vaness Henry’s blog).

(Also while writing this, I totally just remembered that when I was listening to the cognition audios as part of Vaness’ subscriber content, I listened to the inner vision one just for fun and thought, “Oh that sounds cool,” or something. I didn’t listen to any others, just smell, and the inner vision cognition which (I thought) didn’t even apply to me at the time. Maybe my inner vision knew the whole time?)

Circling back to digestion for a sec, my theory is that experimenting with high sound worked because I was being more mindful. I was operating based on my inner vision for my own health.

Environment time!

My tropical astro HD chart environment was markets with a right-facing (external/observer) environment arrow. I literally just published a blog post about coping with the pandemic as a markets external person, which I won’t delete, but will definitely need to update (in case you haven’t noticed, my “new” chart feels more true for me).

I actually really liked the idea of markets. I liked what it meant – and it matched the vision I had for myself (i.e. living in the centre of a cute, European city, observing the bustle of activity).

Markets people like having choices and options, and being able to be selective. The right-facing arrow indicated more fluidity with one’s environment, like lots of travel, and changing up your environment often. For markets external people, the right-facing arrow also means your environment should relax you.

My new environment is caves selective (observed/left-facing arrow). This means my correct environment should bring out my activity. This doesn’t necessarily mean I’ll feel like being physically active, but it will encourage whatever “activity” I’m drawn to (like, right now for example, it’s writing this lengthy blog post).

The caves environment is about feeling safe, secure, and cozy (like a hermit??). In any particular room, for example, having one door or one entrance would be ideal, and a caves person would want to face that entrance.

I do actually find that I really dislike being on packed public transit (pre-covid), in the middle of a crowd of people, with people behind me. In this case, I prefer to tuck myself into a corner, near the doors, so I can easily escape/get off the bus/train/etc.

In my room and for my sleeping position, I must be able to see the door from my bed, though needing the door closed hasn’t felt as important for me (also I have cats, and I need them to be able to get in and out at night).

Overall, I’d say I need to experiment more with my environment to see what really feels right.

Something I’m just starting to learn more about is motivation. Since I’m just starting to dive into this aspect of human design, I haven’t really experimented much with it.

My tropical HD motivation was need, with the master trajectory, which meant responding to or meeting a need. I would be motivated to act based on the need for something. The trajectory piece is about starting out as a novice, and becoming a master in something.

My sidereal HD motivation is hope (with an anti-theist trajectory), which is more about moving toward something based on the trust that it’s right for you. It’s based on a sense of knowing, without really being able to explain why. You don’t need proof, and it doesn’t need to make logical sense, but you know you have to do it. You don’t need to push or force it to work (Vaness Henry’s subscriber content). The trajectory is about starting within a “rigid” belief system, and moving toward anti-theism, or “away” from a rigid belief system. I don’t think this means that you don’t believe in anything, but it’s more about moving toward believing and trusting in yourself, rather than seeking answers outside of yourself.

The hope motivation definitely resonates with me more, and I can see how it’s played out in past events and decisions (i.e. walking away from an au pair job in Paris with no plan but to stay in Europe for 3 months, and quitting my 9-5 job then subsequently quitting my business just because I knew I had to…).

So, that just about covers everything (that I understand about HD so far). The final piece is the incarnation cross.

My tropical HD incarnation cross was Right Angle Cross (RAX) of Rulership 4. My sidereal HD incarnation cross is RAX Contagion 4 (umm, contagion??).

To be really honest, I’ve never felt connected to the whole RAX Rulership thing. As a result, I’ve just never thought much about it, or looked into a whole lot. I was kind of like, “Hmm, interesting, I guess we’ll see…” and then put it out of my mind.

RAX Rulership 4 says that your life theme is to rule – that people naturally look to you as a leader, as the one with the knowledge and resources to take charge (The Book of Destinies).

It also says that, “promoting leadership comes easy to you and is readily accepted by those whom you wish to impress” (The Book of Destinies).

This, to me, feels off. However, I allowed for the possibility that my life could play out that way, especially with the 6 line in my (old) profile.

On the other hand, the RAX Contagion 4 incarnation cross suggests a “life theme of transference with the means to convey concepts of potential interest to almost everyone… Being aware of your desires opens you to experiences that expand your senses, and it brings you into intimate contact with life as you transform the lives of others, regardless of whether you are aware of your effect… You are the quintessential torchbearer who loves to inspire others to pay attention to assets and ideals that resonate with you” (The Book of Destinies).

It goes on to say, “With your conscious Sun in gate 14, you have the ability to recognize things of substance and deal with them in a way that makes them interesting and useful. You can draw people to you, combining everyone’s interests in matters of wealth and prosperity. Appreciating the merits of opulence, and often prioritizing that side of your life, you have the ability to commit yourself to almost anything that comes along and make it grow and flourish” (The Book of Destinies).

I feel way more connected to the RAX Contagion 4 description. I feel more excited about it (evidenced by the sheer amount I wanted to share about it in comparison to the RAX Rulership 4 incarnation cross).

To Conclude

I still have a lot to learn, and so much more to experiment with. Despite all of this information, I still feel like I’m just barely scratching the surface of human design.

I’ve shared a bit about how my HD chart differs between tropical and sidereal astrology, and while my type and authority stayed the same, so much has changed!

I definitely feel more drawn to my chart with sidereal astrology. I may eventually write more about my gates in different posts, but based on my initial brief read of each gate, so many of them feel accurate. I found myself reading them, and thinking about specific thoughts or behaviours that fit the description exactly.

So, for now, I’ll be using the sidereal version of my HD chart because that’s what feels right and most accurate for me.

If you happen to look into how your chart differs, experiment for yourself and see what feels best.

Regardless of which version you use, you are not your chart. Your chart is a tool. Human design is a tool. Maybe it helps you describe or understand your reality better, and that’s great, but at the end of the day, trust yourself and your own intuition.