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:: Input mask file to co-add to the mask of the input image. Useful for marking pixels to be ignored from the photometry process beyond the ones which are previously marked in the input image. | :: Input mask file to co-add to the mask of the input image. Useful for marking pixels to be ignored from the photometry process beyond the ones which are previously marked in the input image. | ||
− | : '''-a,''' '''--aperture,''' '''--apertures''' <list of apertures> | + | : '''-a,''' '''--aperture,''' '''--apertures''' <list of circular apertures> |
− | :: List of apertures to be involved in the photometry. Each aperture is defined by three numbers: the radius of the aperture, and the inner radius and thickness of the annulus used for sky background estimation. The aperture specifications | + | :: List of circular apertures to be involved in the photometry. Each circular aperture is defined by three numbers: the radius of the aperture, and the inner radius and thickness of the annulus used for sky background estimation. The aperture specifications must be spearated by commas while these three numbers must be separated by colons. E.g. to perform aperture photometry on a series of apertures with a radius of 1.5, 2.0 and 2.5 pixels, where all of the annuli have an inner and outer radius of 6.5 and 12 pixels (i.e. the thickness is 5.5 pixels), one should write 1.5:6.5:5.5,2.0:6.5:5.5,2.5:6.5:5.5 as an argument for this option. |
+ | |||
+ | : '''-a,''' '''--aperture,''' '''--apertures''' <list of simple polygon apertures> | ||
+ | :: List of polygon shaped apertures. Polygons can only be simple (i.e. non-intersection) or weakly simple polygons which are defined throughout the form of P[x1,y1,...,xn,yn] or polygon[x1,y1,...,xn,yn]. The (x,y)=(0,0) point always refer to the aperture centroid as read from the input list (see '''--input-list''' above). There are two types of pre-defined simple polygons which is useful in astronomical image processing. The first definition is Q[R,n,alpha] or regular[R,n,alpha] which implies a regular polygon having n sides and an area equivalent to a circle with a radius of R and the polygon is rotated w.r.t the xy-plane by alpha degrees. In the asymptotic limit of n '''->''' infinity, this aperture is equivalent to a circular aperture. The second type is T[R,n,dx,dy] or trail[R,n,dx,dy] where this definition implies a nearly oval racetrack-shaped aperture with a curvature radius of R, a net length of L=sqrt(dx^2+dy^2), the round part is approximated by a regular n-gon and the whole shape is rotated w.r.t the x+ axis as defined by the (dx,dy) vector. In the limit of L '''->''' 0, this shape is equivalent to the aperture definition of regular[R,n,alpha]. The trail[....] shape is useful to perform photometry on asteroid or meteoroid trails. One should note that circular and polygon aperture definitions cannot be mixed. In addition, it should be noted that in case of polygon-shaped apertures, the second definition implies the inner edge of the background area and the third definition implies the outer edge of the background area. For instance, the aperture 3:5:5 can be ideal for point sources, the aperture trail[3,16,3.0,4.0]:trail[5,16,3.0,4.0]:trail[10,16,3.0,4.0] can be optimal for a asteroid trail on the same image that has a net length of 5.0 pixels and parallel with the vector (3.0,4.0). In this case, the equivalent radius of the third part is set to 10 which is equivalent to the 5+5=10 pixels of the radius of the outer annulus in the definition of 3:5:5. | ||
: '''-g,''' '''--gain,''' '''--gain-poly''' <gain polynomial> | : '''-g,''' '''--gain,''' '''--gain-poly''' <gain polynomial> |