Reconcile a source-owned apparent-declination/local-hour-angle row into geometric airless center altitude without inventing an ephemeris or visibility verdict.
Built for Astronomy1 documented formulaFocused single-task workflowPrivate in your browser
Use this result well
A quick decision brief for this specific tool
Inputs that matter
One named reviewed planet-altitude coordinate record and revision; exact target row, coordinate source and responsible reviewer; one ISO 8601 UTC source instant; exact observer-site and apparent-coordinate-frame records; geodetic observer latitude, same-instant source apparent declination and same-instant source local hour angle with the explicit negative-east/zero-on/positive-west convention; optional same-target/instant/site/frame geometric-airless center-altitude report plus independent source and reviewer-owned absolute tolerance; and explicit coordinate-generation, horizon/refraction, visibility/observing and event/target/use boundaries
Output to expect
Geometric airless center altitude from the entered horizon-coordinate transform; zenith distance; arithmetic above/on/below relation to the ideal geometric horizon; east/on/west hour-angle direction; optional reported-minus-calculated altitude difference inside the entered tolerance; complete target/time/site/frame/source records; deliberate page-session retention, copy/Markdown/print/share actions; and stable Project outputs that keep ephemeris generation, refraction/local-horizon approval, visibility/observing-quality approval, rise/transit/set generation, target inference and imaging/use/safety approval false
How it works
Convert entered observer latitude, source apparent declination and source local hour angle to radians; evaluate sin(a) = sin(φ)sin(δ) + cos(φ)cos(δ)cos(H), clamp floating-point sine to [−1,1], return a in degrees and zenith distance 90°−a; classify only the arithmetic geometric-horizon and hour-angle relations; optionally compare one same-basis reported altitude inside a reviewer-owned absolute tolerance
The exact target, UTC instant, observer site, apparent coordinate frame, declination and local hour angle must travel together. The Tool never generates a planet position from a name/date/location, derives local hour angle from longitude/time/right ascension, defaults a missing hour angle to transit, mixes astrometric/apparent/geocentric/topocentric/refracted frames or identifies a target from its coordinates.
Positive geometric airless center altitude is not a visibility or observing-quality verdict. Keep atmospheric refraction, horizon dip, terrain/buildings, daylight/twilight, solar elongation, brightness/angular size, transparency, clouds, seeing, light pollution, instrument/observer, rise/transit/set, imaging, use and safety decisions in a responsible observer ephemeris plus local evidence.
Choose your path
Built around the job you need to finish
Reconcile one exact source-owned planet coordinate row into geometric airless center altitude without generating an ephemeris or turning ideal-horizon arithmetic into visibility, observing-quality, event, imaging, use or safety advice.
Beginner transcribing one retained observer-table row
Understand one altitude transform without being told that a planet is visible tonight or that an observing condition is excellent.
Retain one Mars target row, UTC instant, observer site and apparent frame; enter latitude +40°, apparent declination +20° and local hour angle 0°, then reconcile the source-owned row.
Gets 70° geometric airless center altitude,20° zenith distance, an ideal-horizon relation and on-meridian direction with every visibility and observing conclusion explicitly unapproved.
Astronomy-club reviewer checking a same-row altitude report
Catch transcription or basis mismatches without using a tolerance as an ephemeris-accuracy certificate.
Load the same target/instant/site/frame row, retain an independent70.1° geometric-airless center report and choose a0.2° reviewer-owned absolute tolerance.
Gets a signed+0.1° reported-minus-calculated difference inside tolerance; an out-of-tolerance report fails at its own field and retained snapshots remain immutable.
Session planner testing consequence boundaries
Prevent a coordinate worksheet from inventing current planet positions, refracted/local clearance, naked-eye visibility, observing quality, rise/set events or imaging suitability.
Reconcile the supported row, then exercise coordinate-generation, horizon/refraction, visibility/observing and event/target/use refusal choices before restoring each supported boundary.
Every unsupported request removes the current result and actions, focuses the exact owning select with a complete refusal, and requires explicit reconciliation before altitude arithmetic returns.
Authoritative checks for this tool
Outputs and checklists are planning aids. Review the linked current authorities and the records, terms, instructions, and requirements that apply to your exact situation before a consequential decision.
Retain one exact target, UTC instant, observer site, apparent coordinate frame and source. Apparent declination and local hour angle must belong to that same row; the Tool never substitutes a default hour angle or generates either coordinate.
same target + same UTC instant + same site + same frame + same source row
Geometric Airless Center Altitude
Apply the U.S. Naval Observatory horizon-coordinate relationship to observer latitude, source apparent declination and source local hour angle. North latitude and declination are positive; hour angle is negative east, zero on and positive west of the meridian.
sin(a) = sin(φ)sin(δ) + cos(φ)cos(δ)cos(H)
Independent Same-Basis Check
An optional reported altitude must identify the same target, instant, site, coordinate frame and geometric-airless center basis. Reported minus calculated difference is accepted only inside the reviewer-owned absolute tolerance.
JPL observer tables keep apparent versus refracted coordinates, topocentric site, time, daylight/twilight and rise/set definitions explicit. This record therefore refuses ephemeris generation, atmospheric refraction, horizon dip, terrain/building clearance, weather, target brightness, visibility, observing quality, rise/transit/set, target identification, imaging, use and safety conclusions.
Updated: August 2026
Example Scenarios
The reviewer keeps a Mars source row, UTC instant, site and apparent frame together, then enters latitude +40°, declination +20° and local hour angle 0°. The record returns 70° geometric altitude without saying Mars is visible tonight.
A club worksheet reports 70.1° for the same target, instant, site, frame and geometric-airless center basis. With a reviewer-owned 0.2° tolerance, the record reports +0.1° and retains an immutable evidence snapshot.
The planner asks the Tool to generate current coordinates, predict refracted rooftop clearance, declare observing quality or generate rise/set events. Each request fails at its owning boundary until the supported source-row task is restored.
Common Mistakes to Avoid
✕
Leaving hour angle blank and silently treating the object as on the meridian
✓
Require the source-owned local hour angle for the exact instant. Zero is meaningful data, not a safe default.
✕
Calling positive geometric altitude a visibility or observing-quality rating
✓
Keep daylight, solar elongation, brightness, weather, transparency, seeing, light pollution, obstruction, equipment and observer review external.
✕
Mixing an astrometric declination, apparent hour angle or report from another frame or instant
✓
Retain the exact target, UTC instant, observer site, apparent coordinate frame and source row. Reconcile only reports with that same basis.
FAQ
No. It accepts an already identified target and same-instant apparent declination/local hour angle from a responsible source. It does not generate a planet ephemeris or decide visibility.
They prove that latitude, apparent declination and local hour angle belong to one coherent source row. Local hour angle is produced upstream from time, observer longitude and right ascension; mixing instants or frames can make clean arithmetic scientifically meaningless.
No. It is the object's geometric airless center altitude relative to an ideal geometric horizon. Atmospheric conditions, horizon dip, terrain, buildings and other obstructions are not modeled.
No. Visibility also depends on daylight/twilight, solar elongation, target brightness and angular size, transparency, clouds, seeing, light pollution, obstruction, instrument and observer evidence.
No. Those are events across time and require a time-series ephemeris plus an explicit horizon/refraction definition. This record intentionally stops at one retained instant.
Only whether one same-basis reported altitude agrees with this calculation inside a limit chosen by the reviewer. It does not certify ephemeris accuracy, measurements, visibility, equipment or use.
About Reviewed Planet Altitude Coordinate Record
This reviewed record reproduces one horizon-coordinate transform from an exact target row, UTC instant, observer-site record, coordinate frame, apparent declination, local hour angle and latitude. It reports geometric airless center altitude, zenith distance and the arithmetic relation to an ideal geometric horizon. It does not generate planet positions, apply refraction or local obstruction, declare visibility or observing quality, generate rise/transit/set events, infer a target, or approve imaging, use or safety.
