MiCPhot:A prime-focus multicolor CCD photometer on the 85-cm Telescope

We describe a new BVRI multicolor CCD photometric system situated at the prime focus of the 85-cm telescope at the Xinglong Station of NAOC. Atmospheric extinction effects, photometric accuracy and color calibration dependence of the system are investigated. Additional attention was paid to giving observers guidance in estimating throughput, detection limit, signal-to-noise ratio and exposure time.

Measurement of the Average Molecular Weight of Cotton Cellulose Crosslinked by a Polycarboxylic Acid at Different pH Using Multiple Angle Light Scattering Photometer in a DMAc/LiCl Solvent System

Durable press finishing of cotton fabrics with polycarboxylic acid increases fabric wrinkle-resistance at the expense of its mechanical strength. Severe tensile strength loss is the major disadvantage for wrinkle resistant cotton fabrics.Tensile strength loss of cotton fabric crosslinked by a polycarboxylic acid can be attributed to depolymerization and crosslink of cellulose molecules. Measurement of the molecular weight of cotton fabric before and after crosslinked by polycarboxylic acids can offer a possibility of direct understanding of the depolymerization. In this research, amultiple angle laser light scattering photometer was used todetermine the absolute molecular weight of cotton fabric treated with BTCA at different pH and then hydrolyzed with 0. 5 M NaOH solution at 50℃ for 144 h. The results indicate that average molecular weights of cotton fabric treated with polycarboxylic acids at different pH are almost the same.

High-precision temperature retrieval algorithm and verification for mesospheric airglow spectrum photometer

Photometric technology,characterized by its compact structure and relatively high stability,finds wide application in measuring airglow spectra.This instrumentation is anticipated to assume a pivotal role as the primary equipment for extensive network observations of middle and upper atmospheric temperatures in China,thereby providing crucial support for space environmental monitoring and atmospheric dynamic research.Nevertheless,susceptibility to various factors such as instrument inconsistency,variability in observation conditions,and alterations in the background atmospheric environment across different stations poses a challenge,potentially resulting in data inconsistencies in network observations.In response to these challenges,we propose a multiple-parameter iterative inversion(MPII)algorithm for temperature retrieval based on a mesospheric airglow spectrum photometer(MASP)developed by our research group.This algorithm accurately identifies the center of the image circle,corrects image distortion,and thereby obtains an accurate synthetic spectrum reflective of actual observations.It encompasses five adjustable parameters:sky background light,atmospheric temperature,filter temperature,optical system focal length,and degree of synthetic spectrum modulation.Compared to traditional methods,significant enhancements in the accuracy of the inverted temperature are achieved.To validate the effectiveness of the MPII algorithm,we conducted combined active and passive remote sensing synchronous measurements using MASP in conjunction with a sodium fluorescence Doppler lidar developed by the National Space Science Center.By utilizing the lidar temperature as a reference,atmospheric background radiation is mitigated from the MASP data,and the temperature is inverted using the MPII algorithm.Comparative analysis with the traditional method reveals that temperatures calculated by the MPII algorithm exhibit better consistency than those observed by the lidar.

Transient optical properties in fused silica measured by time-resolved high-power laser photometer

A time-resolved high-power laser photometer, which measures the real-time variations of transmission, internal reflection, and scattering simultaneously with picosecond time resolution, was developed to investigate the material response sequence during high-power nanosecond laser irradiation in thick fused silica. It was found that the transient transmission decreased sharply, accompanied by an increase in internal reflection at the rising edge of the laser pulse. The transient transmission recovered, while laser damage did not occur, but it did not recover if the scattering increased, indicating the occurrence of laser damage. The reason for the sharp decrease of transmission and the relationship between the transmission drop and laser damage were discussed.

Research on calibration method in lab of direct solar channels of Sun photometer

We develop a new calibration method in lab by measuring the absolute spectral irradiance responsivity of Sun photometer sun channel. The absolute power responsivity of Sun photometer is obtained when a white laser double monochromator system serve as a source, and a standard transfer detector calibrated against cryogenic absolute radiometer is assembled to measure the absolute power of laser beam. The effective area of aperture is measured through laser raster scanning method, and the relative spectral irradiance responsivity of the corresponding channel is obtained by using tungsten-halogen lamps double monoehromator system. On the basis of the above results, the top of the atmosphere responsive constants V0 （500, 675, and 870 nm） are obtained by integration with extraterrestrial solar spectral irradiance data. Comparing the calibration results with that of CIMEL, France in November 2011, the relative differences are 4.38%, 2.23%, and 2.45%, respectively. The calibration uncertainty reaches to 2.048×10^-2, which shows a remarkable consistency with the Langley plot method. Further, our scheme can overcome the limits of space and atmospheric conditions which are only available at a high-altitude calibration site in particular date. The advantages lie in not only shortening the experiment period but also being of high precision. This new scheme definitely plays an important role in supporting the current and future sun photometry calibration activities which are significant to earth observation.

Theoretical model and quantification of reflectance photometer

The surface morphology of lateral flow （LF） strip is examined by scanning electron microscope （SEM） and the diffuse reflection of porous strip with or without nanogold particles is investigated. Based on the scattering and absorption of nanogold particles, a reflectance photometer is developed for quantification of LF strip with nanogold particles as reporter. The integration of reflection optical density is to indicate the signals of test line and control line. As an example, serial dilutions of microalbunminuria （MAU） solution are used to calibrate the performance of the reflectance photometer. The dose response curve is fitted with a four-parameter logistic mathematical model for the determination of an unknown MAU concentration. The response curve spans a dynamic range of 5 to 200 μg/ml. The developed reflectance photometer can realize simple and quantitative detection of analyte on nanogold-labeled LF strip.

New method for calibration of sun photometers

A new method for calibration of sun photometers based on Bouguer-Beer law is proposed. The developed basic equation of calibration makes it possible to formulate the derivative methods of calibration on the basis of photometric measurements upon optical air masses, the ratio of which is an integer number.

NitroMAC：An instrument for the measurement of HONO and intercomparison with a long-path absorption photometer

Nitro MAC（French acronym for continuous atmospheric measurements of nitrogenous compounds） is an instrument which has been developed for the semi-continuous measurement of atmospheric nitrous acid（HONO）. This instrument relies on wet chemical sampling and detection using high performance liquid chromatography（HPLC）-visible absorption at540 nm. Sampling proceeds by dissolution of gaseous HONO in a phosphate buffer solution followed by derivatization with sulfanilamide/N-（1-naphthyl）-ethylenediamine. The performance of this instrument was found to be as follows： a detection limit of around 3 ppt with measurement uncertainty of 10% over an analysis time of 10 min. Intercomparison was made between the instrument and a long-path absorption photometer（LOPAP） during two experiments in different environments. First, air was sampled in a smog chamber with concentrations up to 18 ppb of nitrous acid. Nitro MAC and LOPAP measurements showed very good agreement. Then, in a second experiment, ambient air with HONO concentrations below250 ppt was sampled. While Nitro MAC showed its capability of measuring HONO in moderate and highly polluted environments, the intercomparison results in ambient air highlighted that corrections must be made for minor interferences when low concentrations are measured.

An Exposure Meter of Lijiang Fiber-fed High-Resolution Spectrograph

In 2016,an exposure meter was installed on the Lijiang Fiber-fed High-Resolution Spectrograph to monitor the coupling of starlight to the science fiber during observations.Based on it,we investigated a method to estimate the exposure flux of the CCD in real time by using the counts of the photomultiplier tubes(PMT)of the exposure meter,and developed a piece of software to optimize the control of the exposure time.First,by using flat-field lamp observations,we determined that there is a linear and proportional relationship between the total counts of the PMT and the exposure flux of the CCD.Second,using historical observations of different spectral types,the corresponding relational conversion factors were determined and obtained separately.Third,the method was validated using actual observation data,which showed that all values of the coefficient of determination were greater than 0.92.Finally,software was developed to display the counts of the PMT and the estimated exposure flux of the CCD in real-time during the observation,providing a visual reference for optimizing the exposure time control.

Rapid instrument exchanging system for the Cassegrain focus of the Lijiang 2.4-m Telescope

As a facility used for astronomical research, the Lijiang 2.4-m telescope of Yunnan Astronomical Observatories, requires the ability to change one auxiliary instrument with another in as short a time as possible. This arises from the need to quickly respond to scientific programs （e.g. transient observation, time domain studies） and changes in observation conditions （e.g. seeing and weather conditions）. In this paper, we describe the design, construction and test of hardware and software in the rapid instrument exchange system （RIES） for the Cassegrain focal station of this telescope, which enables instruments to be quickly changed at night without much loss of observing time. Tests in the laboratory and at the telescope show that the image quality and pointing accuracy of RIES are satisfactory. With RIES, we observed the same Landolt standard stars almost at the same time with the Princeton Instruments VersArray 1300B Camera （PICCD） and the Yunnan Faint Object Spectrograph and Camera （YFOSC）, while both were mounted at the Cassegrain focus. A quasi-simultaneous comparison shows that the image quality of the optical system inside the YFOSC is comparable with that provided by the PICCD.

Research on Testing System for Three-dimensional Distribution of Luminous Intensity of LED

In terms of asymmetrical three-dimensional distribution(ID) of luminous intensity(LI) of light-emitting-diode(LED),a testing system was conducted in this study. Design and principle of the testing system were introduced. 31 photometers were placed on a concentric circle,and all of them were used to gather LI data of LED at the same time. The data acquisition card(DAC) was used to gather multichannel data and controlled motor. Experimental results indicated that the testing system had achieved the goal of testing three-dimensional distribution of LI. And each parameter could meet the requirements of industrial production and measurement.

Refractory Black Carbon Results and a Method Comparison between Solid-state Cutting and Continuous Melting Sampling of a West Antarctic Snow and Firn Core

This work presents the refractory black carbon(rBC)results of a snow and firn core drilled in West Antarctica(79°55'34.6"S,94°21'13.3"W)during the 2014?15 austral summer,collected by Brazilian researchers as part of the First Brazilian West Antarctic Ice Sheet Traverse.The core was drilled to a depth of 20 m,and we present the results of the first 8 m by comparing two subsampling methods—solid-state cutting and continuous melting—both with discrete sampling.The core was analyzed at the Department of Geological Sciences,Central Washington University(CWU),WA,USA,using a single particle soot photometer(SP2)coupled to a CETAC Marin-5 nebulizer.The continuous melting system was recently assembled at CWU and these are its first results.We also present experimental results regarding SP2 reproducibility,indicating that sample concentration has a greater influence than the analysis time on the reproducibility for low rBC concentrations,like those found in the Antarctic core.Dating was carried out using mainly the rBC variation and sulfur,sodium and strontium as secondary parameters,giving the core 17 years(1998?2014).The data show a well-defined seasonality of rBC concentrations for these first meters,with geometric mean summer/fall concentrations of 0.016μg L^?1 and geometric mean winter/spring concentrations of 0.063μg L^?1.The annual rBC concentration geometric mean was 0.029μg L^?1(the lowest of all rBC cores in Antarctica referenced in this work),while the annual rBC flux was 6.1μg m^?2 yr^?1(the lowest flux in West Antarctica records so far).

Rapid In-situ Determination of Chromium (VI) in Water Using Modified Diphenylcarbazine with Citrate

Diphenylcarbazine citrate was synthesized and a high-speed color reaction of the new reagent with Cr (VI) was developed and used to determine trace Cr (VI) in electroplating water. In acid medium, diphenylcarbazine citrate reacted with Cr (VI) to form a magenta-colored complex. The molar absorptivity of the complex is 3.32×104 L·mol-1·cm-1 at 540 nm. Beer抯 law is obeyed for Cr (VI) in the range of 0.03~2.00 mg/L. Contents of Cr (VI) in electroplating waste water was determined in-situ and satisfactory results were obtained.

Triple Range Imager and POLarimeter(TRIPOL)——a compact and economical optical imaging polarimeter for small telescopes

We report the design concept and performance of a compact, lightweight and economical imaging polarimeter, the Triple Range Imager and POLarimeter(TRIPOL), capable of simultaneous optical imagery and polarimetry. TRIPOL splits the beam in wavelengths from 400 to 830 nm into g′-, r′-and i′-bands with two dichroic mirrors, and measures polarization with an achromatic half-waveplate and a wire grid polarizer. The simultaneity makes TRIPOL a useful tool for small telescopes for the photometry and polarimetry of time variable and wavelength dependent phenomena. TRIPOL is designed for a Cassegrain telescope with an aperture of^1 m. This paper presents the engineering considerations of TRIPOL and compares the expected with observed performance. Using the Lulin 1-m telescope and 100 seconds of integration, the limiting magnitudes are g′~19.0 mag, r′~18.5 mag and i′~18.0 mag with a signal-to-noise ratio of 10, in agreement with design expectation. The instrumental polarization is measured to be^0.3% in the three bands. Two applications, one to the star-forming cloud IC 5146 and the other to the young variable GM Cep, are presented as demonstrations.

Validation of Aerosol Optical Depth from Terra and Aqua MODIS Retrievals over a Tropical Coastal Site in China

This study compares the aerosol optical depth (AOD) Level 2 Collection 5 products from the Terra and Aqua Moderate Resolution Imaging Spectroradiometers (MODIS) with ground-based measurements from a Microtops II sun photometer over Sanya (18.23°N,109.52°E),a tropical coastal site in China,from July 2005 to June 2006.The results indicate that the Terra and Aqua MODIS AOD retrievals at 550 nm have good correlations with the measurements from the Microtops II sun photometer.The correlation coefficients for the linear regression fits (R2) are 0.83 for Terra and 0.78 for Aqua,and the regressed intercepts are near zero (0.005 for Terra,0.009 for Aqua).However,the Terra and Aqua MODIS are found to consistently underestimate AOD with respect to the Microtops II sun photometer,with slope values of 0.805 (Terra) and 0.767 (Aqua).The comparison of the monthly mean AOD indicates that for each month,the Terra and Aqua MODIS retrievals are matched with corresponding Microtops measurements but are systematically less than those of the Microtops.This validation study indicates that the Terra and Aqua MODIS AOD retrievals can adequately characterize the AOD distributions over the tropical coastal region of China,but further efforts to eliminate systematic errors are needed.

Retrieval of PM10 Concentration from an AOT Passive Remote-Sensing Station between 2003 and 2007 over Northern France

A method of retrieving PM10 particles concentrations at the ground level from AOT (Aerosol Optical Thickness) measurements is presented. It uses data obtained among five years during 2003 to 2007 summers in the Lille region (northern France). As PM10 concentration strongly depends on meteorological variables, we clustered the meteorological situations provided by the MM5 meteorological model forced at the lateral boundaries by the operational NCEP model in eight classes (local weather types) for which a robust statistical relationship between AOT and PM10 was found. The meteorological situations were defined by the hourly vertical profiles of temperature and (zonal and meridian) wind components. The clustering of the weather types were obtained by a self-organizing map (SOM) followed by a hierarchical ascending classification (HAC). We were then able to retrieve the PM10 at the surface from the AERONET AOT measurements for each weather type by doing non linear regressions with dedicated SOMs. The method is general and could be extended to other regions. We analyzed the strong pollution event that occurred during August 2003 heat wave. Comparison of the results from our method with the output of the CHIMERE chemical-transport model showed the interest to tentatively combine these two pieces of information to improve particle pollution alert.

Examining the M67 Classification as an Open Cluster

The cluster M67 (= NGC 2682) in Cancer is a rich stellar cluster, usually classified as an open cluster. Using our own observations with the 0.4 m telescope, we show that M67 is a tight group of about 1200 stars. The actual radius of the cluster is about 3.1 pc and the average mass of a star in the system is about . We also show that the ratio of the mean kinetic energy of the cluster to its mean gravitational potential energy , while the value predicted by the virial theorem is equal to . So the system is a gravitationally bound. This value of is considered as an evidence of quasi-stability of the cluster and allows us to use the Chandrasekhar-Spitzer relaxation time for M67 Myr as a characteristic dynamical relaxation time of the system. As the cluster is almost twice older its half-life time , it is argued that M67 was in the past (about 4 Gyr ago, close to its forma-tion) a relatively small ( stars) globular cluster, but got “open cluster” shape due to the dynamical evapora-tion of the majority of its stars.

Spatial and temporal distribution of the cloud optical depth over China based on MODIS satellite data during 2003–2016

The cloud optical depth(COD) is one of the important parameters used to characterize atmospheric clouds. We analyzed the seasonal variations in the COD over East Asia in 2011 using cloud mode data from the AERONET(Aerosol Robotic Network) ground-based observational network. The applicability of the MODIS(Moderate Resolution Imaging Spectroradiometer) COD product was verified and compared with the AERONET cloud mode dataset. There was a good correlation between the AERONET and the MODIS. The spatial and temporal distribution and trends in the COD over China were then analyzed using MODIS satellite data from 2003 to 2016. The seasonal changes in the AERONET data and the time sequence variation of the satellite data suggest that the seasonal variations in the COD are significant. The result shows that the COD first decreases and then increases with the season in northern China, and reaches the maximum in summer and minimum in winter.However, the spatial distribution change is just the opposite in southern China. The spatial variation trend shows the COD in China decreases first with time and gradually increases after 2014. And the trend of COD in the western and central China is consistent with that in China. While the trend of COD shows a continuously increasing over time in northeast China and the Pearl River Delta.