AI Prompts for a Relationship Chart
Astrological calculation with LLM prompts for any AI platform for accurate relationship (synastry) chart interpretations.
Synastry, the comparison of two people's charts, is one of astrology's most useful tools and one of the most calculation-intensive. AI platforms are great at synthesizing astrological insights about relationships, making up for their lack of human intuition with superb pattern recognition skills and an ability to integrate and synthesize massive, complex datasets, which are necessary for accurate relationship chart interpretations. However, you can do a lot of harm by asking an LLM to interpret a relationship chart without giving it accurate astrological data. An LLM cannot perform astronomical calculations, so it will often fabricate planetary positions, leading to wildly false interpretations.
With the astrological interpretaion of a relationship chart, you can gain an understanding of why one relationship feels effortless while another requires constant adjustment, or why a business partnership thrives in some areas and creates friction in others. You can guide the AI to focus on the aspects most important to you, whether the relationship is romantic, family, friendship, or professional.
AstroPrompt has a Relationship view that loads two charts from birth records and asks the LLM to describe the relationship dynamic between the two people. You can guide the conversation toward a specific kind of relationship (romantic, family, friendship, or professional). The full report covers compatibility patterns, points of friction, and what each person can expect from the relationship, all anchored to accurate synastry calculations.
The Relationship view runs Astrolog twice (one chart per person) and then computes the synastry aspect grid between them, with orbs. The LLM receives both natal charts, the synastry grid, and a system prompt that frames the analysis as descriptive rather than prescriptive. The full report prompt asks for a description of relationship dynamics and the practical implications.
For an introduction to the process, see calculation-first AI astrology workflow.
Before you get started
Relationship is an option in the AstroPrompt navigation bar, and the fastest way to get a result is to use AstroPrompt. The tutorial below explains how to obtain the same result from any LLM yourself. To do it yourself you will need to install Astrolog, write the chart output to a file, and combine the Astrolog dataset with the prompts shown below. AstroPrompt makes the workflow easier: it runs Astrolog automatically, lets you pick from popular LLMs (such as OpenAI GPTs, Claude Opus, or Google Gemini), and streamlines the prompt assembly. For advanced users, AstroPrompt Pro lets you edit the prompts so you can customize tone, interpretation, or output structure. Try AstroPrompt now; it is FREE.
Relationship
A relationship interpretation needs to compare two natal charts and produce a synastry analysis. AstroPrompt obtains a dataset from Astrolog that includes charts or both people, a synastry aspect grid listing every cross-chart aspect with orbs, and two house-overlay tables (Person A's planets in Person B's houses and the reverse) when both birth times are known.
You can then send the dataset to any LLM to answer questions like "What are the strengths in this relationship?" The prompt below will produce a full synastry report based on accurate chart calculations.
This tutorial (and the corresponding AstroPrompt view) looks at relationships using only the astrological synastry approach, which overlays two charts to identify interpersonal chemistry, friction, specific triggers and support patterns. Professional astrologers also use two other techniques for relationship analysis, which are not covered here: composite charts and Davison charts, which look at a relationship as a symbolic “third entity” and can be used to see how the relationship develops over time.
How to get an accurate LLM response
AI can't calculate planetary positions accurately or read an ephemeris reliably. To get an accurate and reliable interpretation, you must provide this astrological data:
- The natal positions of both people: planet by planet, with sign, degree, and retrograde flag.
- A synastry aspect grid showing every cross-chart aspect with orbs and aspect type.
- Person A's planets in Person B's houses (one overlay table), when Person B's birth time is known.
- Person B's planets in Person A's houses (the reverse overlay), when Person A's birth time is known.
- Explicit notes when one or both birth times are unknown so the model omits house-based interpretation.
Astrolog commands
AstroPrompt executes three Astrolog commands sequentially and concatenates the output. The first command builds the synastry aspect grid, and the second and third build each direction of the house overlay.
Command 1 (synastry aspect grid):
astrolog -qb {m1} {d1} {y1} {time1} 0 0 {lon1} {lat1} \
-qb2 {m2} {d2} {y2} {time2} 0 0 {lon2} {lat2} \
-r2 -g
Commands 2 and 3 (house overlays, one per direction):
astrolog \
-qb {m_houses} {d_houses} {y_houses} {time_houses} 0 0 {lon_houses} {lat_houses} \
-qb2 {m_planets} {d_planets} {y_planets} {time_planets} 0 0 {lon_planets} {lat_planets} \
-C -r nul nul -v
`-qb`and`-qb2`define chart slot 1 and chart slot 2 with the full nine-arg location signature (month, day, year, time, daylight flag, timezone, longitude, latitude). Both charts are passed in UTC by setting timezone to0.`-r2`produces a relationship comparison between the two charts.`-g`outputs the synastry aspect grid (the matrix used to generate the output).`-C`is added on the overlay commands so house cusps participate in the calculation (the Ascendant and Midheaven matter for synastry conjunctions to angles).`-r nul nul -v`is the overlay incantation: the houses come from chart 1 and the planets from chart 2, written verbosely.`-R Chiron Ceres Pallas Juno Vesta Lilith Fortune Vertex East`is appended when the user has minor objects turned off, restricting both the aspect grid and the overlay tables to the major planets.
If either birth time is unknown, the corresponding overlay command is skipped and a note is inserted in the data so the LLM does not guess.
Prompts
Astrological data is combined with a user's prompt to create the context for a question that begins an AI chat. The LLM receives everything (including its responses to previous questions) as a single context block, but it is easier for us if we assemble the context from three specific prompts: a system prompt, a data description prompt, and a user prompt that asks for a report. In AstroPrompt Pro, you can edit and save each of these prompts to customize tone, interpretation, or output structure. For this tutorial, combine each of these prompts with the astrological data and then paste the entire block into the AI chat.
System Prompt
The foundational instruction that sets the AI's overall tone, style, and approach, which applies to every message in the conversation. The default produces balanced, measured analysis. You can change it to anything: terse bullet-point summaries, a specific cultural or traditional framework, a particular language, or even a lengthy style guide that reproduces your own voice for client-facing work. This is the most powerful lever for fundamentally changing the character of the AI's responses.
The system prompt is shared across every AstroPrompt view. It strips horoscope register and instructs the model to stay neutral and analytical:
When generating astrological forecasts, do not use rhetorical or
persuasive devices typical of popular horoscope writing. Avoid inserting
emotional appeals or literary devices. Avoid the following:
• Imperatives and exhortative tone (e.g., "Embrace change," "Let go of
the past," "Surround yourself with warmth")
• Evocative metaphors and symbolic language (e.g., "personal
renaissance," "magnetic energy," "mirror of the soul")
• Overly enthusiastic, poetic, or cute phrasing
• Vague affirmations or inspirational advice not grounded in planetary
positions
Instead, use a neutral, informative tone. Focus on:
• Relevant planetary influences and their timing
• Which life areas are affected and how
• Expected themes based on astrological interpretation
• Possibility framing using modal verbs (e.g., may, might, could)
without interpretive flourish
• Objective language suitable for readers seeking analysis rather than
affirmation
Structure any planner forecast by timeline or topic (e.g., career,
relationships, health).
AstroPrompt adds a terminology directive (advanced or beginner) based on its settings.
Data Description
This prompt tells the AI what the raw astrological data actually represents. This is how the AI understands the underlying dataset. Advanced users can use this to direct the AI's attention toward specific technical elements they care about most.
After the combined Astrolog output, AstroPrompt appends a one-sentence description so the model knows what it is looking at:
This data contains a synastry (relationship) analysis showing: (1) a
synastry aspect matrix between two people's natal planets with orbs and
aspect types, and (2) house overlay tables showing where each person's
planets fall in the other's houses (when birth times are known).
The "(when birth times are known)" clause matters. If only one overlay is included, the model needs a reason to interpret the relationship asymmetrically rather than guessing the missing direction.
Full Report Prompt
AstroPrompt provides detailed instructions when a user wants a full report. This is typically the longest prompt and has the greatest single impact on report quality and structure. The default walks the AI through a specific analytical sequence. You can replace this entirely as you wish, for example, to focus the report on career and finance, restructure it around specific techniques, or direct the LLM to use the point of view of a favored lineage or tradition.
The full report prompt is the longest in AstroPrompt because LLMs need careful guidance to produce useful synastry interpretations.
You are a Relationship Astrologer specializing in synastry. Use a
neutral, technical, analytical tone only (no metaphors, no inspirational
language, no advice, no imperatives). Interpret only the data provided.
For every technical observation, provide a thematic phrase and short
description of interest to a non-astrologer. You will receive: (1) a
synastry aspect matrix, and (2) OPTIONAL house-overlay tables for both
directions (Person A's planets in Person B's houses AND Person B's
planets in Person A's houses), provided only if both birth times are
known. Analyze the relationship in four domains: 1. Potential for
romantic attraction and stimulation or excitement - Evaluate Sun, Moon,
Mercury, Venus, Mars aspects; include Sun-Moon links, Venus-Mars
contacts, angle-related aspects, and notable interchart geometry. -
Consider aspects involving Uranus and the personal planets, especially
Venus, for exciting or unconventional attractions, especially in the 1st
and 7th houses (if houses are known). - If house overlays are provided,
evaluate attraction from each person's viewpoint (A->B and B->A) by
noting planets in the partner's 5th, 7th, and 8th houses. - Identify
asymmetric patterns (e.g., one partner placing personal planets in the
other's 7th house while not receiving similar placements in return). 2.
Potential for a long-lasting relationship - Examine Saturn aspects,
nodal contacts, and repeated structural configurations (trines,
sextiles, T-squares, rectangles). - If house overlays are included,
evaluate durability indicators in each partner's 4th, 7th, and 8th
houses and identify asymmetries. 3. Sources of conflict - Identify hard
aspects (square, opposition, tight conjunction) involving Mars, Saturn,
Uranus, Neptune, Pluto, Chiron, or the luminaries. - Note tension
configurations (T-squares, oppositions). - Incorporate house-based
conflict indicators ONLY when present in the provided overlays (e.g.,
Mars in partner's 7th), and do so separately for A->B and B->A. 4.
Sources of mutual support and growth - Identify supportive
trines/sextiles, Jupiter contacts, stabilizing Saturn patterns, and
harmonious geometric structures. - If house overlays are included,
evaluate supportive placements for each partner's 1st, 4th, 7th, 9th,
and 11th houses and highlight asymmetries. Instructions and
constraints: - Interpret only the information shown; do not assume
missing houses or angles. - Use possibility language ("may," "might,"
"could"). - No behavioral guidance or emotional commentary. - Do not
reference transits, progressions, composite charts, or Davison charts
unless included. If birth time is known and Ascendant/Descendant
positions are available, for all four domains, look closely at the
planet positions by degree and compare to Ascendant/Descendant
positions. Planets in close orb and major aspect to the partner's
Ascendant/Descendant, especially conjunct or opposition, are highly
significant to the relationship. Aspects in a natal chart that align
with the partner's Ascendant/Descendant positions are even more
significant. Final Output: After the four sections, provide a concise
technical summary synthesizing (a) the synastry aspects, (b) both sets
of house overlays, and (c) the asymmetric differences in how each
partner experiences the relationship. Remember to provide sufficient
non-technical description to hold the interest of a non-astrologer.
The four-domain structure is central. It forces the model to evaluate attraction, longevity, conflict, and support separately rather than collapsing them into "you are compatible." The "do not assume missing houses or angles" line stops the model from inventing data when birth times are unknown.
Unique features of the Relationship prompt
- Three Astrolog commands instead of one, because synastry needs the aspect grid and both directional house overlays.
- Both charts run in UTC (
-z 0) to eliminate timezone collisions between two people from different locations. - The full report prompt explicitly bans advice, metaphors, and imperatives, which keeps synastry from drifting into feel-good coaching.
- Asymmetric interpretation is required: A in B's houses is treated separately from B in A's houses, since one direction can be loaded with no reciprocity.
- House overlays are conditional on birth-time knowledge, and the prompt tells the model to skip overlay-based interpretation when missing.
- The prompt asks for a thematic phrase per technical observation, so the output is readable by a non-astrologer partner without losing the technical substrate.
What's Next
This was written in May 2026, describing the data and prompts used in AstroPrompt version 1.0. Astrologers are just beginning to explore the capabilities of AI as a tool for astrological insight. If you've got suggestions for a better dataset or improved prompts, I'd love to hear from you. Email me at hello@timecasters.com.
