User manual SKY-WATCHER DOBSONIAN SYNSCAN

[. . . ] Dust Cap/Mask (Remove before Viewing) I J K EQ6 A. Dust Cap/Mask (Remove before Viewing) 15 14 B. Mounting Plate 13 12 11 10 SLOW GUIDE 1 2 3 4 5 NM L 2 FAST 1 3 9 5 4 7 6 6 7 SET GO 8 E REFLECTOR FG HI DOBSONIAN SYNSCAN J D K L C BA 16 15 E FG 14 13 12 11 10 9 SLOW GUIDE EQ6 1 2 3 4 5 D C H I J K L A 2 FAST 1 3 5 4 7 6 B 6 7 16 15 14 SET GO DOBSONIAN SYNSCAN A. Eyepiece Focus Tube Focus Knob Dust Cap/Mask (Remove before viewing) Finderscope Finderscope Bracket Alignment Screw Tension Adjustment Screw Piggyback Bracket Tube Rings Telescope Main Body Primary Mirror Location A. [. . . ] In addition, the mount swivels North(+) and South() from the Celestial Equator towards the celestial poles. This plus or minus "altitude" from the celestial equator is called Declination (Dec). Fig. i Equatorial Mount (Northern Hemisphere) Zenith Mount aligned on North Celestial Pole Object you are viewing Right Ascension Polaris Declination Latitude Meridian Line W N S Plane of local horizon E Nadir Apparent movement of stars Plane of Celestial Equator 14 Celestial Pole + Pointing to the NCP b. For the following examples, it is assumed that the observing site is in the Northern Hemisphere. In the first case (Fig. i-1b), the optical tube is pointing to the NCP. This is its probable position following the polar-alignment step. Since the telescope is pointing parallel to the polar axis, it still points to the NCP as it is rotated around that axis counter-clockwise, (Fig. i-1a) or clockwise (Fig. i-1c). Pointing toward the western or eastern horizon Now, consider pointing the telescope to the western (Fig. i-2a) or eastern (Fig. i-2b) horizon. If the counterweight is pointing North, the telescope can be swivelled from one horizon to the other around the Dec axis in an arc that passes through the NCP (any Dec arc will pass through the NCP if the mount is polar-aligned). It can be seen then that if the optical tube needs to be pointed at an object north or south of this arc, it has to be also rotated around the R. A axis. Fig. i-1 a. c. Celestial Pole + Fig. i-2 a. b. Telescope pointing East Counterweight pointing North (These diagrams applicable to DOBSONIAN SYNSCAN and EQ6 mounts) Rotation of the R. A. axis Telescope pointing West Counterweight pointing North 15 Telescopes with long focal lengths often have a "blind spot" when pointing near the zenith, because the eyepiece-end of the optical tube bumps into the mount's legs (Fig. i-3a). To adapt for this, the optical tube can be very carefully slipped up inside the tube rings (Fig. i-3b). Using the figures in the previous magnification example, if your 10mm eyepiece has an apparent field of view of 52 degrees, then the true field of view is 0. 65 degrees or 39 arc-minutes. Apparent Field of View True Field of View = Magnification 52° 80X = = 0. 65° To put this in perspective, the moon is about 0. 5° or 30 arc-minutes in diameter, so this combination would be fine for viewing the whole moon with a little room to spare. Remember, too much magnification and too small a field of view can make it very hard to find things. It is usually best to start at a lower magnification with its wider field and then increase the magnification when you have found what you are looking for. First find the moon then look at the shadows in the craters!Calculating the exit pupil The Exit Pupil is the diameter (in mm) of the narrowest point of the cone of light leaving your telescope. Knowing this value for a telescope-eyepiece combination tells you whether your eye is receiving all of the light that your primary lens or mirror is providing. The average person has a fully dilated pupil diameter of about 7mm. This value, varies a bit from person to person, is less until your eyes become fully dark adapted and decreases as you get older. To determine an exit pupil, you divide the diameter of the primary of your telescope (in mm) by the magnification. Diameter of Primary mirror in mm Exit Pupil = Magnification For example, a 200mm f/5 telescope with a 40mm eyepiece produces a magnification of 25x and an exit pupil of 8mm. [. . . ] The convergent spot is called the Focus or Focal Point. Focal Ratio This is found by dividing an optical system's Focal Length by its Aperture. The resulting value is sometimes called the system's "speed". Focuser A device which brings the light rays in a telescope to a precise focus. [. . . ]