User manual ORION TELESCOPES & BINOCULARS 03640

[. . . ] Good collimation is particularly critical for "faster" Newtonians, those with f-ratios of f/6 or lower. Once the collimation is set, it will hold if care is taken in transporting and handling the optical tube. However, any sharp jolts can knock the mirrors out of alignment, as can jostling of the scope in the trunk of a car or temperature changes over a period of time. Fortunately, these telescopes are equipped with adjustment screws that permit easy recollimation. Barrel (fits 1. 25" focusers) Crosshairs (for centering) Using the Collimating Eyepiece Collimation can be performed in daylight, when it is easier to see what you're doing. [. . . ] The Collimating Eyepiece is a combination of a "sight tube" and a "Cheshire eyepiece. " The sight tube's narrow field of view and crosshairs provide a reference for centering the optical elements during the collimation process. A Cheshire eyepiece has a polished flat set in the barrel at a 45° angle, which directs light entering from a cutout in the side of the barrel down into the optical Newtonian Reflectors 1. With the telescope pointed away from the Sun, look into the front of the telescope tube. Check that the secondary (or diagonal) mirror is positioned in the center of the tube; use a ruler if necessary to measure the distance from the center of the secondary mirror holder to the inside of the tube on different sides. Also, check to see that the primary mirror is centered in the optical tube. If the primary is obviously not centered, it will need to be repositioned in its mirror cell. Customer Support (800) 676-1343 E-mail: support@telescope. com Corporate Offices (831) 763-7000 Providing Exceptional Consumer Optical Products Since 1975 P. O. You will see the secondary mirror and mirror holder as well as reflections of the secondary mirror and its holder, the primary mirror, and your eye. It's pretty confusing, so refer to Figure 1 to sort them all out. (This figure shows what you would see if both the primary and secondary mirrors were out of alignment and the secondary mirror were not centered below the focuser tube. ) 3. Now insert the Collimating Eyepiece into the focuser and look into the sight hole. You'll notice that the field of view is narrower than it was when you were looking through the open focuser tube. You'll also notice that instead of seeing a reflection of your eye, you now see a bright annulus in the reflection of the secondary mirror. The annulus is the reflection of the polished 45° flat of the Collimating Eyepiece. Check whether the secondary mirror is centered underneath the focuser. Use the crosshairs at the bottom of the Collimating Eyepiece as a reference. The center of the secondary mirror should lie right at the intersection of the crosshairs. If it doesn't, adjust the position of the mirror holder until it is centered (Figure 2). For "spider-type" holders, this is usually done by turning the threaded rod that the secondary mirror mount is attached to. For single stalktype holders, you may have to bend the stalk to center the mirror. Now you need to adjust the tilt of the secondary mirror so that the entire reflection of the primary mirror is precisely centered in the secondary mirror (and, thus, also on the crosshairs of the Collimating Eyepiece). Use the three collimation screws on the secondary holder to adjust the tilt. The reflection of the primary mirror is centered when there is an even ring of space between it and the outer edge of the secondary mirror (Figure 3). [. . . ] The view down the focuser tube of a Newtonian reflector with eyepiece removed. In this example, the optical system is badly out of collimation. Care and Maintenance Because there are no lenses in the Collimating Eyepiece, care and maintenance is minimal. It is a good idea to remove any obvious dirt on the inside or outside of the eyepiece so that the dirt does not get into the telescope tube during the collimation process. To clean the eyepiece, use a blower bulb or a moist cotton swab to remove dirt from inside the barrel, and simply wipe the outside with a damp cloth. [. . . ]