Near-infrared imaging of the twilight sky: enhanced detection of noctilucent and high-altitude clouds

Abstract

As part of efforts to improve the methodology for detecting and monitoring noctilucent clouds (NLCs), observations of the twilight sky conducted during the summer season of 2025 were analyzed. The study examines existing approaches to NLC imaging and demonstrates that the information content of ground-based observations can be significantly enhanced through increased image contrast. To achieve this, observations were extended from the visible spectral range to the near-infrared (NIR) region using a modified CANON 1000D camera with enhanced NIR sensitivity and a set of interchangeable optical filters. For the first time, simultaneous monitoring of the twilight sky was performed using two cameras operating in different spectral ranges: a modified CANON 1000D in the near infrared and a CANON 2000D in visible light. Observations carried out from late May to early September 2025 revealed a substantial increase in image contrast in the NIR region compared with conventional visible-light imaging. The obtained results demonstrate the advantages of near-infrared observations for the detection and analysis of noctilucent clouds and other atmospheric phenomena under twilight conditions. The proposed approach expands the capabilities of ground-based optical monitoring and provides a basis for further development of observational techniques for upper-atmosphere studies.

Keywords: twilight segment, noctilucent clouds, image contrast, infrared camera, infrared imaging, cloud monitoring.