THE BIG PIC­TURE

THE KEY TO SUC­CESS IS CAL­I­BRA­TION US­ING FAINT THRESH­OLD STARS

Sky at Night Magazine - - OCTOBER / THE SKY GUIDE -

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.

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