Linked astronomy tools
Quick start (3 steps)
- Choose coordinate input unit (hms/dms or deg).
- Enter point A and point B (Right Ascension and Declination (RA/Dec)).
- Compute separation and Position Angle (PA) (north=0°, eastward positive).
Inputs
Results
| Separation (deg) | — |
|---|---|
| Separation (arcmin) | — |
| Separation (arcsec) | — |
| Position angle PA (deg) | — |
This tool runs in your browser. Inputs are not sent.
Interpretation & notes
- Separation is the great-circle distance on the celestial sphere.
- PA is measured from celestial north (0°) toward east (90°).
- PA is normalized to the range 0..360°.
How to use angular separation effectively
Enter both sky positions in the same unit system, then compute once before changing anything. Keep the first pair as your baseline so it is clear which coordinate change altered the separation or position angle.
What to check first
Confirm whether you are entering sexagesimal values or decimal degrees. A mismatch between those two formats is the most common reason for an unexpected result.
How to read the output
Use the degree, arcminute, and arcsecond values as different views of the same separation. The position angle is measured from celestial north toward the east, normalized to 0-360°.
Common mistakes to avoid
- Mixing hms/dms input with decimal-degree values in the same run.
- Swapping point A and point B without noticing that the position angle can change.
- Comparing rounded arcsecond values without checking the degree result underneath.
- Sharing a result without copying the URL that stores the exact coordinates.
See also
FAQ
How is separation measured on the celestial sphere?
Separation is the great-circle distance between two sky positions, so it accounts for celestial-coordinate curvature rather than flat chart distance.
Why is PA normalized to 0-360 degrees?
Position angle is an orientation measured from celestial north toward east. Wrapping to 0-360 degrees keeps one unambiguous direction format.
What should I check before entering coordinates?
Confirm that both positions use the same format. Do not mix right ascension in hours with decimal-degree input unless the field explicitly expects it.
Why can the position angle change when I swap point A and point B?
Separation stays the same, but position angle is directional. Measuring from A to B is not the same orientation as measuring from B to A.
Which related astronomy tool should I open next?
Use RA/Dec to Altitude and Azimuth (Alt/Az) when you need horizon coordinates, sidereal time when the observing time is the question, and finder-chart tools when you need to place the separation on a chart.