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Diffstat (limited to 'noao/digiphot/apphot/doc/apsums.apps')
| -rw-r--r-- | noao/digiphot/apphot/doc/apsums.apps | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/noao/digiphot/apphot/doc/apsums.apps b/noao/digiphot/apphot/doc/apsums.apps new file mode 100644 index 00000000..ea5843bf --- /dev/null +++ b/noao/digiphot/apphot/doc/apsums.apps @@ -0,0 +1,19 @@ +The apphot and daophot package aperture photometry tasks have been modified +to compute the aperture sums and areas in double precision instead of real +precision. This change minimizes machine precision errors that can become +significant for large apertures and very low noise or synthetic data. + +These tasks have also been modified to output negative values of the total +flux should they occur. Formerly these values were being artificially set to +0.0. This change makes it easier to see the effects of any sky value and machine +errors. + +The modified apertures photometry tasks are available as part of the +external addon package digiphotx. To retrieve and install digiphotx, ftp +to 140.252.1.1, login as anonymous, cd to iraf/extern, retrieve the file +digiphotx.readme, and follow the installation instructions. + + + + Lindsey Davis + davis@noao.edu |