Telescopes and Techniques

The modern aspiring astronomer is faced with a bewil­ dering choice of commercially produced telescopes, including all the designs considered in the preceding chapter. Yet only four decades ago the choice for a small telescope would have been between just a refrac­ tor and a Newtonian reflector. That change has come about because of the enormous interest that has grown in astronomy since the start of the space age and with the mind-boggling discoveries of the past 30 or 40 years. Except for some of the very small instruments which are unfortunately often heavily promoted in general mail order catalogues, camera shops and the like, the optical quality of these commercially pro­ duced telescopes is almost uniformly excellent. Although one product may be slightly better for some types of observation, or more suited to the personal cir­ cumstances of the observer, than another, most of them will provide excellent observing opportunities. The same general praise cannot be applied, however, to the mountings with which many of these telescopes are provided, and those problems are covered in Chapter 6.

Inhalt

Section 1: Telescopes.- 1 Types of Telescope.- Historical Introduction.- Modern Instruments.- Mounting.- Schmidt Camera.- Multi-Mirror and Space Telescopes.- Atmospheric Compensation.- Radio Telescopes.- Interferometers.- 2 Telescope Optics.- Point Sources.- Extended Images.- Objectives.- Eyepieces.- Accessories.- Aberrations.- Interferometers.- Mountings.- Observatories and Observing Sites.- Exercises.- 3 Modern Small Telescope Design.- Making Your Own.- Commercially Produced Telescopes.- Binoculars.- Section 2: Positions and Motions.- 4 Positions in the Sky.- Spherical Polar Coordinates.- Celestial Sphere.- Altitude and Azimuth.- Rotation.- Solar and Sidereal Days.- Declination and Hour Angle.- Time.- Mean Solar Time.- Solar Time.- Civil Time.- Sidereal Time.- Right Ascension and Declination.- Other Coordinate Systems.- Heliocentric Time.- Julian Date.- Spherical Trigonometry.- Exercises.- 5 Movements of Objects in the Sky.- Diurnal Motion.- Circumpolar Objects.- Seasons and Annual Motions.- Movement of the Moon and Planets.- Moon.- Other Solar System Objects.- Proper Motion.- Precession.- Parallax.- Aberration.- Relative Planetary Positions.- Position with Respect to the Earth.- Eclipses.- Position in an Orbit.- Synodic Period.- Exercises.- 6 Telescope Mountings.- Equatorial Mountings.- Alt-Az Mountings.- Making Your Own Mounting.- Alignment.- Setting Circles.- Guiding.- Modern Commercial Mountings.- Section 3: Observing.- 7 Electromagnetic Radiation.- Intensity.- Photons.- Polarisation.- Range.- Measurements.- Photometry.- Spectroscopy.- Polarimetry.- 8 Visual Observing.- General and Practical Considerations and Safety.- Finding.- Moon.- Planets.- Sun.- Finding.- Observing.- Stars.- Stellar Nomenclature.- Magnitudes.- Observing Stars.- Nebulae and Galaxies.- Daytime Observing.- False Observations.- Exercise.- 9 Detectors and Imaging.- The Eye.- Charge Coupled Devices (CCDs).- Image Processing.- Photography.- p-i-n Photodiode.- Superconducting Tunnel Junction Detectors.- Exercise.- 10 Data Processing.- Data Reduction.- Data Analysis.- Linear Regression.- Correlation Coefficient.- Student's t Test.- Exercises.- 11 Photometry.- CCD Photometry.- Photographic Photometry.- Absolute Magnitude.- Wavelength Dependence.- UBV System.- Bolometric Magnitude.- Spatial Information.- Photometers.- Observing Techniques.- Exercises.- 12 Spectroscopy.- Spectroscopes.- Spectroscopy.- Spectral Type.- Luminosity Class.- Radial Velocity.- Spectrophotometry.- Exercise.