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"Nebulae Observers"
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The Complete Guide to the Herschel Objects
Sir William Herschel's contributions to astronomy during the late eighteenth century are unrivalled. His lasting legacy is his dedicated all-sky survey of star clusters and nebulae, and these objects continue to be among the most studied in the night sky. This unique book provides a complete re-examination of Herschel's entire catalogue of non-stellar discoveries, making it the most accurate and up-to-date reference of its kind. Retrace the footsteps of one of history's greatest astronomers and explore every one of Herschel's landmark discoveries, including those considered to be lost or non-existent. Read detailed notes about each object's appearance and physical characteristics, and view hundreds of photos of the most intriguing Herschel objects, along with dozens of sketches of what is visible at the eyepiece. This superb book is a must-have for amateur astronomers seeking new and exciting observing challenges, and as the ultimate reference on the Herschel objects.
eBook
The Observing Guide to the Messier Marathon
The Messier Catalogue is a list of one hundred and ten galaxies, star clusters and nebulae, and includes many of the brightest and best-known objects in the sky. Amateur astronomers can challenge their abilities by attempting to find all the objects on the list in one night, and thus complete the Messier Marathon. This book contains over 90 easy-to-use star maps to guide the observer from one object to the next, and provides tips for a successful night of observing. The book also tells the story of the eighteenth-century astronomer, Charles Messier, and how he came to compile his extensive catalogue. This complete guide to the Messier Marathon will help the amateur astronomer to observe the Messier Objects throughout the year, using a small telescope or even a pair of binoculars.
eBook
The secret deep
In this fresh list, Stephen James O'Meara presents 109 new objects for stargazers to observe. The Secret Deep list contains many exceptional objects, including a planetary nebula whose last thermal pulse produced a circumstellar shell similar to the one expected in the final days of our Sun's life; a piece of the only supernova remnant known visible to the unaided eye; the flattest galaxy known; the largest edge-on galaxy in the heavens; the brightest quasar; and the companion star to one of the first black hole candidates ever discovered. Each object is accompanied by beautiful photographs and sketches, original finder charts, visual histories and up-to-date astrophysical information to enrich the observing experience. Featuring galaxies, clusters and nebulae not covered in other Deep-Sky Companions books, this is a wonderful addition to the series and an essential guide for any deep-sky observer.
eBook
Measuring nebular temperatures: the effect of new collision strengths with equilibrium and kappa-distributed electron energies
In this paper we develop tools for observers to use when analysing nebular spectra for temperatures and metallicities, with two goals: to present a new, simple method to calculate equilibrium electron temperatures for collisionally excited line flux ratios, using the latest atomic data; and to adapt current methods to include the effects of possible non-equilibrium '{\\kappa}' electron energy distributions. Adopting recent collision strength data for [O iii], [S iii], [O ii], [S ii], and [N ii], we find that existing methods based on older atomic data seriously overestimate the electron temperatures, even when considering purely Maxwellian statistics. If {\\kappa} distributions exist in H ii regions and planetary nebulae as they do in solar system plasmas, it is important to investigate the observational consequences. This paper continues our previous work on the {\\kappa} distribution (Nicholls et al. 2012). We present simple formulaic methods that allow observers to (a) measure equilibrium electron temperatures and atomic abundances using the latest atomic data, and (b) to apply simple corrections to existing equilibrium analysis techniques to allow for possible non-equilibrium effects. These tools should lead to better consistency in temperature and abundance measurements, and a clearer understanding of the physics of H ii regions and planetary nebulae.
Paper
Statistical Studies of Long - Period Variable Stars in Odessa
The studies of pulsating variable stars are traditional subjects of astronomers in Odessa. In the last half of the 20th century, the studies of the physical variable stars were the topics of 15 PhD theses of the collaborators of the Odessa State (now National) University. Continuing the tradition of studies of long-period variable stars in the Astronomical Observatory of Odessa University, we try to conduct a detailed classification of the Mira-type stars, semi-regular variable stars and also find out the location of symbiotic stars among other long-period variables in their evolution to the planetary nebulae, using the compiled material from own observations and that of other authors. For the research, we have used observations from the databases of the French Association of Variable Stars Observers (AFOEV) and Variable Stars Observers League of Japan (VSOLJ), which allow study of the variability of these stars during the time interval of about 100 years. Some stars were studied using the observations of the American Association of Variable Star Observers (AAVSO). Modern research of long-period variable stars in Odessa is conducted in several directions: 1. The analysis of correlations between the photometric parameters. 2. The study of changes on time of individual characteristics of the light curves. 3. The study of variability of the objects which are transitional between the Mira-type and the semi-regular variables. The conclusions are discussed.
Paper
Upgrading electron temperature and electron density diagnostic diagrams of forbidden line emission
Diagnostic diagrams of forbidden lines have been a useful tool for observers in astrophysics for many decades now. They are used to obtain information on the basic physical properties of thin gaseous nebulae. Some diagnostic diagrams are in wavelength domains which were difficult to take either due to missing wavelength coverage or low resolution of older spectrographs. Furthermore, most of the diagrams were calculated using just the species involved as a single atom gas, although several are affected by well-known fluorescence mechanisms as well. Additionally the atomic data have improved up to the present time. Aim of this work was a recalculation of well-known, but also of sparsely used, unnoted diagnostics diagrams. The new diagrams provide observers with modern, easy-to-use recipes to determine electron temperature and densities. The new diagnostic diagrams are calculated using large grids of parameter space in the photoionization code CLOUDY. For a given basic parameter (e.g. electron density or temperature) the solutions with cooling-heating-equilibrium are chosen to derive the diagnostic diagrams. Empirical numerical functions are fitted to provide formulas usable in e.g. data reduction pipelines. The resulting diagrams differ significantly from those used up to now and will improve the thermodynamic calculations. To our knowledge, for the first time detailed directly applicable fit formulas are given, leading to electron temperature or density from the line ratios.
Paper