Tools

ExifTool by Phil Harvey

   http://www.sno.phy.queensu.ca/~phil/exiftool/

Pixel editor

   Standard edition : https://pixlr.com/editor/

   Express edition : https://pixlr.com/express/

Sun Calc

   http://www.suncalc.net/

Twilight Calculator "Blue Hour / Golden Hour Table"

   http://jekophoto.eu/tools/twilight-calculator-blue-hour-golden-hour

Servicio de Hidrografia Naval Argentina

   http://www.hidro.gov.ar/Observatorio/Sol.asp