PolarDrift Calculator

臨天文攝影者自動導向極對準助理

PolarDrift calculator is a simple polar alignment assistant tool helping astrophotographers to solve the question of optimum polar alignment sufficient to minimize the effects of field rotation. It is targeting typical auto-guiding setups. By understanding allowable error in polar alignment, field rotation can be controlled to be under the minimum visible threshold.

A number of details increase or decrease the requirement for precision. Factors that require higher precision include: longer exposure duration, increased distance between the guide star and the edge of the imaging field, and declinations that approach the pole. Factors that tolerate more error include: shorter duration exposure, centering of the guide star and a smaller imaging field, and declinations that approach the equator.

Drift polar alignment via a guide camera and guide scope allows a precise measurement of the rate of movement of a guide star. By using tools to measure the drift rate during ALTITUDE and AZIMUTH adjustment phases of the drift procedure, a value of error can be calculated. Some drift alignment tools report this error in pixels or arc seconds.

After entering the values in the Imaging setup parameters menu, then entering the values of Declination and Exposure Duration on the main screen, the maximum allowable error is displayed. During drift alignment, the speed star movement should be recorded and entered as Measured Drift to determine current conditions.

Note: You can tap the parameter's description on the main screen to see a more detailed explanation for the corresponding value.

This tool allows an astrophotographer to better understand the limits of their setup, so that they can determine if a configuration is feasible.

The idea, calculations algorithm, and instructions text by Stephen Migol.

Calculations are provided from:

Hook, R.N., Polar axis alignment requirements of astronomical photography, Journal of the British Astronomical Association, vol. 99, no. 1, p. 19-22 (Feb. 1989) http://adsabs.harvard.edu/full/1989JBAA...99...19H

Barrett, Frank, Determining Polar Alignment Accuracy, 2009 http://celestialwonders.com/articles/polaralignment/PolarAlignmentAccuracy.pdf

You may find more information and contact the developer directly at http://app.kukarin.com