Effects of a long entrance aperture upon the azimuthal response of spherical section electrostatic analyzers

1978 ◽  
Vol 49 (9) ◽  
pp. 1260-1268 ◽  
Author(s):  
J. T. Gosling ◽  
J. R. Asbridge ◽  
S. J. Bame ◽  
W. C. Feldman
Keyword(s):  
Entrance Aperture ◽  
Spherical Section

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.

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