ODAA4
Hundreds of regular observers are sharing their work providing very valuable data to professional astronomers. This is very valuable at a time when professional astronomers face increasing competition accessing observational resources. Additionally, networks of amateur observers can react at very short notice when triggered by a new event occurring on a solar system object requiring observations, or can contribute to a global observation campaign along with professional telescopes.
Moreover, some experienced amateur astronomers use advanced methods for analysing their data meeting the requirements of professional researchers, thereby facilitating regular and close collaboration with professionals. Often this leads to publication of results in peer-reviewed scientific journals. Examples include planetary meteorology of Jupiter, Saturn, Neptune or Venus; meteoroid or bolide impacts on Jupiter; asteroid studies, cometary or exoplanet research.
Space missions also sollicitate amateur astronomers support. For example, to understand the atmospheric dynamics of the planet at the time of Juno flybys, NASA collaborates with amateur astronomers observing the Giant Planet. It showcases an exciting opportunity for amateurs to provide an unique dataset that is used to plan the high-resolution observations from JunoCam and that advances our knowledge of the Giant planet Jupiter. Contribution of amateurs range from their own images to Junocam images processing and support on selecting by vote the feature to be observed during the flybys. Other probes like Ariel or Lucy sollicitate amateur astronomers observation to support exoplanets and small bodies science.
This session will showcase results from amateur astronomers, working either by themselves or in collaboration with members of the professional community. In addition, members from both communities will be invited to share their experiences of pro-am partnerships and offer suggestions on how these should evolve in the future.
Session assets
Over the past few years, the Unistellar network has grown into the world’s largest citizen science telescope network, with more than 15,000 smart, digital and robotic telescopes (eVscopes) operated by amateur astronomers across the globe. The network has evolved into a powerful scientific tool, enabling coordinated observations that contribute directly to professional research. One of the most active and impactful areas has been the physical characterization of asteroids via optical photometry and stellar occultations—two complementary techniques that together provide critical constraints on asteroid spin states, shapes, sizes, and binarity.
Unistellar observers regularly participate in global campaigns coordinated through a dedicated Citizen Science website, Slack workspace, and Science mode in the Unistellar mobile app, which include tailored event predictions, observation guidelines, and data upload tools. Once uploaded, the data are processed through automated pipelines, where photometric time series are calibrated, modeled, and reported back to the community. The resulting lightcurves are not only used to determine rotation periods but also feed into lightcurve inversion algorithms to derive 3D shape models and spin axes. In parallel, high-time-resolution occultation observations allow for direct size measurements and detection of features such as satellites or ring systems.
We present results from recent Unistellar campaigns that demonstrate the scientific return of this distributed observational network. A highlight is the multi-chord occultation of asteroid (16583) Oersted, which yielded 10 positive detections and one grazing chord, enabling the first robust size and shape model of this main-belt asteroid. The occultation profile was combined with sparse photometry and lightcurve data to constrain the spin state via the ADAM algorithm, demonstrating the synergy between the two observational techniques.
Another successful campaign targeted the TNO 2013 LU28, a particularly challenging object due to the rarity of bright star occultation events. A dedicated global coordination effort led to three positive Unistellar chords—an exceptional achievement for a distant, slow-moving object—providing constraints on its size and shape, and highlighting the potential of amateur contributions even in the outer Solar System.
In the realm of lightcurve photometry, the Unistellar network has recently contributed to the rotation state characterization of several near-Earth asteroids (NEAs), where timely observations are critical due to their short visibility windows and fast apparent motion. The successful period determination of asteroid (7335) 1989 JA, for example, provided essential input for planetary defense modeling and was later published with citizen scientists as co-authors. In a related effort, targeted Unistellar campaigns led to dense lightcurve coverage of slowly rotating main-belt asteroid (319) Leona, contributing to derivation of its shape and pole orientation. Additionally, shape models of (775) Ampella and (211) Isolda were obtained by combining Unistellar photometry with archival data, demonstrating the network’s capacity to contribute to physical modeling of large object.
Ongoing campaigns are now focusing on main-belt asteroids from ancient collisional families, which offer a window into early Solar System evolution, as well as a new set of targets from young asteroid families that are suspected to be parent bodies of meteorites. These families, only a few million years old, offer an opportunity to study pristine spin and shape distributions, unaltered by long-term thermal torques or collisions. Photometric data from Unistellar telescopes are being used to derive rotational periods and, where data are sufficient, to construct shape models that will be compared with dynamical evolution simulations and meteorite spectral matches.
All these efforts are tightly linked to professional research projects such as the Czech Science Foundation (GAČR) project "Gaia–XSHOOTER: Survey of 'promising' asteroid families" (ID 25-16789S), where student-led analyses of lightcurve and occultation data from Unistellar observers play a direct role in advancing the science. Importantly, these projects create a bridge between professional institutions and motivated amateur astronomers, offering clear observational goals, robust data processing pipelines, and opportunities for co-authorship in peer-reviewed publications.
The Unistellar platform demonstrates the power of organized, large-scale amateur contributions to asteroid science. Its structure—combining smart telescope technology, global coordination, and automated pipelines—lowers the barrier to entry while ensuring data quality. Campaigns such as those targeting Oersted, Nezarka, LU28, and multiple NEAs illustrate the network’s capability to contribute meaningfully to current research questions in planetary science, including asteroid evolution, meteorite parent body identification, and planetary defense.
In this presentation, we advocate for further integration of citizen science networks into professional observing strategies, particularly in areas where fast response and geographical diversity are crucial. We will outline best practices for campaign planning, data validation, and community engagement, and reflect on the lessons learned from building an international team of amateur observers who are not just participants—but active contributors—to peer-reviewed planetary science.
Figure 1: Shape model projection of asteroid (16583) Oersted (gray silhouette) overlaid on the occultation chord profile from the April 2024 multi-chord stellar occultation event. The model, derived using the ADAM algorithm, combines lightcurve data and occultation chords to constrain the asteroid’s size, shape, and spin state. The chords represent individual observer detections (solid lines = positive chords; dashed = negative/grazing), and the agreement demonstrates the consistency of the derived physical model.
How to cite: Hanuš, J., Pokorný, P., Marchis, F., Lambert, R., Esposito, T. M., and Ďurech, J.: Unistellar Network Contributions to the Physical Characterization of Asteroids through Lightcurves and Stellar Occultations, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-490, https://doi.org/10.5194/epsc-dps2025-490, 2025.
We investigate the heliocentric brightening behavior of long-period comets as a function of their dynamical age, parameterized by the original reciprocal semimajor axis, 1/a0. The analysis is designed to test longstanding assertions regarding cometary photometric evolution using a substantial dataset of magnitude measurements reported to the Minor Planet Center.
Our sample comprises 272 long-period comets, for which we derive brightening parameters by fitting observed magnitudes with a linear model in logarithmic heliocentric distance of the form T − 5 logΔ = m + k log r, where T is total magnitude, and Δ and r are geocentric and heliocentric distance. The fitted brightening parameters, m and k, allow us to quantify both heliocentric and local brightening rates.
Adopting the dynamical classification scheme introduced by Oort, we separate the comets into three dynamical groups — new, intermediate, and old — and then systematically compare their photometric behavior.
The results indicate that:
- dynamically new comets brighten more gradually than older ones, particularly at heliocentric distances less than 3 AU;
- the brightening rates of new and intermediate comets exhibit a clear dependence on heliocentric distance; and
- new comets tend to be intrinsically brighter and display a tighter correlation between their derived brightening parameters.
This analysis is based on a study accepted for publication in A&A (https://doi.org/10.1051/0004-6361/202453565), and a preprint is available at
https://arxiv.org/abs/2504.00565.
Figure 1 - Number of comets and strands analyzed against reciprocal semi major axis (1/a0). Dynamically new, intermediate, and old comet ranges are indicated.
Figure 2 - Global heliocentric light curve of comet C/2019 U6 (right) and the same data grouped by observatory and filter (left). These grouped sets of data, called strands, allow more reliable relative photometry and assessment of uncertainties.
Figure 3 - Average brightening in magnitudes of long period comets relative to 1 AU, categorized by Oort dynamical group.
Figure 4 - Rate of brightening versus heliocentric distance for LPCs for each Oort group. Different colors split the LPCs into interior and exterior to 2, 3 and 4 au.
Figure 5 - Relation between the brightening parameters m and k for each Oort group. Best fit lines are fit to each group. Inset shows the cumulative distribution of residuals for each fit.
How to cite: Lacerda, P., Guilbert-Lepoutre, A., Kokotanekova, R., Inno, L., Mazzotta Epifani, E., Snodgrass, C., and Biver, N.: Heliocentric Light Curves of Long-Period Comets, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1941, https://doi.org/10.5194/epsc-dps2025-1941, 2025.
Introduction
Jupiter’s northern Equatorial Zone (EZn) and southern North Equatorial Belt (NEBs) are dominated by three features: five-micron hotspots (seen as North Equatorial Dark Features, NEDFs, in the optical), white cloud plumes, and complex local circulation. These features are influenced by the NEBs jet, which is modulated by a meridionally trapped Rossby wave, in conjunction with the high concentration of ammonia in the EZ and the ammonia depletion in the NEB. Numerous measurements have been made of the temperature, aerosol, and ammonia distributions in this region (c.f. Fletcher et al., 2020). And a number of models have been partially successful at explaining the interrelationships between the observed features (c.f Showman & Dowling, 2000). Here we explore the ammonia and cloud height distribution during 2024-25, when NEDFs and five-micron hotspots were prominent, using the optical band-average technique (Hill et al., 2024, Irwin et al., 2025). We show that while many sensing methods highlight the ammonia and aerosol depletion in five-micron hotspots, this band average method highlights enhancements in ammonia to the south of the hotspots.
Observations
Multiple observations on 2025-01-06 were made allowing coverage of a wide range of longitudes and coverage of a given longitude at several zenith angles. Figure 1 shows maps constructed using the method of Hill et al. (2024). An empirical limb correction is applied in addition to a weighted averaging scheme for overlapping observations. The data clearly show that enhanced ammonia regions lie to the south of NEDFs (labeled 1-4 in order of ascending longitude). For the ammonia enhancements we observe a planetary wave number of nine, within the range of hotspot and NEDF wavenumbers typically observed.
Discussion
The NEBs jet speed peaks at about 7° N, which in fact marks the boundary between the NEDFs and the ammonia enhancements. Anticyclonic gyres are a known feature seen in the same location as we show ammonia enhancements (c.f. Choi et al., 2013). We hypothesize that these gyres are regions of uplift and outflow, bringing up ammonia rich air from deeper levels of the atmosphere. The NEDFs are thought to be areas of subsidence, with cyclonic flow, where dryer air descends from above and results in a clearing of aerosols. Figure 1D shows this schematically with upwelling occurring at the gyres, horizontal winds carrying condensates from the upwelling source to the east and northeast as the visible cloud plumes, and descending clear air in the NEDFs.
To further support this hypothesis, we analyze the ammonia mole fraction and cloud pressure at the NEDFs, gyres, and in the plumes through a regions-of-interest (ROI) approach. Figure 2 shows a longitudinal subset of the data in Figure 1, focusing on ammonia regions 3 and 4. Rectangles outline the ROIs which are analyzed for three observation times in Figure 2A. Figure 2B shows a time series of average values at each observation time for cloud pressure and ammonia mole fraction along with statistical errors. Finally, 2C shows scatter plots of the average cloud pressure versus the ammonia abundance. Note the very clear clustering of points where the NEB sample provides a consistent reference with relatively high pressure and very low ammonia abundance. Following the upwelling ammonia, eastward advection of plume aerosols, and NEDF subsidence from Figure 1, we can trace an ammonia cycle between its gaseous source and sink, with an intermediary aerosol state.
Future Work
Hundreds of observations of NEDFs and ammonia enhancements in the EZn have been made in 2024-25 using the Hill et al. (2024) technique. This data set will be analyzed and assessed for the statistical consistency of the results presented here. In addition, this data set will be compared to complementary multispectral observations to help discriminate why the optical method seems to so clearly detect ammonia enhancements at the 1-2 bar pressure level and why these enhancements appear broad enough to overlap NEDFs.
Figure 1. Ammonia mole fraction, cloud pressure, and visual context maps created from observations on 2025-01-06 using an 11 inch Schmidt-Cassegrain telescope. A) Ammonia mole fraction (ppm) with enhanced areas labeled 1-4 in order of ascending longitude. The black circle at left shows the approximate spatial resolution of the data. B) Cloud pressure (mbar). C) Visual context image with selected contour overlays to show enhanced ammonia mole fraction and lowest pressure (highest) clouds. D) Same as C), but with arrows indicating presumed upwelling (black ⊙), downwelling (white ⦻), and horizontal flow (red arrows).
Figure 2. Two ammonia enhancements (4 & 3 from Figure 1), associated plumes, and NEDFs are analyzed for cloud pressure and ammonia abundance. Three observations are assessed with the targets near nadir viewing. A) Ammonia mole fraction, cloud pressure, and visual context image with overlaid rectangles indicating regions-of-interest (ROIs). B) Time series of cloud pressure (left) and ammonia mole fraction (right) over the three observations. C) Scatter plot of all ammonia and cloud measurements in each ROI (left) and of the averages over the three observations. Note that the NEB data are provided as a stable reference.
References
Choi, D. S. et al. 2013. Icarus, 223, 832.
Hill, S. M. et al. 2024. Earth and Space Science, 11(8), e2024EA003562.
Fletcher, L. N. et al. 2020. Journal of Geophysical Research (Planets), 125, e06399.
Irwin, P. G. J. et al. 2025. Journal of Geophysical Research: Planets, 130(1), e2024JE008622.
Showman, A. P., & Dowling, T. E. 2000. Science, 289, 1737-1740.
How to cite: M Hill, S., Irwin, P., Rogers, J., and Fletcher, L.: Optically Observed Ammonia in the Northern Equatorial Zone, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-1174, https://doi.org/10.5194/epsc-dps2025-1174, 2025.
The jet stream on the south edge of the North Temperate Belt (NTBs jet) is liable to spectacular disturbances that emerge from deep below the visible cloud-tops. Between 1970-1990, and since 2007, these have occurred in 4-5-year cycles in which whitening of the belt is followed by outbreaks of brilliant white spots (plumes) travelling at -4.8 to -5.5 deg/day in L1 (u3 = 163-173 m/s), generating dark turbulent wakes behind them and leading to revival of the belt. The white spots are considered to be convective plumes rising from the water-cloud layer below the visible clouds [e.g. refs.1&2]. The observed cloud-top peak speed of the NTBs jet varies through this upheaval cycle. Just after an outbreak it is lowest, then it accelerates over the years before the next one (although perhaps not steadily); then the plumes appear with speeds even faster than winds recorded otherwise (Figure 1).
The latest outbreak in this series began on 2025 Jan.10. It was very well observed by amateur astronomers, and reveals new details of the changes of the winds before and during the upheaval. The plumes in 2025 are described in a companion abstract (session OPS8). Here we consider what the amateur observations have revealed of the overall structure of the jet during the cycle, at the deep layer from which the plumes arise, and at the cloud-top layer which we observe.
System 1 longitude (L1) is used unless otherwise stated. Drift rates (DL1) are given in degrees per day; DL3 = DL1 - 7.364 deg/day. Equivalence to u3 (m/s) is shown in Fig.1.
The three primary plumes:
All three primary plumes first appeared at 24.0-24.6ºN, then drifted south and accelerated eastward within a few days (see companion abstract), to remain at 23.3 (±0.3)ºN with sustained speeds of DL1 = -5.0, -5.1, and -4.8 deg/day. Typical images are in Figs.2&3; tracks are in Fig.4. As usual, they all broke up within a few days when they caught up with the wake of the next plume ahead.
The wake and wake-induced plumelets:
As usual, a complex wake grew rapidly (~5 deg/day) following each primary plume, consisting of the following elements (Fig.3). These had a wide range of speeds, all slower than the plumes.
- i) Large dark patches which formed every few days, at ~23.5-24ºN, with a wave-like appearance. Their slow speeds were ill-defined but consistent with mean speeds in previous outbreaks ranging from DL1 = -0.8 to -1.6 deg/day (u3 = 108-120 m/s), supporting their wave nature.
- ii) White clouds on the northern and southern sides of the wake, apparently streaming behind the plumes.
- iii) ‘Wake-induced plumelets’: small bright, methane-bright spots arising at the following end of the growing wake, accelerating to speeds similar to the main plume but short-lived. We tracked at least five of them (Fig.4). We suggest that they are similar plumes triggered by the approach of the following end of the wake, but in this situation they are less intense and are short-lived (see companion abstract).
Zonal drift profile & zonal wind profiles:
The drift rates and latitudes of tracked spots are plotted as a zonal drift profile (included in Fig.5B). All the bright spots – plumes, plumelets, and smaller white spots on the N edge of the wake – fit onto a consistent curve. The northern part of this, representing the wake-induced plumelets and the first few days of the main plumes, matches the typical spacecraft-measured zonal wind profile (ZWP) in quiescent states, so it cannot determine whether the speed at deeper levels is different from that at the cloud-tops. However, the main plumes then extend the profile to faster speeds and lower latitudes. All fit a profile which peaks at 23.3ºN, DL1 = -5.1 deg/day (u3 = +166.6 m/s).
As the plumes are believed to be driven from a deep layer, this may represent the ZWP down at that level. But how are the observed cloud-top winds affected by the deeper winds, either before or during the outbreak? Does the deep ZWP take over the cloud-top winds, or is it only manifested by the plumes themselves? To investigate these issues, we have established the ZWP using hi-res amateur images taken two months before the initial outbreak and several weeks after it, and we compare the results with those published for previous outbreaks (Fig.5).
Previously published pre-outbreak ZWPs all had peaks at 160-163 m/s (1979-2009) or 156-159 m/s (2015-16) at 23.6-23.9ºN, with no systematic change during the year before the outbreak. Our pre-outbreak profile, in 2024 Nov., had a sharp peak at 150 m/s at 23.5ºN. This slightly slower speed could be connected to the reduced interval between outbreaks since 2012. The plume speeds in 2020 and 2025 were likewise somewhat slower than before. Otherwise, all these results are highly consistent.
Our profiles in 2025 Feb. – covering the wake – are the earliest yet produced during an outbreak, and range from a narrow peak at ~141 m/s to a broad peak at ~126-136 m/s. When compared with previous ZWPs from spacecraft, these profiles confirm that there is no detectable acceleration of the cloud-top ZWP during the outbreak, apart from broadening on the flanks of the wake; instead, it quickly collapses to a slower but sometimes broader state. Then it recovers gradually over the next two years or so.
These results confirm that the jet is faster at depth than at the cloud-tops, comparable to the NEBs (7ºN) jet as shown by the Galileo Probe. The plumes and plumelets erupt from the deep-level jet, but other features at cloud-tops in that latitude do not achieve this speed.
The plumes in 2025 are described in a companion abstract (session OPS8). Full details of these studies are in our 2024/25 Report no.5 [ref.3]
References:
- Sanchez-Lavega A et 24 al. (2008) Nature 451, 437-440.
- Sanchez-Lavega A, Rogers JH, et al.(2017). GRL 44, 4679–4686. DOI: 10.1002/2017GL073421
- Rogers J et al.(2025). https://britastro.org/section_information_/jupiter-section-overview/jupiter-in-2024-25/report-no-5-ntbs-outbreak
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Figure 5: 
How to cite: Rogers, J., Mizumoto, S., Adamoli, G., Bullen, R., Hahn, G., Jacquesson, M., Mettig, H.-J., and Vedovato, M.: Jupiter’s NTBs jet outbreak 2025: Zonal winds at cloud-tops and below, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-51, https://doi.org/10.5194/epsc-dps2025-51, 2025.
Introduction
Since its launch in 2010, COBS has become an essential resource for both amateur and professional astronomers. Currently, it contains over 288,700 observations of more than 1,640 different comets, making it the most extensive comet observation database available [1].
Recent feature upgrades have significantly expanded COBS's functionalities. A major addition is the ability to fit comet light curves using the Henyey-Greenstein (HG) model, which explicitly accounts for the forward scattering of sunlight by dust in the comet’s coma, which can cause comets to appear substantially brighter at large phase angles [2, 3]. This option allows more accurate predictions of visual comet magnitudes.
In addition to analysis upgrades, the COBS Observation planner has also been enhanced. It now offers users expanded filtering options for selecting comet targets based on observational constraints like altitude, limiting magnitude, and proximity to the Sun or Moon. These improvements facilitate better session planning and help observers optimize their observing opportunities.
Scatter Fit of Comet’s Light Curve
The COBS analysis page was recently upgraded to support advanced light-curve fitting. It now allows users to apply a compound Henyey-Greenstein (HG) function to model the scattering of light by dust particles in comets coma. The fitting process is performed using Python’s SciPy library. The parameters fitted, along with their corresponding ranges, are summarized in Table 1. These parameters describe the comet's intrinsic brightness, its photometric behavior with respect to heliocentric distance, and the scattering properties of dust within the coma.
Table 1: Parameter Ranges for Henyey-Greenstein Function Fitting [3].
|
Parameter |
Symbol |
Range |
Description |
|
Absolute magnitude at 1 AU from Sun and Earth |
H0 |
-5 to 20 |
Intrinsic brightness of the comet |
|
Photometric slope parameter |
n |
2 to 6 |
Describes the rate of brightness change with heliocentric distance |
|
Forward scattering asymmetry factor |
gf |
0.8 to 1 |
Degree of forward scattering |
|
Backward scattering asymmetry factor |
gb |
-1 to -0.5 |
Degree of backward scattering |
|
Partitioning coefficient |
k |
0.8 to 1 |
Ratio between forward and backward scattering contributions |
|
Dust-to-gas brightness ratio |
δ90 |
1 to 10 |
Relative contribution of dust scattering to gas emission in the coma |
This new functionality was tested on Comet C/2023 A3 (Tsuchinshan–ATLAS) [4]. Early predictions for that comet indicated that the comet would exhibit strong forward scattering effects following its perihelion passage, significantly enhancing its observed brightness [5].
As illustrated in Figure 1 the standard light-curve fit (solid line) systematically underestimated the comet's brightness during early October 2024, shortly after perihelion on September 22, 2024, when the phase angle approached 180°. This discrepancy is most notable near the peak of the light curve, where forward scattering dominates the apparent visual magnitude. By applying the scatter-fit model (dashed line), the fitted curve aligns much more closely with the observed data points.
This comparison demonstrates the critical importance of including forward scattering effects in light-curve analyses for comets observed at large phase angles.
Figure 1: Comparison between standard comet light curve fit and fit corrected for light scatter due to forward scattering.
Upgrade of the COBS Observation Planner
The COBS Observation Planner was recently enhanced to assist observers in efficiently selecting and prioritizing comet targets. Users can specify an session date, observer location (either manually or by selecting from MPC location codes), and the session start time, which is based on the Sun's altitude, ranging from sunset to the end of astronomical twilight.
Additional filters, such as limiting magnitude, minimum target altitude, and minimum elongation from the Sun and Moon, allow further refinement of the candidate target list (Figure 2).
Figure 2: User interface of the upgraded COBS Observation Planner, showing options for setting observational constraints.
After submitting the input parameters, COBS calculates significant astronomical events and generates a list of potential comet targets. For each target, the optimal viewing time, coordinates, altitude, and apparent motion are provided (Figure 3).
Figure 3: Example of a generated list of potential comet targets produced by the COBS Observation planner. Three targets have been selected for further ephemeris generation.
Observers can then select multiple targets and quickly generate detailed ephemerides for the selected date, aiding real-time observation planning (Figure 4).
Figure 4: Ephemeris generated for the selected targets, showing detailed positional data for the observation session. This data can be used directly at the telescope or be exported for further planning.
In addition, the target list now includes a direct link to a comet finding chart provided by in-the-sky.org [6]. These charts show the comet’s position in the sky and display comparison stars labeled with their V-band magnitudes, making them particularly valuable for visual observers.
Figure 5: Example of a finding chart from in-the-sky.org for comet P/2010 H2 (Vales), showing the comet's path and nearby comparison stars with labeled V-band magnitudes.
Summary and Conclusions
The Comet Observation Database (COBS) remains a vital and evolving tool for the comet observing community. Recent upgrades, particularly the introduction of scatter fitting using the Henyey-Greenstein model, have greatly improved the ability to analyse and interpret the brightness evolution of comets, especially in cases where forward scattering significantly impacts observed magnitudes. While the scatter fitting feature provides a valuable analytical improvement, users should apply it with caution to avoid overfitting, which could misrepresent a comet's true behavior.
The enhanced COBS Observation Planner provides an intuitive and flexible means of planning observing sessions, considering key observational factors such as object altitude, solar and moon elongation. Users can efficiently generate, refine, and export target lists, enhancing their productivity at the telescope.
Through continuous upgrades, COBS reinforces its role as a vital platform for the cometary science community, helping observers to maximize the scientific value of their observations.
Acknowledgements
We gratefully acknowledge Dominic Ford, author of in-the-sky.org, for adapting the comet finding chart output to meet the specific needs of visual comet observers.
How to cite: Zakrajšek, J., Mikuž, H., and Warell, J.: The Comet Observation Database (COBS) - Recent feature upgrades, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-160, https://doi.org/10.5194/epsc-dps2025-160, 2025.
Clear nights were quite rare during the winter of 2024-2025. Although there may have been more clear nights compared to the previous season, variable cloudiness often persisted even during these clear nights, or the continuous cloudless periods were too short for effective exoplanet light curve measurements.
The THO research team managed to make transit observations for the first time at the beginning of September 2024, and then again only at the end of December. While weather was not always the sole factor, frequent rains, cloudiness, and unpredictable weather changes posed significant challenges. Despite these difficult observation and measurement conditions, the observation routine and results remained reasonably good. The figures below illustrate some of the measurements performed at THO.
In the fall of 2024, the traditional Czech TRESCA ETD database site underwent a major redesign and is now called VarAstro (var.astro.cz). During the observation season, the beta test version of the VarAstro site was still in use. Nevertheless, the THO research team continued to submit observations there for further use. Previously, the site was a completely open environment where observations could be submitted "on the fly." Of course, the measurement results of the uploaded files had to be reasonable, so no erroneous data could be submitted. Currently, to submit measurement results, access to the site requires registration and administrator approval. Although the usability of the site has some challenges and new features to learn, it remains quite functional.
All observations presented here were made with the Celestron 14” SC telescope and SBIG ST-8XME CCD camera using a photometric R filter on the viewing platform.
TOI-1845.01b
September 6–7, 2024, 18:19–00:01 (UTC)
Dimming 19.9 mmag, recorded value 20.1 mmag. Transit duration 136.1 min, recorded duration 156.3 min. Host star brightness 13.6 mag. The target has been observed only seven times in total on VarAstro. A 120-second exposure was used for imaging.
TOI-6316.01b
September 6–7, 2024, 18:19–00:01 (UTC)
Dimming 22.6 mmag, recorded value 13.1 mmag. Transit duration 231.9 min, recorded duration 215.6 min. Host star brightness 13.2 mag. The target has been observed only three times in total on VarAstro. A 120-second exposure was used for imaging.
TOI-2578.01b
September 9, 2023, 14:54–20:23 (UTC)
Dimming 8.5 mmag, recorded value 11.0 mmag. Transit duration 201 min, recorded duration 157 min. Host star brightness 11.4 mag. This target has also been observed only three times in total on VarAstro. A 60-second exposure was used for imaging.
TOI-1259.01b
December 29, 2024, 00:36–05:13 (UTC)
Dimming 30.8 mmag, recorded value 28.7 mmag. Transit duration 142 min, recorded duration 148 min. Host star brightness 12.1 mag. The target has been observed a lot, a total of 31 times on VarAstro. A 60-second exposure was used for imaging.
HAT-P-36b
December 30–31, 2024, 21:02–01:11 (UTC)
Dimming 21.3 mmag, recorded value 20.4 mmag. Transit duration 111 min, recorded duration 133 min. Host star brightness 12.2 mag. The target has been observed a lot, nearly 300 times in total on VarAstro. A 100-second exposure was used for imaging.
How to cite: Hentunen, V.-P., Haukka, H., Nissinen, M., Salmi, T., Aartolahti, H., Juutilainen, J., Heikkinen, E., Vilokki, H., and Honkanen, J.: Exoplanet Observations from Taurus Hill Observatory for the Season 2024–2025, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-456, https://doi.org/10.5194/epsc-dps2025-456, 2025.
Introduction
A group of amateur astronomers from the Sabadell Astronomical Society is using small professional telescopes to obtain exoplanets transits photometry for the ExoClock project and ARIEL mission.
Through this collaboration, we have faced cases like CoRoT-10b where the transit occurs more than four hours ahead of schedule. What does this mean?
TTV transit timing variation in multiplanetary systems
TTV in multiplanetary systems helps determining the masses of small exoplanets, that cannot be determined by radial velocities, like in the TRAPPIST system, where the mass of the 7 rocky planets, in resonance, have been determined thanks to TTV. Some times, a single planet showing TTV can be a clue to the existence of another planet, that does not transit, case of TOI 2015b and TOI 2015c.
TTV, orbital decay, nodal precession
Orbital decay has been reported in very few cases. The planet, like WASP-12b, is falling on its hosting star, and so show a small variation in its period. It needs long time of observations and scientist are searching for them actively.
Finally, the strange case of nodal precession, where the exoplanet transits only a part of its nodal precession cycle because of the inclination of its orbital plane. There are only four cases reported at the moment: WASP-33b, Kepler-13Ab, KELT-9b, TOI-1518b.
In this presentation we will focus on CoRoT-10b and TOI-2015b, both with several hours TTV, one still needs more observation, the second has proven the TOI-2015c existence.
CoRoT-10b, a study in process
The exoplanet CoRoT-10b has been observed by our Sabadell Group several times, not always with success as it is a very difficult target. The star has a magnitud of 15.5 in R and the depth 15.3 mmag, and because of its coordinates, it remains visible few months in our latitudes, and the frequence of ideal transits is low. The orbital period is 13. 24 days, the eccentricity is 0.53, the transit duration 3.02 hours. Until this year, there are no other published transit than ours. The last observations were published finally on ExoClock webpage. First, half a transit 17/7/2024, with a TTV of -235.15 minutes. Then on the 8/9/2024, the exoplanet shows a TTV of -262 minutes.
What can cause this long TTV?
The TTV is a gravitational phenomenon. It depends on the relation of the exoplanets masses and the stellar mass. But also on many other factors like the distances, the eccentricities, apsidal precession, the existence of another planet that does not transit… Or maybe new calculation of period or eccentricity is needed. These few observed transits are not sufficient to arrive at any conclusion. So CoRoT-10b remains a key target of our group and we plan to observe it when scheduled.
A resolved case: discovery of a non-transiting exoplanet thanks to TTV, TOI-2015 b and c.
Paper: Ref. Khalid Barkaoui, October 19, 2024, TOI-2015b: a mini-Neptune in strong gravitational interaction with an outer non-transiting planet.
TOI-2015b TTV varies from -2 hours to + 2 hours as we see in this figure
This investigation produced an improvement of TOI-2015b data, especially of its mass: 3.311+/- 0.012 R Earth à determination of average density: 1.5 g/cm3 so we face a Neptune type planet.
TOI-2015b is compatible with 70% water planet, could have atmosphere between 5-10% of its mass.
Discovery of TOI-2015c
The TTVs of TOI-2015b make it possible to identify a companion, TOI-2015c which does not transit, in a resonance ratio close to 5:3, although other scenarios are not ruled out. Orbital period: 5.582904d +/- 0.0004 d, its mass: 9.52+/- 0.42 Earth Mass; temperature: 450ºK, the radium is not known
The conclusion in this case is that the perturbation comes from the existence of a second exoplanet, that does not transit.
How to cite: Libotte, F., Correa, M., Ginard, A., Domènech, G., and Barkaoui, K.: Exoplanet observations and TTV, transit timing variation interesting cases, EPSC-DPS Joint Meeting 2025, Helsinki, Finland, 7–13 Sep 2025, EPSC-DPS2025-173, https://doi.org/10.5194/epsc-dps2025-173, 2025.