The Co-alignment of Winged H{\alpha} Data Observed by the New Vacuum Solar Telescop

TL;DR

This paper presents an optical flow-based algorithm for co-aligning winged Hα data from the NVST, achieving high accuracy and facilitating solar physics research with standardized high-resolution spectroscopic data.

Contribution

It introduces a novel alignment algorithm for winged Hα data, improving accuracy and standardization of NVST solar observations.

Findings

Alignment accuracy reaches about 0.1 arcseconds.

Algorithm effectively aligns images with off-band differences below 0.6 Å.

Final data product enhances usability for solar physicists.

Abstract

The New Vacuum Solar Telescope (NVST) has been releasing its novel winged Ha data (WHD) since April 2021, namely the Ha imaging spectroscopic data. Compared with the prior released version, the new data are further co-aligned among the off-band images and packaged into a standard solar physics community format. In this study, we illustrate the alignment algorithm used by the novel WHD, which is mainly based on the optical flow method to obtain the translation offset between the winged images. To quantitatively evaluate the alignment results of two images with different similarities, we calculate the alignment accuracies between the images of different off-band and line center, respectively. The result shows that our alignment algorithm could reach up to the accuracy of about 0.1 "when the off-band of winged image is lower than 0.6 \.A. In addition, we introduce the final product of the WHD in detail, which can provide convenience for the solar physicists to use high-resolution H{\alpha} imaging spectroscopic data of NVST.