Drift & Polar Alignment
Turn measured drift into alignment error.
Measure signed north–south star movement over time. The configured full imaging train converts detector pixels into sky angle.
Purpose and method
What this calculator does
How far out is my polar alignment? Estimate polar-axis error from measured stellar drift.
In words: Measured drift over time estimates the corresponding polar-axis error.
The saved imaging scale converts measured detector drift into sky drift. Latitude, hour angle, duration and signed pixel movement remain observation-specific.
Working geometry
Polar drift geometry
Alignment error produces a measurable signed drift over elapsed time.
Inputs
Measured drift and geometry
Calculated now
Alignment estimate
- Image scale
- 0.776″ / px
- Sky drift rate
- 1.551″ / min
- Azimuth-axis error
- 9.62′ (positive signed error)
- Altitude-axis error
- Low sensitivity at this hour angle
Equations
For azimuth error, sensitivity S = cos(latitude) cos(hour angle). For altitude error, S = sin(hour angle).
Treat one axis at a time: near the meridian mainly tests azimuth; near six hours east or west mainly tests altitude. Camera orientation determines how a detector direction maps to north or south, so verify the sign before adjusting the mount.