{'fraction_non_alphanumeric': 0.03987240829346093, 'fraction_numerical': 0.018341307814992026, 'mean_word_length': 4.227083333333334, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 1, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Telescopes: a very short introduction

© 2018 B. Ishak https://doi.org/10.1080/00107514.2018.1448448 was from the infrared observation with Spitzer, published in 2008. What it actually showed was the Galaxy with two well-defined major spiral arms, Perseus and Scutum–Centaurus, with at least two minor ones, Norma and Sagittarius. None of the arms was missing although it was hyped as such.1 In 2014, the radio Red MSX Source (RMS) survey showed evidence of four arms. Two or four clearly depends on not only the wavelength but also the objects observed. Spitzer was tracing the long-lived, low-mass stars while RMS the short-lived, massive ones. Any which way, it seems everyone is happy to accept the traditional four-arm view. Early in the book, a few mistakes can already be spotted. One is when John Herschel is said to have been responsible for the creation of New General Catalogue of Non-Stellar Objects. The author then goes on to say: ‘The so-called NGC ...’. This is inaccurate. John Hershel’s catalogue is called General Catalogue of Nebulae and Clusters of Stars, known as GC. John Dreyer was the one responsible for the creation of NGC but the full name of which is New General Catalogue of Nebulae and Clusters of Stars, an update to GC. Could there be a source somewhere that calls Herschel’s catalogue NGC as it has been called that in at least one other publication? See e.g. this review [2]. As it is, general catalogues of non-stellar objects is a collective name for all the catalogues of non-stellar objects, see [3]. However, Catalogue of NonStellar Objects2 does exist. The other is when Yerkes Observatory is said to have a 46-inch telescope. It is a 40-inch. Perhaps, this is a typo or a misreading of a hand-written manuscript or the fault of the proof-reader. But let us not excuse it. The telescope is famous for being the largest refractor in the world. And yet another is when Edward Barnard is said to have published ‘An Atlas’ of Selected Regions of the Milky Way not ‘A Photographic Atlas’ of Selected Regions of the Milky Way as it should be. Do these errors matter? As popular astronomy the book caters specially for the non-experts, to whom these errors are as good as invisible. Thus, it is not done to misinform the untrained readers, inadvertently or not. Plus this is all history, so it really is not done to be so inaccurate. Worst, this is all only half-way into Chapter 2, a chapter titled, ironically, Historic Perceptions. Would the readers bother with the rest?