arXiv subjects

Matti Gehlen

Publications and source records attributed to Matti Gehlen.

3 recordsLinked to original sources

arXiv2026

Direct Imaging and Gradient-Based Analysis of the 12 August 2026 Partial Solar Eclipse from a Freely Rotating High-Altitude Balloon

We report a proof-of-concept observation of the partial solar eclipse of 12 August 2026 using a freely rotating high-altitude balloon launched from Oldenburg, northern Germany. The payload carried two Insta360 ONE RS cameras equipped with 4K Boost wide-angle lenses; covered by filter material taken from a BRESSER eclipse viewing glass. Interval photographs were acquired every 10 s at ISO 800 and 1/1000 s. Of approximately 1,300 images, 21 contained a directly visible image of the eclipsed Sun, spanning 19:19:15-20:38:21 CEST and both sides of the local eclipse maximum. To test whether quantitative eclipse information could be recovered from these small, non-stabilized wide-angle images, the visible solar area was estimated using a two-dimensional gradient-based solar edge analysis and normalized to the first observation. The image-derived obscuration followed the independently calculated eclipse geometry with Pearson r = 0.959, a mean absolute difference of 9.5 percentage points, and an RMSE of 11.5 percentage points. Systematic deviations are consistent with the limitations of an uncalibrated action-camera system, including point-spread function, field-dependent lens response, filter geometry, and camera-to-camera differences. The results demonstrate that passive payload rotation can yield both visually useful and semi-quantitative direct eclipse observations without active solar pointing, and define a calibration strategy for future balloon-borne eclipse measurements.

astro-ph.IM↗

arXiv2025

Beyond the Clouds: Advanced Data Analysis of a Dutch Sky Quality Meter Network

Light pollution is an increasing environmental concern, impacting both ecological systems and human health. This report presents an analysis of light pollution data from the washetdonker.nl SQM network from 2020 until 2023, with a focus on indirect light pollution, commonly known as skyglow. By integrating measurements from Sky Quality Meter (SQM) stations in the network and cloud cover data from EUMETSAT, we conducted a comprehensive analysis of night sky brightness across a region encompassing northern Netherlands and the western part of the German Wadden Coast. Yearly changes in brightness for 27 locations were ranked and plotted, revealing that in the darkest areas, light pollution is increasing at a rate of 2.78 to 6.68 percent per year. A trend emerged showing that brighter areas experienced lower variability in brightness, while darker zones exhibited higher variability. This is due to the dominance of artificial light sources, such as street lighting, in brighter areas, which reduces the influence of natural light sources like the Moon, stars, and cloud backscatter. Seasonal patterns and the effects of the Milky Way were also investigated. Density plots were employed to visualize these changes in night sky brightness, helping to identify specific sources of light pollution, such as greenhouse lighting and streetlight turn-off times. These findings emphasize the need for systematic monitoring of light pollution and offer valuable insights that can guide public awareness initiatives and inform light pollution mitigation strategies.

astro-ph.IM↗

arXiv2022

Robotic observation pipeline for small bodies in the solar system based on open-source software and commercially available telescope hardware

The observation of small bodies in the Space Environment is an ongoing important task in astronomy. While nowadays new objects are mostly detected in larger sky surveys, several follow-up observations are usually needed for each object to improve the accuracy of orbit determination. In particular objects orbiting close to Earth, so called Near-Earth Objects are of special concern as a small but not negligible fraction of them can have a non-zero impact probability with Earth. Telescopes are often hosted by amateur observatories. With upcoming new NEO search campaigns by very wide field of view telescopes, like the Vera C. Rubin Observatory, NASA's NEO surveyor space mission and ESA's Flyeye telescopes, the number of NEO discoveries will increase dramatically. This will require an increasing number of useful telescopes for follow-up observations at different geographical locations. While well-equipped amateur astronomers often host instruments which might be capable of creating useful measurements, both observation planning and scheduling, and also analysis are still a major challenge for many observers. In this work we present a fully robotic planning, scheduling and observation pipeline that extends the widely used open-source cross-platform software KStars/Ekos for INDI devices. The method consists of algorithms which automatically select NEO candidates with priority according to ESA's NEOCC. It then analyses detectable objects (based on limiting magnitudes, geographical position, and time) with preliminary ephemeris from the Minor Planet Center. Optimal observing slots during the night are calculated and scheduled. Immediately before the measurement the accurate position of the minor body is recalculated and finally the images are taken. Besides the detailed description of all components, we will show a complete robotic hard- and software solution based on our methods.

astro-ph.IM↗