How to read A/B codes
Quick start (3 steps)
- Set location, date, and timezone.
- Optionally adjust horizon correction.
- Read moon age/illumination, rise/set, and altitude curve.
Inputs
Results
| Moon age (days) | — |
|---|---|
| Moon illumination fraction | — |
| Phase name | — |
| moonrise | — |
| moonset | — |
| Moon transit | — |
| Peak moon altitude (deg) | — |
| Resolved TZ | — |
Moon altitude chart
Definitions & notes
- Moon rise/set in v1: crossing of moon center altitude through 0° (with horizon correction).
- Azimuth: N=0°, E=90°, S=180°, W=270°.
- Altitude: horizon=0°, zenith=+90°.
- Longitude sign: east positive, west negative.
- Moon illumination fraction is 0..1.
How to use this calculator effectively
This guide helps you use Moon visibility (altitude, rise/set, illumination) in a repeatable way: define a baseline, change one variable at a time, and interpret outputs with explicit assumptions before you share or act on results.
How it works
The page applies deterministic logic to your inputs and shows rounded output for readability. Treat it as a comparison workflow: run one baseline case, adjust a single parameter, and measure both absolute and percentage deltas. If a result seems off, verify units, time basis, and sign conventions before drawing conclusions. This approach keeps your analysis reproducible across teammates and sessions.
When to use
Use this page when you need a fast estimate, a classroom check, or a practical what-if comparison. It works best for planning and prioritization steps where you need direction and magnitude quickly before investing in deeper modeling, manual spreadsheets, or formal external review.
Common mistakes to avoid
- Changing multiple parameters at once, which hides the true cause of output movement.
- Mixing units (percent vs decimal, monthly vs yearly, gross vs net) across scenarios.
- Comparing with another tool without aligning defaults, constants, and rounding rules.
- Using rounded display values as exact downstream inputs without re-checking precision.
Interpretation and worked example
Run a baseline scenario and keep that result visible. Next, modify one assumption to reflect your realistic alternative and compare direction plus size of change. If the direction matches your domain expectation and the size is plausible, your setup is usually coherent. If not, check hidden defaults, boundary conditions, and interpretation notes before deciding which scenario to adopt.
See also
FAQ
What does moon illumination fraction mean?
It is the fraction of the lunar disk lit by sunlight, expressed as 0.0 to 1.0. This does not include atmospheric extinction or local seeing.
Why can moonrise or moonset be missing?
At some latitudes and dates, the moon can stay continuously above or below your local horizon correction line, so no crossing happens in the selected day.
Can I use moon illumination to infer visibility quality?
Use this as a first-pass filter, then combine with altitude, air mass, and phase constraints in Observability time plotter (A7) for practical planning.
What should I do first on this page?
Start with the minimum required inputs or the first action shown near the primary button. Keep optional settings at defaults for a baseline run, then change one setting at a time so you can explain what caused each output change.
Why does this page differ from another tool?
Different pages often use different defaults, units, rounding rules, or assumptions. Align those settings before comparing outputs. If differences remain, compare each intermediate step rather than only the final number.