Re: "Inverted light curve"
Posted by karenacollins on Aug 08, 2014; 7:46am
URL: http://astroimagej.170.s1.nabble.com/Inverted-light-curve-tp170p171.html
Hi David,
Under the Multi-plot Main->Y-axis menu, you have two options to display the y-axis orientation ("Invert Y-axis" and "Negate relative magnitude calculations"). Set these to display in the orientation that you prefer.
The "rel_flux_T1" columns contains the raw values after dividing the target star integrated counts by the total of the comp star integrated counts. This is neither normalized nor in magnitude. However, you can display the data in relative magnitude by selecting "Out Mag" on the desired plot row in the Multi-plot Y-data panel.
On the other hand, if you want to display the data normalized to a region of the data, in the Multi-plot Y-data panel select a "Norm/Mag Ref" mode, such as
to normalize
using the out-of-transit portion of a light curve (i.e. the
baseline), and then using the Multi-plot Main "Fit and Normalize
Region Selection" controls for "Left" and "Right" to define T1
(start of ingress) and T4 (end of egress points). Then the baseline
data will be normalized to an average value of 1.0. The error data
will be normalized by the same multiplier. This is essentially the
percent relative flux change that you are asking for (divided by
100).
To save any normalized data or plotted in magnitude, click to "New Col" button
on the left hand side of the corresponding plot row (in
the Multi-plot Y-data panel). This will allow you to add the newly
formatted data to new columns in the table to use in other programs
or to submit to collaborators.
To find information on all of the data columns, go to Multi-plot Main->Help->Data naming convention...".
If you haven't discovered section 10 in the latest version of the user guide (10. Step-by-Step Guide to Differential Photometry in AIJ), I would encourage you to work through that section. For reference, the guide is here:
http://www.astro.louisville.edu/software/astroimagej/guide/AstroImageJ_User_Guide_2.1.4.pdf
Karen
URL: http://astroimagej.170.s1.nabble.com/Inverted-light-curve-tp170p171.html
Hi David,
Under the Multi-plot Main->Y-axis menu, you have two options to display the y-axis orientation ("Invert Y-axis" and "Negate relative magnitude calculations"). Set these to display in the orientation that you prefer.
The "rel_flux_T1" columns contains the raw values after dividing the target star integrated counts by the total of the comp star integrated counts. This is neither normalized nor in magnitude. However, you can display the data in relative magnitude by selecting "Out Mag" on the desired plot row in the Multi-plot Y-data panel.
On the other hand, if you want to display the data normalized to a region of the data, in the Multi-plot Y-data panel select a "Norm/Mag Ref" mode, such as
to normalize
using the out-of-transit portion of a light curve (i.e. the
baseline), and then using the Multi-plot Main "Fit and Normalize
Region Selection" controls for "Left" and "Right" to define T1
(start of ingress) and T4 (end of egress points). Then the baseline
data will be normalized to an average value of 1.0. The error data
will be normalized by the same multiplier. This is essentially the
percent relative flux change that you are asking for (divided by
100). To save any normalized data or plotted in magnitude, click to "New Col" button
on the left hand side of the corresponding plot row (in
the Multi-plot Y-data panel). This will allow you to add the newly
formatted data to new columns in the table to use in other programs
or to submit to collaborators.To find information on all of the data columns, go to Multi-plot Main->Help->Data naming convention...".
If you haven't discovered section 10 in the latest version of the user guide (10. Step-by-Step Guide to Differential Photometry in AIJ), I would encourage you to work through that section. For reference, the guide is here:
http://www.astro.louisville.edu/software/astroimagej/guide/AstroImageJ_User_Guide_2.1.4.pdf
Karen
On 8/8/2014 3:19 AM, David [via
AstroImageJ] wrote:
Hello,
First, AstroImageJ has been a great help in my work, thank you.
Second, I was making a light curve of an exoplanet transit and the
transit feature showed up inverted. I know that can happen if one subtracts the target
from calibrator instead of the other way around, so is it possible
for someone to accidently do this with AstroImageJ ?
I take it that the units of "rel_flux_T1" is in magnitudes, it could be useful
if instead one used percentage flux change instead.
Thank you
David
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