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SalsaJ
Didactical software for image and data handling 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
SalsaJ: a multilingual interface
Digital Images
Digital Images
Digital Images 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
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
Digital Images 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)
SalsaJ Open
SalsaJ Brightness/Contrast
Measurements In pixels
Scale
In km
doublet du sodium
SalsaJ Pixel size=1500/(80-7)=20.54m/pixel Crater size ~ (177-52)x20.54~2567.5m Image obtained with Mars Global Surveyor (NASA/JPL/Malin Space Sciences Systems)
SalsaJ 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 1/2
SalsaJ : photometry Use: Fstar= Sum of intensity (pixels with r<r1) –Sky*N1 N1 = Number of pixels in the radius r1 Sky = Sum of intensity (pixels with r2<r <r3) / N23 N23 = Number of pixels in the corona r2 < r < r3 r3 Use: Instrumental value proportional to the stellar object flux (luminosity) r1 r2
SalsaJ
SalsaJ Cepheids in the SMC distances
SalsaJ Perspectives: Addition of other astronomical functionalities (astrometry, PSF photometry, etc.) Optimisation of the tool with intensive testing in schools Extension to biological imaging and developments of more synergy with ImageJ (sustainability of the software). Translation in other languages