THE BIG PICTURE
THE KEY TO SUCCESS IS CALIBRATION USING FAINT THRESHOLD STARS
Algol is a bright variable star which is well placed for viewing in the UK. Its regular dips in brightness make it a fascinating astrophotographic subject but the big challenge is how to capture them effectively. Variations in sky transparency create issues with calibration so here we look at a simple way to achieve a rough image calibration sufficient to show just how much Algol’s brightness changes over its short, but regular period of variability. The main thrust of this method is to identify several faint threshold stars. If you can record them correctly, then the brightness of Algol can be confidently compared from one shot to another.