Index: /trunk/archive/pslib/include/psPhotom.h
===================================================================
--- /trunk/archive/pslib/include/psPhotom.h	(revision 252)
+++ /trunk/archive/pslib/include/psPhotom.h	(revision 252)
@@ -0,0 +1,49 @@
+#if !defined(PS_PHOTOM_H)
+#define PS_PHOTOM_H
+
+/** \file psPhotom.h
+ *  \brief Photometric transformations
+ *  \ingroup AstroGroup
+ */
+
+/** photometry system transformation types */
+enum {
+    PS_PHOT_SYS,
+    PS_PHOT_REF,
+} psPhotTransformType
+
+/** photometry system definition */
+typedef struct {
+    int ID;
+    char *name;
+    char *camera;
+    char *filter;
+    char *detector;
+} psPhotSystem;
+
+/** photometry transformations */
+typedef struct {
+    psPhotSystem src;
+    psPhotSystem dst;
+    psPhotSystem colorPlus, colorMinus;	///< Colour reference
+    psPolynomial2D colorAirmasTerm;
+    psPhotTranformType type;
+} psPhotTransform;
+
+# endif
+
+/**** examples & explanations 
+ *
+ * examples of psPhotSystem values:
+ * data from Megacam, g' filter, CCD 01:
+ *
+ * magnitude conversions
+ * instrumental mag -> rough mag -> system mag -> reference mag
+ *  
+ * Mruf = -2.5*log(DN) + 2.5*log(exptime) + PS_ZERO_POINT
+ * Minst = Mruf - 2.5*log(exptime) - PS_ZERO_POINT
+ * Msys = Mruf + C_w + K_w (airmass - 1) + SUM (X_{w,i} (color - color_ref)^i)
+ * Mref = Msys + C_w + SUM (X_{w,i} (color - color_ref)^i)
+ *  
+ */
+