[...]... Section I Galaxies, Cluster of Galaxies, and their Data Galaxies and clusters of galaxies are certainly among the most popular targets for amateur astronomers They show an incredibly diverse range of size, shape, and internal structure has undoubtedly lead to their fascination among both amateurs and professional astronomers alike However, this sheer complexity of form and evolution makes it necessary to. .. compact galaxies (BCD) Quasars show a variation between 0.0 and 1.0 while Seyfert galaxies are around 0.5 Total and Standard Magnitude, Standard Diameter To measure the brightness of galaxies one often uses a diaphragm The value of the integrated magnitude depends on its aperture With increasing size, the magnitude rises to reach saturation, representing an “infinite” aperture This limit is called “total... gravity and angular 3 Galaxies, Cluster of Galaxies, & their Data Fig 1.1 Galaxy pair NGC 5090 and NGC 5091 in Centaurus momentum, clouds of primordial hydrogen and helium slowly fragment into smaller portions (“protogalaxies”) Early star formation and gravitational coalescence eventually convert them into the “first” true galaxies We now know that the development of galaxies strongly depends on gravitational... also known from the study of elliptical galaxies To resume, lenticular galaxies have connections to both elliptical and spiral galaxies thus are well placed by Hubble Common features of ordinary spiral galaxies (S) and barred spiral galaxies (SB) are the bulge (the spherical central region), and the surrounding disk containing the spiral arms Ordinary spirals show two or more spiral arms starting smoothly... the familiar subdivision into a, b, c, d, and m The other classes (elliptical, lenticular, and irregular galaxies) show similar differentiations Features titled “additional” must be set; to choice are c and d for elliptical galaxies as well as the stages (applicable for all types) in the last row The symbols (R) and (R′) are prefixes, pec and sp are suffixes; the symbols “:” and “?” are inserted at the... knots and dark rifts and lanes But even then don’t expect to see in the eyepiece anything similar what is present on photographic images! Photography (especially if in color) and visual observation are different worlds Starting the observing career with galaxies thus might cause some initial frustration Visually galaxies are shy targets, which must be handled with care Using the right equipment and learning... out to be promising targets Examples are NGC 6946 (mpg = 10.5 mag, V = 9.0 mag; Fig 1.16) and IC 10 (mpg = 13.5 mag, V = 11.8 mag) Classification In the past, the incredibly diverse appearance of galaxies was a major roadblock to their understanding A way to bring order into the chaos of their optical appearance is through various classification schemes [21] The observed shapes and structures of galaxies. .. Cluster of Galaxies, & their Data Galaxies, Cluster of Galaxies, & their Data Chapter 1 Galaxies are vast aggregates of stars, dust, and gas ranging from a few thousand to nearly a million light-years in diameter (see e.g., the classic book of Hodge) Their respective masses show a similarly broad range from less than a million to well over trillion solar masses [1] This variety of shape and form is... facts about the structure and dynamics of our galaxy Fortunately, the interstellar matter is pretty transparent for radio and infrared radiation It took some time of 4 Galaxies, Cluster of Galaxies, & their Data Fig 1.2 The rich galaxy cluster A 1656 in Coma Berenices applying sophisticated astrometric, statistical, and spectral methods to our galaxy and studying external galaxies to reach our current state... and ∆l = l - l0 its shift (difference between measured and labor value), then z is defined by z = ∆l / l The Doppler effect gives the relation z = v/c (c = velocity of light), thus the shift is proportional to the velocity Most galaxies show a redshift due to a “recession velocity.” A few nearby ones, like the Andromeda Nebula, show a blueshift, thus approaching us The Hubble law has been confirmed to . this series Nebulae and How to Observe Them Steven Coe Asteroids and How to Observe Them Lawrence Garrett Venus and Mercury and How to Observe Them Peter Grego Jupiter and How to Observe It John. McAnally Supernovae and How to Observe Them Martin Mobberley Total Eclipses and How to Observe Them Martin Mobberley The Messier Objects and How to Observe Them Paul L. Money The Herschel Objects and How to Observe. series Star Clusters and How to Observe Them Mark Allison Saturn and How to Observe It Julius Benton The Moon and How to Observe It Peter Grego Double & Multiple Stars and How to Observe Them James