IMAG­ING FOR SCIENCE PART 3: ME­TE­ORS

Pete Lawrence ex­plains how a hand­ful of im­ages can give you an idea of a me­teor’s speed, over­all shower ac­tiv­ity and more

Sky at Night Magazine - - CONTENTS -

You can glean a great deal from these fleet­ing flashes in the sky – from speed to com­po­si­tion.

Me­te­ors are one of the most ac­ces­si­ble as­pects of the night sky, yet on top of their un­doubted splen­dour there’s much valu­able sci­en­tific anal­y­sis that am­a­teurs can get stuck into. The core el­e­ment of me­teor anal­y­sis is sta­tis­ti­cal record­ing. Date and time stamps on im­ages are im­por­tant to iden­tify when a me­teor trail oc­curred. To do this, syn­chro­nise a cam­era’s clock with a re­li­able time source, like an on­line atomic clock. It’s also rec­om­mended that you use UT. Trail tim­ing can only be de­ter­mined to the ac­cu­racy of the ex­po­sure start time plus the ex­po­sure length. A con­tin­u­ous record of con­di­tions is also im­por­tant as vari­a­tions in fac­tors such as sky trans­parency have no­table ef­fects on rates.

Most dig­i­tal cam­eras store their set­tings in an EXIF (Ex­change­able Im­age File For­mat) file header writ­ten into each im­age. How­ever, if you’re us­ing man­ual lenses add a de­scrip­tion of the lens and its set­tings as this in­for­ma­tion isn’t nor­mally in­cluded in the EXIF header.

Many video and high frame rate cam­era con­trol pro­grams also pro­vide log­ging op­tions to record the co­pi­ous set­ting vari­ants that can be ap­plied. Fi­nally, make a note of the cen­tre of the sky area be­ing pho­tographed in RA and dec. Hardware & Soft­ware HARDWARE DSLR, CCD cam­era, high frame rate cam­era, video astro cam­era, mid- to wide-an­gle lenses

SOFT­WARE Im­age viewer such as FastS­tone (www.fasts­tone.org/FSView­erDe­tail.htm) Pho­to­shop or Gimp (www.gimp.org) UFOCap­ture, UFOA­n­a­lyzer, UFOOr­bit (sono­taco.com/soft/e_in­dex.html) MetRec (www.metrec.org)

Many dig­i­tal cam­eras save im­ages with an EXIF header (in­set), con­tain­ing all the vi­tal info about the set­tings used

ABOUT THE WRITER Pete Lawrence is an ex­pert as­tronomer and astropho­tog­ra­pher who holds a par­tic­u­lar interest in dig­i­tal imag­ing

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