Magnitudes Of Stars Research Articles

The Microlensing Event Rate and Optical Depth from MOA-II 9 Yr Survey Toward the Galactic Bulge

Abstract We present measurements of the microlensing optical depth and event rate toward the Galactic bulge using the data set from the 2006 to 2014 MOA-II survey, which covers 22 bulge fields spanning ∼42 deg2 between −5° < l < 10° and −7° < b < −1°. In the central region with ∣l∣ < 5°, we estimate an optical depth of τ = [ 1.75 ± 0.04 ] × 1 0 − 6 exp [ ( 0.34 ± 0.02 ) ( 3 ∘ − ∣ b ∣ ) ] and an event rate of Γ = [16.08 ± 0.28] × 10−6 exp [ ( 0.44 ± 0.02 ) ( 3 ∘ − ∣ b ∣ ) ] star − 1 yr − 1 using a sample consisting of 3525 microlensing events, with Einstein radius crossing times of t E < 760 days and a source star magnitude of I s < 21.4 mag. We confirm our results are consistent with the latest measurements from the OGLE-IV 8 yr data set. We find our result is inconsistent with a prediction based on Galactic models, especially in the central region with ∣b∣ < 3°. These results can be used to improve the Galactic bulge model, and more central regions can be further elucidated by upcoming microlensing experiments, such as the PRime-focus Infrared Microlensing Experiment and Nancy Grace Roman Space Telescope.

Using Gaia and synthetic photometry for the absolute flux calibration of planetary cameras: The case of BepiColombo/SIMBIO-SYS

Context. The absolute flux calibration of a planetary camera is pivotal for a quantitative analysis of the brightness that is reflected by a celestial body to a) characterise its microphysical properties, b) analyse changes caused by exogenic or endogenic activity, and c) produce high-quality image mosaics to understand the geology of the body. This is usually done by observing a few standard stars. We propose an alternative method that relies on the Gaia catalogue and consider the Spectrometer and Imagers for Mpo Bepicolombo Integrated Observatory SYStem (SIMBIO-SYS) suite of imagers on board BepiColombo, which is currently flying towards planet Mercury, as a test case. We discuss the advantages of this method and its implications for the future exploration of Mercury, as well as the applicability to other cameras. Aims. We evaluate whether Gaia low-resolution spectra (XPSP) are suitable to supply a set of reference stars for an absolute calibration of a planetary camera. We assess the performances of this approach and discuss its advantages with respect to more traditional methods. While this was validated for common astronomical facilities, it has never been used for planetary cameras. Methods. We used synthetic photometry from Gaia low-resolution (BP/RP) spectra to produce magnitudes in all the passbands of SIMBIO-SYS. We used a set of very reliable spectrophotometric standard stars to correct small residual systematics that affect externally calibrated BP/RP spectra, and we thus defined the SIMBIO-SYS photometric system tied to the flux scale of the CALSPEC spectrophotometric library. We evaluated the uncertainties on the final calibration of this photometric system by assessing the accuracy (average of the residuals) and precision (standard deviation of the residuals) of the reproduced magnitudes of stars in the CALSPEC spectrophotometric library. Results. We find an accuracy better than 0.1% and a precision ranging from 0.4% to 1.0%, depending on the considered passband, in the magnitude and colour ranges that are relevant for stars that can be used as photometric standards for the SIMBIO-SYS instrument. Conclusions. Our results imply an improvement in the flux uncertainty through the absolute calibration of a factor 2–12 with respect to pre-existing imaging data of Mercury, and of a factor 2–7 with respect to the Colour and Stereo Surface Imaging System (CaSSIS), which is a similar camera with the same detector that orbits Mars, for which the absolute calibration details are available in the literature. In the context of the future exploration of Mercury, these improvements imply an unprecedented sensitivity of the SIMBIO-SYS instrument that will provide a novel view of the present-day surface activity on Mercury and of the photometric properties of the Hermean surface.

Automatic Compressive Sensing of Shack–Hartmann Sensors Based on the Vision Transformer

Shack–Hartmann wavefront sensors (SHWFSs) are crucial for detecting distortions in adaptive optics systems, but the accuracy of wavefront reconstruction is often hampered by low guide star brightness or strong atmospheric turbulence. This study introduces a new method of using the Vision Transformer model to process image information from SHWFSs. Compared with previous traditional methods, this model can assign a weight value to each subaperture by considering the position and image information of each subaperture of this sensor, and it can process to obtain wavefront reconstruction results. Comparative evaluations using simulated SHWFS light intensity images and corresponding deformable mirror command vectors demonstrate the robustness and accuracy of the Vision Transformer under various guide star magnitudes and atmospheric conditions, compared to convolutional neural networks (CNNs), represented in this study by Residual Neural Network (ResNet), which are widely used by other scholars. Notably, normalization preprocessing significantly improves the CNN performance (improving Strehl ratio by up to 0.2 under low turbulence) while having a varied impact on the Vision Transformer, improving its performance under a low turbulence intensity and high brightness (Strehl ratio up to 0.8) but deteriorating under a high turbulence intensity and low brightness (Strehl ratio reduced to about 0.05). Overall, the Vision Transformer consistently outperforms CNN models across all tested conditions, enhancing the Strehl ratio by an average of 0.2 more than CNNs.

A Preliminary Comparative Study on the Centering Algorithms for Cassini-ISS NAC Images

Obtaining high precision is an important consideration for astrometric studies using images from the Narrow Angle Camera (NAC) of the Cassini Imaging Science Subsystem (ISS). Selecting the best centering algorithm is key to enhancing astrometric accuracy. In this study, we compared the accuracy of five centering algorithms: Gaussian fitting, the modified moments method, and three point-spread function (PSF) fitting methods (effective PSF (ePSF), PSFEx, and extended PSF (xPSF) from the Cassini Imaging Central Laboratory for Operations (CICLOPS)). We assessed these algorithms using 70 ISS NAC star field images taken with CL1 and CL2 filters across different stellar magnitudes. The ePSF method consistently demonstrated the highest accuracy, achieving precision below 0.03 pixels for stars of magnitude 8–9. Compared to the previously considered best, the modified moments method, the ePSF method improved overall accuracy by about 10% and 21% in the sample and line directions, respectively. Surprisingly, the xPSF model provided by CICLOPS had lower precision than the ePSF. Conversely, the ePSF exhibits an improvement in measurement precision of 23% and 17% in the sample and line directions, respectively, over the xPSF. This discrepancy might be attributed to the xPSF focusing on photometry rather than astrometry. These findings highlight the necessity of constructing PSF models specifically tailored for astrometric purposes in NAC images and provide guidance for enhancing astrometric measurements using these ISS NAC images.

On the use of field RR Lyrae as Galactic probes

Context. The Vera C. Rubin Observatory will start operations in 2025. During its first two years, too few visits per target per band will be available, meaning that the mean magnitude measurements of variable stars will not be precise and thus standard candles such as RR Lyrae (RRL) will not be usable. Light curve templates (LCTs) can be adopted to estimate the mean magnitude of a variable star with a few magnitude measurements, provided that their period (plus the amplitude and reference epoch, depending on how the LCT is applied) is known. The LSST will provide precise RRL periods within the first six months, enabling exploitation of RRLs if LCTs are available. Aims. We aim to build LCTs in the LSST bands to enhance the early science with LSST. Using them will provide a one- to two-year advantage with respect to the classical approach concerning distance measurements. Methods. We collected grί-band data from the ZTF survey and z-band data from DECam to build the LCTs of RRLs. We also adopted synthetic grίz band data in the LSST system from pulsation models, plus SDSS, Gaia and OGLE photometry, inspecting the light amplitude ratios in different photometric systems to provide useful conversions to apply the LCTs. Results. We have built LCTs of RRLs in the grίz bands of the LSST photometric system; for the z band, we could build only fun damental mode RRL LCTs. We quantitatively demonstrated that LCTs built with ZTF and DECam data can be adopted on the LSST photometric system. The LCTs will decrease the uncertainty on distance estimates of RRLs by a factor of at least two with respect to a simple average of the available measurements. Finally, within our tests, we have found a brand new behavior of amplitude ratios in the Large Magellanic Cloud.

Radial velocities from Gaia BP/RP spectra

Aims. The Gaia mission has provided us full astrometric solutions for over 1.5B sources. However, only the brightest 34M of them have radial velocity measurements. This paper aims to close that gap by obtaining radial velocity estimates from the low-resolution BP/RP spectra that Gaia now provides. These spectra are currently published for about 220M sources, with this number to increase to the full ~2B Gaia sources with Gαία Data Release 4. Methods. To obtain the radial velocity measurements, we fitted Gaia BP/RP spectra with models based on a grid of synthetic spectra. From this we obtained the posterior probability on the radial velocity for each object. Our measured velocities show systematic biases that depend mainly on the colours and magnitudes of stars. We corrected for these effects by using external catalogues of radial velocity measurements. Results. We present a catalogue of about 6.4M sources with our most reliable radial velocity measurements and uncertainties of <300 km s−1 obtained from BP/RP spectra. About 23% of them have no radial velocity measurement from the Gaia RVS. Furthermore, we provide an extended catalogue that contains all 125M sources for which we were able to obtain radial velocity measurements. This catalogue, however, also contains a fraction of measurements for which the reported radial velocities and uncertainties are inaccurate. Conclusions. Although typical uncertainties in the catalogue are significantly higher compared to those obtained with precision spec-troscopy instruments, the number of potential sources to which this method can be applied is orders of magnitude higher than any previous radial velocity catalogue. Further development of the analysis could therefore prove extremely valuable in our understanding of Galactic dynamics.

The Galactic bulge exploration

We present a new set of period–absolute magnitude–metallicity (PMZ) relations for single-mode RR Lyrae stars calibrated for the optical GBP, V, G, GRP, near-infrared I, J, H, and Ks passbands. We compiled a large dataset (over 100 objects) of fundamental and first-overtone RR Lyrae pulsators consisting of mean intensity magnitudes, reddenings, pulsation properties, iron abundances, and parallaxes measured by the Gaia astrometric satellite in its third data release. Our newly calibrated PMZ relations encapsulate the most up-to-date ingredients in terms of both data and methodology. They are intended to be used in conjunction with large photometric surveys targeting the Galactic bulge, including the Optical Gravitational Lensing Experiment (OGLE), the Vista Variables in the Vía Láctea Survey (VVV), and the Gaia catalog. In addition, our Bayesian probabilistic approach provides accurate uncertainty estimates of the predicted absolute magnitudes of individual RR Lyrae stars. Our derived PMZ relations provide consistent results when compared to benchmark distances to globular clusters NGC 6121 (also known as M 4), NGC 5139 (also known as omega Cen), and Large and Small Magellanic Clouds, which are stellar systems rich in RR Lyrae stars. Lastly, our Ks-band PMZ relations match well with the previously published PMZ relations based on Gaia data and accurately predict the distance toward the prototype of this class of variables, the eponymic RR Lyr itself.

Hybrid Grid Pattern Star Identification Algorithm Based on Multi-Calibration Star Verification.

In order to solve the star identification problem in the lost space mode for scientific cameras with small fields of view and higher instruction magnitudes, this paper proposes a star identification algorithm based on a hybrid grid pattern. The application of a hybrid pattern generated by multi-calibration stars in the initial matching enables the position distribution features of neighboring stars around the main star to be more comprehensively described and avoids the interference of position noise and magnitude noise as much as possible. Moreover, calibration star filtering is adopted to eliminate incorrect candidates and pick the true matched navigation star from candidate stars in the initial match. Then, the reference star image is utilized to efficiently verify and determine the final identification results of the algorithm via the nearest principle. The performance of the proposed algorithm in simulation experiments shows that, when the position noise is 2 pixels, the identification rate of the algorithm is 96.43%, which is higher than that of the optimized grid algorithm by 2.21% and the grid algorithm by 4.05%; when the magnitude noise is 0.3 mag, the star identification rate of the algorithm is 96.45%, which is superior to the optimized grid algorithm by 2.03% and to the grid algorithm by 3.82%. In addition, in the actual star image test, star magnitude values of ≤12 mag can be successfully identified using the proposed algorithm.

Pay Premiums and Peer Spillovers: Unpacking the Value Proposition of Employing Stars as They Age

An open question among scholars and practitioners is whether and when the employment of star employees is likely to pay off. Addressing this query, we integrate insights related to star performers’ experiences of cumulative advantage and disproportionate bargaining power with insights from the careers literature to develop theory related to stars’ direct and indirect value creation and value capture as they age. Specifically, we first develop arguments that stars, as a function of their disproportionate status and bargaining power, will enjoy higher pay relative to individual performance (PRIP) in comparison to their non-star peers. Second, we argue that this difference in PRIP will be greater among older employees, as stars’ cumulative advantage is a progressive phenomenon that continues to widen the initial gaps in their PRIP relative to others over their careers. Next, countering the apparent implication that the value proposition associated with employing stars deteriorates as stars age, we find that the magnitude of stars’ indirect contributions through positive spillovers to their peers’ performance increases with age. Lastly, we account for some of the mechanisms through which older stars have a more positive impact on their peers. General support for predictions is found in a financial services organization.

The General Theory of Magnitudes

As a continuing of the previous Theory of Magnitudes, this a General Theory
 The previous theory dealt only with the closest star in a ratio of its greatest inverse apparent magnitude. My new theory shows the distance between 2 stars anywhere on a photograph of the
 nights sky using centimeters. I am extending that beginning formula adding on a new equation with the integral calculus formula using the number value at that given to be raised to exponent 2 divided by 2 . All stars are using inverse Apparent Magnitudes like my first paper.
 My new formulas as stated 1+ Inverse Apparent Magnitudes one = Q 1
 1 + Inverse Apparent Magnitude two = Q2
 
 (Q1 + Q2) – (Q1 – Q2) times 2.5 divided by / (Q1 + Q2) + (Q1- Q2) times 8 pi take the square root of that by which was divided. take the natural logarithm of that and you get the value P
 take P squared and then divide P by 2 . call all of this formula W
 My second equation ; Euler’s number raised to its exponent is such ; total addition of the inverse apparent magnitudes in a centimeter using times that in centimeter plus one times 8 pi . . 
 take natural logarithm of that total using square root of total of this divided by 3 pi
 Take this second equation and square it the multiply this equation called Y by w then subtract
 this total by w ;Then divide the previous equation by the Natural Logarithm in This set of the Inverse apparent magnitude of the reference star raised to the exponent of 10 } .

Optimized temporal binning of comparison star measurements for differential photometry

ABSTRACT Ground-based, high precision observations of the light curves of objects such as transiting exoplanets rely on the application of differential photometry. The flux of the target object is measured relative to a comparison star in the same field, allowing correction for systematic trends in the light curve, mainly due to atmospheric effects including the variation of extinction with airmass. However, the precision of the light curve is then limited by the random noise for the measurements of both the target object and the comparison star. For time-resolved photometry using short exposure times of up to a few tens of seconds, the time-scale of the systematic variations due to atmospheric (or other) effects can be much longer than the cadence of the observations. In this case, the overall signal-to-noise ratio of the observation may be improved significantly by applying some temporal binning to the measurements of the comparison star, before comparison with the target object, without reducing the cadence of the overall light curve. In this paper, we will describe a data reduction pipeline for implementing this method which optimizes the number of frames to be binned for the comparison star, and we present example results for time-resolved photometric data. An example of applying the technique on an exoplanet transit light curve of WASP-166b is presented using four comparison stars of different magnitudes.

Estimating the number of planets that PLATO can detect

Context. The PLATO mission is scheduled for launch in 2026. It will monitor more than 245 000 FGK stars of magnitude 13 or brighter for planet transit events. Among the key scientific goals are the detection of Earth-Sun analogs; the detailed characterization of stars and planets in terms of mass, radius, and ages; the detection of planetary systems with longer orbital periods than are detected in current surveys; and to advance our understanding of planet formation and evolution processes. Aims. This study aims to estimate the number of exoplanets that PLATO can detect as a function of planetary size and period, stellar brightness, and observing strategy options. Deviations from these estimates will be informative of the true occurrence rates of planets, which helps constraining planet formation models. Methods. For this purpose, we developed the Planet Yield for PLATO estimator (PYPE), which adopts a statistical approach. We apply given occurrence rates from planet formation models and from different search and vetting pipelines for the Kepler data. We estimate the stellar sample to be observed by PLATO using a fraction of the all-sky PLATO stellar input catalog (PIC). PLATO detection efficiencies are calculated under different assumptions that are presented in detail in the text. Results. The results presented here primarily consider the current baseline observing duration of 4 yr. We find that the expected PLATO planet yield increases rapidly over the first year and begins to saturate after 2 yr. A nominal (2+2) 2-yr mission could yield about several thousand to several tens of thousands of planets, depending on the assumed planet occurrence rates. We estimate a minimum of 500 Earth-size (0.8−1.25 RE) planets, about a dozen of which would reside in a 250–500 days period bin around G stars. We find that one-third of the detected planets are around stars bright enough (V ≤11) for RV-follow-up observations. We find that a 3-yr-long observation followed by 6 two-month short observations (3+1 yr) yield roughly twice as many planets as two long observations of 2 yr (2+2 yr). The former strategy is dominated by short-period planets, while the latter is more beneficial for detecting earths in the habitable zone. Conclusions. Of the many sources of uncertainties for the PLATO planet yield, the real occurrence rates matters most. Knowing the latter is crucial for using PLATO observations to constrain planet formation models by comparing their statistical yields.

Research on Stellar Occultation Detection with Bandpass Filtering for Oxygen Density Retrieval

Stellar occultation instruments detect the transmission of stellar spectra through the planetary atmosphere to retrieve densities of various atmospheric components. This paper introduces an idea of using instruments with bandpass filters for stellar occultation detection. According to the characteristics of the occultation technique for oxygen density measurement, a full-link forward model is established, and the average transmission under a typical nocturnal atmosphere is calculated with the help of the HITRAN database, occultation simulation and a 3D ray-tracing program. The central wavelength and bandwidth suitable for 760 nm oxygen A-band absorption measurement are discussed. This paper also compares the results of the forward model with GOMOS spectrometer data under this band, calculates the observation signal-to-noise ratio corresponding to different instrument parameters, and target star magnitudes. The results of this paper provide a theoretical basis for the development of a stellar occultation technique with a bandpass filter and guidance on the instrument design.

GaiaData Release 3

Context.GaiaData Release 3 (DR3) contains the first release of magnitudes estimated from the integration of Radial Velocity Spectrometer (RVS) spectra for a sample of about 32.2 million stars brighter thanGRVS ∼ 14 mag (orG ∼ 15 mag).Aims.In this paper, we describe the data used and the approach adopted to derive and validate theGRVSmagnitudes published in DR3. We also provide estimates of theGRVSpassband and associatedGRVSzero-point.Methods.We derivedGRVSphotometry from the integration of RVS spectra over the wavelength range from 846 to 870 nm. We processed these spectra following a procedure similar to that used for DR2, but incorporating several improvements that allow a better estimation ofGRVS. These improvements pertain to the stray-light background estimation, the line spread function calibration, and the detection of spectra contaminated by nearby relatively bright sources. We calibrated theGRVSzero-point every 30 h based on the reference magnitudes of constant stars from the HIPPARCOScatalogue, and used them to transform the integrated flux of the cleaned and calibrated spectra into epoch magnitudes. TheGRVSmagnitude of a star published in DR3 is the median of the epoch magnitudes for that star. We estimated theGRVSpassband by comparing the RVS spectra of 108 bright stars with their flux-calibrated spectra from external spectrophotometric libraries.Results.TheGRVSmagnitude provides information that is complementary to that obtained from theG,GBP, andGRPmagnitudes, which is useful for constraining stellar metallicity and interstellar extinction. The median precision ofGRVSmeasurements ranges from about 0.006 mag for the brighter stars (i.e. with 3.5≲GRVS≲6.5 mag) to 0.125 mag at the faint end. The derivedGRVSpassband shows that the effective transmittance of the RVS is approximately 1.23 times better than the pre-launch estimate.

Carbon stars as standard candles – III. Un-binned maximum likelihood fitting and comparison with TRGB estimations

ABSTRACTIn the second paper of this series, we developed a new distance determination method using the median J magnitude of carbon-rich asymptotic giant branch stars (CS) as standard candles and the Magellanic Clouds as the fundamental calibrators. The J-band CS luminosity function was modelled using a modified Lorentzian distribution whose parameters were used to determine whether the Large or Small Magellanic cloud was the most suitable calibrator. In this third paper of the series, we expand our sample of galaxies and introduce a more robust method to determine the parameters of the Lorentzian model. The new fitting method uses an un-binned maximum likelihood estimator to determine the parameters of the Lorentzian model resulting in parameter errors that are significantly smaller compared to the second paper. We test our method in NGC 6822, IC 1613, NGC 3109, and WLM. We also estimate the distances to the same sample of galaxies via the tip of the red giant branch (TRGB) detection method. Our results from the CS measurements agree well with those obtained from the TRGB.

Asgard/NOTT: L-band nulling interferometry at the VLTI

Context. NOTT (formerly Hi-5) is a new high-contrast L′ band (3.5–4.0 µm) beam combiner for the VLTI designed with an ambitious aim to be sensitive to young giant exoplanets down to 5 mas separation around nearby stars. The performance of nulling interferometers in these wavelengths is affected both by fundamental noise from the background and contributions of instrumental noise. This motivates the development of end-to-end simulations to optimize these instruments. Aims. The aim of this study is to enable a performance evaluation of NOTT and inform the design of such instruments with current and future infrastructures in mind, taking into account the different sources of noise and their correlation. Methods. SCIFYsim is an end-to-end simulator for single-mode-filtered beam combiners, with an emphasis on nulling interferometers. We use it to compute a covariance matrix of the errors. We then use statistical detection tests based on likelihood ratios to compute compound detection limits for the instrument. Results. With the current assumptions as to the performance of the wavefront correction systems, the errors are dominated by correlated instrumental errors down to stars of magnitude 6–7 in the L band, beyond which thermal background from the telescopes and relay system becomes dominant. Conclusions. SCIFYsim is suited to anticipating some of the challenges of design, tuning, operation, and signal processing for integrated-optics beam combiners. The detection limits found for this early version of NOTT simulation with the unit telescopes are compatible with detections at contrasts up to 105 in the L band at separations of 5–80 mas around bright stars.

TESS–Gaia Light Curve: A PSF-based TESS FFI Light-curve Product

The Transiting Exoplanet Survey Satellite (TESS) is continuing its second extended mission after 55 sectors of observations. TESS publishes full-frame images (FFIs) at a cadence of 1800, 600, or 200 s, allowing light curves to be extracted for stars beyond a limited number of pre-selected stars. Simulations show that thousands of exoplanets, eclipsing binaries, variable stars, and other astrophysical transients can be found in these FFI light curves. To obtain high-precision light curves, we forward model the FFI with the effective point-spread function (PSF) to remove contamination from nearby stars. We adopt star positions and magnitudes from Gaia DR3 as priors. The resulting light curves, called TESS–Gaia light curves (TGLCs), show a photometric precision closely tracking the prelaunch prediction of the noise level. The TGLCs’ photometric precision reaches ≲2% at 16th TESS magnitude even in crowded fields. We publish TGLC aperture and PSF light curves for stars down to 16th TESS magnitude through the Mikulski Archive for Space Telescopes for all available sectors and will continue to deliver future light curves. The open-source package tglc 3 3 Via 10.17909/610m‐9474. is publicly available to enable any user to produce customized light curves.

The scientific capabilities of the Evanescent Wave Coronagraph EvWaCo

The Evanescent Wave Coronagraph, EvWaCo, is an in-development prototype coronagraph, designed for use on the 2.4m Thai National Telescope (TNT), in the R and I-band filters. This work examines the astronomical capabilities of EvWaCo using the results from Fourier-analysis simulations. Fourier optics simulations were applied to the EvWaCo prototype to analyse its performance, combining different sources of contrast degradation that will be present in the system. The simulations used for the main analysis assume a good night at the Thai National Observatory (TNO) and include the fitting error, aliasing, measurement noise and lag, providing a radially averaged contrast curve. From the contrast curve, the detection limit, as defined by a minimum signal to noise ratio of 5 for a typical observation time, can be calculated for different primary star magnitudes. The relative fluxes of various binary stars, with a range of spectral classes and separations, were modelled allowing comparison to the EvWaCo detection curves. The photon-noise limited detection curves provide a theoretical baseline for the performance that will be achieved with EvWaCo; they, therefore, give an indication of the types of objects EvWaCo can observe. Along with a broader discussion of observable objects, a number of known binary systems are suggested for observations on the TNT using EvWaCo.

THE STUDY OF ARABIC CONSTELLATION FROM THE BOOK SUWAR AL-KAWAKIB AL-THABITA USING STELLARIUM SOFTWARE

The constellations originating from Arab civilization were still very little known and studied. Al-Ṣūfi's book, al-Kawākib al-Thābitah, contains the record of coordinates, approximate magnitudes, and star details with graphs. This study examines the difference of stars in the sample constellation, compares the visual appearance of the illustrations on the Stellarium software, and studies the differences between the western constellations and the Arabic constellations. The result shows some differences between the constellations of the almagest and al-Kawākib al-Thābitah in the number of stars in the sample constellations, differences in illustrations from the orientalized figures, and the star magnitude in al-Ṣūfi's work that similar to Ptolemy's works. Al-Sufi identified a total of 134 additional stars, 65 stars located in the Northern constellations, 41 stars in the Zodiac constellation, and 28 stars in the Southern constellations. His observations showed that the magnitude values of 520 stars out of a total of 1022 stars were identical between al-Sufi and Ptolemy. Stellarium provides an excellent visual presentation of the Arabic constellations according to Al-Sufi's book that shows position, illustration, and mapping in the night sky.

Design of a Ultra-Stable Low-Noise Space Camera Based on a Large Target CMOS Detector and Image Data Analysis.

To detect faint target stars of 22nd magnitude and above, an astronomical exploration project requires its space camera's readout noise to be less than 5e- with long-time working stability. Due to the limitation of satellite, the traditional CCD detector-based camera does not meet the requirements, including volume, weight, and power consumption. Thereby, a low-noise ultra-stable camera based on 9 K × 9 K large target surface CMOS is designed to meet the needs. For the first time, the low-noise ultra-stable camera based on CMOS detector will be applied to space astronomy projects, remote sensing imaging, resource survey, atmospheric and oceanic observation and other fields. In this paper, the design of the camera is introduced in detail, and the camera is tested for several rounds at -40 °C; it also undergoes further testing and data analysis. Tests proved super stability and that the readout noise is lower than 4.5e-. Dark current, nonlinearity and PTC indicators meet the requirements of the astronomical exploration project.