Leos Ondra Home Page
Starry night

I must begin by feeling love; and I must first observe a wholeness.
After that I may proceed to study the components and their groupings.
But I shall not trouble to investigate these raw materials unless they
are dominated by something on which my heart is set.

Antoine de Saint-Exupéry, Citadelle
Translated by Stuart Gilbert

Welcome to the home page of a Czech amateur astronomer interested in all aspects of stellar astrophysics (history, modern observations, current concepts as well as education). I prepare a handbook on the most interesting objects in the sky.

My pages are optimized for PC (Windows 95) with SVGA monitor (1024x768 pixels, 16-bit color) and Internet Explorer 4.0+, but should degrade gracefully in other browsers. For your convenience, I give content length along links to the other pages on this site. So Weighing a star (20/7) page has 20k in total, but just 7k if you disable autoloading images. The small blue arrow () labels pages which include a backward link to my home page.

Mizar on the Rhone Mizar, Alcor & Sidus Ludoviciana (195/46)

Everything you wanted to know (or believed you knew) about the most well-known double star and two stars nearby, but were affraid to ask about.

Vincent van Gogh: Starry Night on the Rhône (1888), detail.

Jupiter in pieces Put Jupiter together (365 IE / 489 Netscape / 0)

I am not much into planets, comets and other solar system stuff, but have chosen cool images of the royal planet (taken from Solar System Simulator) to introduce my new webtoy, JavaScript. With this programming language one can put content of pages into different layers, move them relatively to each other, hide them, find position of mouse's cursor, get current time and much more. Its potential for creating really interactive and dynamic astronomical pages is enormous. Requires Internet Explorer 4+ or Netscape Navigator 4+. The Netscape version is somewhat larger but plays sound (when you put the puzzle together).

Lensed Albert Light bent by gravity (119/21)

One's work and hobby can have unexpected points of contact. While my heart is definitely set on stars, at present I earn my living in desktop publishing. Quite recently I realized that Adobe Photoshop, a software I routinely use to edit scanned images, lets users create their own filters, including a realistic gravitational lens simulator.

Albert's name is being distorted (without his kind permission) by Gravitational Lenser 1.2, a new plug-in filter for Adobe Photoshop 3.0+ and many other graphical programs.

Pleiades nebulae coctail Mix your own reflection nebula (18/4)

Enjoy a beautiful experiment described in The Feynman Lectures of Physics and learn more about where the blue color of dust nebulae comes from. You need just a baker (or an ordinary glass) and two common chemical substances, sodium thiosulfate or hypo, used in photography to fix developed films, and diluted sulfur acid to prepare this cool drink for your next star party.

Astronomy Deep Sky New variable star in the Dumbbell nebula (88/12)

To tell the truth, it isn't a new discovery, since I have found it already several years ago. But Goldilocks' variable, though apparent on hundreds of published photographs of M 27 and conspicuous (due to its red color) on amateur CCD images of the planetary, still waits for a good long-term photometry to be officially accepted and named.

Believe it or not, Goldilocks' variable was discovered by comparing these covers of Astronomy and Deep Sky. Reproduced by permission. Copyright © 1990, Kalmbach Publishing Company.

Portrait of W. Tempel A man who discovered the Pleiades nebulae (62/13)

You may or may not know it was the German lithographer Wilhelm Tempel (1821–1889). Living and observing in Denmark, Italy and France, he discovered not only the most well-known reflection nebula (and some 150 other objects of the original NGC), but also dozens of asteroids and comets, including 55P/Tempel-Tuttle, the parent body of the Leonid meteor shower.

Wilhelm Tempel in his old age. Woodcut by Albert Lang, based on a lost oil painting. Reproduced from #70 of Vorträge und Schriften, Archenhold-Sternwarte Berlin-Treptow.

Göttingen observatory The first HR diagram to be published (64/21)

Think it was prepared by Ejnar Hertzsprung or Henry Norris Russell? Then visit my page that tells the true story. For those who like authentic sources, a facsimile of the historic article from the Astronomische Nachrichten is available (300 dpi scan converted to PostScript) along with its translation into English kindly prepared by Jan Hollan (Nicholas Copernicus Observatory and Planetarium Brno).

Modern view of the University Observatory Göttingen where that happened. Courtesy Dirk Grupe.

V42 in Messier 5 Messier 5 and its variables (46/23)

Article on my favorite globular cluster (much more interesting than famous M13 in Hercules). Originally written for Deep Sky Journal several years ago and later published in Monthly Notes of the Astronomical Society of Southern Africa (MNASSA), this piece is now extended, updated and first of all available online thanks to Hartmut Frommert, the webmaster of the SEDS Messier Pages.

Did you find the variable V 42 among the cluster stars?

Five-solar-masses story Stellar evolution on PC (40/4)

One of the handbook byproducts is StarClock 2.0, a simple free program for PC/DOS machines with VGA graphics that animates stellar evolution in the Hertzsprung-Russell diagram. Based on a grid of models computed recently at Geneva Observatory. Look for the best site to download it.

Composite of two StarClock snapshots - the evolutionary track of the 5 solar masses star (red, blue and green reflect different phases) is superposed on the diagram of central temperature changes.

Libra Weighing a star (20/7)

Use just a ruler, a common calculator and two enclosed diagrams (available in PostScript) to find mass of Capella, the brightest star of Auriga and the textbook double-lined binary. The laboratory exercise based on spectroscopical data published by Barlow, Fekel and Scarfe ( PASP 105, 476, 1993), and observations with the Mark III interferometer (Hummel et al., Astron. J. 107, 1859, 1994 ).

Constellation Libra in Johann Hevelius's atlas Firnamentum Sobiescianum sive Uranographia (1690).

Animated graphics by GIF Construction Set

Leos Ondra
May 1, 2000
Na vrcholu