Calculate Star Offset Position

Latitude degrees
Longitude degrees
Altitude Alignment Error arcmins
Azimuth Alignment Error arcmins
Reference Right Ascension hours
Reference Declination degrees

Target Right Ascension hours
or
Target Declination degrees
or

Instructions:
This calculator may be used to calculate the star offset position to effect a correction in polar alignment. The model assumes that a reference star is selected near the meridian and calculates the offset position required so that when the mount is adjusted and the reference star re-centered the mount will be closely aligned. For more information on this topic see my On Polar Axis Alignment web page.

Latitude: Enter your latitude in degrees. If you know the degrees, arcminutes, and arcseconds enter it in the form DD.MMSS or DD.MM and click "Convert DD.MMSS".

Longitude: Enter your longitude in degrees. West is negative. If you know the degrees, arcminutes, and arcseconds enter it in the form DD.MMSS or DD.MM and click "Convert DD.MMSS".

Altitude Alignment Error: Enter the altitude alignment error in arcminutes. If you know this value as arcminutes and arcseconds enter it as MM.SS and click "Convert MM.SS".

Azimuth Alignment Error: Enter the azimuth alignment error in arcminutes. If you know this value as arcminutes and arcseconds enter it as MM.SS and click "Convert MM.SS".

Reference Right Ascension: Enter the right ascension of the reference star in decimal hours. If you know the hours, minutes, and seconds enter it in the form HH.MMSS or HH.MM and click "Convert HH.MMSS".

Reference Declination: Enter the declination of the reference star in decimal degrees. If you know the degrees, arcminutes, and arcseconds enter it in the form DD.MMSS or DD.MM and click "Convert DD.MMSS".

Calculate: When you have entered and converted all your inputs to the proper units, click "Calculate." The Target Right Ascension and Target Declination will be calculated and displayed in the fields below. Point your scope to these coordinates and recenter the reference star by making an altitude or azimuth adjustment to the mount.