Visual Observing
In this chapter it is assumed that the reader has access to a small- to medium-sized telescope (10–30 cm, or 4–12 in.) on a motor-driven mounting. For visual work the field rotation inherent to alt-az mounted telescopes (Figs. 6.4 and 6.5 ) matters litt
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Visual Observing
Introduction In this chapter it is assumed that the reader has access to a small- to medium-sized telescope (10–30 cm, or 4–12 in.) on a motor-driven mounting. For visual work the field rotation inherent to alt-az mounted telescopes (Figs. 6.4 and 6.5) matters little. If the observer intends to go on to do significant amounts of imaging, though, an equatorial mounting will be the significantly better choice (Chap. 9).1 Descriptions of how to find and track objects in the sky are based upon what is needed for a basic mounting with just simple setting circles. Owners of instruments with computer-controlled mountings will probably not need much of the advice that is given here – although when confronted with finding objects not in their computer’s databases, such as novae, supernovae or comets, such observers will still have to resort to the old-fashioned methods. If the telescope is smaller than 10 cm, then many of the fainter objects will be difficult or impossible to see. If the telescope is larger than 30 cm – congratulations! Other types of observing such as imaging, photometry and spectroscopy are considered in later chapters. Visual work is an aspect of imaging (Chap. 9); nowadays it is sometimes regarded as inferior to methods providing a permanent record. It certainly can be a subjective process (see later), and is limited in the wavelengths and intensities detectable. Nonetheless, with care and practice it can still give very valuable results; after all, for half the time since their invention, telescopes could be used with no other type of detector than the eye. Furthermore, one of the principal joys of astronomy is seeing for yourself the mysteries and wonders of the universe, and it
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Some, but not all, commercially produced alt-az mountings can be converted to equatorials simply by attaching them to a wedge whose apex angle equals 90 minus the observer’s latitude. The vertical (azimuth) axis then becomes the polar axis and the horizontal (altitude axis) the declination axis. Computer-controlled mountings are likely to have an equatorial option available or even automatically to recognize their orientation during setting-up. C. R. Kitchin, Telescopes and Techniques, Undergraduate Lecture Notes in Physics, 151 DOI 10.1007/978-1-4614-4891-4_8, # Springer Science+Business Media New York 2013
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8 Visual Observing
should never be forgotten that one of the great strengths of the science is that the vast majority of astronomers study the subject for pleasure and interest (how many amateur solid-state physicists do you know?).
General and Practical Considerations and Safety Whether in an observatory or not, telescopes are often used in damp conditions, and obviously at low levels of illumination. It is therefore advisable for all equipment to be of low voltage. Any high voltages should always be taken through rapid circuit breakers (RCBs – also known as Residual Current Devices [RCDs], Residual Current Circuit Breakers [RCCBs], Ground Fault Circuit Interrupters [GFCIs], Ground Fault In
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