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2 SalsaJ

3 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

4 SalsaJ: a multilingual interface

5 Digital Images

6 Digital Images

7 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

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 : 32-bits : real values

9 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)

10 SalsaJ Open

11 SalsaJ Brightness/Contrast

12 Measurements In pixels

13 Scale

14 In km


16 doublet du sodium

17 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)

18 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

19 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

20 SalsaJ

21 SalsaJ Cepheids in the SMC distances

22 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

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