Linked astronomy tools
Quick start (3 steps)
- Enter location, date/time, timezone, and target Right Ascension and Declination (RA/Dec).
- Click Compute to get Altitude and Azimuth (Alt/Az) at the selected time.
- Inspect 24h curve and export CSV if needed.
Inputs
Results
| Alt (deg) | — |
|---|---|
| Az (deg, N=0 E=90) | — |
| Hour Angle (HA) (hms) | — |
| LST (hms) | — |
| Air mass | — |
| Resolved TZ | — |
This tool runs in your browser. Inputs are not sent. Geometric altitude (no refraction correction).
24h altitude curve
Interpretation & notes
- Azimuth is normalized to 0..360 with north=0, east=90.
- Airmass is shown only when altitude is above the horizon.
- CSV columns: local/UTC timestamps + coordinates + Alt/Az + air mass.
How to use this calculator effectively
Use this page to convert right ascension and declination into altitude and azimuth for a specific observing site and time, then review the 24-hour altitude curve for planning.
How it works
The calculator combines the target RA/Dec, observer latitude and longitude, date, time, and timezone to estimate local sidereal time and horizon coordinates. Altitude tells you how high the target is above the horizon, while azimuth gives compass direction with north as 0 degrees and east as 90 degrees.
When to use
Use it to check whether a target is above the horizon, when it culminates, which direction to face, and whether the altitude is high enough for a practical observation or imaging session.
Common mistakes to avoid
- Mixing east-positive and west-positive longitude conventions.
- Entering RA in degrees when the source gives hours, minutes, and seconds.
- Using the wrong timezone or date for an overnight observing session.
- Expecting exact agreement with tools that apply refraction, precession, or local horizon obstructions differently.
Interpretation and worked example
Start with one target and one observing site. Check the current Alt/Az, then use the altitude curve to find the highest part of the night. If the target stays below the horizon or near very low altitude, switch targets or location before planning exposure time.
See also
FAQ
What inputs are required?
You need target RA/Dec, observer latitude and longitude, and the date and time. Timezone matters because the same sky coordinate appears at different horizon positions as Earth rotates.
Why does azimuth wrap around 360 degrees?
Azimuth is normalized to 0..360 degrees. The jump is a wraparound of the circular range, not a physical discontinuity.
Why is air mass hidden at low altitude?
Air mass is not defined below the horizon. The tool hides that value and continues to show altitude and azimuth for context.
Why can another astronomy tool differ?
Differences usually come from timezone handling, longitude sign, refraction, epoch/precession assumptions, rounding, or local horizon masking. Align those settings before comparing values.