Celestron StarSense Explorer 150mm Smartphone App-Enabled Tabletop Dobsonian Tel - Page 14
Collimating The Optics
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COLLIMATING THE OPTICS Collimation is the process of aligning the telescope's optics. Dobsonians use the Newtonian reflector optical design, which consists of a parabolic primary mirror and a flat secondary mirror. To ensure best performance, you should periodically check the alignment of the optics. To help with this, we have included a special "collimation cap" you can use. In addition, the primary mirror is center-marked with an adhesive ring label to aid in collimation. To check alignment of the mirrors, first remove any eyepieces. Make sure the 2"-to-1.25" adapter is installed in the focuser. Then, place the collimation cap in the focuser (Figure 15). It is easiest to collimate a telescope during the day with the telescope pointed toward a blank wall. This will provide a high-contrast view, making it easier to determine which adjustments should be made. Use the supplied hex key(s) to make adjustments. The 8" SSE Dob comes with 2mm and 2.5mm hex keys. The 10" SSE Dob comes with a single 2mm hex key. For the 8" SSE Dob, you'll also need to use the supplied Phillips head screwdriver. First, adjust the secondary mirror at the front of the telescope using the 2mm hex key. While making adjustments, we recommend positioning the tube horizontally. This prevents anything from falling onto the primary mirror. 1. Y ou should be able to see the reflection of the entire primary mirror centered within the secondary mirror as shown in Figure 16. If you can't (like in Figure 17, for example), use the three socket-head set screws in the secondary mirror holder to adjust the tilt of the secondary mirror (Figure 18). Edge of secondary mirror Figure 15: To check the alignment of the mirrors, use the included collimation cap in the focuser. Look through the small hole in the center of the collimation cap. The view should look like Figure 16. If it does not, you'll need to make some adjustments to the mirrors' alignment. Reflection of your eye Edge of secondary mirror Bottom edge of focuser drawtube Reflection of primary mirror Reflection of primary mirror Figure 17: If the reflection of the primary mirror is not centered within the secondary mirror as shown above, you will need to adjust the tilt of the secondary mirror. Secondary mirror holder Reflection of secondary mirror holder Primary mirror clip Figure 16: If your telescope is properly aligned, the view through the collimation cap should look like the drawing above. 2mm Hex key Figure 18: The three socket head set screws in the secondary mirror holder adjust the tilt of the secondary mirror. 14 I ENGLISH