User manual BUSHNELL 78-4502

[. . . ] Most all of the visible stars in the sky have an address in a book called a Star Atlas (roadmap of stars) that is expressed in terms of its Right Ascension and then its Declination. It will look something like this: 23hr 42min 03sec, 78. 3deg N When using an equatorial mount, you can move your telescope to these settings and find the star that corresponds to that address. It is generally around 25 to 45 degrees up from the horizon in North America. The second star you will need to be able to identify in the sky is a little bit harder. [. . . ] They connect to the telescope mount only one way so I won't cover their attachment procedure. 898 Declination Fine Adjustment 23 22 21 20 19 18 Right Ascension Fine Adjustment If your equatorial mount is set up correctly, you can move just the Right Ascension Fine Adjustment Knob ONLY to follow any star across the sky! 190-200-210-220-230- 4 Telescope Axis's When using your fine adjustment cables, you'll be moving these two axis's. This instruction manual refers to 3 axis's in which the telescope will turn. This diagram illustrates these axis's where the telescope can move. 5 The Barlow Lens and Eyepieces Here are a few things you'll need to know and know how to do before getting started. The following explains what the pieces are and in what order they should go into the telescope. 3X This the Barlow lens. Generally it will say something like 2X or 3X on the side of it, meaning that it multiplies the magnification by that much. The eyepiece along with the focal length of the telescope determines the magnification. Most the time they are 20mm and 4mm. The eyepieces can fit directly into the focusing tube as well as into the Barlow Lens. Regardless, you must have an eyepiece in to see anything through the telescope. 6 Figuring the Magnification To figure the magnification you must first know the focal length of your telescope. Focal Length in mm Magnification = Eyepiece in mm X Barlow Lens (ie 2X or 3X) Eyepiece Eyepiece 3X Barlow Lens Focusing Tube on the telescope. Assuming the eyepiece is 20mm and the focal length is 900mm, here are the magnifications of each set up. 900÷20 = 45 45 Power 135 Power (900÷20)X3=135) Focusing Tube on the telescope. 7 Aligning the Finderscope You will need to line up the Finderscope with your telescope. A finderscope acts kind of like a riflescope in that it helps you aim. To get started you should always use the highest number eyepiece (lowest power) without the Barlow lens. If you use too powerful of an eyepiece (low number) then it may be very hard to find an object or it will be too dark to see anything as higher powers cause light loss. Below is an example of why aligning the finderscope is important. Without an aligned finderscope you might think you are aiming directly at a star or planet but you could actually be way off! But with an aligned finderscope, you can find objects in the sky a lot faster and easier! 8 To get started, put the 20mm eyepiece in the focusing tube without the Barlow lens. Since the finderscope has a slight magnification to it, put it on so that when viewing through it you see the magnification. If you put it in backwards, everything will appear small and far away. (open end of the telescope) Start with a large object about 200 yards away. You do not have to be absolutely accurate with the distance as it will not help you or hinder you if you are not exact. In this example I'll use a house as the object Note: It is recommended for best viewing to not look through a window when aligning the finderscope or even when viewing things through the telescope. If fogging occurs let the telescope sit outside for approximately 30 minutes to allow it to clear up. 9 Next, find the object in the telescope and center it in the viewing area. Finally, get the object centered in the finderscope. If the finderscope is not the crosshair type but instead the dot kind, get the dot directly in the middle of the object then tighten the finderscope best as possible. Note: The finderscope just like the telescope turns the image upside down also. Know that finderscopes sometimes have a red dot in them as opposed to crosshairs. Sometimes they adjust with thumbscrews on the outside of the mounting bracket and sometimes they have actual fine adjustment knobs on the finderscope itself. [. . . ] See the Star Atlas and it will show you some fairly easy stars that should be bright in the sky during different times of the year. When you have identified your star, move the TELESCOPE TUBE along the Declination Axis until the pointer is on the declination address of the star according to the Star Atlas. 16 Even though it is not shown, the Right Ascension Setting has numbers on it. 190-200-210-220-230- Finally, move the tube of the telescope along the Right Ascension Axis until the star you have chosen as your second star is visible in the telescope. Then with your fingers, move the dial on the Right Ascension Setting to match what the Star Atlas's Right Ascension Settings are for that star. Once again, there is a pointer/arrow that you'll align the Right Ascension number up with. [. . . ]