SYSTEM: V2.9
NUMBER: 131 MODULE: artdata.mkobjects SYSTEM: V2.9 DATE: Mon Jul 23 10:53:43 MST 1990 FROM: valdes BUG: The moffat function size scaling (as set by the radius parameter) is incorrect. STATUS: The shape of the function is based on the correct beta but the size is scaled for a function with beta of: beta1 = 2 * beta - 2 Another way to look at it is that the flux level corresonding to the specified radius is different than the half intensity. The actual flux level is: F(radius) = 0.5 ** (beta / beta1) Finally, the radius which must be specified, rfudge, to get a desired radius at half intensity, rhalf, is: rfudge = rhalf * sqrt ((2**(1/beta1)-1) / (2**(1/beta)-1)) Note that there is no error for beta=2, the size is too large for beta>2, and the size is too small for beta<2. The workaround is to adjust the specified radius for a desired radius at half intensity using the above formula.