Amateur astronomers often contribute to activities such as monitoring changes in the brightness of variable stars and supernovae, tracking asteroids, and observing occultations to determine both the shape of asteroids and the shape of the terrain at the apparent edge of the moon from Earth. With more advanced equipment, but still cheap compared to professional facilities, amateur astronomers can measure the spectrum of light emitted by astronomical objects, which can provide high-quality scientific data if measurements are made carefully. A relatively new role for amateur astronomers is the search for neglected phenomena (e.g., the Kreutz Sungrazers) in the vast libraries of digital images and other data captured by ground-based and space-based observatories, many of which are available on the Internet. NGC 5897: This globular cluster sparse in Libra is difficult in small telescopes and appears as a unified haze dotted with faint stars in large backyard instruments. The comprehensive A New General Catalogue of Nebulae and Clusters of Stars, the catalogue of the late Sir John F. W. Herschel, Bart., has revised, corrected and expanded the basic reference list of star clusters, nebulae and galaxies. It was compiled in 1888 by Danish astronomer Johan Ludvig Emil Dreyer, who based his work on earlier Herschel family lists of British astronomers. Dreyer included 7,840 celestial objects, a total of 13,226 through his first and second index catalogues (ICs), published in 1895 and 1908 respectively. With these additions, the NGC covers the entire sky, although many objects visible with modern instruments are not listed. This NASA and ESA Hubble Space Telescope image captures the spiral galaxy NGC 105, located about 215 million light-years away in the constellation Pisces. Although it looks like NGC 105 is going to crash into a collision with a nearby galaxy from the front, this is only the result of the random alignment of the two objects in the night sky.
NGC 105`s elongated neighbor is actually much farther away and remains relatively unknown to astronomers. These deceptive conjunctions often occur in astronomy – for example, stars in constellations are located at very different distances from Earth and seem to form patterns only through the random alignment of their component stars. Amateur astronomers also use star maps, which, depending on experience and intentions, can range from simple planispheres to detailed maps of very specific areas of the night sky. A number of astronomy software are available and used by amateur astronomers, including software that creates sky maps, software to support astrophotography, observational planning software, and software to perform various calculations on astronomical phenomena. Amateur astronomers often like to keep records of their observations, which are usually made in the form of an observation protocol. Observation logs usually record details about the objects observed and when, and describe the details that were seen. The sketch is sometimes used in protocols, and photographic recordings of observations have also been used recently. The information collected is used to support studies and interactions between amateur astronomers at annual meetings. While this is not professional or credible information, it is a way for leisure enthusiasts to share their new observations and experiences.
NGC 457: Also known as the owl cluster, this formation of bright, bird-like stars sparkles in small telescopes. Nearly 800 objects are listed as “non-existent” in the RNGC. The designation is applied to objects that are duplicate catalog entries, those that were not discovered in subsequent observations, and a number of objects catalogued as star clusters that were considered random groupings in subsequent studies. A 1993 monograph considered the 229 star clusters that did not exist in the RNGC. They have been “misidentified or have not been found since their discovery in the 18th and 19th centuries.”  It turned out that one of the 229 – NGC 1498 – was not really in the sky. Another five were duplicates of other entries, 99 existed “in one form or another,” and the remaining 124 required additional research to resolve them.  Most amateur astronomers work at visible wavelengths, but a small minority experiment with wavelengths outside the visible spectrum. One of the early pioneers of radio astronomy was Grote Reber, an amateur astronomer who built the first purpose-built radio telescope in the late 1930s to track Karl Jansky`s discovery of radio wavelength emissions from space.
Non-visual amateur astronomy includes the use of infrared filters on conventional telescopes and the use of radio telescopes. Some amateur astronomers use homemade radio telescopes, while others use radio telescopes that were originally built for astronomical research, but have since been made available to hobbyists. The One-Mile telescope is an example. More advanced methods of locating objects in the sky include telescope mounts with adjustment circles, which help point telescopes at places in the sky known to contain objects of interest, and GOTO telescopes, which are fully automated telescopes that can locate objects when needed (after they have been calibrated first). Astronomers recently carefully analyzed distances to a sample of galaxies, including NGC 105, to measure how fast the universe is expanding — a value known as the Hubble constant. Their results do not agree with the predictions of the most widely used cosmological model, and their analysis shows that there is only a 1 in a million chance that this discrepancy was caused by measurement errors. This discrepancy between galaxy measurements and cosmological predictions has long been a source of consternation for astronomers, and these latest findings provide compelling new evidence that something is wrong or missing in our standard model of cosmology. Scientific research is often not the main goal of many amateur astronomers, unlike professional astronomers. However, work of scientific value is possible, and many amateurs successfully contribute to the knowledge base of professional astronomers. Astronomy is sometimes promoted as one of the few remaining sciences for which amateurs can still contribute useful data.
To honor this, the Astronomical Society of the Pacific annually awards amateur excellence awards for significant amateur contributions to astronomy. These letters are abbreviations for astronomical catalogues – published lists of stars, nebulae, supernova remnants, galaxies and other known objects in space. The advent of mobile applications for use in smartphones has led to the development of many dedicated applications.   These apps allow any user to easily locate celestial objects of interest by simply pointing the smartphone device at the sky in that direction. These apps use the hardware built into the phone, such as GPS location and gyroscope. Useful information about the sharp object such as celestial coordinates, object name, constellation, etc. is provided for quick reference. Some paid versions provide more information. These applications are gradually being used regularly during observation for the telescope alignment process.  The NGC/IC project is a collaboration between professional and amateur astronomers founded in 1993.
Completed in 2017, it aimed to identify all NGC and IC objects, correct errors, collect basic astronomical images and data. The main members of the team were Harold G. Corwin Jr., Steve Gottlieb, Malcolm Thomson, Robert E. Erdmann and Jeffrey Corder.  Assembly of the NGC was difficult, as Dreyer had to deal with many contradictory and unclear reports made with a variety of telescopes with apertures ranging from 2 to 72 inches. Although he checked some himself, the large number of objects meant that Dreyer had to accept them as objects published by others for his compilation. The catalogue contained several errors, mainly related to position and descriptions, but Dreyer referred to the catalogue, which allowed later astronomers to examine the original references and issue corrections to the original NGC.  Amateur astronomers use a range of instruments to study the sky, depending on a combination of their interests and resources. Methods include simply looking at the night sky with the naked eye, using binoculars, and using a variety of optical telescopes of varying power and quality, as well as additional sophisticated equipment such as cameras to study the light of the sky in both the visual and non-visual parts of the spectrum.