the algorithm of daophot.phot

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the algorithm of daophot.phot

haha

10/25/2013 03:46PM (Read 1645 times)

Chatty

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Generally pixel table is full of grids.But the photrometric aperture is a circle.

Question is how to deal with the grids which are partly in the aperture?
If we use an area weighting, the calculation will not be easy.

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fitz

10/25/2013 06:54PM

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I'm not sure I fully understand the question, however DAOPHOT uses fractional pixel value when computing the magnitudes. See the Photometry documentation at https://iraf.net/irafdocs for details on algorithms used.

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haha

10/26/2013 11:55AM

Chatty

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Quote by: fitz

I mean the aperture is a circle.When we do photometry, how does the iraf command phot deal with the pixels partly(they lie on on the circle) in the circle(we take one pixel as a square)? Their contribution should be considered.
But how to deal with their contribution?

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fitz

10/26/2013 08:18PM

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By 'fractional pixels' I mean that if say half the pixel is covered by the circular annulus then only half the flux value will be used.

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haha

11/03/2013 02:41PM

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Quote by: fitz

By 'fractional pixels' I mean that if say half the pixel is covered by the circular annulus then only half the flux value will be used.

You mean for every pixel daophot.phot will calculate the area in the aperture?

The highly cited paper http://adsabs.harvard.edu/abs/1987PASP...99..191S did not mention it.

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