Which Small Telescope Should You

The answer to this question involves many variables. Here are a few What is your environment, rural or urban Are you an apartment dweller or do you have a backyard or garden Can you easily travel to a less light-polluted area Are you likely to take the telescope with you when you travel Are you a science educator who wishes to have a versatile telescope for use with students Are you a science educator who occasionally gives public presentations for which a portable telescope could be useful Do...

The Afocal Field of View

The effective focal length of the combination of objective lens, camera lens and eyepiece is given by where Fo is the focal length of the objective, Fc the focal length of the camera lens and Fe the focal length of the eyepiece. For a 400-mm objective combined with a 7.9-mm camera lens and a 25-mm eyepiece, the effective focal length is 126.4 mm. The effect of the eyepiece in this example is to act as a focal Figure 5.2. A digital camera with an afocal adapter on a 25-mm eyepiece. Figure 5.2. A...

Analyzing the Photographs

After you have downloaded them, select the best low power and high magnification photographs. Sharpen them and adjust the brightness and contrast to represent the moon as you see it visually in the telescope. Make a full-page print of each of the best. Use the print showing the entire moon to measure the diameters of a few of the larger craters. Then use those values to calibrate the high magnification prints from which shadow measurements will be made. Here is the procedure To measure the...

Taking the Photographs

In order to easily observe the changing position of Barnard's star, a large print scale and therefore a long focal length is necessary. An 80-mm f 11 refractor or 90-mm Maksutov is recommended for these photographs. Accurate polar alignment of the telescope is imperative. An 80-mm f 5 refractor can be used but it will take twice as long between photographs to detect appreciable motion in the star. Figure 17.1. A finder chart for Barnard's star the arrow indicates the star's position. Figure...

Preparation for Observation

Beginning observers should make a list of a few easy-to-find long period variable stars (see Table 12.1) that will be approaching maximum brightness during their observation. For 80-mm refractors, the stars should have maxima brighter than eighth magnitude. When these stars approach maximum brightness their reddish color becomes obvious and they usually stand out among other stars in the field. Lists of variable star maxima for each month are published in Sky and Telescope, Astronomy Now and...

Measuring Position Angle

Convert the binary star image to a black-and-white negative and do the same for the star trail image taken with the drive off. Then open the binary star image and drag the star trail image to overlay it. Transparent fade the star trail so that it and the binary are clearly visible together on the screen. Then use the following procedure 1. Drag the star trail so the primary of the binary is centered in it as in Figure 10.6. The star trail defines the east-west direction for determining the...

Software

Earth Equator

Although Guide 8.0 doesn't come with some of the bells and whistles and beautiful pictures of more expensive software packages, it is the best and least expensive software available for use with this book. It provides the ability to construct star charts with labeled magnitudes to the limit of any telescope and for any field of view. With it you can also label and identify variable stars and asteroids and obtain all the parameters necessary for observation of the Sun, Moon and Jovian...