Export light curve in AAVSO format¶
The AAVSO Extended format is one of the export formats supported by the Muniwin application. The format is used to submit the CCD or DSLR to the American Association of Variable Star Observers (AAVSO).
General overview¶
In order to save your observation in the format that the AAVSO accepts, take the following steps:
Process your observation data and create a light curve. The light curve should consists of differential magnitudes; this is the default for the standard light curve generation process in the Muniwin application.
Open the dialog for saving the light curve: .
Select the AAVSO Extended Format as the file type. Choose a directory where the file shall be stored to and fill in the name of the file. Confirm the dialog.
A new dialog appears. The dialog allows you to fill in the information about the observation and the observer. Follow the steps in the dialog and fill in the data. When its last page is confirmed, the file is generated.
Detailed description¶
Process your observation data and create a light curve. The light curve should consists of differential magnitudes; this is the default for the standard light curve generation process in the Muniwin application. A detailed description of these steps can be found in the chapter Light curve.
The following steps are optional:
If you check the option to compute the heliocentric correction, you will have the choice to save heliocentric Julian dates to the exported file. You need to fill in celestial coordinates of the variable star.
You can also check the option to include the air mass coefficient values as well. If you do so, the values will be saved to the file. You have to fill in celestial coordinates of the variable star and also geographic coordinates of the observation location.
Make a light curve¶
In the next dialog, select the stars. If you follow the standard photometry scheme with one comparison star, you have to mark at least the variable star and one comparison star. It is recommended to pick up one check star, which helps you to choose an optimum aperture.
The enseble photometry mode is also supported. In this mode, you combine several comparison stars together; in this case, marking at least one check star is mandatory. More about this mode can be find in the chapter Ensemble photometry.
Mark the variable star (red), comparison star (green) and check stars (blue).¶
In the next dialog, select the aperture. If you marked at least one check star, the dialog shows a graph of standard deviation between the comparison star and the check star vs. the aperture size. Usually it is a V-like curve. Choose the aperture with minimum value and select it.
Select an aperture with minimum value¶
A new dialog shows a light curve:
Light curve of the variable star. Please note, that the magnitudes are differential (V-C).¶
In the window with a light curve, click on the –> Save` item in the local menu. A new dialog appears. Locate the folder where you want to save the results (1) and fill in the name of the output file (2). Choose the file type to be AAVSO Extended Format (3). If you checked the option to compute heliocentric correction, you have the choice to export Julian dates helicentric or geocentric (4). Confirm the dialog by the Save button (5).
Specify directory and file name, choose the correct file type.¶
A new dialog appears:
Fill in the observation data (page 1)¶
Fill in the observation data:
(1) Star identification - use the AAVSO Designation, the AAVSO Name, or the AAVSO Unique Identifier, but NOT more than one of these.
(2) Observer code - the official AAVSO Observer Code for the observer which was previously assigned by the AAVSO.
(3) Observation type - specify type of the camera - CCD or DSLR.
(4) Filter - click the Browse button to choose the color filter used.
(5) Chart - please use the sequence ID you will find in red at the bottom of the photometry table. If a non-AAVSO sequence was used, please describe it as clearly as possible.
(6) Notes - comments or notes about the observation. Leave this field blank if you don’t want to specify any notes.
Click the Next button to continue. The dialog is switched to the next page.
Fill in the observation data (page 2)¶
The next page is designated to fill in the data about the comparison star. Provide the comparison star identifier (usually an integer number) and brightness of the comparison star according to the filter you used. Click the Next button to continue.
In case of the ensemble photometry, you don’t need to fill in anythink on this page, just click the Next button to continue.
The dialog is switched to the next page.
Fill in the observation data (page 3)¶
The last page is shown only if you selected a check star. Please note, that in case of the ensemble photometry, using the check star is mandatory. Provide the check star identifier (20). Click the Save button to finish the dialog. When the dialog is finished the file is generated.
You can review the content of the file using a text editor:
Generated file with exported observation in the AAVSO Extended Format shown in the Notepad application.¶
Standardized magnitude¶
Under the AAVSO Extended format, the brightness of a variable star is reported in the form of the standardized magnitude, defined as:
V_{std} = (V_{ins} - C_{ins}) + C_{std}
where V_{ins} and C_{ins} are the instrumental magnitude of the variable and the comparison, respectively, and C_{std} is the chart magnitude for the comparison. The (V_{ins} - C_{ins}) part is the V-C value that you find in the (differential) light curve created in the software. You specify C_{std} values for your comparison in the export settings (see above).
See this page for the original description.
Unlike the variable, which is reported as a standardized magnitude, the brightness of the comparison and the check star is reported in form of the instrumental magnitude - C_{ins}. Please note, that there is a different in reporting comparison and check star magnitude in the standard (single comparison star) and the ensemble photometry (multiple comparison stars).
Ensemble photometry¶
When multiple stars are used to stand in for a comparison, the value of C_{std} needs be computed from chart magnitudes of all stars which are incorporated in the ensemble. The C-Munipack software uses flux averaging, so the instumental magnitude of the comparison C_{ins} is replaced in the above equation by the following formula.
C_{ins} = -2.5 log_{10} (\frac{1}{N} \sum 10^{-0.4 C_{ins,i}})
where N is a number of stars in the ensemble, and C_{ins,i} is the instrumental magnitude of i-th star in the ensemble.
Similarly, we define the chart magnitude of the comparison C_{std}:
C_{std} = -2.5 log_{10} (\frac{1}{N} \sum 10^{-0.4 C_{std,i}})
where C_{std,i} is the chart magnitude of i-th star in the ensemble.
See also
- AAVSO Extended Format
- AAVSO Observer Code
- AAVSO Unique Identifier
- Standardized magnitude