ABSTRACT Recent silicon photomultipliers (SiPMs) boast excellent production quality, eliminating the need for individual breakdown voltage calibration. We present measurements of cross-talk probability and relative gain for 122 SensL MicroFJ60035-TSV SiPMs. These semiconductor photosensors have replaced photomultiplier tubes in many applications due to their single-photon resolution, insensitivity to magnetic fields, robustness, and cost-effective photon detection at lower voltages. Light guides expand SiPMs’ small photosensitive area, and optical coupling reduces cross-talk probability compared to bare sensors at nominal bias voltage, as demonstrated in this study.

RESUMEN Los fotomultiplicadores de silicio (SiPMs) de generaciones recientes tienen una alta calidad de producción, lo que elimina la necesidad de calibrar individualmente el voltaje de caída. En este estudio, se midió la probabilidad de interferencia y la ganancia relativa de 122 SiPMs SensL MicroFJ-60035-TSV. Estos dispositivos semiconductores reemplazan a los tubos fotomultiplicadores en diversas aplicaciones debido a su capacidad para detectar un solo fotoelectrón, su insensibilidad a campos magnéticos, su robustez, y su mejora en la eficiencia de detección de fotones con menor voltaje y costos. Para aumentar el área fotosensible de los SiPMs se utilizan guías de luz. Al comparar sensores acoplados ópticamente a guías de luz con sensores aislados a voltaje base, se observa que el acoplamiento óptico reduce significativamente la interferencia en los sensores estudiados.

Resumen Objetivo: Desarrollar recomendaciones basadas en la evidencia para el diagnóstico, la rehabilitación funcional y el seguimiento de personas con baja visión entre 7 y 18 años y mayores de 18 años. Método: Se conformó el grupo desarrollador con la participación de pacientes. Se hizo una búsqueda sistemática y se evaluaron la calidad de los estudios y el cuerpo de la evidencia. Las recomendaciones se hicieron utilizando Grade Evidence to Decision Framework, las cuales fueron validadas con expertos nacionales. Resultados: En el apartado de diagnóstico, la calidad de la evidencia respecto a agudeza visual y campo visual fue baja; en estas pruebas se generó recomendación débil a favor del uso de la cartilla Early Treatment Diabetic Retinopathy Study y de microperimetría, respectivamente. En cuanto a sensibilidad al contraste, la calidad de la evidencia fue muy baja y se da recomendación débil a favor del uso de la prueba de Pelli-Robson. En cuanto al tratamiento, la calidad de la evidencia respecto a ayudas ópticas electrónicas fue moderada y se da recomendación débil a favor para su uso. En cuanto a las lupas manuales, electrónicas, telescopios y tabletas, la calidad de la evidencia fue muy baja y se da recomendación débil a favor para su uso. En el apartado de rehabilitación, la calidad de la evidencia para personas mayores de 16 años fue moderada y se da recomendación fuerte a favor de la rehabilitación multidisciplinaria y multicomponente, mientras que la calidad de la evidencia respecto a rehabilitación para personas entre 7 y 16 años fue baja y se da recomendación fuerte a favor de su uso. La calidad de la evidencia para intervenciones de terapia ocupacional fue baja y se da recomendación débil a favor de su uso. Con relación a psicología, la calidad de la evidencia para las intervenciones de este tipo fue baja y se da recomendación fuerte a favor de su uso. Finalmente, la calidad de la evidencia para el uso de escalas de seguimiento fue alta y se da recomendación fuerte a favor del uso del National Eye Institute Visual Function Questionnaire-25. Conclusiones: Las recomendaciones emitidas permiten dar un lineamiento general para el manejo integral de la baja visión, reduciendo la variabilidad indeseada en el diagnóstico, la rehabilitación y el seguimiento.

Abstract Purpose: To develop evidence-based recommendations for the diagnosis, functional rehabilitation, and follow-up of people with low vision between 7 and 18 years of age and over 18 years of age. Method: A development group was formed with the participation of patients. A systematic search was performed, and the quality of the studies and the body of evidence were evaluated. Recommendations were made using the Grade Evidence to Decision Framework, which were validated with national experts. Results: In the diagnostic section, the quality of the evidence regarding visual acuity and visual field was low; in these tests, a weak recommendation was generated in favor of the use of the Early Treatment Diabetic Retinopathy Study and Microperimetry primer, respectively. Regarding contrast sensitivity, the quality of the evidence was very low and a weak recommendation was given in favor of the use of the Pelli-Robson test. As for treatment, the quality of evidence regarding electronic optical aids was moderate and a weak recommendation is given in favor of their use. Regarding manual and electronic magnifiers, telescopes and tablets, the quality of evidence was very low and a weak recommendation in favor of their use is given. In the section on rehabilitation, the quality of the evidence regarding this aspect for persons over 16 years of age was moderate, and there is a strong recommendation in favor of multidisciplinary and multicomponent rehabilitation. On the other hand, the quality of the evidence regarding rehabilitation for people between 7 and 16 years of age was low, and there is a strong recommendation in favor of its use. The quality of evidence for occupational therapy interventions was low and a weak recommendation is given in favor of its use. Regarding psychology, the quality of the evidence for interventions of this type was low and a strong recommendation is given in favor of their use. Finally, the quality of evidence for the use of follow-up scales was high and strong recommendation is given in favor of the use of the National Eye Institute Visual Function Questionnaire-25. Conclusions: The recommendations issued allow giving a general guideline for the comprehensive management of low vision, reducing unwanted variability in diagnosis, rehabilitation, and follow-up.

RESUMEN En este trabajo presentamos un algoritmo general para calcular el punto de coma cero para telescopios reflectores clásicos y no clásicos con superficies asféricas. Programamos una función de trazado de rayos general aplicable a superficies cónicas con asfericidad, desplazamientos e inclinaciones, que puede ser modificada por los usuarios, según sus especificaciones. Esta función se utiliza para evaluar la coma transversal y determinar la conjunción óptima de desplazamiento e inclinación del espejo secundario que evita la introducción de coma axial durante el proceso de colimación. Presentamos el cálculo del punto de coma cero para los telescopios clásicos del Observatorio Astronómico Nacional, San Pedro Mártir, México. Además, mostramos el ejemplo de un telescopio de campo amplio con superficies asféricas, como será el caso de los telescopios TAOS-II, para los que no se puede utilizar la expresión analítica clásica.

ABSTRACT In this work we present a general algorithm to calculate the zero coma point for classical and non-classical reflecting telescopes with aspherical surfaces. We programmed a general ray tracing function applicable to conical surfaces with asphericity, displacements, and inclinations that can be modified by the users, according to their specifications. This function is used to evaluate the transverse coma and determine the optimal conjunction of shift and tilt of the secondary mirror that prevents the introduction of axial coma during the collimation process. We present the calculation of the zero coma point for the classical telescopes of the National Astronomical Observatory, San Pedro Mártir, Mexico. Furthermore, we show an example of a wide-field telescope with aspherical surfaces, as will be the case of the TAOS-II telescopes, for which the classical analytical expression cannot be used.

Abstract International Scientific Optical Network (ISON) is an open international voluntary project specializing in observations of the near-Earth space objects. Observatories collaborating with ISON provide the global coverage and successfully combine the observations of the space debris and asteroids. The network includes more than 50 telescopes of 27 observatories in 15 countries and has been working since 2005. ISON monitors the whole GEO region and tracks the objects at GEO, GTO, HEO and LEO. ISON data allowing maintenance of the database of the space objects orbits, validating space debris population model and providing conjunction assessment analysis for satellites at high orbits. ISON develops the technology of asteroid survey with small telescopes and arranges regular photometry observations of near-Earth asteroids (NEA) to investigate the YORP effect, search new binary NEAs, and support radar experiments.

Abstract Gamma-ray bursts (GRBs) are the most energetic and mysterious events in the Universe, which are observed in all ranges of electromagnetic spectrum. Most valuable results about physics of GRB are obtained by optical observations. GRBs are initially detected in gamma-rays with poor localization accuracy, and an optical counterpart should be found. The faster the counterpart is found, the more it can give to physics. This first phase, as a rule, corresponds to an early afterglow. The next phases of the observations are multicolor photometry, polarimetry, spectroscopy, and few days later the search for a supernova or kilonova associated with the GRB, and finally, observations of the host galaxy. To manage the problem of fast optical observations, telescopes with a small aperture are suitable. They can have a large field of view, which is necessary to cover initial localizations of GRBs. The sensitivity of the telescope+detector may be sufficient to record statistically significant light curve with fine time resolution. We describe one of the networks of telescopes with a small aperture IKI-GRB FuN, and present the results of early optical observation of GRB sources, and discuss the design requirements of the optical observations for effective GRB research in the next decade.

Abstract The Intelligent Observatory (IO) refers to the vision of the South African Astronomical Observatory (SAAO) to meet the scientific needs of both the South African and international astronomical communities by providing a better and more efficient service. The idea behind the IO is to harmonise the astronomical operations of all the hosted and local astronomical facilities on the Sutherland Plateau. The vision requires both upgrades to some of the telescopes and a re-design of the current Sutherland operations model. The primary science driver, for the IO, is time-domain and transient science.

Abstract SiTian is an ambitious ground-based all-sky optical monitoring project, developed by the Chinese Academy of Sciences. The concept is an integrated network of dozens of 1-m-class telescopes deployed partly in China and partly at various other sites around the world. The main science goals are the detection, identification and monitoring of optical transients (such as gravitational wave events, fast radio bursts, supernovae) on the largely unknown timescales of less than 1 day; SiTian will also provide a treasure trove of data for studies of AGN, quasars, variable stars, planets, asteroids, and microlensing events. To achieve those goals, SiTian will scan at least 10,000 square deg of sky every 30 min, down to a detection limit of $V \approx 21$ mag. The scans will produce simultaneous light-curves in 3 optical bands. In addition, SiTian will include at least three 4-m telescopes specifically allocated for follow-up spectroscopy of the most interesting targets. We plan to complete the installation of 72 telescopes by 2030 and start full scientific operations in 2032.

Abstract Space debris division of PMO is devoted to play an important role in the research of orbital mechanics and the development of space debris observation techniques in China. To support the work, this division builds and operates a large optical network across China. The observational network include two major subsets, large field survey telescopes and precise tracking telescopes. The main objective of the network is to maintain cataloged orbital debris and detect uncatalogued debris. CHES at YaoAn site is the most recent facility, for higher orbits survey. New operational software and data pipeline that aims at detecting unresolved objects has being developed. This paper presents the details of this facility and related activities.

Abstract This paper is based on a proposal submitted for a BRICS astronomy flagship program, which was presented at the 2019 meeting of the BRICS Astronomy Working Group, held in Rio de Janeiro from 29 September to 2 October 2019. The future prospects for the detection and study of transient phenomena in the Universe heralds a new era in time domain astronomy. The case is presented for a dedicated BRICS-wide flagship program to develop a network of ground-based optical telescopes for an all-sky survey to detect short lived optical transients and to allow follow-up of multi-wavelength and multi-messenger transient objects. This will leverage existing and planned new facilities within the BRICS countries and will also draw on the opportunities presented by other multi-wavelength space- and ground-based facilities that exist within the BRICS group. The proposed optical network would initially perform followup observations on new transients using existing telescopes. This would later expand to include a new global network of \sim ∼70 wide-field 1-m telescopes which will cover the entire sky, simultaneously, with a cadence of less than a few hours. This realization would represent a ground-breaking and unique global capability, presenting many scientific opportunities and associated spin-off benefits to all BRICS countries.

Abstract We present a brief description of the activities of the infrared astronomy group of Tata Institute of Fundamental Research with special emphasis on the near-infrared instrumentation for star formation studies using 2 - 4-meter class Indian ground-based telescopes.

Resumo Uma atividade didática para o estudo teórico e experimental do princípio de funcionamento do telescópio refrator é proposta para cursos de graduação em física, tecnologia e engenharia. Utilizou-se o formalismo matricial para determinar as propriedades do telescópio, como a distância entre as lentes e a magnificação, em função dos comprimentos focais das lentes objetiva e ocular e da distância objeto-telescópio. Na parte experimental, foi montado um arranjo com o telescópio em si e um olho artificial, composto de uma lente positiva como cristalino e um anteparo plano como retina. A magnificação foi medida diretamente da retina do olho artificial e comparada, à luz dos cálculos de propagação de incertezas, com medidas obtidas com o auxílio de expressões extraídas do método matricial.

Abstract A didactical activity aiming the theoretical and experimental study of the refractive telescope is proposed for undergraduate physics, technology and engineering courses. The matrix method was used for determining the telescope properties like distance between the lenses and magnification, as a function of the lenses focal lengths and the distance between the object and the telescope. In the experiments the optical setup was comprised by the telescope itself and an artificial eye, which in turn is comprised by a positive lens as the eye lens and a planar screen as the retina. The magnification was directly measured from the retina and compared with the measurements obtained with the help of the equations retrieved from the matrix method, concerning the uncertainty propagation.

Resumo Neste trabalho mostramos como observar um trânsito planetário com um telescópio de pequena abertura, bem como a estratégia utilizada para selecionar o objeto, fazer as observações, o tratamento e a análise dos dados. Como exemplo observamos o trânsito planetário na estrela WASP 76 e fizemos uma estimativa do tempo do trânsito, do raio do planeta, do semieixo da órbita e da inclinação orbital. Os resultados obtidos mostram que mesmo com telescópios com configurações instrumentais modestas e instalados em locais com poluição luminosa é possível obter dados satisfatórios do trânsito planetário em estrelas brilhantes. A partir desse resultado defendemos que é possível realizar trabalhos de Astronomia observacional com telescópios de pequena abertura, como os inúmeros que existem nos diversos miniobservatórios instalados em universidades e centros de pesquisa do Brasil, de forma a proporcionar o letramento científico de estudantes de cursos de graduação e do ensino médio.

Abstract In this paper we describe how to observe a planetary transit using a small aperture telescope, as well as the strategies used to select the object, make the observations, the treatment and the data analysis. As an example, we observed the planetary transit on the WASP 76 star and estimated the transit time, the radius, the orbit semi major-axis and the orbital inclination of the planet. The results show that telescopes with modest instrumental configuration can be used to obtain satisfactory data about exoplanets that transit bright stars. Based on this result, we propose that it is possible to do observational astronomy with small-aperture telescopes, such as the instruments that exist in the different small-observatories installed in universities and a research centers in Brazil, to provide scientific literacy for undergraduate students and from high school students.

ABSTRACT Using uvby − β photoelectric photometry obtained with the 0.84 m telescope of the Observatorio Astrónomico Nacional de San Pedro Mártir, México, we deter-mined some of the physical characteristics, such as effective temperature and surface gravity of the high amplitude Delta Scuti star V2455 Cyg (=HD 204615). Newly determined times of maximum light gathered at the Observatorio Astrónomico Nacional de Tonantzintla, México with small 10 inch telescopes equipped with CCD cameras were combined with times of maxima in the literature, and used to study the secular variation of the pulsational period of the star.

RESUMEN A partir de fotometría fotoeléctrica uvby − β adquirida con el telescopio de 0.84 m del Observatorio Astrónomico Nacional de San Pedro Mártir, México de la estrella Delta Scuti de gran amplitud V2455 Cyg (=HD 204615) hemos determinado sus parámetros físicos tales como temperatura efectiva y gravedad superficial. Con nuevos tiempos de máximo recopilados con telescopios pequeños de 10 pulgadas provistos de c´amaras CCD en el Observatorio Astrónomico Nacional de Tonantzintla, México, junto con tiempos de máximo de la literatura, hemos estudiado el período secular de la estrella.

ABSTRACT We report the development of a high-time resolution, 3-colour, simultaneous optical imaging system for the 2.1 m telescope in the San Pedro Mártir Observatory, México. OPTICAM will be equipped with three 2,048×2,048 pixel Andor Zyla 4.2-Plus sCMOS cameras and a set of SDSS filters allowing optical coverage in the 320-1,100 nm range. OPTICAM will nominally allow sub-second exposures. Given its instrumental design, a wide range of fast-variability astrophysical sources can be targeted with OPTICAM including X-ray binaries, pulsating white dwarfs, accreting compact objects, eclipsing binaries and exoplanets. OPTICAM observations will be proprietary for only six months and will then be made publicly available to the astronomical community.

RESUMEN Informamos sobre el desarrollo de un sistema de imagen óptica simultáneo en 3 colores y alta resolución temporal para el telescopio de 2.1 m del Observatorio Astronómico Nacional en San Pedro Mártir, México. OPTICAM estará equipado con tres cámaras sCMOS Andor Zyla 4.2-Plus y un conjunto de filtros SDSS que permitirán cobertura óptica en el rango de 320-1,100 nm. OPTICAM permitirá nominalmente exposiciones en el orden de sub-segundos. Dado su diseño instrumental, un amplio rango de fuentes astrofísicas de rápida variabilidad pueden ser observadas con OPTICAM incluyendo estrellas binarias de rayos X, enanas blancas pulsantes, objetos compactos en acrecentamiento, estrellas binarias eclipsantes y exoplanetas. Las observaciones realizadas con OPTICAM serán de propiedad exclusiva durante seis meses y luego se pondrán a disposición pública para la comunidad astronómica.

RESUMEN El telescopio es un instrumento que permite observar objetos muy lejanos. Si queremos comprender su funcionamiento necesitamos algunos conceptos basicos de óptica, pero antes vamos a clasificar los principales tipos de telescopios. Posteriormente, describiremos los conceptos de optica más relevantes, presentaremos algunos ejemplos y dejaremos algunos problemas propuestos.

ABSTRACT The telescope is an instrument that allows for the observation of very far objects. To understand how they work we need to classify the main types of telescopes and to understand some basic optical concepts. Finally, we describe the most relevant optical principles with examples and answer some frequently asked questions.