Astronomical Camera Research Articles

Analysis of synchronism and response velocity in instrumental assemblies for the observation of stellar occultations

Currently the stellar occultation technique is one of the most effective methods for observing minor bodies of the Solar System. Due to the collaborative nature of these observations, precise synchronization and short response times are necessary in instrumental assemblies. This paper presents the development of a methodology that allows for the evaluation of the temporal performance of the detectors used in the observation of stellar occultations. The software “TimesCCam” was developed, which, when being photographed by astronomical cameras, graphically represents the parameters of exposure time, dead time, and jitter referenced to UTC. The process of alignment and focus is obtained, thanks to a structure built with movement in the three axes. The methodology was applied in the evaluation of STF-8300M, ST-2000XM and QHY174M-GPS cameras, using different driver software, synchronization methods, and exposure times. In real exposure times, insignificant variations were identified. Dependency was found between the dead times and the configurations used for the CCD cameras, and it was determined that the dead time and its instability in the ST-2000XM camera prevent its use for the observation of stellar occultations. The results show that the STF-8300M camera is convenient for the observation of asteroid occultations, while the QHY174M-GPS camera given its dead time and synchronization, is suitable for the observation of occultations by trans-Neptunian objects.

Background-limited Imaging in the Near Infrared with Warm InGaAs Sensors: Applications for Time-domain Astronomy

Abstract We describe test observations made with a customized 640 × 512 pixel indium gallium arsenide (InGaAs) prototype astronomical camera on the 2.5 m DuPont telescope. This is the first test of InGaAs as a cost-effective alternative to HgCdTe for research-grade astronomical observations. The camera exhibits a background of 113 e– s–1/pixel (dark + thermal) at operating sensor temperature T = −40°C, maintained by a simple thermoelectric cooler. The optomechanical structure floats at ambient temperature with no cold stop, unlike most IR instruments which must be cooled to mitigate thermal backgrounds. Measurements of the night sky using a reimager scaled at 0.″4/pixel show that the sky flux in Y is comparable to the dark current. At J the sky exceeds dark current by a factor of four, dominating the noise budget. The read noise (∼43 e−) falls below sky + dark noise for exposures of t > 7 s in Y and 3.5 s in J. We observed several representative science targets, including two supernovae, a z = 6.3 quasar, two local galaxies monitored for IR transients, and a galaxy cluster at z = 0.87. We observe a partial transit of the hot Jupiter HATS-34b, demonstrating the photometric stability to detect a 1.2% transit. A tiling of larger-format sensors would produce an IR survey instrument with significant cost savings relative to HgCdTe-based cameras, if one is willing to forego the K band. Such a camera would be sensitive for a week or more to isotropic emission from r-process kilonova ejecta similar to that observed in GW170817, over the full 190 Mpc horizon of Advanced LIGO.

Mexico-UK Sub-millimeter Camera for Astronomy

MUSCAT is a large format mm-wave camera scheduled for installation on the Large Millimeter Telescope Alfonso Serrano (LMT) in 2018. The MUSCAT focal plane is based on an array of horn coupled lumped-element kinetic inductance detectors optimised for coupling to the 1.1mm atmospheric window. The detectors are fed with fully baffled reflective optics to minimize stray-light contamination. This combination will enable background-limited performance at 1.1 mm across the full 4 arcminute field-of-view of the LMT. The easily accessible focal plane will be cooled to 100 mK with a new closed cycle miniature dilution refrigerator that permits fully continuous operation. The MUSCAT instrument will demonstrate the science capabilities of the LMT through two relatively short science programmes to provide high resolution follow-up surveys of Galactic and extra-galactic sources previously observed with the Herschel space observatory, after the initial observing campaigns. In this paper, we will provide an overview of the overall instrument design as well as an update on progress and scheduled installation on the LMT.

Note: Design and implementation of a home-built imaging system with low jitter for cold atom experiments.

A novel home-built system for imaging cold atom samples is presented using a readily available astronomy camera which has the requisite sensitivity but no timing-control. We integrate the camera with LabVIEW achieving fast, low-jitter imaging with a convenient user-defined interface. We show that our system takes precisely timed millisecond exposures and offers significant improvements in terms of system jitter and readout time over previously reported home-built systems. Our system rivals current commercial "black box" systems in performance and user-friendliness.

PlanetCam UPV/EHU: A Two-channel Lucky Imaging Camera for Solar System Studies in the Spectral Range 0.38–1.7 μm

We present PlanetCam UPV/EHU, an astronomical camera designed fundamentally for high-resolution imaging of Solar System planets using the “lucky imaging” technique. The camera observes in a wavelength range from 380 nm to 1.7 μm and the driving science themes are atmosphere dynamics and vertical cloud structure of Solar System planets. The design comprises two configurations that include one channel (visible wavelengths) or two combined channels (visible and short wave infrared) working simultaneously at selected wavelengths by means of a dichroic beam splitter. In this paper the camera components for the two configurations are described, as well as camera performance and the different tests done for the precise characterization of its radiometric and astrometric capabilities at high spatial resolution. Finally, some images of solar system objects are presented as well as photometric results and different scientific cases on astronomical targets.

Developments in Time-Division Multiplexing of X-ray Transition-Edge Sensors.

Time-division multiplexing (TDM) is a mature scheme for the readout of arrays of transition-edge sensors (TESs). TDM is based on superconducting-quantum-interference-device (SQUID) current amplifiers. Multiple spectrometers based on gamma-ray and X-ray microcalorimeters have been operated with TDM readout, each at the scale of 200 sensors per spectrometer, as have several astronomical cameras with thousands of sub-mm or microwave bolometers. Here we present the details of two different versions of our TDM system designed to read out X-ray TESs. The first has been field-deployed in two 160-sensor (8 columns × 20 rows) spectrometers and four 240-sensor (8 columns × 30 rows) spectrometers. It has a three-SQUID-stage architecture, switches rows every 320 ns, and has total readout noise of 0.41 μΦ0/√Hz. The second, which is presently under development, has a two-SQUID-stage architecture, switches rows every 160 ns, and has total readout noise of 0.19 μΦ0/√Hz. Both quoted noise values are non-multiplexed and referred to the first-stage SQUID. In a demonstration of this new architecture, a multiplexed 1-column × 32-row array of NIST TESs achieved average energy resolution of 2.55±0.01 eV at 6 keV.

Black-Body SNR Formulation of Astronomical Camera Systems

In this paper, we present a formulation for the computation of the SNR of an image system designed for astronomical star observations by combining research results from different disciplines such as physics, astronomy, optics, and electronics. Starting from the energy emitted by the stars and their catalogued magnitudes, we formulate the amount of electrons formed in the pixels of an image sensor using the camera parameters and then compute the quality of the signal in terms of SNR. We provide formulations for both space bound and earth bound observations of stars and present example numerical data for a camera and a telescope system. The formulation given here, although not novel if considered separately in its components, combines the information from different disciplines in an effort to present a complete resource that relates the full image chain from the source to the finally formed image in the hope that it will be a self-contained reference for other researchers working on astronomical camera systems.

Observation of the Moon and the Planets with a Small Telescope and an Astronomical Video CCD Camera

Observation of the Moon and the Planets with a Small Telescope and an Astronomical Video CCD Camera

Chang’E-3 scientific payloads and its checkout results

The scientific objectives of ChangE-3 mission were to: examine the texture, mineralogy, and structure of the local lunar terrain; determine the distribution and composition of minerals, rocks, and soils surrounding the landing sites; image the Earths plasmasphere and operate an ultraviolet astronomy camera on the moon. Four kinds of scientific instruments are chosen as the payloads for ChangE-3 lander, which include topography camera, lunar optical telescope, extreme ultraviolet imager and landing camera so on. And other four kinds of scientific instruments are chosen as the payloads for lunar rover, which include panoramic cameras, lunar radar, IR acousto-optic spectrometer, X-ray spectrometer and so on. This paper mainly introduces scientific exploration mission, the scientific payloads design and construction. The checkout results are also described in detail.

A LITTLE-KNOWN 3-LENS CATADIOPTRIC CAMERA BY BERNHARD SCHMIDT

The authors investigate a prototype 3-lens f/1 catadioptric camera, built in 1934 by the famous optician Bernhard Schmidt at the Hamburg-Bergedorf Observatory in Germany, where Schmidt worked before his death in 1935. The prototype is in the observatory's collection of Schmidt artifacts, but its nature was not understood before the authors' recent examination. It is an astronomical camera of a form known as 'Buchroeder-Houghton', consisting of a spherical mirror and a 3-element afocal corrector lens placed at the mirror's center of curvature. The design is named for R.A. Buchroeder and J.L. Houghton who independently published this and related forms of wide-field spherical-lens cameras after 1942. Schmidt died before he could publish his own design. The authors disassembled the prototype and measured its optical parameters. These they present together with a transmission test of the corrector lens. The authors also consider the theoretical performance of the design as built, the theory of Houghton cameras, Schmidt's possible path to his invention, and the place of the prototype in his scientific output.

Construction of astronomical camera captured on time-lapse video

Construction of astronomical camera captured on time-lapse video

Stellar Positioning System (Part I): An Autonomous Position Determination Solution

Two theoretical approaches for determining position using star observations are presented, the Attitude Matrix Solution and Inner Product Solution. Both approaches are designed for implementation in an autonomous Stellar Positioning System that uses the following measurement sources: an astronomical camera, a clock, and a set of two inclinometers. Before presenting the algorithms, the reference frames utilized throughout are defined. The two position estimation techniques are then individually presented, followed by a discussion of gravity model and geometric model refinements.

Removing Internal Reflections from Deep Imaging Data Sets

ABSTRACTWe present a means of characterizing and removing internal reflections between the CCD and other optical surfaces in an astronomical camera. The stellar reflections appear as out-of-focus images and are not necessarily axisymmetric about the star. Using long exposures of very bright stars as calibration images, we are able to measure the position, size, and intensity of reflections as a function of their position on the field. We also measure the extended stellar point-spread function out to 1°. Together this information can be used to create an empirical model of the excess light from bright stars and reduce systematic artifacts in deep surface photometry. We then reduce a set of deep observations of the Virgo cluster with our method to demonstrate its efficacy and to provide a comparison with other strategies for removing scattered light.

A highly reliable and budget‐friendly Peltier‐cooled camera for biological fluorescence imaging microscopy

The SAC8.5, a low-cost Peltier-cooled black and white 8-bit CCD camera for astronomy, was evaluated for its use in imaging microscopy. Two camera-microscope configurations were used: an epifluorescence microscope (Nikon Eclipse TE2000-U) and a bottom port laser scanning confocal microscope system (Zeiss LSCM 510 META). Main advantages of the CCD camera over the currently used photomultiplier detection in the scanning setup are fast image capturing, stable background, an improved signal-to-noise ratio and good linearity. Based on DAPI-labelled Chinese Hamster Ovarian cells, the signal-to-noise ratio was estimated to be 4 times higher with respect to the currently used confocal photomultiplier detector. A linear relationship between the fluorescence signal and the FITC-inulin concentrations ranging from 0.05 to 1.8 mg mL(-1) could be established. With the SAC8.5 CCD camera and using DAPI, calcein-AM and propidium iodide we could also distinguish between viable, apoptotic and necrotic cells: exposure to CdCl(2) caused necrosis in A6 cells. Additional examples include the observation of wire-like mitochondrial networks in Mito Tracker Green-loaded Madin-Darby canine kidney cells. Furthermore, it is straightforward to interface the SAC8.5 with automated shutters to prevent rapid fluorophore photobleaching via easy to use astrovideo software. In this study, we demonstrate that the SAC8.5 black and white CCD camera is an easy-to-implement and cost-conscious addition to quantitative fluorescence microfluorimetry on living tissues and is suitable for teaching laboratories.

Angular distribution of radiation beneath forest canopies using a CCD-radiometer

An astronomical digital camera is equipped with a fish-eye lens and exchangeable filters to study the fine angular structure of radiation field in forests in the red and near infrared (NIR) spectral bands. A few examples of the angular distribution of downward radiances in conifer and broadleaf forests are given. The results of field measurements are compared with the spectral flux measurements by a field radiometer and with the calculations of radiance by a combined geometric-optical/radiative transfer (RT) model. The test measurements demonstrated that the hemispheric-view imaging radiometer is a good tool to validate canopy RT models.

Astronomical imaging with quantum well infrared photodetectors

Quantum well infrared photodetectors (QWIPs) are attractive for use in astronomy because they offer good sensitivity, are very stable, are easily manufactured in large sizes, and have (comparatively) warm operating temperatures. We describe an astronomical camera based on an 8.5 μm QWIP array which was built at the Jet Propulsion Laboratory and is operated at the Palomar 5-m telescope. We highlight some science results obtained with this instrument, then discuss the prospects for QWIP arrays in future NASA astronomy missions.

STARDIAL: AN AUTONOMOUS ASTRONOMICAL CAMERA ON THE WORLD WIDE WEB

ABSTRACT We describe the use of an autonomous astronomical camera, called ''Stardial,'' for undergraduate instruction. Stardial delivers images of the night sky nearly in real-time to the world wide web (www.astro.uiuc.edu/~stardial/). The world wide web (WWW) interface is robust, inexpensive, and accommodates many students asynchronously with respect to the instructors. The guiding philosophy is to provide students with authentic astronomical data so that they may learn about science by doing it themselves. Students respond favorably to the opportunity to learn from their own experiences with authentic data, complete with its irregularities and its surprises. Stardial has been operational for one academic year (1996-97) at the University of Illinois at Urbana-Champaign. In this paper we describe Stardial's instrumentation, some of the curriculum based upon Stardial's unique data, and the experiences of students who have used Stardial. We conclude with possible research topics using Stardial data and with a brief look to the future of remote laboratories.

Astronomical imaging camera lens for 035–09 µm with variable chromatic correction

An imaging lens at f/4 is designed to have zoomlike variable chromatic and spherochromatic correction for imagery in each of the astronomical U, B, V, and R bands.

Fluorescence imaging of local membrane electric fields during the excitation of single neurons in culture

The spatial distribution of depolarized patches of membrane during the excitation of single neurons in culture has been recorded with a high spatial resolution (1 micron2/pixel) imaging system based on a liquid-nitrogen-cooled astronomical camera mounted on an inverted microscope. Images were captured from rat nodose neurons stained with the voltage-sensitive dye RH237. Conventional intracellular microelectrode recordings were made in synchrony with the images. During an action potential the fluorescence changes occurred in localized, unevenly distributed membrane areas, which formed clusters of depolarized sites of different sizes and intensities. When fast conductances were blocked by the addition of tetrodotoxin, a reduction in the number and the intensities of the depolarized sites was observed. The blockade by tetrodotoxin of voltage-clamped neurons also reduced the number of depolarized sites, although the same depolarizing voltage step was applied. Similarly, when a voltage-clamped neuron was depolarized by a constant-amplitude voltage step, the number of depolarized sites varied according to the degree of activation of the voltage-sensitive channels, which was modified by changing the holding potential. These results suggest that the spatial patterns of depolarization observed during excitation are related to the operations of ionic channels in the membrane.

Goddard Space Flight Center astronomical Fabry–Pérot imaging camera

An astronomical camera is described which consists of a scanning Fabry–Pérot Interferometric (FPI) system coupled to a charge coupled detector (CCD) imaging system. The Fabry–Pérot etalon equipment consists of a commercially available Queensgate system. The CCD equipment is a commercially available Photometrics system employing one of the early developmental CCD chips of the Space Telescope Imaging Spectrograph (STIS) project. The camera is controlled by a Digital Equipment Corporation Microvax II computer. Control of a filter wheel system and other housekeeping duties are done through a Kinetic Systems Camac controller commanded by the computer.