Atmospheric dispersion has a great impact on high-precision astronomical observation. This paper studies the influence of atmospheric dispersion on the imaging system of large aperture astronomical telescope, and the UMAC-based atmospheric dispersion correctors (ADC) control system is designed. According to the data of zenith distance, temperature, humidity and air pressure, the influence of atmospheric dispersion on the imaging system of the telescope is calculated through the theoretical model of atmospheric refraction. The results show that when the zenith distance is greater than 24.83°, the influence of atmospheric dispersion has exceeded 0.3”, that is the requirement of telescope imaging system. So it is necessary to correct the influence of atmospheric dispersion. ADC adopts the structure of two relative rotation glued prisms. The larger the zenith distance is, the higher the requirement of the relative angle control accuracy of the two glued prisms is. According to the results of optical calculations, when the relative rotation accuracy of the two glued prisms is less than 60”, it can meet the imaging quality requirements of the telescope. According to that, the control system of ADC is designed. The rotation control of atmospheric dispersion correction mechanism adopts two-stage reduction mechanism, the first stage is reduction box, the second stage is reduction gear, and the total reduction ratio is 600:1. In order to realize the synchronous control of the two glued prisms, UMAC is used as the main controller, two servo motors are used to drive the rotation of the two glued prisms, and Renishaw encoder is used as the position feedback for position closed-loop control. The peak-to-peak control accuracy of the relative rotation angle of the control system is less than 20”, which meets the control accuracy requirements of the ADC.
Indoor air turbulence had a certain degree of influence on optical testing or optical system image quality. A long optical testing path was built in tower which was one of the largest vertical towers for optical testing in China with about 23-meter high. The relevant influence characteristics were measured and studied in a specific state. First, the air turbulence was formed using air conditionings. Then, the optical wave fronts were sampled by interferometer with two conditions of undisturbed situation and disturbed situation in which the air conditioners were turned on for a while and then turned off some time and sampling was beginning. After the statistical analyzing to the sampling results, the following several evaluation results of image quality were acquired in different status, the Radius of Encircled 80% Energy (REE), the evaluation factor of modulation transfer function (MTF), the Strehl Ratio (SR), the traditional evaluation method PV/RMS value of wave fronts, and the turbulent correlation length of atmospheric r0. The statistical calculation results showed that turbulence intensity increased and optical image quality was deteriorated after air disturbed.
This paper reports optical system of Time Domain Observatory (TIDO) for Nanjing University(NJU). TIDO is a telescope array dedicated to survey of exoplanetary science and astronomical phenomena in the time domain. TIDO consists of 6 robotic telescopes which can image 336 square degrees(SD) of the sky in once observation, outfitted for high-resolution photometry efficiently. TIDO began in 2014 and has been in operation for 4 years. Some preliminary observation has been made, but the full operation will be by the end of 2019. In this paper, we describe the optical system of TIDO, including a 1-meter primary-focus telescope with field of view (FOV) of 9 SD, three 0.3-meter improved Marcostov telescopes with FOV of 64 SD, one 0.18-meter telescopes with FOV of 144 SD, one 0.3 meter RC telescope with FOV of 0.04 SD, and present the results of initial performance simulations using ZEMAX software.
Ground-based telescope imaging model is developed in this paper, the relationship between the atmospheric disturbances and the ground-based telescope image quality is studied. Simulation of the wave-front distortions caused by atmospheric turbulences has long been an important method in the study of the propagation of light through the atmosphere. The phase of the starlight wave-front is changed over time, but in an appropriate short exposure time, the atmospheric disturbances can be considered as “frozen”. In accordance with Kolmogorov turbulence theory, simulating atmospheric disturbances of image model based on the phase screen distorted by atmospheric turbulences is achieved by the fast Fourier transform (FFT). Geiger mode avalanche photodiode array (APD arrays) model is used for atmospheric wave-front detection, the image is achieved by inversion method of photon counting after the target starlight goes through phase screens and ground-based telescopes. Ground-based telescope imaging model is established in this paper can accurately achieve the relationship between the quality of telescope imaging and monolayer or multilayer atmosphere disturbances, and it is great significance for the wave-front detection and optical correction in a Multi-conjugate Adaptive Optics system (MCAO).
SONG (Stellar Oscillation Network Group) is an international project to form a global observing network of eight 1- meter class telescopes. China joined this project and funded one node telescope for this network. By the end of 2013, the Chinese SONG telescope has been installed on the Delinha observing site of Purple Mountain Observatory in Qinghai province. This paper will give the introduction of this telescope, including its optical system, structure and control system. Besides, the preliminary observing performance of the telescope on site will be given in the second part of this paper.
SONG is initiated by Danish to design, build, and utilize a global network of eight 1-meter class telescopes to be
operated as a whole-Earth telescope. China has joined the international SONG project in 2009 and will build one 1-meter
telescope as the node of SONG global network in China. Now the telescope is during the period of building. This paper
will give an introduction of Chinese SONG telescope, including telescope requirements, telescope design and other
information.
The standard SONG node structure of control system is presented. The active optical control system of the project is a
distributed system, and a host computer and a slave intelligent controller are included. The host control computer collects
the information from wave front sensor and sends commands to the slave computer to realize a closed loop model. For
intelligent controller, a programmable logic controller (PLC) system is used. This system combines with industrial
personal computer (IPC) and PLC to make up a control system with powerful and reliable.
The paper reports optical system of a 1 meter diameter telescope dedicated to Stellar Observations
Network Group (SONG) for the National Astronomical Observatories, CAS. SONG is an international
cooperative project, Optimize the design for Asteroseismology purposes. According to the prototype of
SONG, Chinese SONG telescope includes Cassegrain telescope, Nasmyth platform, Coudé train,
Coudé focal plane, Shack-Hartmann wavefront sensor and spectrograph. The telescope will provide a
field of view of 65 arcsec at the Nasmyth F/36.67 focus, 10 arcsec at the F/6 Coudé focus. The rotating
tertiary mirror directs the light to the two Nasmyth foci, one for Shack-Hartmann wavefront sensor, the
other for Nasmyth platform and spectrograph.
A novel laser ranging method use Geiger mode APD (avalanche photodiode) array is introduced in this paper. In the
proposed method, echo signal is received by APD arrays at gate mode, system fulfill photon counting, curve recover,
start-point distinguish, determine the distance of target ultimately. The results show that with this method, we can get a
higher precision, farther distance with less laser power, comparing with the traditional laser ranging methods. So a new
thinking way for the laser ranging is provided.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.