Last updated on

You are visitor number


Visual Observing with SCTs

    �If the Lord Almighty had consulted me before embarking on the Creation,
      I would have recommended something simpler.�

Alfonso X of Castile, a medieval patron of astronomy, A.D. 1221-1284
   [the Alfonsine Tables, one of the earliest lists of planetary positions
   (based on Ptolemy�s models of planetary motions) were named after him.]

So now you have a good scope and you�re ready to take it out and see all those wonderful objects you were promised. They really are out there, but it�s a big sky - how do you decide what to look for?  The Milky Way galaxy alone contains 100 trillion stars, and astronomers have detected some 30,000 galaxies - you do the math <grin>. (As an aside, do the math and you�ll see that the idea that we are the only intelligent life form in the universe is statistically absurd; whether they have visited here in UFOs or not is, of course, a different issue...)  Sure, the computers in GoTo scopes make tens of thousands of those objects available at a push of a button, but that isn�t helpful by itself - you can push a lot of buttons before you get to an object visible from your location in the season you�re in. 

This isn�t meant to discourage you, but to motivate you to do some preparatory work before you start seriously using your scope.  I recommend two steps: use a good book to guide you to the great sights available in the night sky each season and/or an annual observer�s guide magazine, and then use your scope�s databases, built into its GoTo computer, to find them:

Learning to See
You need to develop some experience in using your eyes to their best advantage when looking at dim objects at night.  Click on the Learning to See button above, for basic information on learning to observe deep-sky objects with a telescope.

Viewing Conditions
There are a variety of meteorological conditions that can interfere with your ability to see objects with your scope, beyond the obvious problem of cloud cover. Click on the Learning to See button above for more information on how to determine, or to predict, the atmospheric viewing conditions for your location at a particular time..

A planisphere is a drawing of the stars in the sky, on a wheel that can be rotated against a circumference with months of the year around it. A planisphere shows the sky at any date and time during the year, and is used to locate constellations and determine what�s visible at any given time. It is an indispensable observing aid.  There are several planispheres available; many of us prefer The Night Sky by David Chandler.  It is produced in several different northern-hemisphere latitude ranges - if you choose the one for your location it will be somewhat more accurate than a single one created for all of the northern hemisphere. But its best feature is that it shows the southern sky in more detail on the reverse side.  Since many of the best deep-sky objects are well to the south from northern latitudes, more detail there is very helpful.  (There is also a version for southern-hemisphere observers.)  It is available from Scopestuff or

There are a lot of great books available for observing with a telescope, and I highly recommend that you purchase one or more of these observing books. Click on the Books button above for a discussion of good books to help you plan your observing sessions.

Both Astronomy and Sky & Telescope magazines publish an annual �observer�s guide� issue, that describes the night sky, month by month, for an entire year. The issues for year 2004 are entitled Skywatch 2004 from Sky & Telescope magazine, and Explore the Universe 2004 from Astronomy magazine.  They are available in places that have a good magazine selection (Border�s Books is one such place). However, there is more detail within the monthly issues of each of these magazines (especially on the planets), so you should seriously consider a subscription to one of them as an alternative to purchasing their annual observing issues.

Sky Chart Software
There are a number of software applications that will plot a night sky chart for your location (latitude and longitude) and observing time. Most are commercial products that can tend to be expensive (due to their limited audience and consequent limited sales opportunities) but one excellent one is free - Cartes du Ciel (Sky Charts) by Patrick Chevalley - click on the Software button above for more information about when to use sky chart software and CduC.

Sky chart software is helpful when you need a detailed chart for a specific part of the night sky, but it can�t really provide a list of all the objects available for you to observe at any given time, across the night sky visible at any location. So, you will want some observing lists.

Observing Lists
There are a number of lists that compile the �best things you can see with your scope�.  Click on the Lists button for these.

Web Links
Check the Links page on this site for Web sites that will help you select objects to observe.

What kinds of things can I see? (An overview discussion)

Deep-Sky Objects
Major attractions for a scope are stars, star clusters, nebulae, and galaxies, collectively referred to as deep-sky objects (sometimes clusters, nebulae and galaxies are called non-stellar objects). The objects I named are listed in decreasing order of ease of seeing - star clusters are bright collections of stars (usually) in our own Milky Way galaxy; a nebula is a cloud of gas or dust also in our galaxy and often bright enough for an 8� scope; and, galaxies are millions of light-years away and thus usually much less bright.  (There are also clusters of galaxies; a galaxy within a galaxy cluster has a good chance of a near-collision with another galaxy, within its lifetime.)  Another term occasionally used is �Asterism�, which is a distinct, interesting, and easily recognized group of stars that is typically not physically a cluster (i.e. the stars are not near each other and thus gravitationally bound together) - the grouping of stars in an asterism is merely an artifact of our view from Earth towards that direction.

Some of the prettiest objects in the sky are double stars, especially where the two stars are of different color; many stars have really striking colors and glisten like jewels. (Note however that no star emits light in the part of the spectrum we see as green. You may occasionally read that an observer sees a star as green but this is an illusion. Typically this occurs when observing a double star with contrasting colors, one of which is red. Our eyes can be tricked into seeing the other star as green, but there really are no green stars.)

The Planets
You can find the locations of the planets from month to month from the astronomy magazines I mention above (or from sky chart software).  Click on Planets in the navigator at the top of this page for photos of the planets taken by the Hubble Space Telescope, just for fun.

The Sun
See the Solar Observing page for more information on observing the sun.

Keeping an Eye on the Moon
The phase of the moon has a significant impact on your ability to observe deep-sky objects - when the moon is close to full your ability to observe anything but the moon becomes limited. Therefore, when planning an observing session experienced observers remain aware of the moon�s phases as much as weather forecasts. Argun Tekant of Locutus Codeware has written a small shareware ($3.00) application named MoonPhase that displays the phase of the moon in the Windows task bar. It works well and uses almost no system resources; I believe you will find it helpful and you can download it from Robomagic Software.  An older version for Windows 95/98 only, is available here for download:

Also, the US Naval Observatory publishes a Phases of the Moon Calendar which provides the date and time for moon phases for the previous and next decades.  But if you don�t want to use the Internet for this calculation, you can download a free application called Tonite for Windows, which will compute the moon rise and set times for your location, from the Downloads page of the Atlanta Astronomy Club.
   Lunar observing itself is a lot of fun.  In the April, 2004 issue, Sky and Telescope magazine published astronomer Charles Wood�s �Lunar 100 � list, of the 100 most interesting lunar features for observers - it�s worth taking a look at that list.

A High-Tech Alternative
You can also use a computer to aim almost any GoTo scope, with software applications such as Cartes du Ciel (which is free) or �The Sky� by Software Bisque.  These applications show a chart of the night sky in your computer, and will aim the scope at an object you choose with your mouse.  (This generally requires an inexpensive cable connecting the serial port on the computer to the appropriate port on the scope.)  I believe it would be better for you to wait on this technique until you learn more about the night sky and the objects in it, by reading some of the books I mention above and using your scope�s hand controller. Automating your scope with a computer is a good step later, especially when you decide to jump into astrophotography.  But at that point you will have first needed to have gained a good working knowledge of sky objects and where they are.  However, sky chart software has other beneficial uses - see the the Software button above for more information


[Home] [SCT Basics] [Observing] [SCT Tips] [Photo Basics] [Glossaries] [Links] [SITE SEARCH]