Multiple entrance aperture dispersive optical spectrometer

1985 ◽  
Vol 40 (7) ◽  
pp. ii
Keyword(s):  
Entrance Aperture

Channeltron entrance aperture gain variations for energetic heavy ions

1976 ◽  
Vol 47 (1) ◽  
pp. 138 ◽  
Author(s):  
B. Hird ◽  
H. C. Suk ◽  
A. Guilbaud
Keyword(s):  
Heavy Ions ◽  
Entrance Aperture

The LPL Radial Accelerometer

1984 ◽  
Vol 88 ◽  
pp. 63-86 ◽  
Author(s):  
R.S. McMillan ◽  
P.H. Smith ◽  
J.E. Frecker ◽  
W.J. Merline ◽  
M.L. Perry
Keyword(s):  
Optical Fiber ◽  
Radial Velocity ◽  
Doppler Shift ◽  
Focal Plane ◽  
Incident Light ◽  
The Sun ◽  
Stellar Spectrum ◽  
Entrance Aperture ◽  
Fabry Perot ◽  
Interference Order

AbstractWe have begun to observe radial velocities of stars with an optical spectrometer designed for unusually high accuracy. Light from a star image in the focal plane of a telescope is fed to the entrance aperture of the spectrometer by a single optical fiber. Wavelengths are calibrated by transmission of collimated light through a tilt-tunable Fabry-Perot interferometer. The scrambling of incident light rays by the optical fiber and the intrinsic stability of the Fabry-Perot etalon provide immunity to the sources of systematic errors that plague conventional radial velocity meters. The spectrum is dispersed by an echelle grating crossed with another plane reflection grating. Several echelle orders in the vicinity of 4250-4600 Å are imaged in a two-dimensional format on a charge-coupled (CCD) array of detectors. About 350 distinct points on the profile of the stellar spectrum are sampled by successive orders of interferometrie transmission through the etalon. In the vicinity of 4300 Å each interference order is 47 milliangstroms wide and the sample points are 0.64 Å apart, resulting in distinct , widely-spaced monochromatic images of the entrance aperture to be formed in the focal plane of the camera. Changes in Doppler shift cause changes in the relative intensities of these images, according to the slope of the spectral profile at each point sampled. The instrument is being operated as a null-measurement accelerometer, sensitive only to changes in radial velocity, which simplifies operation and enhances sensitivity. With an argon-filled, iron hollow cathode emission line lamp, the interferometer can be calibrated to two parts in 100 million; this corresponds to ± 6 meters/sec in Doppler shift. Calibrations of the interferometer show variations of ± 27 meters/sec on a time scale of months; observations of stars are corrected for such changes. The internal repeatability of observations of the differential Doppler shift of light from the integrated disk of the Sun is ± 6 meters/sec. The corresponding result from about 70 observations of Arcturus (Kl IIIb; B=1.19) is ± 40 meters/sec internal repeatability for each exposure of 20 square-meter seconds. The external repeatability (day-to-day differential accuracy) of nightly averages of stellar observations is ± 20 meters/second. Since the internal precision on the sun and the argon lamp is much better than it is with short exposures on Arcturus, the quality of our observations of stars is limited by the rate of detected photons. This justifies averaging a number of short exposures of a star to approach “laboratory” precision.

Interface Region Imaging Spectrograph (IRIS) entrance aperture design

2014 ◽  
Author(s):  
P. Cheimets ◽  
S. Park ◽  
H. Bergner ◽  
C. Chou ◽  
R. Gates ◽  
...  
Keyword(s):  
Interface Region ◽  
Entrance Aperture ◽  
Imaging Spectrograph

Development of the lateral eye of American horseshoe crabs: Visual field and dioptric array

1995 ◽  
Vol 12 (3) ◽  
pp. 485-492 ◽  
Author(s):  
Michael J. Shih ◽  
William W. Weiner ◽  
Kathleen Kier Wheatley ◽  
Jennifer L. DePonceau ◽  
Mary Anne Sydlik ◽  
...  
Keyword(s):  
Visual Field ◽  
Sexual Maturity ◽  
Adult Animal ◽  
Significant Trend ◽  
Aperture Diameter ◽  
Entrance Aperture ◽  
Lateral Eye ◽  
Horseshoe Crabs ◽  
Optical Alignment ◽  
Animal Size

AbstractWe used a precision two-circle goniometer mounted to the stage of a compound microscope to determine the optical alignment and to measure the entrance aperture diameter of individual cuticular cones in the dioptric array of the lateral eye of juvenile horseshoe crabs in order to learn about the development of the visual field. Our results show that the extent of the visual field of juvenile horseshoe crabs with prosomal lengths about 20% ofadult size (14–21 mm) is about 70% that of the visual field of adult horseshoe crabs (prosomal lengths: 100+ mm). The visual field of such juvenile animals covers between 77 and 85 deg vertically and 140 and 145 deg horizontally. Assuming that the dioptric array is uniform and square packed, the average interommatidial angle of the juvenile animals is between 5.6 and 6.0 deg as compared to 4.6 deg for an adult animal. The diameter of the entrance aperture of individual cuticular cones increases markedly with increasing animal size. In addition, we noted a statistically significant trend for entrance aperture diameters to increase from anterior to posterior within the eye for animals of all sizes. There may be a slight trend for entrance aperture diameters to increase from dorsal to ventral within the eye. Our results indicate that the extent of the visual field and the resolution of the lateral eye approach adult values in advance of animals' reaching sexual maturity.

scholarly journals IUE Observations of the Bipolar Planetary Nebula NGC 2346

1983 ◽  
Vol 103 ◽  
pp. 57-58
Author(s):  
W. A. Feibelman ◽  
L. H. Aller
Keyword(s):  
Orbital Period ◽  
Planetary Nebula ◽  
Eclipsing Binary ◽  
Entrance Aperture ◽  
Low Dispersion

The nucleus of NGC 2346 (=PK 215 + 3°1; α = 7h06m49.S7, δ = −0°43′29″, 1950) was recently discovered by Kohoutek (1982a,b) to be an eclipsing binary with a deep (~ 2.m2) minimum in the visible and an orbital period of 17.2 ± 0.4 days. We observed NGC 2346 with the IUE on 4 occasions between 1982, Feb. 24 and May 13 and obtained 6 SWP and 4 LWR low dispersion spectrograms. These were taken at different phases, using the large entrance aperture centered on the nucleus.

Design of an anidolic concentrator and evaluation of daylight enhancement under an overcast sky

2016 ◽  
Vol 48 (8) ◽  
pp. 917-929
Author(s):  
MG Nair ◽  
K Ramamurthy ◽  
AR Ganesan
Keyword(s):  
Performance Evaluation ◽  
Acceptance Angle ◽  
Light Pipe ◽  
Entrance Aperture ◽  
Overcast Sky ◽  
Better Than

This paper discusses the performance evaluation of anidolic concentrators in an overcast sky condition. The concentrators were designed, with acceptance angles of 60°, 70° and 80°, first by maintaining the profile of the concentrator’s uniform and secondly by keeping the height uniform. Studies were done using these concentrators with a model light pipe and the performance was compared with that of an acrylic dome and a profiled Fresnel collector. For a given condition, the illuminance ratio (ratio of illuminance measured at the base of the pipe to external illumination) increased with the acceptance angle. For a given acceptance angle, the concentrator with uniform height and variation of entrance aperture, performed better than a concentrator having a uniform profile.

scholarly journals The Effects of Collimation and Oblique Incidence in Length Interferometers. II.

1955 ◽  
Vol 8 (2) ◽  
pp. 241 ◽  
Author(s):  
BS Thornton
Keyword(s):  
Oblique Incidence ◽  
Fringe Pattern ◽  
Finite Size ◽  
Multiple Beam ◽  
Entrance Aperture

It is important in length determinations by interferometry to know the effect on the fringe pattern of an entrance aperture of finite size through which the light enters the interferometer. The correction generally applied has been found to be in error (Bruce 1955). This paper is a further discussion of this correction. Both two-beam and multiple-beam systems are discussed and show, in accordance with experiment, that the correction at present applied for the finite size of the aperture appears to be invalid.

Design and applications of a post-column imaging filter

1992 ◽  
Vol 50 (2) ◽  
pp. 1192-1193
Author(s):  
O.L. Krivanek ◽  
A.J. Gubbens ◽  
N. Dellby ◽  
C.E. Meyer
Keyword(s):  
Electron Beam ◽  
Diffraction Pattern ◽  
Ccd Camera ◽  
Slit Width ◽  
Normal Operation ◽  
Entrance Aperture ◽  
Principal Parts

We have designed and built an imaging filter which can can be attached to most standard TEMs, and is capable of operating at primary energies of up to 400 keV. The column-mounted hardware consists of 8 principal parts (Fig. 1): 1) entrance aperture, 2) pre-prism focussing and alignment coils, 3) magnetic prism, 4) spectrum-magnifying quadrupoles, 5) pneumatically retractable energy-selecting slit, 6) quadrupole-sextupole imaging assembly, 7) pneumatically retractable TV-rate CCD camera, and 8) slowscan CCD (SSC) camera. In normal operation, the entrance aperture selects a part of an image (or a diffraction pattern) that is projected by the microscope into the viewing chamber, and a doubly-focused spectrum is produced at the energy selecting slit (with a dispersion of 6 μm / eV at 200 keV). The slit width is piezoelectrically adjustable, and the whole slit assembly can be withdrawn pneumatically from the electron beam. Similar to the TEM column which can either produce an image or a diffraction pattern, the post-slit quadrupole-sextupole assembly can produce either a focussed spectrum at the SSC (or the TV), or a magnified image of the specimen.

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