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{ Practical astronomy | Appendices | About the site and author }

About the site and author

This is my personal web site, where I make resources available to friends, family, and anyone else who may find them. The name "chiandh" – although even more difficult to spell – is shorter than my real name, Horst Meyerdierks. I have been an amateur astronomer since 1974, and χ & h Persei is a double star cluster that we used to direct our binoculars at a long time ago. I have been using cameras and computers for nearly as long; the computers at least have always also been instruments to assist with the astronomy.

The information on this site is provided in good faith, but no warranty can be made for its accuracy. Copyright exists in all original material and is in general held by myself. Other copyright is declared on individual pages where applicable. Words, expressions and devices used may be trademarks or registered trademarks of their respective owners. I am not responsible for any information contained on the pages linked to from my pages. If you notice something incorrect or have a comment, feel free to email me. Unsolicited bulk email is not welcome.

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The background image of the cover page shows the Milky Way in and around the constellation of Scorpius; the very bright "star" is Jupiter. I took this in 2007 on a visit to the European Southern Observatory on Cerro Paranal in northern Chile.

Who is Horst Meyerdierks

I am a German who has lived in Scotland as an EU citizen between 1990 and 2021. I have a degree in physics and a doctorate in astronomy, both from the Rheinische Friedrich-Wilhelms-Universität Bonn. After the PhD, I worked as application programmer for the UK astronomers at the Department of Astronomy (now Institute for Astronomy) of the University of Edinburgh, then briefly as a research assistant at the Department of Computing Science of the University of Glasgow. I then worked in the IT Group at the Royal Observatory Edinburgh, until I retired in 2020. I am a member of the Astronomical Society of Edinburgh (ASE), the British Astronomical Association (BAA), the Institute of Physics (IoP), and the Olbers-Gesellschaft in Bremen.

The Apollo programme to take humans to the Moon got me interested in human spaceflight. In the early 1970s, I met a friend who converted me to amateur astronomy; I still have the telescope I bought in 1977, plus two more recent acquisitions. Then, we founded our own small society, which probably folded in the mid 1980s. While at university, I joined the Volkssternwarte Bonn and for a few years worked on the editorial staff of their publication Telescopium. When university studies turned me into a professional astronomer for a while, amateur astronomy took a back seat from about 1985. In 1999, I resumed the hobby and joined the Astronomical Society of Edinburgh (ASE). I was their President for one year in 2009/2010 and Secretary from 2010 to 2018.

I began university in 1979 and graduated in physics in 1986. From 1986 to 1989 I wrote my PhD thesis at the Radioastronomisches Institut der Universität Bonn (now part of the Argelander Institut für Astronomie) with the title The string and the ring – A galactic-disc loop caused by infalling halo clouds?. I used mainly microwave and millimetre-wave spectroscopy to investigate the local interstellar medium and the gaseous galactic halo. The fresh far-infrared images from the IRAS satellite also played a major part in this work.

In this period I worked as student operator at the Stockert radio telescope. One of the appendices on this site presents some articles about and images of the Stockert telescope and surrounding landscape.

I am not so sure when my interest in computer programming began. Computers age faster than telescopes, so I have gone from using a PET 2001 at school, then a TI-59 programmable pocket calculator to a Commodore C64. As part of the research work at university, I went on to VAX/VMS computers and Fortran 77 as a programming language. I've made the conversion from VMS to Unix twice, first at the University of Bonn in 1989 and again at the Royal Observatory Edinburgh in 1992. I've also taught myself C, C++ and Java and now work in Python.

During the 1990s, my C64 home computer was replaced by a Mac Plus, then a Power Macintosh, which I later converted from MacOS 7 to Linux. At work, we began Linux in the incarnation called Red Hat, but we later converted to the Debian distribution of Linux. The last project before retirement was to convert the site "back" to CentOS.

I've always combined astronomy and computing, mostly by calculating astronomical ephemeris in some form or another. In the last few years, the computer is also taking over on the observational side, as I use a webcam and a dSLR to image objects in the sky.

What is χ and h

double star cluster chi and h Persei
The Perseus Double Cluster. χ Per is left and h Per is right. They are just under 1° apart.

χ Persei and h Persei look like the names of stars, but they are in fact two open star clusters. It was Bayer in 1603 who introduced the naming of stars with a Greek letter and the name of the constellation they belong to (here Perseus, Persei being the genitive). Usually the order of the letters in the Greek alphabet is the same as the magnitude order of the stars within the constellation, so that e.g. α Per is the brightest star in Perseus. All 88 constellations have a three letter abbreviation of their genitive, hence "Per" stands for "Persei" or "of Perseus".

In dark skies the double cluster is visible as a hazy patch of light about midway between the constellations of Perseus and Cassiopeia (the W-shaped constellation north of Perseus). Hipparchus and Ptolemy already mention these objects as a nebular or cloudy spot, at least as far back as 150 BC. In contrast, Charles Messier never included these objects in his catalogue. The modern-day professional names are from Herschel's New General Catalogue - NGC 869 (h Per) and NGC 884 (χ Per). Each cluster appears about 30 arcmin in diameter and contains 300 or 400 stars. The brightest stars are about 7th magnitude and would on their own not be visible to the naked eye. The clusters are about 7000 or 8000 light years away. They are probably not a true pair. Rather, χ Per is thought to be almost 1000 light years further away than h Per. (Burnham 1978, p.1438ff.)


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