VariableStarsObserver

Variable Stars Observer is based on the well-known PixInsight Dynamic PSF process.
It provides PixInsight users with an easy way to estimate the magnitude of variable stars.

I am seeking feedback from experienced astronomers in variable star analysis.

To use VariableStarsObserver, simply open an image in PixInsight and launch the VariableStarsObserver process from the menu PROCESS > ImageInspection. In the process dialog box, click on Apply button on bottom left of the dialog box or the grey star on the top right corner of the "Variable Stars Observer" section.

The process will query the International Variable Stars Index to retrieve all variable stars available in the image's field of view. It will then perform a second query to the AAVSO Plotter to retrieve all the constant stars and associated data.

Next, the process will perform a PSF (Point Spread Function) measurement on each constant and variable star. The magnitude of the variable stars will be estimated based on the constant stars. The stars will then be sorted by channel and magnitude (either reference magnitude or estimated magnitude).

The process will automatically select a variable star near the center of the image. Constant stars with magnitudes close to the variable star will be automatically selected as comparison and check stars.

A new calculation of the variable star's magnitude will be performed based on selected compare star and displayed in the text box.

Table in Variable Stars Observer section provides following information based on selected stars in picklists.

Variable star:

• Name of variable star.
• Magnitude estimated based on compare star.
• Error estimated based on local Signal/Noise Ration (SNR).
• Local Signal/Noise Ration (SNR) measured.

As reminder, the estimation of magnitude is Mv = Mc - 2.5 x Log10(Fv/Fc)

Compare star:

• AAVSO Unique ID (AUID) of the compare star.
• Known reference magnitude from the AAVSO.
• Error from the AAVSO.
• B-V index from AAVSO.
• Local Signal/Noise Ration (SNR) measured.
• Instrumental magnitude (-2.5 * log10(flux)).

Check star:

• AAVSO Unique ID (AUID) of the compare star.
• Known reference magnitude from the AAVSO and gap with estimated magnitude.
• Error from the AAVSO.
• B-V index from AAVSO.
• Local Signal/Noise Ration (SNR) measured.
• Instrumental magnitude (-2.5 * log10(flux)).

Additional information are povided on the right:

• AAVSO chart Id used by the process.
• Center Right Ascension and Declination.
• Observation time.
• Channel analyzed and filter considered.
• Airmass is displayed if provided in FITS header.
• Instrumental magnitude (-2.5 * log10(flux)).

The parameters in the Variable Stars Observer section allow users to:

• Select a specific view.
• Define the limit magnitude of constant and variable star searches.
• Specify the field of view to be considered during the star search (percentage of the image diagonal).
• Select different variable, comparison, or check stars.

Additional buttons provide the following functionality:

• Yellow star button: Search only for variable stars.
• Green star button: Search only for constant stars.
• Information button: Display AAVSO data for selected stars.

Compare to Dynamic PSF, the star list, on top of the process dialog box, contains additional information:

• Star type (Green for constant stars, Yellow for variable stars, Red for saturated stars, Blue for custom variable stars).
• Star AUID when defined in AAVSO referencial.
• Star Label from AAVSO Plotter chart (constant stars) or star name (variable stars).
• Star magnitude (either from AAVSO for constant stars or estimated based on constant stars magnitude and signal).
• Magnitude error (either from AAVSO for constant stars else estimated based on local star noise / signal ratio).
• B-V index (based on AAVSO reference or estimated).
• Local Signal/Noise Ration (SNR).
• Right Ascension / Declination of the star based on AAVSO data.
• Coordinates of the star in the image, derived from AAVSO RA/Dec.

Additional sorting options are available in the dedicated sort-by dialog box:

• Sort by Magnitude (default).
• Sort by SNR.
• Sort by B-V.
• Sort by Type.
• ...

From this star list user can:

• Double-click on a star to directly select the star as variable or comparison star (depending on star type clicked).
• hold Control and double-click on constant star to select a check star.

When a new variable star is selected, the process will automatically select default comparison and check stars based on magnitude. You can then manually select different stars if needed.

From the image, a simple click on a star will add it to the list as a custom variable star.

When Sort by Channel and Magnitude is selected, all saturated stars are moved to the end of the list and are excluded from any magnitude calculation. Users can delete any stars from the star list. A new magnitude calculation will be performed, and the report will be automatically updated. The process can work with monochrome, tri-color images, or a selected channel from a tri-color image. In this first version, process will consider mono channel images as TG band and tri-color image as TR, TG, TB bands.

The user can fill Observer Code and click on Exoprt button to generate a formal AAVSO report in Extended format (CSV file). User can click on Submit button to open official AAVSO submit page.

Before submission, AAVSO will display a graph comparing your measurement to those of other observers. Below a real example show a difference below 0.002 in magnetude versus other reports at same date.

Enjoy!