Telescope System Research Articles

Physical properties and trigonometric distance of the peculiar dwarf WISE J181005.5−101002.3

Aims. Our goal is to characterise the physical properties of the metal-poor brown dwarf population. In particular, we focus on the recently discovered peculiar dwarf WISE 1810055−1010023. Methods. We collected optical iz and near-infrared J-band imaging on multiple occasions over 1.5 years to derive accurate trigonometric parallax and proper motion of the metal-depleted ultra-cool dwarf candidate WISE J1810055−1010023. We also acquired low-resolution optical spectroscopy (0.6−1.0 μm) and new infrared (0.9−1.3 μm) spectra of WISE J1810055−1010023 that were combined with our photometry, other existing data from the literature and our trigonometric distance to determine the object’s luminosity from the integration of the observed spectral energy distribution covering from 0.6 through 16 μm. We compared the full optical and infrared spectrum with state-of-the-art atmosphere models to further constrain its effective temperature, surface gravity and metallicity. Results. WISE J1810055−1010023 is detected in the iz bands with AB magnitudes of i = 23.871 ± 0.104 and z = 20.147 ± 0.083 mag in the Panoramic Survey Telescope and Rapid Response System (PanSTARRS) system. It does not show any obvious photometric variability beyond 0.1−0.2 mag in any of the z- and J-band filters. The very red z − J ≈ 2.9 mag colour is compatible with an ultra-cool dwarf nature. Fitting for parallax and proper motion, we measure a trigonometric parallax of 112.5 −8.0+8.1 mas for WISE J1810055−1010023, placing the object at only 8.9−0.6+0.7 pc, about three times closer than previously thought. We employed Monte Carlo methods to estimate the error on the parallax and proper motion. The object’s luminosity was determined at log L/L⊙ = −5.78 ± 0.11 dex. From the comparison to atmospheric models, we infer a likely metallicity of [Fe/H] ≈ −1.5 and an effective temperature cooler than 1000 K. The estimated luminosity and temperature of this object are below the known substellar limit. Despite its apparent low metallicity, we derive space motions that are more typical of the old disc than the halo of the Milky Way. We confirm that WISE J1810055−1010023 has an ultra-cool temperature and belongs to a new class of objects with no known spectral counterparts among field L- and T-type dwarfs. Conclusions. WISE J1810055−1010023 is a very special substellar object and represents a new addition to the 10 pc sample. The optical to near-infrared spectra show strong features due to water vapour and H2 collision induced absorption. Our trigonometric distance has strong implications on the density of metal-poor brown dwarfs in the solar vicinity, which may be higher than that of metal-poor stars.

Modeling and simulation of electro-hydraulic telescopic elevator system controlled by programmable logic controller

Traditional hydraulic <span>cylinders are widely used in industry as load lifting tools. There is difficulty in employing these cylinders in narrow installation space like building elevators as well as they require a long working stroke, so solving this problem requires using the telescopic hydraulic cylinder instead. This cylinder is a unique hydraulic cylinder design that uses a sequence of decreasing diameters to create a long operating stroke in a compact-retracted form. In this work, the Auto Station software is used to build a telescopic hydraulic cylinder model that includes hydraulic elements such as double-acting hydraulic telescopic cylinders, pump, valves, pipeline, and filter, as well as electrical parts such as programmable logic controller (PLC), push-bottoms, and position sensors. The proposed model is operated by a PLC controller and has three floors with an overall height of around 300 cm for lifting a 100 kg payload. The accuracy and validity of this model in lifting big weights were demonstrated by the analytical findings of characteristic curves for cylinder position and velocity. This model can be used a basic reference to analyze and construct hydraulic cylinders with any number of stages. The findings of simulations reveal that a quick change in pressure due to phase change causes multi-phase vibration.</span>

Optical system of aplanatic telescope with a 100 m spherical primary mirror

We propose an optical system of an extremely large telescope for ground-based or planetary use. The system comprises a segmented spherical mirror with a diameter of 100 m and f-number of f / 1. There are three annular zones on the primary mirror, which corresponds to three annular telescopes (ATs) with f-numbers f / 2, f / 3.2, and f / 5.2, all using a concave cardioidal secondary mirror with a maximum diameter of 3.18 m. This two-mirror system satisfies Fermat’s principle and the Abbe’s sine condition. The central zone of the primary mirror with a diameter of 23.8 m is used for the central three-mirror telescope, which is based on an afocal two-mirror system with a convex aspheric secondary mirror with a diameter of 3 m. Four possible configurations are presented for the central telescope, which makes it possible to vary the f-number in a wide range with design examples given for f / 1, f / 4.2, f / 14, and f / 33 systems. The ATs form three coherent images of the same astronomical object, which offers possibilities of simultaneous observations at three different wavelengths or image processing of a combined image with enhanced angular resolution. The main goal of the paper is to investigate the properties of new optical systems for ground-based and space telescopes with a fast spherical primary mirror for which aberration correction is achieved with a minimum number of auxiliary aspheric mirrors near the prime focus.

Design and evaluation of an active secondary mirror positioning system for a small telescope

This publication presents an active compensation system for the position of the secondary mirror of a small Ritchey–Chrétien telescope system. The goal is to maintain the optical imaging quality under varying gravitational and thermal influences, by compensation for the relative position deviations between the primary and secondary mirrors. An extensive analysis concerning the feasibility of such a system for a commercial off-the-shelf small telescope is performed and used as a basis for the design of the precision measurement and positioning system. The developed prototype uses dimensional metrology to capture relative position errors of the secondary mirror. A newly designed actuator with three degrees of freedom for the secondary mirror allows us to compensate for these deviations in a closed-loop control manner and ensures optimal positions of the two mirrors at all times. The support structure design requirements are reduced, allowing the utilization of more lightweight structures, as the artificial stiffness of the compensation system takes care of keeping the telescope mirrors in place. Furthermore, the measurement principle requires no light from the telescope, thus providing 100% of the collected light for the observation. The developed actuation and measurement principles are designed for simple scalability to larger representatives of small telescopes. The implemented setup is evaluated in various poses and temperature influences, successfully demonstrating that the calculated Strehl ratio is kept well above the diffraction limit of 80% for the used telescope system.

Development of Adaptive-Optics Systems for Ground-Based Solar Telescopes

Development of Adaptive-Optics Systems for Ground-Based Solar Telescopes

Adaptive Imaging and Stabilization System for a Large-Aperture Solar Telescope

Adaptive Imaging and Stabilization System for a Large-Aperture Solar Telescope

Antarctic Survey Telescope 3-3: Overview, System Performance and Preliminary Observations at Yaoan, Yunnan

The third Antarctic Survey Telescope array instrument at Dome A in Antarctica, the AST3-3 telescope, has been in commissioning from March 2021. We deployed AST3-3 at the Yaoan astronomical station in Yunnan Province for an automatic time-domain survey and follow-up observations with an optimised observation and protection system. The telescope system of AST3-3 is similar to that of AST3-1 and AST3-2, except that it is equipped with a 14 K × 10 K QHY411 CMOS camera. AST3-3 has a field of view of 1.65∘×1.23∘ and is currently using the g band filter. During commissioning at Yaoan, AST3-3 aims to conduct an extragalactic transient survey, coupled with prompt follow-ups of opportunity targets. In this paper, we present the architecture of the AST3-3 automatic observation system. We demonstrate the data processing of observations by representatives SN 2022eyw and GRB 210420B.

Design and Verification of a Double-Grating Spectrometer System (DGSS) for Simultaneous Observation of Aerosols, Water Vapor and Clouds

Simultaneous observation of aerosols, water vapor, and clouds is conducive to the analysis of their interactions, and the consistency of observation equipment, instrument performance, and observation time is crucial. Molecular oxygen A-band (758–778 nm) and water vapor absorption band (758–880 nm) are two bands with similar wavelengths, and the hyperspectral remote sensing information of these two bands can be exploited to invert the vertical profile of aerosol and water vapor. In this paper, a double-grating spectrometer system (DGSS) was developed. DGSS uses a telescope system and fiber to introduce multi-angle, double-band sunlight, and it splits light synchronously (non-sequentially) to different positions of the detector through a slit plate and two gratings. The DGSS was calibrated in the laboratory and observed in the external field. The results indicated that the spectral resolution reached 0.06 nm (molecular oxygen A-band, 758–778 nm) and 0.24 nm (water vapor absorption band, 758–880 nm). Meanwhile, the spectra of the two bands (three angles in each band) are not aliased on the detector. Besides, the multi-angle simultaneous observation of the high-resolution spectra of the two bands is realized, which proves the effectiveness of this method. This study will provide a scientific basis for the observation of aerosol, water vapor, and cloud ground-based networks.

Circuit designs for construction of pancratic telescopes

The improvement of classical telescopes designed to observe distant objects is currently associated with the provision of operating modes with interchangeable magnification and the possibility of photo and video recording. The purpose of the paper is to propose circuit designs for optical systems of high-magnification pancratic telescopes and substantiate the possibility of their use in engineering. The paper is based on the engineering design of two variants of telescope optical systems with a magnification of 20 to 60 times, in the first of which the pancratic change of magnification is provided by the movements of the components in the ocular part, in the second - in the objective part. The characteristics of pancratic telescopes are considered. It was revealed that in modern models the pancratic change of magnifications is carried out in the ocular and objective parts of the system. Computer simulation methods were used to synthesize optical schemes in the paraxial approximation, followed by the implementation of systems with finite apertures and thicknesses. The developed systems can be used at domestic enterprises of optical instrumentation.

C33 PERCUTANEOUS CLOSURE OF MITRAL PARAVALVULAR LEAK (PVL): WHEN REVERSAL MAKES ALL THE DIFFERENCE

Abstract PVL is a complication associated with the implantation of a prosthetic valve. Since surgical re–intervention has a high operative risk, percutaneous closure (PC) has emerged due to its reduced invasiveness and the development of dedicated materials. We describe the case of a 66–year–old man with a mechanical oscillating disc mitral prosthesis who was admitted for acute heart failure. An echo showed a left ventricle with normal motion and a postero–medial mitral PVL with significant regurgitation. A transoesophageal echo confirmed the PVL in the 5 o’clock viewing portal with severe regurgitation. After optimising the medical therapy and with no change in echo findings, a cardiac catheterisation showed persistent post–capillary pulmonary hypertension, and therefore PC of the PVL was scheduled. Given the postero–medial location of the PVL, a transseptal puncture was performed using a 8.5 Fr Agilis introducer (Terumo) with telescoping system of a 6 r. JR4 catheter. The PVL was passed through with a Terumo 0.035 J–shaped guide, but without managing to advance the catheter beyond the leak. The guide was therefore advanced into the abdominal aorta and an arteriovenous circuit was created, which allowed the catheter to be advanced beyond the PVL and a closure device (AVPIII 14/5,Abbott St.Jude) was positioned with anterograde placement, with a distal disc on the ventricular side. Obliteration of the PVL, interference with the prosthetic disc and high transprosthetic gradients were observed despite several attempts to relocate the AVP, which was therefore removed. A second procedure was performed at a distance, creating a similar arteriovenous circuit by using a long introducer (110cm–Cook) which was advanced from the femoral artery beyond the leak in the opposite direction. An AVPIII (12/5) with a distal disc on the atrial side was positioned, this time with retrograde placement, with effective closure of the PVL and minimal residual regurgitation, without interference with the prosthesis. The course was free of complications; after one month the echo confirmed the result. Transcatheter closure of the PVL is a complex procedure, but relatively safe in experienced hands. This case is of particular interest due to the difficulty presented by the location of the PVL, which required measures of high technical complexity and because it describes a possible complication of the procedure, which was resolved by the simple reversal of the placement of the device.

Spectral beam combining of 2.8 μm fiber laser based on telescope system

We reported a spectral beam combining (SBC) of 2.8 μm erbium-doped fluoride glass fiber laser based on a telescope system. The application of the telescope system compressed the spectra of SBC significantly and allowed more fiber lasers to be combined. The SBC of three fiber lasers with a beam combining the efficiency of 68% was demonstrated. This work shows the ability of SBC in fluoride fiber power scaling.

Constraining branon dark matter from observations of the Segue 1 dwarf spheroidal galaxy with the MAGIC telescopes

We present the first search for signatures of brane-world extra-dimensional dark matter (DM) in the very-high-energy gamma-ray band by scrutinizing observations of the dwarf spheroidal galaxy Segue 1 with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescope system. Branons are new degrees of freedom that appear within flexible brane-world models: they are weakly interacting massive particles and natural DM candidates. The ground-based gamma-ray telescopes MAGIC could indirectly detect branon DM in the multi-TeV mass range by observing secondary products of DM annihilation into Standard Model particles. In the absence of a signal, we place constraints on the branon DM parameter space by using a binned likelihood analysis of almost 160-hours deep exposure on the Segue 1 dwarf spheroidal galaxy by the MAGIC telescopes. Our most stringent limit to the thermally-averaged annihilation cross-section (at 95% confidence level) corresponds to 〈σv〉 ≃ 1.4 × 10-23 cm3 s-1 at a branon mass of ∼ 0.7 TeV.

Design and tolerance analysis of a large-diameter diffractive telescope

The large-diameter diffractive telescope has the advantage of observing space debris. Some of the key issues are the design and tolerance analysis of the telescope with the segmented primary lens. In this paper, we design a space large-diameter sub-aperture stitching diffractive telescope that can achieve a large diameter of 1438 mm, a long focal length of 2000 mm, and a full field of view (FOV) of 0.34°. Considering the manufacturing and stitching errors of the sub-aperture can affect the telescope’s image quality, we provide a tolerance analysis method based on Monte Carlo analysis, which makes the consequence of the tolerance analysis nearly reality. The tolerance ranges are proposed not only for the segmented primary lens but also for the whole telescope system.

Super telescopic catheter system parallel to a contralateral stiff guide wire to cross extremely complex pulmonary arteries

Access to complex stenotic pulmonary arteries can be challenging due to their anatomy or secondary to prior multiple surgeries and interventions. Two techniques have been previously described to address this issue: the telescopic catheter-in-long sheath parallel to a stiff guidewire technique and the use of a microcatheter in a telescopic scope. We integrated and modified these techniques creating a super telescopic system with a SuperCross® microcatheter-in-catheter-in-long sheath, parallel to a contralateral stiff guidewire to access a previously repaired and stented left pulmonary artery. The stiff wire support and the 90° flexiblity of the Supercross® microcatheter assembled coaxial to the diagnostic catheter and the long sheath contributed to the successful ballooning and stenting-in-stent of the pulmonary artery.

Large‐scale asymmetry in galaxy spin directions: Analysis of galaxies with spectra in DES, SDSS, and DESI Legacy Survey

AbstractMultiple previous studies using several different probes have shown considerable evidence for the existence of cosmological‐scale anisotropy and a Hubble‐scale axis. One of the probes that show such evidence is the distribution of the directions toward which galaxies spin. The advantage of the analysis of the distribution of galaxy spin directions compared to the cosmic microwave background anisotropy is that the ratio of galaxy spin directions is a relative measurement, and therefore less sensitive to background contamination such as Milky Way obstruction. Another advantage is that many spiral galaxies have spectra, and therefore allow to analyze the location of such axis relative to Earth. This paper shows an analysis of the distribution of the spin directions of over 90K galaxies with spectra. That analysis is also compared to previous analyses using the Earth‐based Sloan Digital Sky Survey, Panoramic Survey Telescope and Rapid Response System, and Dark Energy Spectroscopic Instrument Legacy Survey, as well as space‐based data collected by Hubble Space Telescope. The results show very good agreement between the distribution patterns observed with the different telescopes. The dipole or quadrupole axes formed by the spin directions of the galaxies with spectra do not necessarily go directly through Earth.

A new concept for superior energy dissipation in hierarchical materials and structures

We propose a new conceptual approach to reach unattained dissipative properties based on the friction of slender concentric sliding columns. We begin by searching for the optimal topology in the simplest telescopic system of two concentric columns. Interestingly, we obtain that the optimal shape parameters are material independent and scale invariant. Based on a multiscale self-similar reconstruction, we end-up with a theoretical optimal fractal limit system whose cross section resembles the classical Sierpiński triangle. Our optimal construction is finally completed by considering the possibility of a complete plane tessellation. The direct comparison of the dissipation per unit volume δ with the material dissipation up to the elastic limit δel shows a great advantage: δ∼2000δel. Such result is already attained for a realistic case of three only scales of refinement leading almost (96%) the same dissipation of the fractal limit. We also show the possibility of easy recovering of the original configuration after dissipation and we believe that our schematic system can have interesting reliable applications in different technological fields.Interestingly, our multiscale dissipative mechanism is reminiscent of similar strategies observed in nature as a result of bioadaptation such as in the archetypical cases of bone, nacre and spider silk. Even though other phenomena such as inelastic behavior and full tridimensional optimization are surely important in such biological systems, we believe that the suggested dissipation mechanism and scale invariance properties can give insight also in the hierarchical structures observed in important biological examples.

Wayne State University’s Dan Zowada Memorial Observatory: Characterization and Pipeline of a 0.5 m Robotic Telescope

Wayne State University’s Dan Zowada Memorial Observatory is a fully robotic 0.5 m telescope and imaging system located under the dark skies of New Mexico. The observatory is particularly suited to time domain astronomy: the observation of variable objects, such as tidal disruption events, supernovae, and active galactic nuclei. We have developed a software suite for image reduction, alignment and stacking, and calculation of absolute photometry in the Sloan filters used at the telescope. Our pipeline also performs image subtraction to enable photometry of objects embedded in bright backgrounds such as galaxies. The 5σ detection limit of the Zowada Observatory for integration of 16 × 90 s exposures is 19.0 mag in g-band, 18.1 mag in r-band, 17.9 mag in i-band, and 16.6 mag in z-band. For a 3σ detection limit, measurements may be performed with greater uncertainties as deep as 19.9, 19.1. 18.9 and 17.5 mag in griz bands, respectively.

VVVX Near-IR Photometry for 99 Low-mass Stars in the Gaia EDR3 Catalog of Nearby Stars

Context. Red dwarf stars, which represent 75% of stars in the Milky Way, can be studied in great detail in the solar neighborhood, where the sample is more complete. Aims. We intend to better characterize red-dwarf candidates selected from the Gαìα Catalog of Nearby Stars using optical and near-infrared multi-filter photometry from the Vista Variables in the Vía Láctea extended (VVVX) Survey, the DECam Plane Survey, the Panoramic Survey Telescope and Rapid Response System, and the Wide-field Infrared Survey Explorer. Methods. We performed a cross-matching procedure among the positions of a color-selected sample of M dwarfs in the VVVX Survey and the Gaia Early Data Release 3 sub-catalog of nearby stars. We explored their stellar parameters and spectral types using the Virtual Observatory SED Analyzer (VOSA). Radii were also obtained from the computed luminosities and Teff using the Stefan-Boltzmann equation. Masses and ages were computed for some of the objects using evolutionary tracks and isochrones. Additional mass estimations were obtained with the MKs – M*, relation. We then validated our results for the stellar parameters of two of our objects with spectra obtained with the TripleSpec instrument at the SOAR telescope, as well as those of our total amount of stars through a direct comparison with an independent sample from the literature. We revised the objects in our sample and compared their proper motion vectors with other sources within 30′′ to identify possible companions and probed their renormalized unit weight error (RUWE) values to identify unresolved companions. Results. We present a catalog of physical parameters for 99 low-mass objects with distances from 43.2 to 111.3 pc. Effective temperatures range from 2500 to 3400 K, with the majority of stars in the sample compatible with the status of M4 dwarfs. We obtained a good agreement between the stellar parameters computed with VOSA and the estimations from observed spectra, also when comparing with an independent sample from the literature. The distribution of masses obtained with VOSA is concentrated toward the very low-mass regime. Eight objects present values of RUWE ≥ 1.4 and seven are consistent with being part of a binary system.

Dynamics Modeling of a Delta Robot with Telescopic Rod for Torque Feedforward Control

This paper presents dynamics modeling of a Delta robot with three revolute legs and a telescopic rod. Firstly, two generalized coordinate systems are established to describe the relationship between the movement of the telescopic rod and the position of the moving platform, and the telescopic rod system kinematics are established through singularity analysis. Secondly, taking the telescopic rod as the research object, the corresponding dynamics model is established using the Euler–Lagrange method. Moreover, this paper proposes a method to convert the force exerted by the telescopic rod motion on the moving platform into actuator torques. Thirdly, the dynamics model of the Delta robot with a telescopic rod is established, and numerical simulations are performed to demonstrate this approach. Finally, the influence of the telescopic rod on the actuator torques is verified using an experiment. A comparison is drawn between the two dynamics models used in torque feedforward control to validate the proposed dynamics model.

Experimental investigation in nodal aberration theory (NAT): separation of astigmatic figure error from misalignments in a Cassegrain telescope.

We present simulations and experimental validations for separating astigmatic figure error from misalignments in Nodal Aberration Theory (NAT) with a high-precision Cassegrain telescope. Both the primary mirror figure error and the secondary mirror misalignments induce binodal astigmatism for the telescope systems. The separation of these two aberration factors plays a crucial role in the telescope alignment process. In this study, the figure error of the aspheric primary mirror of the Cassegrain telescope induced by the mirror mounts was measured interferometrically utilizing a computer-generated hologram (CGH). According to the primary mirror figure error, the astigmatic node locations in the image plane were simulated using real raytracing. The center of the nodes was located on the field center, and the nodes were placed symmetrically with respect to the field center in the image plane. The telescope's alignment was performed using the simulation results, and the node locations were measured on a grid of field points interferometrically. Thereafter, secondary mirror misalignments around the coma-free pivot point were introduced into the optical system, and the node's center was shifted from the field center in the image plane as predicted by NAT. The simulations and interferometric field measurements were performed and compared on a grid of field points for the misaligned state in the presence of primary mirror figure error. The experimental results confirm the predictions from NAT. Statistical analysis was also performed to confirm the accuracy and stability of the measurements.