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Article
Correlation between the Twelve High-velocity Neutral Hydrogen Clouds and a Feature of the Sky in the Radio Continuum
Hulsbosch and Raimond1 have discovered a region, 100° in diameter, which contains twelve clouds of neutral hydrogen distinguishable from the general background emission by their exceptionally high Doppler shifts....
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Article
Filamentary Nebulosity in the Vicinity of the Cetus Arc
FORMING large diameter circles across the sky are three ridges of enhanced radio emission. They are the North Polar Spur1, 111° in diameter, the Cetus Arc2, 91° diameter, and a third, unnamed, 60° diameter loop c...
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Article
An astronomical Fabry-Pérot interferometer
A description is given of an improved version of Flynn's photo-electric, pressure-scanning, Fabry-Pérot (F.-P.) interferometer which has been built for the purpose of studying line emission from diffuse gaseou...
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Article
Filter and interferometer observations of twoHii regions
The Rosette Nebula was photographed through filters isolating the Hα,OII andOIII nebular emission lines. Isophotes were constructed at these wavelengths. Measurements of the radial velocity differences across the...
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Article
Cameras and filters for nebular photography
The parameters of filter-cameras for nebular photography are outlined and a method of using confocal paraboloids to give the basic camera a higher resolution is investigated. Some astronomical problems requiri...
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Article
An investigation of a peculiar nebula in monoceros
A faint nebula, between the Rosette and NGC 2264, appears to be a supernova remnant. This was photographed with long exposures through narrow filters centred on the bright nebular emission lines. Interferogram...
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Article
Scanning Fabry-Pérot interferometers for nebular studies
The reasons for applying scanning Fabry-Pérot interferometers to the study of faint but extensive gaseous nebulae are outlined. Three ways of increasing the luminosity-resolutin product of the Fabry-Pérot are ...
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Article
The variations of the electron density within M8
The ratios of the brightnesses of the [Oii] lines at 3729 Å and 3726 Å were measured at 37 positions across M8. A multiple shell model was then constructed to estimate the large-scale variations of this ratio wit...
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Article
Further observations of the filamentary nebulosity around the cetus Arc (Loop 2)
Previously some filamentary nebulosity was discovered around the outer edge of the Cetus Arc (Loop 2). Some further observations have now been made of this. To determine an upper limit to its proper motion it ...
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Article
Fine Structure of Nebular Emission Lines
THE fact that nebular lines may have significant fine structure seems to have been neglected by nebular spectroscopists who have been considering the turbulent and thermal broadening of these lines. For exampl...
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Article
The variations of the electron density throughout the Orion Nebula
New measurements are reported of the [OII] brightness ratio across the Orion Nebula. These are compared to all previous measurements of this ratio. The variations of the local electron density throughout the v...
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Article
Observations of high velocities inHii regions with a two-etalon Fabry-Pérot spectrometer
High internal motions of the ionized material in theHii regions M 8, M16, M 17 and the Orion Nebula were searched for with a two-etalon Fabry-Perot monochromotor. The profiles of the [Oiii], 5007 Å and in one cas...
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Article
Observations of the general background Hα emission from the galactic plane
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Article
A reappraisal of several extensive phenomena of the high galactic latitudes
This is the first of two papers dealing with the extensive high latitude phenomena. The relationships between the diffuse and filamentary gaseous nebulosity, the giant radio loops and the high, medium and low ...
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Article
A two-beam, multi-mode, nebular-stellar photometer
The design, construction and use of a multi-purpose photometer is discussed. It is intended to work between 9000 Å to 3700 Å on the 25-inch Turner-Newall refractor of the Athens National Observatory and eventu...
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Article
Electronographic measurements of the ionised helium abundance in the core of the Orion Nebula
Measurements have been made with an electronographic image tube spectrograph of two helium and three hydrogen lines at twenty nine positions in the dense core of the Orion Nebula.
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Article
The structure of the dense cores of Hii regions
The latest observational and theoretical evidence which suggests the existence of a large number of partially ionized globules (PIG's) in the cores of Hii regions is presented.
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Article
Observations of major ionization fronts in M42 and M8
Image tube filter photographs taken in the light of the low ionization energy [Nii] and high ionization energy [Oiii] lines of the core of M42 are presented. These were taken with the 98-in. Isaac Newton telescop...
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Chapter and Conference Paper
Recent optical observations of some evolved HII regions
A variety of recent optical observations of the HII regions in the MagellanicClouds, M42, M8, M16 and M17 are compared with observations of molecular complexes and thermal radio emission. It appears that all t...
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Article
A survey of the unusual motions in M17 with a Fabry-Perot monochromator
The results of the most extensive survey ever undertaken of the profiles of the [Oiii] line over M17 are presented. These were obtained with an optically-contacted, pressure-scanned, single-etalon Fabry-Perot mon...
