Re: Aperture radius settings in the Seeing Profile dialog
Posted by
karenacollins on
Mar 17, 2020; 12:58pm
URL: http://astroimagej.170.s1.nabble.com/Aperture-radius-settings-in-the-Seeing-Profile-dialog-tp1304p1313.html
Hi Richard,
Wow, good catch. It's been calculated in an unexpected way for many
years due to a bug found looking into your report. The bug is fixed
now, but it was decided to change the original 1.7-1.9-2.55
multipliers as part of the bug fix, because in our experience with
bright stars attempting to achieve mmag time-series photometry,
those values are too small. For now, I have changed to 2.0-4.0-6.0
for the three FWHM multipliers.
These values will be too large for a fainter star, so really what is
needed is an interface to allow the multipliers to be set by the
user. Unfortunately, I don't have time to implement that right now.
Of course the paper will still be wrong until I have a chance to
update it also.
If you are interested in the new version of AIJ, you can update to
the daily build (3.4.0.04 or later).
Karen
On 3/15/2020 12:35 PM, Richard Lee [via
AstroImageJ] wrote:
Hello
Question about aperture radius settings in the Seeing Profile
dialog, Fig 16 in the extended AIJ paper 2017.
Based on the aperture radius-to-FWHM factors in the figure script
& A.5 Radial Profile, I get the following aperture radius
values for FWHM = 10.5 pixels, compared with figure annotations
(nn).
Source radius = 1.7 x 10.5 = 17.9 (20)
Bkgnd inner radius = 1.9 x 10.5 = 20.0 (35)
Bkgnd outer radius = 2.55 x 10.5 = 26.7 (53)
The inner & outer radii are roughly 2x the computed values, so
maybe the figure shows diameter instead of radius?
Running version 3.4.0.01 I get a similar discrepancy, the source
aperture matches but the bkgnd apertures are about twice the
expected radius.
Regards
Richard Lee