User manual CELESTRON 80MM Instruction Manual

[. . . ] Model #21072 F80 EQ WA 80mm (3. 1") REFRACTOR TELESCOPE INSTRUCTION MANUAL Figure 1 Finderscope Tube Ring Knurled Screw (opposite of tube ring hinge) Finder Bracket Focusing Set Screw Square Extrusions Mounting Platform Figure 2 5 1. INTRODUCTION Thank you for purchasing this Celestron 80mm Refractor Equatorial Telescope. This telescope is a precision scientific instrument. With it you will enjoy numerous objects in the sky--planets, nebulae, star clusters, galaxies and other astronomical objects. [. . . ] These distances are measured in degrees, minutes and seconds of arc. There are 60 minutes of arc in each degree, and 60 seconds of arc in each arc minute. Declinations north of the celestial equator are "+" and declinations south are "-". The north pole is +90 and the south pole is -90 . The celestial meridians of longitude are called "coordinates of right ascension (R. A. )", and like the Earth's longitude meridians they extend from pole to pole. coordinates, evenly spaced around the 360º equator, one every 15º. coordinates are a measure of time as well as angular distance. We speak of the Earth's major longitude meridians as being separated by one hour of time because the Earth rotates once every 24 hours (one hour = 15°). The same principle applies to celestial longitudes since the celestial sphere appears to rotate once every 24 hours. Right ascension hours are also divided into minutes of arc and seconds of arc, with each hour having 60 minutes of arc and each arc minute being divided into 60 arc seconds. Astronomers prefer the time designation for R. A. coordinates even though the coordinates denote locations on the celestial sphere, because this makes it easier to tell how long it will be before a Figure 4 particular star will cross a particular north-south line in the sky. coordinates are marked off in units of time eastward from an arbitrary point on the celestial equator in the constellation Pisces. coordinate which passes through this point is designated "O hours O minutes O seconds". We call this reference point the vernal equinox where it crosses the celestial equator. All other coordinates are names for the number of hours, minutes and seconds that they lag behind this coordinate after it passes overhead moving westward. Given the celestial coordinate system, it now becomes possible to find celestial objects by translating their celestial coordinates using telescope pointing positions. The declination setting circle is factory set and should not need any adjustment if it reads accurately as noted in 4. B (7). The right ascension setting circle (#5) must be aligned. Choose a bright and easy to find star in a star chart and note the coordinates (right ascension and declination). Find the star and center it in the finderscope and then in the telescope. Now, rotate the right ascension circle to match the coordinates of the star with the indicator mark. The right ascension setting circle does not move as the telescope moves in right ascension and thus it must by aligned each time you want to use it to find a new object. [. . . ] Celestron International (CI) warrants this telescope to be free from defects in materials and workmanship for one year from the date of purchase. CI will repair or replace such product or part thereof which, upon inspection by CI, is found to be defective in materials or workmanship. As a condition to the obligation of CI to repair or replace such product, the product must be returned to CI together with proof-of-purchase satisfactory to CI. The Proper Return Authorization Number must be obtained from CI in advance of return. [. . . ]