Small Telescopes Research Articles

Characterization of the Small Robotic Telescope Instrument and Implementation at ITERA Lampung Astronomical Observatory

As time has passed, the technological advances used to run these telescope systems have become faster, more reliable, and more user-friendly. Institut Teknologi Sumatera (ITERA) has installed a small robotic telescope at the Meteorology–Climatology–Geophysics Observing Station in collaboration with an ASTELCO System. The telescope system is designed to make fully robotic observations and can operate in both interactive and unattended robotic modes. This study's primary focus is on the OZT-ALTS telescope robotic system with the optical system using triplet apochromatic lens technology manufactured by LZOS with a focal ratio of f/8 refractor design. The telescope mount is a German Equatorial (NTM-500 manufactured by ASTELCO) with a direct drive system with an absolute encoder, and it allows fully programmable tracking speeds with a typical slewing speed of 20°/sec and a tracking accuracy range of 0.3–1.0 arcsec. For the process of collecting moon observation images, we use Manta G-031B. The OZT-ALTS robotic telescope is now contributing to monitoring crescent moon observation and astronomical studies. This paper presents the scientific motivation behind the OZT-ALTS robotic telescope and the facility's specifications and unique features. Furthermore, we present to characterize the result of the hardware OZT-ALTS robotic telescope system to increase the mechanical and optical performance of the telescope system based on the in-situ test observations. Based on the result, setting the Gain on the camera at 3.5 e-/ADU is the limit for the CCD to produce good-quality output images by utilizing the entire dynamic range without saturation. We also present an example of the science we have performed with the OZT-ALTS robotic telescope. The OZT-ALTS can observe young crescent moon events in the daylight after implementing the CLAHE technique to enhance contrast objects. On the other hand, the OZT-ALTS can also observe WASP-16b and WASP-34b exoplanets by using the transit method to analyze the decreasing light curve when a planet passes between a star and its observer.

The Simons Observatory: Design, Integration, and Testing of the Small Aperture Telescopes

The Simons Observatory (SO) is a cosmic microwave background survey experiment that includes small-aperture telescopes (SATs) observing from an altitude of 5200 m in the Atacama Desert in Chile. The SO SATs will cover six spectral bands between 27 and 280 GHz to search for primordial B-modes to a sensitivity of σ(r) = 0.002, with quantified systematic errors well below this value. Each SAT is a self-contained cryogenic telescope with a 35° field of view, 42 cm diameter optical aperture, 40 K half-wave plate, 1 K refractive optics, and <0.1 K focal plane that holds >12,000 transition edge sensor detectors. We describe the nominal design of the SATs and present details about the integration and testing for one operating at 93 and 145 GHz.

Improving Radio Signal from Baghdad University Radio Telescope Using the Savitzky-Golay Filter

Astronomical radio observations from a small radio telescope suffer from various types of noise. Hence, astronomers continuously search for new techniques to eliminate or reduce such noise and obtain more accurate results. This research investigates the impact of implementing the Savitzky-Golay filter on enhancing radio observation signals retrieved from the Baghdad University Radio Telescope (BURT). Observations from BURT were carried out for different Galactic coordinates, and then a MATLAB code was written and used to implement the Savitzky-Golay filter for the collected data. This process provides an assessment of the ability of the filter to reduce noise and improve the quality of the signal. The results of this research clearly showed that applying the Savitzky-Golay filter reduces the noise and enhances the signal of astronomical radio observations. However, the filter should be used appropriately to preserve the original features of the signal. In conclusion, the filter is considered an efficient tool for enhancing the radio signal by reducing the noise and smoothing the signal. Therefore, the filter provides a substantial contribution and improvement to the field of radio astronomy.

Online Resources for Teaching Astronomy

The Internet has transformed the teaching of astronomy. In the past, instructors were mostly reliant on printed textbooks, 35-mm slides, and their own lecture notes. Depending on local resources they might also be able to incorporate labs, hands-on activities, and use of small telescopes. Now they can choose from a wide, and occasionally bewildering, array of online resources to augment what they do in the classroom. A challenge is to find tools that are either evaluated in peer-reviewed publications or have proven their efficacy in other ways. A selective list is provided.

Periodic variable A-F spectral type stars in the southern TESS continuous viewing zone

Aims. Our primary objective is to accurately identify and classify the variability of A-F stars in the southern continuous viewing zone of the TESS satellite. The brightness limit was set to 10 mag to ensure the utmost reliability of our results and allow for spectroscopic follow-up observations using small telescopes. We aim to compare our findings with existing catalogues of variable stars. Methods. The light curves from TESS and their Fourier transform were used to manually classify stars in our sample. Cross-matching with other catalogues was performed to identify contaminants and false positives. Results. We have identified 1171 variable stars (51% of the sample). Among these variable stars, 67% have clear classifications, which includes δ Sct and γ Dor pulsating stars and their hybrids, rotationally variables, and eclipsing binaries. We have provided examples of the typical representatives of variable stars and discussed the ambiguous cases. We found 20 pairs of stars with the same frequencies and identified the correct source of the variations. Additionally, we found that the variations in 12 other stars are caused by contamination from the light of faint nearby large-amplitude variable stars. To compare our sample with other variable star catalogues, we have defined two parameters reflecting the agreement in identification of variable stars and their classification. This comparison reveals intriguing disagreements in classification ranging from 52 to 100%. However, if we assume that stars without specific types are only marked as variable, then the agreement is relatively good, ranging from 57 to 85% (disagreement 15–43%). We have demonstrated that the TESS classification is superior to the classification based on other photometric surveys. Conclusions. The classification of stellar variability is complex and requires careful consideration. Caution should be exercised when using catalogue classifications.

The Discovery and Evolution of a Possible New Epoch of Cometary Activity by the Centaur (2060) Chiron

Centaurs are small solar system objects on chaotic orbits in the giant planet region, forming an evolutionary continuum with the Kuiper Belt objects and Jupiter-family comets. Some Centaurs are known to exhibit cometary activity, though unlike comets, this activity tends not to correlate with heliocentric distance, and the mechanism behind it is currently poorly understood. We utilize serendipitous observations from the Asteroid Terrestrial-impact Last Alert System, Zwicky Transient Facility, Panoramic Survey Telescope and Rapid Response System, Dark Energy Survey, and Gaia in addition to targeted follow-up observations from the Las Cumbres Observatory, TRAnsiting Planets and PlanetesImals Small Telescope South (TRAPPIST-South), and Gemini North telescope to analyze an unexpected brightening exhibited by the known active Centaur (2060) Chiron in 2021. This is highly indicative of a cometary outburst. As of 2023 February, Chiron had still not returned to its prebrightening magnitude. We find Chiron's rotational lightcurve, phase curve effects, and possible high-albedo surface features to be unlikely causes of this observed brightening. We consider the most likely cause to be an epoch of either new or increased cometary activity, though we cannot rule out a possible contribution from Chiron's reported ring system, such as a collision of as-yet-unseen satellites shepherding the rings. We find no evidence for a coma in our Gemini or TRAPPIST-South observations, though this does not preclude the possibility that Chiron is exhibiting a coma that is too faint for observation or constrained to the immediate vicinity of the nucleus.

Deep Optical Emission-line Images of Nine Known and Three New Galactic Supernova Remnants

Deep optical emission-line images are presented for nine known plus three new Galactic supernova remnants (SNRs), all but one having at least one angular dimension >1°. Wide-field images taken in Hα and [O iii] λ5007 reveal many new and surprising remnant structures including large remnant shock extensions and “breakout” features not seen in published optical or radio data. These images represent over 12,000 individual images totaling more than 1000 hr of exposure time taken over the last 2 yr mainly using small aperture telescopes, which detected fainter nebular line emissions than published emission-line images. During the course of this imaging program, we discovered three new SNRs, namely G107.5-5.1 (the Nereides Nebula), G209.9-8.2, and G210.5+1.3, two of which have diameters >1.°5. In addition to offering greater structural detail on the nine already known SNRs, a key finding of this study is the importance of [O iii] emission-line imaging for mapping the complete shock emissions of Galactic SNRs.

Detecting the Early Optical Flashes of Gamma-Ray Bursts with Small Telescope Arrays

We present an observational approach for the independent detection of the early optical emission of long gamma-ray bursts (GRBs). For this purpose, we explore the potential of the Large Array Survey Telescope (LAST). This array of small optical telescopes can be used to scan a wide region of the sky, and to focus on a smaller field of view with increased sensitivity, as needed. The modularity of the array facilitates dynamic scanning of multiple fields, by shifting telescope pointing directions with high cadence. This can significantly increase the effective sky-coverage of a blind survey on short timescales. For events associated with gamma-ray counterparts, the valuable early time data can supplement high-energy observations. Regardless of gamma-ray association, detections can potentially be used to explore various phenomena associated with GRBs, such as orphan afterglows; dirty fireballs; and choked jets. We simulate a sample of GRBs and their respective optical signals at early times. After accounting for dynamic cadence, the light curves are given as input to a machine-learning classifier, used to identify astrophysical transients. We find that, by dedicating half of an LAST array to a blind search, one would expect to independently detect 7–11 GRBs yr–1, corresponding to an approximate intrinsic event rate of 0.12 deg–2 yr–1.

Miniaturized high signal-to-noise ratio optical air data system using a compact multi-axis parallel transceiver for airborne application

We have developed a miniaturized multi-channel parallel optical air data system with high signal-to-noise ratio for airborne application. In the system, we designed a fiber amplifier with multi-channel high-energy output that was respectively used as the transmitting signals and a compact multi-axis transceiver with an entrance pupil diameter of 70 mm that was used to receive multi-channel signals simultaneously. We demonstrated the performance of our system both on ground and on board. On ground, the measured line-of-sight speed had an average error of 0.02 m/s and a standard deviation of 0.15 m/s. On board, the standard deviation between the true air speed, angle of attack, and angle of sideslip measured by our system and a commercial Swiss air data system was 1 kt, 0.68°, and 0.54°, respectively, and those standard deviation between our system and a system with the same design but employing multiple single-axis telescopes with entrance pupil diameter of 30 mm was 0.34 kt, 0.36°, and 0.28°, respectively. The signal-to-noise ratio of our system was 4.5 times higher than that of the system with small single-axis telescopes. Our system is very promising for airborne applications because of its small volume, high signal-to-noise ratio, and high data rate.

The Simons Observatory: Pipeline comparison and validation for large-scale B-modes

Context. The upcoming Simons Observatory Small Aperture Telescopes aim at achieving a constraint on the primordial tensor-to-scalar ratio r at the level of σ(r = 0)≲0.003, observing the polarized CMB in the presence of partial sky coverage, cosmic variance, inhomogeneous non-white noise, and Galactic foregrounds. Aims. We present three different analysis pipelines able to constrain r given the latest available instrument performance, and compare their predictions on a set of sky simulations that allow us to explore a number of Galactic foreground models and elements of instrumental noise, relevant for the Simons Observatory. Methods. The three pipelines employ different combinations of parametric and non-parametric component separation at the map and power spectrum levels, and use B-mode purification to estimate the CMB B-mode power spectrum. We applied them to a common set of simulated realistic frequency maps, and compared and validated them with focus on their ability to extract robust constraints on the tensor-to-scalar ratio r. We evaluated their performance in terms of bias and statistical uncertainty on this parameter. Results. In most of the scenarios the three methodologies achieve similar performance. Nevertheless, several simulations with complex foreground signals lead to a &gt; 2σ bias on r if analyzed with the default versions of these pipelines, highlighting the need for more sophisticated pipeline components that marginalize over foreground residuals. We show two such extensions, using power-spectrum-based and map-based methods, that are able to fully reduce the bias on r below the statistical uncertainties in all foreground models explored, at a moderate cost in terms of σ(r).

Airborne single-photon LiDAR towards a small-sized and low-power payload

Single-photon light detection and ranging (LiDAR) has played an important role in areas ranging from target identification and 3D imaging to remote sensing. Its high sensitivity provides the feasibility of lightweight LiDAR systems for the resource-limited airborne and spaceborne platforms. Here, we design and demonstrate an airborne single-photon LiDAR towards the compact, small-sized, and low-power payload. To reduce the system size, we utilize small telescopes with an optical aperture of 47 mm and develop the sub-pixel scanning approach to enhance the imaging resolution. With the fine scanning mirrors, we validate the super-resolution ability in the ground experiment by surpassing the system’s resolution by 2.5 times and achieve high-resolution 3D imaging in the airborne experiment. To realize low-power LiDAR, we employ photon-efficient computational algorithms and high-quality single-photon avalanche diode (SPAD) arrays. This enables us to reconstruct images from noisy data even under challenging conditions of two signal photons per pixel. Using the airborne single-photon LiDAR system, we demonstrate 3D imaging during daytime over a large area for remote sensing applications and show the capability to reveal the detailed features of various landforms and objects.

A Data-driven Approach for Mitigating Dark Current Noise and Bad Pixels in Complementary Metal Oxide Semiconductor Cameras for Space-based Telescopes

In recent years, there has been a gradual increase in the performance of complementary metal oxide semiconductor (CMOS) cameras. These cameras have gained popularity as a viable alternative to charge-coupled device cameras in a wide range of applications. One particular application is the CMOS camera installed in small space telescopes. However, the limited power and spatial resources available on satellites present challenges in maintaining ideal observation conditions, including temperature and radiation environment. Consequently, images captured by CMOS cameras are susceptible to issues such as dark current noise and defective pixels. In this paper, we introduce a data-driven framework for mitigating dark current noise and bad pixels for CMOS cameras. Our approach involves two key steps: pixel clustering and function fitting. During the pixel clustering step, we identify and group pixels exhibiting similar dark current noise properties. Subsequently, in the function fitting step, we formulate functions that capture the relationship between dark current and temperature, as dictated by the Arrhenius law. Our framework leverages ground-based test data to establish distinct temperature–dark current relations for pixels within different clusters. The cluster results could then be utilized to estimate the dark current noise level and detect bad pixels from real observational data. To assess the effectiveness of our approach, we have conducted tests using real observation data obtained from the Yangwang-1 satellite, equipped with a near-ultraviolet telescope and an optical telescope. The results show a considerable improvement in the detection efficiency of space-based telescopes.

A survey for variable young stars with small telescopes – IX. Evolution of spot properties on YSOs in IC 5070

ABSTRACT We present spot properties on 32 periodic young stellar objects in IC 5070. Long term, ∼5 yr, light curves in the V, R, and I-bands are obtained through the HOYS (Hunting Outbursting Young Stars) citizen science project. These are dissected into 6 months long slices, with 3 months oversampling, to measure 234 sets of amplitudes in all filters. We fit 180 of these with reliable spot solutions. Two thirds of spot solutions are cold spots, the lowest is 2150 K below the stellar temperature. One third are warm spots that are above the stellar temperature by less than ∼2000 K. Cold and warm spots have maximum surface coverage values of 40 per cent, although only 16 per cent of warm spots are above 20 per cent surface coverage as opposed to 60 per cent of the cold spots. Warm spots are most likely caused by a combination of plages and low-density accretion columns, most common on objects without inner disc excess emission in K − W2. Five small hot spot solutions have &amp;lt;3 per cent coverage and are 3000–5000 K above the stellar temperature. These are attributed to accretion, and four of them occur on the same object. The majority of our objects are likely to be accreting. However, we observe very few accretion hot spots as either the accretion is not stable on our time-scale or the photometry is dominated by other features. We do not identify cyclical spot behaviour on the targets. We additionally identify and discuss a number of objects that have interesting amplitudes, phase changes, or spot properties.

Taxonomy of Subkilometer Near-Earth Objects from Multiwavelength Photometry with RATIR

We present results from observations of 238 near-Earth objects (NEOs) obtained with the RATIR instrument on the 1.5 m robotic telescope at San Pedro Martir’s National Observatory in Mexico, in the frame of our multiobservatory, multifilter campaign. Our project is focused on rapid response photometric observations of NEOs with absolute magnitudes in the range 18.1–27.1 (diameter ≈ 600 and 10 m, respectively). Data with coverage in the near-infrared and visible range were analyzed with a nonparametric classification algorithm, while visible-only data were independently analyzed via Monte Carlo simulations and a 1-Nearest Neighbor method. The rapid response and the use of spectrophotometry allows us to obtain taxonomic classifications of subkilometer objects with small telescopes, representing a convenient characterization strategy. We present taxonomic classifications of the 87 objects observed in the visible and near-infrared. We also present the taxonomic distribution of an additional 151 objects observed in the visible. Our most accurate method suggests a nonfeatured-to-featured ratio of ≈0.75, which is consistent with the value found by the Mission Accessible Near-Earth Object Survey, which conducted a similar study using a spectral analysis. The results from the Monte Carlo method suggest a ratio of ≈0.8, although this method has some limitations. The 1-Nearest Neighbor method showed to be not suitable for NEO classifications.

Small but mighty: High-resolution spectroscopy of ultra-hot Jupiter atmospheres with compact telescopes

When observing transmission spectra produced by the atmospheres of ultra-hot Jupiters (UHJs), large telescopes are typically the instrument of choice given the very weak signal of the planet’s atmopshere. The aim of the present study is to demonstrate that, for favourable targets, smaller telescopes are fully capable of conducting high-resolution cross-correlation spectroscopy. We apply the cross-correlation technique to data from the 2.1 m telescope at the Wendelstein Observatory, using its high-resolution spectrograph FOCES, in order to demonstrate its efficacy in resolving the atmosphere of the UHJ KELT-9 b. Using three nights of observations with the FOCES spectrograph and one with the HARPS-N spectrograph, we conduct a performance comparison between FOCES and HARPS-N. This comparison considers both single-transit and combined observations over the three nights. We then consider the potential of 2 m class telescopes by generalising our results to create a transit emulator capable of evaluating the potential of telescopes of this size. With FOCES, we detected seven species in the atmosphere of KELT-9b: Ti II, Fe I, Fe II, Na I, Mg I, Na II, Cr II, and Sc II. Although HARPS-N surpasses FOCES in performance thanks to the mirror of the TNG, our results reveal that smaller telescope classes are capable of resolving the atmospheres of UHJs given sufficient observing time. This broadens the potential scope of such studies, demonstrating that smaller telescopes can be used to investigate phenomena such as temporal variations in atmospheric signals and the atmospheric loss characteristics of these close-in planets.

Near-Earth Object Observations using Synthetic Tracking

Synthetic tracking (ST) has emerged as a potent technique for observing fast-moving near-Earth objects (NEOs), offering enhanced detection sensitivity and astrometric accuracy by avoiding trailing loss. This approach also empowers small telescopes to use prolonged integration times to achieve high sensitivity for NEO surveys and follow-up observations. In this study, we present the outcomes of ST observations conducted with Pomona College’s 1 m telescope at the Table Mountain Facility and JPL’s robotic telescopes at the Sierra Remote Observatory. The results showcase astrometric accuracy statistics comparable to stellar astrometry, irrespective of an object’s rate of motion, and the capability to detect faint asteroids beyond 20.5th magnitude using 11 inch telescopes. Furthermore, we detail the technical aspects of data processing, including the correction of differential chromatic refraction in the atmosphere and accurate timing for image stacking, which contribute to achieving precise astrometry. We also provide compelling examples that showcase the robustness of ST even when asteroids closely approach stars or bright satellites cause disturbances. Moreover, we illustrate the proficiency of ST in recovering NEO candidates with highly uncertain ephemerides. As a glimpse of the potential of NEO surveys utilizing small robotic telescopes with ST, we present significant statistics from our NEO survey conducted for testing purposes. These findings underscore the promise and effectiveness of ST as a powerful tool for observing fast-moving NEOs, offering valuable insights into their trajectories and characteristics. Overall, the adoption of ST stands to revolutionize fast-moving NEO observations for planetary defense and studying these celestial bodies.

A survey for variable young stars with small telescopes – VIII. Properties of 1687 Gaia selected members in 21 nearby clusters

ABSTRACT The Hunting Outbursting Young Stars (HOYS) project performs long-term, optical, multifilter, high cadence monitoring of 25 nearby young clusters and star-forming regions. Utilizing Gaia DR3 data, we have identified about 17 000 potential young stellar members in 45 coherent astrometric groups in these fields. Twenty one of them are clear young groups or clusters of stars within 1 kpc and they contain 9143 Gaia selected potential members. The cluster distances, proper motions, and membership numbers are determined. We analyse long-term (≈ 7 yr) V-, R-, and I-band light curves from HOYS for 1687 of the potential cluster members. One quarter of the stars are variable in all three optical filters, and two-thirds of these have light curves that are symmetric around the mean. Light curves affected by obscuration from circumstellar materials are more common than those affected by accretion bursts, by a factor of 2–4. The variability fraction in the clusters ranges from 10 per cent to almost 100 per cent, and correlates positively with the fraction of stars with detectable inner discs, indicating that a lot of variability is driven by the disc. About one in six variables shows detectable periodicity, mostly caused by magnetic spots. Two-thirds of the periodic variables with disc excess emission are slow rotators, and amongst the stars without disc excess two-thirds are fast rotators – in agreement with rotation being slowed down by the presence of a disc.

The Simons Observatory: Cryogenic half wave plate rotation mechanism for the small aperture telescopes.

We present the requirements, design, and evaluation of the cryogenic continuously rotating half-wave plate (CHWP) for the Simons Observatory (SO). SO is a cosmic microwave background polarization experiment at Parque Astronómico de Atacama in northern Chile that covers a wide range of angular scales using both small (⌀0.42m) and large (⌀6m) aperture telescopes. In particular, the small aperture telescopes (SATs) focus on large angular scales for primordial B-mode polarization. To this end, the SATs employ a CHWP to modulate the polarization of the incident light at 8Hz, suppressing atmospheric 1/f noise and mitigating systematic uncertainties that would otherwise arise due to the differential response of detectors sensitive to orthogonal polarizations. The CHWP consists of a 505mm diameter achromatic sapphire HWP and a cryogenic rotation mechanism, both of which are cooled down to ∼50K to reduce detector thermal loading. Under normal operation, the HWP is suspended by a superconducting magnetic bearing and rotates with a constant 2Hz frequency, controlled by an electromagnetic synchronous motor. We find that the number of superconductors and the number of magnets that make up the superconducting magnetic bearing are important design parameters, especially for the rotation mechanism's vibration performance. The rotation angle is detected through an angular encoder with a noise level of 0.07 μrad s. During a cooldown process, the rotor is held in place by a grip-and-release mechanism that serves as both an alignment device and a thermal path. In this paper, we provide an overview of the SO SAT CHWP: its requirements, hardware design, and laboratory performance.

Photometric and colorimetric studies of target objects using small and medium-size telescopes

Photometric and colorimetric studies of target objects using small and medium-size telescopes

A variety of binary targets for small telescopes

A variety of binary targets for small telescopes