University Lowbrow Astronomers

University Lowbrow Astronomers Telescope Observer’s Guide

by Dave Snyder
Revised: March, 2002

This page contains suggested projects for amateur astronomers using a with a new (or not so new) telescope. We cannot cover every option here, however we will present a few suggestions.

Finding Your Way Around

To be able to find your way around, you need to be familiar with how stars and other astronomical objects are given names and how to read a star chart. If you haven’t done so already, see “How Astronomical Objects Are Named.”

While the NGC and IC lists contain many of the objects an amateur astronomer would be interested in, they have some gaps, some of those gaps are indicated in the following sections.

The position of astronomical objects is specified by using two coordinates: The right ascension (RA) and the declination (dec). The RA and declination of solar system objects change over time, but the RA and declination of stars (other than the sun) and of deep space objects do not change (well they do change, but so slowly it doesn’t matter in most cases).

There are three basic methods of locating objects with a telescope.

Setting circles can be temperamental, they are not always able to accurately determine the telescope’s position, so some manual repositioning may be needed. Knowing how to position the telescope is important. Also setting circles can not compensate for clouds or the fact that many objects are visible at certain times of the year and not visible at other times of the year.

If you are using setting circles (either mechanical or digital), you may be interested in our database of approximately 1900 objects that can be seen through small telescopes. This database gives RA and declination for each object along with other information. Go here for more information.

For a list of objects organized by constellation, we have provided the following articles (more constellations will be added later).

Also for a few suggested objects within Andromeda, Aquarius, Cassiopeia, Pegasus and Perseus, see Mark Deprest. “At the Open House & What to Show the Public.” October, 1997.

The Sun

Before using a telescope to observe the sun, be sure to use proper filters. Failure to do so can result in permanent eye damage, and may ruin your telescope.

There are two types of filters you can use to observe the sun, solar filters and hydrogen alpha filters. Solar filters are less expensive and easier to use, however make sure you purchase a filter from a reputable manufacturer. Using a solar filter will allow you to observe sunspots. Sunspots are more common at the peak of the solar cycle (which occurs every 11 years). If you invest in a hydrogen alpha filter, you can observe prominences and other solar activity which cannot be seen with a normal solar filter.

For the ambitious amateur astronomer, it is possible to build a specialized telescope that is optimized for solar observing. One design is known as a “Coronagraph” and another is known as a “Spectroheliograph.” Both devices work by passing a narrow band of light and are alternatives to purchasing a separate hydrogen alpha filter. Either type of telescope will allow you to see prominences, however most people consider the Coronagraph to be a better choice.

For more information see SpaceWeather.com: Science News and Information about the Sun-Earth environment.

The Moon

Almost any telescope will allow you to view craters on the Moon. With a little effort you can also see mountain ranges on the surface.

One of the biggest problems with observing the moon is the image can be bright (bright enough to be painful), this is particularly true of large aperture telescopes. If this is a problem, there are two solutions, one is to purchase a “Lunar Filter,” this reduces the amount of light entering the telescope. Another solution is a simple device called an “Aperture Stop.” Usually made of cardboard that blocks about 2/3 of the light entering a telescope and has the added bonus of stopping light from going through the supports on your secondary mirror (if you are using a reflecting telescope). If you use a refractor telescope, you may wish to use a yellow filter instead of a simple Lunar filter. Otherwise you may will discover purple fringes on your images caused by chromatic aberration.

Full Moon is actually the worst time to observe the moon. The best approach is to observe the moon at various times during the Lunar cycle, if you do this you will note the changing light angle will allow details to be seen on some parts of the cycle, but not others. A good exercise is to try to observe as many days of a complete cycle as you can, sketching your observations as you go (you may need to do this over several cycles, particularly if you are clouded out frequently).

For more information see The Association of Lunar and Planetary Observers.

The Planets and Asteroids

In general, observing planets is easiest when the planet is high above the horizon (when it is low in the sky a planet’s image will be subjected to more atmospheric effects and possibly more light pollution).

Of the planets, Jupiter and Saturn are the easiest to observe. Saturn’s rings can be seen by all but the smallest telescopes (except when the rings are edge on). It is also possible to see bands within Jupiter’s atmosphere. A challenge is to see Cassini’s Division (a gap in the rings which is not visible in small telescopes, but is in medium or large telescopes). Both planets have moons that are easily seen in amateur telescopes.

Observing Mars is a challenge. The only time it is worthwhile to look at Mars through a telescope, is near opposition (which occurs approximately every two years). Under good conditions, you can see light and dark areas, polar caps, and possibly even clouds. Some clouds are yellow in color and can develop into dust storms, when a major dust storm hits it can be impossible to observe any surface detail until the storm subsides.

It is easier to observe Mars if you use colored filters. If you wish to observe surface details, a dark yellow, red and/or orange filter is helpful. Violet and blue filters are helpful if you want to observe clouds and other atmospheric phenomena (but not yellow clouds or dust storms). Green filters are helpful for observing the polar caps and other white areas, yellow clouds and dust storms. If you have made either Jupiter or Saturn observations, you may want eyepieces that provide slightly more magnification than the eyepieces you used for Jupiter and Saturn.

Mars has two moons, Deimos and Phobos, however they are very difficult to see in an amateur telescope. Observations of the Martian moons should only be attempted near Mars opposition.

Venus shows no surface detail under a telescope, however it is possible to see the phase change over the course of a Venus year.

Mercury is a difficult telescope object. It is never far from the sun, which means the only time it is high above the horizon is during daylight. If you plan ahead, you can observe Mercury near the time of greatest elongation, which is the easiest time to observe the planet. Mercury has craters, however they are not easy to observe from ground based telescopes.

Uranus and Neptune are not difficult to observe, you just need to know where to point your telescope.

Pluto and the various Asteroids are not difficult to observe either, however they are difficult to distinguish from nearby stars. The only reliable way to be sure an object is Pluto or an asteroid and not a star is to watch it every night for a few nights, if it moves then it is not a star.

For more information see The Association of Lunar and Planetary Observers.

Extra-Solar Planets

Amateurs can help verify data concerning possible extra-solar planets, for more information, see the Amateur Radial Velocity Studies site.

Meteors

It is possible to observe meteors with a telescope. Telescope observers will occasionally see meteors, and this can happen at any time.

You can set up a telescope with the specific goal of looking for meteors, however this can be a tedious and disappointing process. You may see dim meteors that are not visible with the naked eye, but your field of view is smaller. In most cases you need to observe for long periods to see any meteors. In any event, naked eye observations are easier and more likely to be successful. Both naked eye and telescope observing are easier during a meteor shower.

Comets

Bright comets are easy to see with the naked eye; however a telescope shows details of the comet nucleus that are not visible to the eye. Dimmer comets can only be seen with a telescope. With persistence, it is possible to discover a comet that no one else has seen, however most people do not have the level of determination this requires.

To determine the magnitude of a comet, you can defocus your telescope so nearby stars appear as big as the comet; You then find a star that has the same brightness as the comet, the magnitude of the star is the magnitude of the comet.

For a list of comets that are currently visible, see IAU: Astronomical Headlines.

Variable Stars

Given enough time (say several billion years) all stars change. For some stars, changes can be observed over the course of a few hours to a few months, even by amateur astronomers. The American Association of Variable Star Observers (AAVSO) is an organization that is devoted to assisting amateur astronomers who wish to observe these changes. The AAVSO has several observing programs which include the following:

Any amateur astronomer 16 years of age or older can participate in an observing program and may possibly contribute to basic research. See The American Association of Variable Star Observers site for more information.

Double and Multiple Stars

Two stars that are located close to each other in the sky are called double stars. Double stars are common as are multiple stars (where three or more stars are located close to each other in the sky. When observing a double or multiple star, if you can distinguish the components, then you have “split” the star. Several factors affect whether you can split a double (or multiple) star:

In a multiple star system, the brightest star is called the primary. If you measure the direction from the primary to any other star in the system, this direction is called the position angle (position angles vary from zero degrees to 359 degrees).

If the two members of a double star orbit each other, then the system is called a binary star. If they do not orbit each other, then the system is called an optical double. Binary stars and optical double stars are not easy to distinguish, but can be done. When binary stars are observed over a period of years, the position angle will change in a pattern that repeats in a cyclical pattern (going from zero degrees to 90 degrees to 180, to 270 and back to zero). Also spectroscopic analysis, particularly in repeated over a period of years, can show changes in velocity that indicate a binary star.

Star Clusters

The main types of star clusters are: open clusters, globular clusters, stellar associations and stellar streams. The NGC and IC catalogs do not include all open clusters, this is particularly true of open clusters that occupy a wide field. They do not include any associations or streams. A number of catalogs cover open clusters, associations and streams. For example the Collinder catalog lists many open clusters and associations.

Nebulae

There are four types of nebulae. Emission nebulae, planetary nebulae, reflection nebulae and dark nebulae.

When observing emission nebulae and planetary nebulae it often helps to use a device known as a nebula filter (particularly when observing faint nebulae in light polluted skies). The article Doug Scobel. “Get a 60 Inch Telescope for $100.00!” December, 1995. discusses nebula filters.

The NGC and IC catalogs do not include any dark nebulae, the best list of dark nebulae is “Barnard’s Catalog of 349 Dark Objects in the Sky.” That list plus a few others should be consulted if you are interested in dark nebulae.

Now that nebula filters are more common, amateur astronomers searching for planetary nebulae should not limit themselves to the NGC and IC catalogs. A good catalog to include is Perek and Kohoutek, Catalogue of Galactic Planetary Nebulae which includes objects, many of which are not in the NGC or IC catalogs, between magnitude 13 and 16.

Galaxies

Many galaxies are visible with amateur telescopes. While the magnitude of the galaxy is an issue, there are different methods of measuring magnitude. In general if a galaxy has low surface brightness, then it will be more difficult to observe than a galaxy with a high surface brightness. In general edge-on galaxies are easier to see than face-on galaxies with the same magnitude.

Radio Astronomy

Some amateurs have built and operated small radio telescopes. These radio telescopes can fit in a back yard and can be used to observe the universe in radio waves. For more information see Radio Astronomy Links.

Opportunities For Research

Amateur astronomers can contribute to research. Professional astronomers can be engaged in any of a number of different research projects, however in many cases professionals are limited in the amount of data they can collect due to limited observing time on big telescopes. For this reason, there are numerous opportunities for amateurs to contribute to astronomical research. See the following resources:

Telescope Observing Hints

See the Reflections of the University Lowbrow Astronomers (the club newsletter) for suggestions on telescope hardware as well as how and what to observe.

Books

There are several books that you may find helpful. For example:

Levy, David H. 1991. The Sky: A User’s Guide. Cambridge: Cambridge University Press.

David Levy is an amateur astronomer who (among other things) discovered a series of comets. This book provides people new to astronomy numerous insights into amateur astronomy (however more experienced amateurs will gain something from the book as well). It contains a list of resources for those who want to learn more.

For suggestions on star catalogs, star maps and the like, see University Lowbrow Astronomers Intermediate Book List.

Observational Mishaps

If use a telescope to do research, you may end up with blurry photographs (or other problems) that make it impossible to gain any results from that night’s observations. Some cases are easy to correct, other cases may not be.

There is a gallery of common observational mishaps along with suggested solutions. See the Observational Mishaps Web Site.

Links

Copyright Info

Copyright © 2014, the University Lowbrow Astronomers. (The University Lowbrow Astronomers are an amateur astronomy club based in Ann Arbor, Michigan).
This page revised Sunday, March 9, 2014 4:30 PM.
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