AstroSequence Explorer

This is the first public release of AstroSequence Explorer, a GUI application for semi-automated full-field astronomical time-series photometry.
AstroSequence Explorer is designed for astrophotographers who want to explore the science content of their image sequences, searching for variable stars, eclipsing binaries, and even transiting exoplanets, with the push just three buttons.

Candidate review panel with light curves, reference-field cutouts, manual labels, ML suggestions, and catalog information.

What AstroSequence Explorer does

AstroSequence Explorer turns a calibrated and aligned astronomical image sequence into a searchable field-wide time-domain dataset. Instead of measuring one target at a time, it performs automatic aperture photometry for all detected point sources within the linearity range of the detector. It builds light curves, ranks variability candidates, and helps the user identify known or new variable stars, eclipsing systems, and transit-like events with automatic matching of the GAIA DR3 database, GAIA variability and The International Variable Star Index (VSX) databases.

The program is designed for observers who acquire long FITS sequences of the same field and want a practical way to answer questions such as:

• Which stars in this field are variable?
• Are there transit-like or eclipse-like dips in the sequence?
• Are my candidates already known VSX or Gaia DR3 variables?
• Which candidates deserve manual inspection or follow-up observations?

Features

• Guided full-field analysis workflow
• Point-source detection and all-star aperture photometry
• Candidate ranking for variability and transit-like events
• Machine-learning assistance to spot real variability from noise
• Interactive candidate inspection
• Plate solving and catalog matching

Recommended input data

AstroSequence Explorer expects a sequence of calibrated and aligned FITS images of the same field.
It is not intended to replace a raw-image calibration pipeline. Bias/dark/flat correction, and image alignment should be performed before loading the sequence. For a fast, reliable and free reduction software, you can try ExoPhotoCurve.

System Requirements

• Python 3.10+
• Screen resolution of at least 1600×900 px. Optimal resolution: 1920×1080 or larger
• Recommended for plate solving: ASTAP with a suitable local star database (D50 works fine)
• Main Python dependencies include: numpy, astropy, matplotlib, scipy, photutils, astroquery, scikit-learn, joblib, and FreeSimpleGUI

A standalone Windows installer is also available.

Installation

You can install AstroSequence Explorer using pip:

pip install astrosequence-explorer

Then run:

astrosequence-explorer

On Windows, you can just download the installer and install the application, without requiring Python.

Quick Start

Preliminary steps to perform just once:

1. Download and install the ASTAP application and at least the D50 catalog for WCS (plate solving) here
2. Recommended: Download an updated local copy of the AAVSO VSX catalog (with more than 10 million variable stars) from CDS FTP here. You should select the FTP tab, and download the vsx.dat file in fits format (about 2 GB). AstroSequence Explorer can use also the online query for the VSX, but this approach is not very reliable, so maintaining an updated local copy of the catalog is very useful.

Analysis

1. Download and unzip the example sequence centered on the transit of KELT-10b exoplanet here.
2. Open AstroSequence Explorer.
3. Select the folder containing the FITS sequence.
4. Click Load sequence.
5. Click Set automatic parameters and wait until the pre-analysis is done.
6. Optional: enable ASTAP plate solving (if you have it installed) and set the path to ASTAP cli application (usually in Program Files for Windows)
7. Optional: with AStAP activated, you can activate also the Gaia/VSX catalog matching.
8. Click Run full analysis and wait few minutes.
9. Inspect the ranked candidates in the Candidate review tab. Green highlighted rows show the best candidate variable stars found.
10. Wait the catalog match to be completed and find out which candidate variable is already known in the GAIA variability and VSX catalogs.
11. Click candidates to preview their light curves and reference-field cutouts.
12. Select a candidate (for example the first one) with no correspondence in the GAIA variability and VSX databases and perform a deep search using all the available online catalogs via right click --> deep catalog search. Wait for the response. AstroSequence Explorer will tell you that this variable appears in the SIMBAD database and therefore is not a new discovery. Try with the next one on the list that has no correspondence with the GAIA variability and VSX catalogs to see if you are more lucky.

How candidate ranking should be interpreted

AstroSequence Explorer is designed to find and prioritize interesting candidates, not to make final scientific classifications automatically.

The ranking combines interpretable photometric indicators such as scatter excess, robust amplitude, and dip-like behavior. The ML suggestion is an additional prioritization aid. A source marked as ML-interesting is worth inspecting first, while ML-uncertain candidates should not be ignored when the light curve or catalog information looks promising.

All candidates should be visually checked, especially in crowded fields, near the image border, close to saturated stars, or in sequences affected by clouds, tracking issues, meridian flips, or variable background.

License

AstroSequence Explorer is distributed under the license included in the LICENSE file. Please check the repository license before using, redistributing, or modifying the software.

Contact & Contributions

Found a bug? Want to suggest a feature?
Drop me an email!
Contact: Daniele Gasparri – daniele.gasparri@gmail.com
Take a look also at my website, if you are interested in astronomy: https://www.danielegasparri.com/