Draconic Charts and the Tobey Transformation: Changing the Reference

Add the same angle to every planetary longitude and the signs and degrees may change, while the planets retain their longitudinal aspects to each other. This distinction is the starting point for understanding draconic and Tobey charts: you are changing the reference from which positions are measured.

A draconic transformation places the selected North Node at 0° Aries. The Tobey transformation in Hermes adds the difference between the source Ascendant and Sun to each position, then builds equal houses from the transformed Ascendant. The two methods need not shift the chart by the same amount.

This guide covers three entries in the Hermes transformation menu:

Why does the North Node become zero in a draconic chart?

Let λ be a source longitude and N the North Node’s longitude in the same reference system. The transformation is:

Draconic longitude = normalize(λ − N)

All values are in degrees. normalize brings the result into the interval 0° inclusive to 360° exclusive. Add 360° as needed to a negative result; 360° itself becomes 0°. For example, −65° becomes 295°.

Substituting the node’s own longitude gives N − N = 0°. If the South Node is opposite it, the result is 180°, or 0° Libra. These two values provide a useful check on which reference has been used.

Contemporary practitioner María Blaquier likewise explains the calculation by subtracting the tropical node’s longitude. The calculation section of her own article illustrates the method. The Hermes calculation also subtracts a nodal anchor from the source longitude.

Moving a reference point to zero does not describe a physical relocation in the sky. The transformed chart presents source positions measured from another longitude origin.

What changes when you choose the True or Mean Node?

Both draconic options perform the same operation; they subtract different nodal longitudes. With N_mean for the Mean Node and N_true for the True Node:

λ_true − λ_mean ≡ N_mean − N_true (mod 360°)

If the source longitudes are identical, every planet has the same circular difference between the two outputs. If one moves backwards by 1°30′ and another forwards by 4°, something beyond the choice of nodal reference has changed.

For an exercise, take a Mean Node of 75° and a True Node of 76°30′. These are teaching values, not ephemeris results for a particular date.

Both points move backwards by 1°30′ when you switch from the mean-node to the true-node result. A position close to the Aries boundary may cross into another sign; that change is not physical planetary motion.

Record the ordinary chart’s Lunar Node setting separately from its Zodiac transformation. In a fresh Hermes calculation, the draconic option selects its own node type. A transformation based on a previously calculated chart can instead use its existing North Node record. Compare fresh calculations with transformations from an existing chart pane.

Why should you check houses separately from aspects?

Adding the same angle c to two planetary longitudes preserves their difference:

(λ₁ + c) − (λ₂ + c) = λ₁ − λ₂

A longitudinal conjunction, square or trine within that chart therefore remains the same under a common shift. An aspect between a draconic planet and a planet in the source chart can change: you are comparing two separate reference layers.

Houses need an additional check. If every original cusp shifts by the same angle as the planets, the planets keep their positions within those houses. If the house ring is rebuilt under another rule, that conclusion no longer follows automatically.

Hermes’s shared transformation path processes planets, zodiac points, house cusps, the Ascendant, Midheaven and available Vertex points. After the draconic shift, Whole Sign and certain derived house options can be rebuilt. It would be too broad to promise unchanged house placements in every house system.

Begin with Placidus, the same source data and the Normal cusp setting. Treat Whole Sign as a separate trial: record whether cusps simply shift or are reset to sign boundaries. A check of longitudinal aspects does not also verify declination or parallel aspects.

Where does the Sun go in the Tobey transformation?

In the Hermes formula, A is the source Ascendant, S the source Sun, and λ the longitude of the point being transformed:

Tobey longitude = normalize(A + λ − S)

Two useful results follow:

• For the Sun, λ = S: transformed Sun = source Ascendant.
• For the Ascendant, λ = A: secondary Ascendant = normalize(2A − S).

The Sun’s destination need not be the new Ascendant. Saying that the Sun reaches “the new chart’s Ascendant” confuses the source Ascendant with the secondary one.

For a worked example, choose a source Ascendant of 140° = 20° Leo and Sun of 40° = 10° Taurus. These illustrative inputs give a common shift of 100°:

The Hermes Tobey path builds equal houses from the new Ascendant. Here, the first three cusps are 240°, 270° and 300°; the fifth is 0°, after normalising 360°. A source Placidus chart’s unequal house arcs would not survive in this new equal-house ring.

If both charts use equal houses beginning at their respective Ascendants, a common shift preserves distances within houses. That condition matters when making a statement about unchanged house positions.

Tobey’s two-stage explanation and the word “Secondary”

The Bonnie Lee Hill republication of Lesson 21, The Secondary Chart, in Tobey’s Correspondence Course in Astrology, contains two stages. The main lesson shifts planets until the Sun reaches the source Ascendant. Its supplement applies the operation to the Ascendant too, then builds houses at 30° intervals from that new point. Hermes uses the same Ascendant transformation and equal-house construction from that new point.

“Secondary” here does not instruct the program to advance time through secondary progressions. The formula derives new positions from one chart’s longitudes; it requires neither a target age nor a later ephemeris date. Seeing different signs after selecting Tobey does not mean the chart has been progressed to a future date.

Distinguishing the main lesson from its supplement also clarifies why an explanation might say “bring the Sun to the Ascendant” while another describes a chart with its own secondary Ascendant.

How can you compare the three options in Hermes?

Use the proposed synthetic data 20 March 2000, 12:00:00 UTC, 41° north, 29° east; Gregorian calendar. Convert the time appropriately if the form expects local time. Use this as an exercise and record your own calculated result.

Start with the tropical zodiac, Normal coordinate view, Normal cusp setting and Normal transformation. A sidereal starting chart requires a separate check of the node’s reference system; keep the zodiac unchanged in your first trial.

1. Record the source values. Take the Sun, one planet, Ascendant, Midheaven, North Node and house cusps. Include the node type and house system.
2. Select mean-node draconic. Check that the node used as the anchor becomes 0° Aries and that every planet has the same longitude subtracted from its source value.
3. Try true-node draconic from the same source. Do not use the already transformed chart as a new source. Check whether the difference between the two outputs is common to all planets.
4. Return to the source chart for Tobey. Begin with an equal-house source. Check the Sun against the source Ascendant, the secondary Ascendant against 2A − S, and the 30° cusp intervals.
5. Run a separate Tobey trial from a Placidus source. Record its original house arcs separately from the transformed equal-house cusps.

Compare the two draconic trials through both fresh calculations and transformations from an existing chart pane. If you also change the ordinary chart’s node setting, record each combination separately. Changing several settings together makes the cause of a difference harder to identify.

The calculation returns to the Normal transformation and produces a warning field if it cannot calculate the required draconic node, or if Tobey has no Sun record. Read the output reference and any warning alongside the option’s name.

Name the chart layer when interpreting it

Blaquier associates the draconic chart with memories, habits and inner motivations. That is a practitioner’s astrological framework; calculating the formula correctly does not establish those psychological associations experimentally. Her own explanation sets out both the calculation and her interpretive approach.

Write “the Sun in the Tobey transformation…” or “the true-node draconic Sun…” in your notes, rather than leaving the chart layer implicit. This helps you distinguish a statement about the source chart from one about its transformed positions.

For saving settings and distinguishing them from new-chart defaults, see the Hermes Chart Settings guide. Add one short question to your first record: Which point did I move to which reference, and did I transform the houses by the same rule?