INSTRUMENTS

ASTRAL TELESCOPE

BASIC NOTES

page 15

SMALL MOTORS
As we have previously seen, once the correct equatorial position has been established, it is possible to follow the stars by moving the telescope along one axis (polar axis). This can be done either manually or by means of a small motor mounted on the instrument. These accessories can be divided into two categories: chrono-guide or stepper-motor. The first of these is a small motor feed by the domestic electricity supply, it follows the motion of the stars hut permits no variation in speed . It is a simple but reliable device. (Remember that when our telescope doesn't follow the stars perfectly it is more often than not due to an in- correct equatorial positioning. The greater the error, the more inaccurate it will be) In the stepper-motor type (with a push-button), we have the chance to alter the movement of the telescope during observation reducing or increasing speed. On professional telescopes, mechanisms exist for changing the declination of the telescope, which is useful for making small corrections.

PRACTICAL SUGGESTIONS
At the beginning, the sky should be observed without the use of a telescope. In this way, the astronomer will learn to recognize visible constellations by using a stellar atlas. It will not be a waste of time. The advantages of doing this will only become apparent when the time comes to aim the telescope. Observation with a telescope must be prepared in advance. If the telescope as to be taken from a heated environment to a colder one, particularly during the cold season, the drop in temperature will also require adjustment on the part of the eyes. It is necessary to wit for about half an hour. In the meantime, you can proceed with the positioning of the telescope and the preparation of accessories. Our eyes too, need at least fifteen minutes to adjust to dim light. To write or to consult a map, a red light should be used as this has little effect on the desensitizing of the eyes.

THINGS TO AVOID
1) Observation through a window
2) Observation of stars near the horizon
3) Observation of stars requiring a line of aim passing near warm rooftops.
In all three of these cases, images will be distorted. This is due to air currents in the first case, notable atmospheric turbulence in the second and gusts of hot, uprising air in the third case.
- Observation during the time of a full moon is also to be avoided, as its brilliance, stretching as far as the horizon, hides the view of many stars and weaker objects.
- Avoid touching the optics with your hands Shield the ocular from external light sources to avoid reflections
- Do not try for magnification beyond the scope of your instrument.