Http://www.euhou.net. SalsaJ Pedagogical resources : SalsaJ software Didactical software for image and data handling Such A Lovely Software for Astronomy,

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http://www.euhou.net Slide 2 SalsaJ Slide 3 Pedagogical resources : SalsaJ software Didactical software for image and data handling Such A Lovely Software for Astronomy, in Java Multi-platform (Windows, Linux, Mac) Java, modularity; easily extensible to implement new fonctionnalities Adaptation in different languages; recently in arabic; chinese in progress Free of charge (download from the EU-HOU web site); open-source Up to date sources (derived from the free medical research tool ImageJ developed at NIH); adapted to astronomy (FITS format; photometry); friendly tool for classrooms Developed by F-HOU ; SalsaJ v2.0 to be released by the end of 2007 Slide 4 SalsaJ: a multilingual interface Slide 5 Digital Images Slide 6 Slide 7 A digital image is a set of values gathered in a 2D (or 3D) array Each element is a pixel (picture element) Each pixel has a corresponding physical size Each pixel can have one or more values 1 value = black&white images 3 values = true-color RGB images Slide 8 Digital Images Black and white images are actually gray-level images Each pixel has one value corresponding to a particular shade of gray 0 for black and max for white max depends on the dynamics of the image 8-bits : 255 16-bits : 65 535 32-bits : real values Slide 9 Example : Black : (0,0,0)White : (255,255,255) Red : (255,0,0)Green : (0,255,0) Blue : (0,0,255)Cyan : (0,255,255) Magenta : (255,0,255) Yellow : (255,255,0) Orange : (255,190,93) Gray : (128,128,128) Digital Images Slide 10 SalsaJ Open Slide 11 SalsaJ Brightness/Contrast Slide 12 Measurements In pixels Slide 13 Scale Slide 14 In km Slide 15 Slide 16 doublet du sodium Slide 17 Image obtained with Mars Global Surveyor (NASA/JPL/Malin Space Sciences Systems) Pixel size=1500/(80-7)=20.54m/pixel Crater size ~ (177-52)x20.54~2567.5m SalsaJ Slide 18 Stellar objects = point sources Convolved by the Point Spread Function (PSF) of the instrument (atmosphere + optics) PSF ~ bell-like shape function ~ Gaussian + tails Characterised by its Full Width Half Maximum (FWHM) in arcsec (cf pixel size) Good sampling: FWHM ~2-3 pixel size 1/2 FWHM SalsaJ Slide 19 r1r1 r3r3 F star = Sum of intensity (pixels with r