User manual CELESTRON FIRSTSCOPE 90EQ Instruction Manual

[. . . ] FIRSTSCOPE 70 & 90 EQ TELESCOPE INSTRUCTION MANUAL Firstscope 70 EQ - #21076 Firstscope 90 EQ - #21085 17 1 2 16 15 3 14 4 5 13 6 12 7 11 8 10 9 Firstscope Refractor 70mm EQ shown 2 IDENTIFYING PARTS OF YOUR FIRSTSCOPE 1. Objective Lens INTRODUCTION Thank you for purchasing this Celestron Refractor Telescope. With it you will enjoy numerous objects in the sky--planets, nebulae, star clusters, galaxies and other astronomical objects. The equatorial mount contains setting circles and slow motion cables to make it easier to locate and track astronomical objects. [. . . ] First move the telescope in declination to the correct declination coordinate. Then move the telescope in right ascension until the indicator points to the correct coordinate. After moving the telescope to the correct celestial coordinates, look through the lower power eyepiece to see if you have located the object you wish to view. If the object is not visible in the eyepiece, gradually pan the telescope, using the right ascension and declination cables, until the object is visible. Always start by using your lowest power eyepiece (20mm) then switching to higher power once you have found the desired object. 2. 6. 11 MAGNIFICATION (POWER) The magnification (or power) of a telescope is variable depending upon the focal length of the eyepiece being used along with the focal length of the telescope. In equation format, the formula looks like this: Magnification = FL(telescope) FL( eyepiece) To determine the magnification using the standard 20mm eyepiece, simply divide the focal length of your telescope by the focal length of the eyepiece (20mm). For example, dividing the focal length of the Firstscope 90 (1000mm) by 20mm yields a magnification of 50 power. These limits are determined by the laws of optics and the nature of the human eye. The maximum usable power is equal to 60 times the aperture of the telescope (in inches). For example, using the 70mm model (2. 8") then your maximum useful power is 168x (2. 8" x 60). You can create power higher than this limit but the images will be dark and blurred with poor contrast. The maximum power is used only under ideal conditions which are not common. Higher powers are used mainly for lunar and planetary observing under ideal seeing conditions. Determining Field of View Determining the field of view is important if you want to get an idea of the angular size of the object you are observing. To calculate the actual field of view, divide the apparent field of the eyepiece (supplied by the eyepiece manufacturer) by the magnification. In equation format, the formula looks like this: Apparent Field of Eyepiece True Field = Magnification As you can see, before determining the field of view, you must calculate the magnification. Using the example in the previous section, we can determine the field of view using the same 20mm eyepiece. To convert degrees to feet at 1, 000 yards, which is more useful for terrestrial observing, simply multiply by 52. 5. Continuing with our example, multiply the angular field . 9° by 52. 5. This produces a linear field width of over 47 feet at a distance of one thousand yards. The apparent field of each eyepiece that Celestron manufactures is found in the Celestron Accessory Catalog (#93685). 12 CELESTIAL OBSERVING Now that your telescope is set up, you're ready to use it for observing. This section covers visual observing for both solar system and deep-sky objects. Observing the Moon In the night sky, the moon is a prime target for your first look because it is extremely bright and easy to find. [. . . ] As a condition to the obligation of Celestron to repair or replace such product, the product must be returned to Celestron together with proof-of-purchase satisfactory to Celestron. The Proper Return Authorization Number must be obtained from Celestron in advance of return. Call Celestron at (310) 3289560 to receive the number to be displayed on the outside of your shipping container. All returns must be accompanied by a written statement setting forth the name, address, and daytime telephone number of the owner, together with a brief description of any claimed defects. [. . . ]