On-Line Links

Help for Beginners

The Astronomy Connection has a Beginners section at http://www.observers.org/beginner/. It's organized as a list of articles containing information on how to select a telescope, how to interpret all those telescope terms, how and what to look for in the night sky, and much more. The general TAC web site at http://www.observers.org/ has a lot of stuff too.

Astrometry and Photometry

The Hipparcos Space Astrometry Mission at http://astro.estec.esa.nl/Hipparcos/. Chock full of interesting stories and data. You can find out more than you wanted to know about the 150 closest, brightest, or fastest-moving stars.

The Hipparcos and Tycho-1 Databases at ftp://cdsarc.u-strasbg.fr/pub/cats/I/239/. These catalogs are derived from observations made by the Hipparcos (High-Precision Parallax Collecting Satellite) orbiter during the late 1980s and early 1990s. The Hipparcos catalog contains high-precision astrometric and photometric data on about 120,000 of the brightest stars (to about magnitude 8.5 or so); the Tycho-1 database contains somewhat lower-precision data (and no parallax data) on about a million stars (including the Hipparcos stars, which are indexed here). However, as you can probably tell from the name, there's an updated version of the Tycho catalog…

The Tycho-2 Database at http://www.astro.ku.dk/~erik/Tycho-2/. This is an updated reduction of the Hipparcos observations, resulting in a catalog of over two million stars, with somewhat greater precision than in the original Tycho-1. This site contains some user information in addition to links to the databases.

The Guide Star Catalog at ftp://adc.gsfc.nasa.gov/pub/adc/superseded/1/1220/. This is Version 1.1 of the Hubble Guide Star Catalog, which contains on the order of 15 million stars. It is often used by commercial star atlas programs, although it is only designed as a reference for guiding the Hubble Space Telescope. It is adequate astrometrically, but not photometrically; some magnitudes for the dimmer stars are off by as much as 1 or 2 magnitudes! Use at your own risk. (Note: Version 2.0 of GSC is supposed to be much more accurate photometrically, but it is not yet available to the general public.)

Want to look up star and celestial object catalogues? You can find all you want and more at the VizieR Service at http://adc.gsfc.nasa.gov/viz-bin/VizieR.

Celestial Mechanics

Keith Burnett's Astronomical Calculations web site at http://www.btinternet.com/~kburnett/kepler/ gives algorithms and BASIC code for various celestial mechanics tasks, such as computing the right ascension and declination of any planet for a given time, the rise and set times for the Sun and Moon, the positions of the Galilean satellites, and so on.

Somewhat more involved, but still quite readable, is Paul Schlyter's How to Compute Planetary Positions, at http://home.tiscali.se/~pausch/comp/ppcomp.html. It covers a bit more than Keith's site (in fact, Keith based much, though not all, of his material on Paul's site), but no code is included.


The Sky and Telescope web site at http://www.skypub.com/ does much more than just promote its flagship publication. There are lots of free on-line resources, including product reviews, BASIC programs, Javascript utilities, and a quick overview of the week and month in celestial events. My only gripe is that it used to include links to selected articles from recent issues, but that disappeared a couple of years ago.

Astronomy magazine has its own web site at http://www.astronomy.com/. The magazine and web site are slightly more geared toward the armchair astronomer than Sky and Telescope is, but it's still basically for the beginning hobbyist. Of course, that means that there will often be significant overlap between the two.


The Cincinnati Observatory Center at http://www.cincinnatiobservatory.org/. According to them, it's the oldest observatory in the United States.

On-Line Club Newsletters

The San Jose Astronomy Association publishes its monthly newsletter, the Ephemeris, at http://ephemeris.sjaa.net/. It normally has one of my favorite features, The Celestial Tourist Speaks, piloted by well-known sci.astro.amateur luminary, Jay Reynolds Freeman. As I write this, he's taken a couple of months off, but you can find his write-up of hunting for Herschel 400 objects with his 55 mm fluorite in the May 1999 issue of Sky and Telescope.

Interactive Astronomy

Kerry Shetline's Sky View Cafe can be found, naturally enough, at http://www.skyviewcafe.com/. It's a computerized planisphere, 3-D orrery, ephemeris generator, all in one, and it's free! It runs on Java, so you need to enable that before starting it, but it's quite well done.

The Castle Point Astronomy Club has an on-line Jupiter and Saturn satellite Java application at http://www.cpac.org.uk/, written by Brendan Murphy. Unix users using Netscape 4.x may have problems with it, but it works fine with Mozilla.

The Case Western Reserve University Nassau Station has a robotic telescope that the public can submit requests to. You can find it at http://astrwww.astr.cwru.edu/nassau/useroptions.html. You have to register first before you use it. (I haven't yet checked this service out.)

Equipment Reviews

Allister St Claire runs the Cloudy Nights review site at http://www.cloudynights.com/. Unlike other review sites, Allister runs his as a clearinghouse for reviews submitted by other amateurs. You can even find my review of the C5+ there.

Ed Ting's Telescope Review Site at http://www.scopereviews.com/. I've seen a few equipment review pages on the web, and given the generally scientific nature of the pursuit, you'd be surprised at how non-techy they are. This one is no exception. It's almost entirely done in fixed-width text—just a solid hunk of reviews, from the basest accessory to the most rarefied apochromat reflector.

Todd Gross's Telescope Minireviews at http://www.weatherman.com/scope.htm. In the spirit of Ed Ting's site, here's a fast and furious rundown of several dozen scopes. One of the advantages is that all the reviews are on one page, making for convenient printing no matter what scopes you're interested in. One of the disadvantages is that all the reviews are on one page, making that print-out a bit on the long side.

Observing Programs

The Association of Lunar and Planetary Observers (ALPO) at http://www.lpl.arizona.edu/alpo/. Some people feel that because the Voyager spacecraft have visited most of the outer solar system, there isn't any point in planetary observing. This site belies that claim. Here, you can find out what we still don't know about our solar system companions.

On-Line Observing Catalogs

The Constellations at http://www.dibonsmith.com/. Soon to be a best-selling (well, not really) book near you, this web site contains lots of information about each constellation, including maps, mythology, and a list of attractions in the area.

The SEDS Messier Database at http://www.seds.org/messier/. Each Messier object gets a page (and then some) in this on-line catalog, which gives positions, notes, and historical background for each of the 110 objects (yes, they even give a possible identify for the spurious M102!).

The Interactive NGC Database at http://www.seds.org/~spider/ngc/ngc.html. By the same people who brought you the SEDS Messier Database, this catalog contains information on all 7000-odd NGC (New General Catalogue) objects, and the IC (Index Catalogue) objects too. As an added bonus, it also provides links to plenty of other NGC-related sites, including…

The NGC/IC Project at http://www.ngcic.com/. A bit more sophisticated but less personal site than the preceding, the NGC/IC Project is nevertheless an indispensable reference source for your NGC/IC observing needs.

The NGC 2000.0 at ftp://adc.gsfc.nasa.gov/pub/adc/archives/catalogs/7/7118/. This is a revision of the 1888 New General Catalogue, updated for 2000.0 coordinates and with some additional corrections. Still not a great non-stellar object database, but an improvement on the original.

Copyright (c) 1998, 1999, 2000, 2001 Brian Tung