scholarly journals An Autocollimation Circle Reading System for the Infrared Meridian Instrument

1995 ◽  
Vol 166 ◽  
pp. 361-361
Author(s):  
V.N. Yershov ◽  
A.A. Nemiro
Keyword(s):  
Optical Axis ◽  
Angular Position ◽  
Optical Center ◽  
Meridian Circle ◽  
Primary Mirror ◽  
Axis Position ◽  
Spherical Mirrors ◽  
Reading System ◽  
Zero Points ◽  
New System

A new autocollimation circle reading system is proposed for the reflector meridian circle (Nemiro and Streletsky, 1988). The instrument will be used for observations in the K-infrared waveband. Instead of the divided circle fixed to the instrument tube the new system has small spherical mirrors polished at the lateral surfaces of the primary mirror. The primary mirror is made from sitall and has an autocollimation system aimed at monitoring its optical axis position. The small spherical mirrors of the circle reading system link the circle readings with the primary's optical axis. The divided circles are fixed unmovable opposite to both lateral surfaces of the primary's optical block. Both surfaces have four spherical mirrors. The distance between the divided circles and the mirrors is equal to the mirrors' radii of curvature. The scales of each circle are illuminated from outside (where the measuring microscopes are placed). The mirrors form autocollimated images of the divisions at the plane of the divisions itself. Averaged coordinates of a division and its autocollimated image give the position of the mirror's optical center, and the semi-difference of the coordinates gives the angular position of the telescope. So, the measurements of the circle positions are differential ones, and any displacements of the microscope zero-points are not critical. The precision of measurements is estimated to be better then 0.05″ (random) and 0.005″ (systematical). The work was supported by the Russian Foundation of Fundamental Investigations (the project's code is 93-02-17095).

scholarly journals PbS and CCD Array Autocollimation Micrometers for the Infrared Meridian Circle

1995 ◽  
Vol 167 ◽  
pp. 337-338
Author(s):  
V. N. Yershov
Keyword(s):  
Focal Plane ◽  
Optical Axis ◽  
Meridian Circle ◽  
Pulkovo Observatory ◽  
Primary Mirror ◽  
Small Constant ◽  
Ccd Array ◽  
Secondary Mirror ◽  
Axis Position ◽  
Optical Unit

A new infrared meridian instrument is being developed at Pulkovo Observatory. The main purpose of the instrument is to extend the fundamental coordinate system to the K-infrared waveband and to faint stars at visual and I-wavebands. The instrument has a 30-cm primary mirror made from astrositall. An intermediate focal plane is used to introduce luminous reference marks. One can obtain autocollimated images of the marks at the intermediate focal plane with the use of a polished chamber located around the central hole of the primary mirror. The secondary mirror of the telescope forms images of the marks and of their autocollimated counterparts and passes them to the plane of a photodetector (Fig. 1.). The luminous marks give a reference frame for the measurements. These measurements are not affected by displacements of any optical unit placed after the intermediate focal plane or by displacements of the detector. The measurements are done relative to the coordinates of the average between positions of the luminous mark and its autocollimated image. Any small constant difference between the center of curvature and the optical axis position can be determined in the laboratory.

scholarly journals A Giant Meridian Circle - Reflector

1995 ◽  
Vol 166 ◽  
pp. 360-360
Author(s):  
V.N. Yershov
Keyword(s):  
Focal Plane ◽  
Optical Axis ◽  
Focal Length ◽  
Vertical Plane ◽  
Optical Scheme ◽  
Infrared Observations ◽  
Secondary Mirror ◽  
Axis Position ◽  
Reference Grid ◽  
Reading System

A 1.5 m reflector is proposed for infrared and optical meridian observations in order to extend the fundamental coordinate system to faintest objects and to the K-infrared waveband. Classical meridian circles are unfit for the infrared observations because their lens objectives do not give good images in the infrared. But reflectors are almost never used as meridian circles due to uncertainties in their optical axis position. The main problem is that the secondary mirror is not connected with the micrometer and the circle reading system. In order to overcome this difficulty the author proposes to use an intermediary focal plane between the primary and the secondary mirrors where a luminous reference grid of wires might be placed. The Gregory optical scheme has such a focal plane, and its secondary mirror forms images of a star and the grid at the micrometer's detecting area. At the same time a special champher around the primary's central hole forms anautocollimated image of the grid near the grid itself. The micrometer measures the star image coordinates relative to two images of the reference grid. So, observations will not be affected by displacements of the secondary mirror and by those of the micrometer. The telescope's equivalent focal length has been chosen as 3 m, and the optical system has been transformed into an aplanatic Mersenne combined with an aplanatic focal reducer corrector (Popov, 1988). A new autocollimated circle reading system is chosen for the instrument (Yershov and Nemiro, 1994). The observations will be linked to the fixed optical axis of two long-focus collimators placed at the prime vertical plane.

scholarly journals Modernization of the Belgrade meridian circle

1998 ◽  
pp. 127-129
Author(s):  
G. Pinigin ◽  
I. Pakvor ◽  
A. Shulga
Keyword(s):  
Meridian Circle ◽  
Reading System

The purpose of the modernization of the Belgrade Meridian Circle is laid out. The description of the technical elements of the planned undertaking is also presented. The modernization includes the CCD micrometer, automatic circle reading system (CRS) and the telescope setting system (TSS).

scholarly journals 8. Positional Astronomy

1970 ◽  
Vol 14 (1) ◽  
pp. 39-51
Author(s):  
A. A. Nemiro ◽  
W. Fricke ◽  
A. N. Adams ◽  
P. Lacroute ◽  
R. H. Stoy ◽  
...  
Keyword(s):  
Meridian Circle ◽  
New Materials ◽  
Digital Readout ◽  
New Techniques ◽  
Primary Mirror ◽  
Astronomical Instruments ◽  
Large Numbers ◽  
On Line ◽  
Positional Astronomy ◽  
And Control

It is with deep regret that we mention the death, on 15 July 1969, of Prof. Dr G. Demetrescu who has done so much for the development of Astronomy in Roumania.This report is based on letters received from members of the Commission, whom I wish to thank most cordially.The most important events in the development of positional astronomy during the three past years were:(1)The construction and use of new types of astronomical instruments based on new techniques, and(2)The collective observations of large numbers of stars, especially in the Southern hemisphere on the basis of international cooperation.At the USNO a design study for a ten-inch automatic meridian circle (ATC)was completed in 1968. Construction and installation should be completed by the end of 1970. A modified Cassegrainian optical system with a Cer-Vit primary mirror is being used. For some other important parts of the instrument new materials will also be used. At each end of the horizontal axis of the instrument Inductosyns will be mounted.An Inductosyn system for digital readout of the pointing angle of the telescope was installed on the six-inch transit circle of the USNO in 1967 for testing and calibration. An IBM-1800 data acquisition and control system was on line with the same instrument.

scholarly journals Determination of the Division Corrections of the Bordeaux Declination Circle by the Benevides-Boczko Method

1986 ◽  
Vol 109 ◽  
pp. 543-550
Author(s):  
Y. Requième ◽  
M. Rapaport
Keyword(s):  
Standard Deviation ◽  
Meridian Circle ◽  
Reading System

The automatic declination reading system implemented on the Bordeaux meridian circle with a new divided circle is shortly presented. The determination of the division errors by the Benevides-Boczko method was carried out in December 1982 and in March 1983: the standard deviation between the two sets of corrections is about 0.015″.

scholarly journals Calibration of Photometry from the Gemini Multi-Object Spectrograph on Gemini North

2009 ◽  
Vol 26 (1) ◽  
pp. 17-30 ◽  
Author(s):  
Inger Jørgensen
Keyword(s):  
Systematic Errors ◽  
Random Errors ◽  
Standard Star ◽  
Primary Mirror ◽  
Color Terms ◽  
User Community ◽  
Color Term ◽  
The Individual ◽  
Zero Points

AbstractAll available observations of photometric standard stars obtained with the Gemini Multi-Object Spectrograph at Gemini North in the period from August 2001 to December 2003 have been used to establish the calibrations for photometry obtained with the instrument. The calibrations presented in this paper are based on significantly more photometric standard star observations than usually used by the individual users. Nightly photometric zero points as well as color terms are determined. The color terms are expected to be valid for all observations taken prior to UT 2004 November 21 at which time the Gemini North primary mirror was coated with silver instead of aluminium. While the nightly zero points are accurate to 0.02 mag or better (random errors), the accuracy of the calibrations is limited by systematic errors from so-called ‘sky concentration’, an effect seen in all focal reducer instruments. We conclude that an accuracy of 0.035 to 0.05 mag can be achieved by using calibrations derived in this paper. The color terms are strongest for very red objects, e.g. for objects with (r′ – z′) = 3.0 the resulting z′ magnitudes will be ≈0.35 mag too bright if the color term is ignored. The calibrations are of importance to the large Gemini user community with data obtained prior to UT 2004 November 21, as well as future users of achive data from this period in time.

scholarly journals The Photoelectric Meridian Circle of the Pulkovo

1986 ◽  
Vol 109 ◽  
pp. 407-411
Author(s):  
V.N. Ershov ◽  
V.E. Pliss ◽  
Yu. S. Streletsky
Keyword(s):  
Standard Errors ◽  
Meridian Circle ◽  
Pulkovo Observatory ◽  
Reading System

The paper reports on the new semiautomatical meridian circle of the Pulkovo observatory. It is equipped with a scanning photoelectric micrometer and a photoelectric circle reading system. The standard errors of a single registration of a star are 0s.016 and 0″.35 in RA and declination, respectively. The limiting magnitude is 10.5m. The instrument can be used for IRS differential observations.

Design and Optimize the Supporting Structure of Large-Diameter Lightweight Mirror

2012 ◽  
Vol 224 ◽  
pp. 170-173
Author(s):  
Wen Yi Chai ◽  
Yong Jie Xie ◽  
Wei Wang ◽  
Meng Yuan Wu ◽  
Xue Wu Fan
Keyword(s):  
Work Environment ◽  
Simulation Analysis ◽  
Optical Axis ◽  
Large Diameter ◽  
Primary Mirror ◽  
Supporting Structure ◽  
Final Project ◽  
Flexible Support ◽  
Ground Test ◽  
Design Requirements

This paper describe design and optimize of the lightweight primary mirror assemblies for the space telescope, aim at supporting structure of the primary mirror with an aperture of 530mm for the Cassegrain optical. We design three kinds of flexible support structure for the mirror, and numerical simulation analysis the accuracy of reflective shape for mirror assemblies on the ground test and in-orbit work environment, compare the results of analysis and optimize parameters of flexible structure, determine the final project and put it into production. The results show that the component should be aligned and tested in the same direction of the mirror optical axis and the gravity, the accuracy of reflective shape is PV<λ/25 and RMS<λ /125 (λ = 632.8nm), under the state ofΔ4oC temperature change, the RMS<λ/234 (λ = 632.8nm), the project meet design requirements of the optical system.

scholarly journals Flux profile at focal area of concentrating solar dishes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
M. Ebrahim Foulaadvand ◽  
Amir Aghamohammadi ◽  
Parvin Karimi ◽  
Hadi Borzouei
Keyword(s):  
Concentration Ratio ◽  
Flux Distribution ◽  
Optical Axis ◽  
Radial Dependence ◽  
Energy Harvest ◽  
Spherical Mirror ◽  
Line Region ◽  
Solar Radiation Flux ◽  
Flux Profile ◽  
Spherical Mirrors

AbstractWe analytically, experimentally and computationally explore the solar radiation flux distribution in the interior region of a spherical mirror and compare it to that of a paraboloidal one with the same aperture area. Our investigation has been performed in the framework of geometrical optics. It is shown that despite one can assign a quasi focus, at half the radius, to a spherical mirror, the light concentration occurs as well on an extended line region which starts at half-radius on the optical axis. In contrast to a paraboloidal concentrator, a spherical mirror can concentrate the radiation parallel to its optical axis both in a point-focus and in a line-focus manner. The envelope of the reflected rays is also obtained. It is shown that the flux distribution has an axial symmetry. The radial dependence of the flux on a flat circular receiver is obtained. The flux longitudinal dependence is shown to exhibit three distinctive regions in the interval [0, R] (R is mirror radius). We obtain the radiational (optical) concentration ratio characteristics and find the optimal location of the flat receiver of a given size at which the concentration ratio is maximised. In contrast to a parabolic mirror, it is shown that this location depends on the receiver size. Our findings offers that in spherical mirrors one can alternatively use a line receiver and gains a considerable thermal energy harvest. Our results are supported by Monte Carlo ray tracing performed by Zemax optical software. Experimental validation has been performed in lab with a silver-coated lens as the spherical mirror.

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