imsurfit ‘hole’

spacermase wrote on Aug 25, 2010

Greetings all,

I'm currently doing photometry on some images of Rhea, and I've been using imsurfit to remove the gradient from Saturn. It's been doing this pretty well, but I've noticed that, after subtracting the background away from the image, frequently the area immediately around Rhea will end up darker than the rest of the sky in the final image, which is probably interfering with the photometry (see attached). Is there anyway to reduce or eliminate this dark 'hole' around Rhea? Thanks!

I'm using regions=invcircle, with a circle radius of 6. Parameters are below.

input = Input images to be fit
output = Output images
xorder = 3 Order of function in x
yorder = 3 Order of function in y
(type_ou= fit) Type of output (fit,residual,response,clean)
(functio= spline3) Function to be fit (legendre,chebyshev,spline3)
(cross_t= yes) Include cross-terms for polynomials?
(xmedian= 1) X length of median box
(ymedian= 1) Y length of median box
(median_= 50.) Minimum fraction of pixels in median box
(lower = 0.) Lower limit for residuals
(upper = 0.) Upper limit for residuals
(ngrow = 0) Radius of region growing circle
(niter = 0) Maximum number of rejection cycles
(regions= invcircle) Good regions (all,rows,columns,border,sections,c
(rows = *) Rows to be fit
(columns= *) Columns to be fit
(border = 50) Width of border to be fit
(section= ) File name for sections list
(circle = ) Circle specifications
(div_min= INDEF) Division minimum for response output
(mode = ql)

[img:70124ae678]http://a.imageshack.us/img153/6349/rheaq.jpg[/img:70124ae678]

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Mike Fitzpatrick wrote on Aug 25, 2010

I don't see where you've specified the 'circle' parameter to define what region is to be excluded. Maybe this is all there is to it? Maybe use a bigger radius to avoid edge effects?

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Last post on Aug 25, 2010