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Collimating the Optics (Aligning the Mirrors) Collimating is the process of adjusting the mirrors so they are aligned with one another. Precise collimation of the optics is especially critical for fast Newtonian optics such as in the f/3.9 astrographs. If the mirrors are even slightly misaligned, image quality will suffer. So you should check the collimation before every observing or imaging session, to make sure it is dead- on. The process of collimation is a relatively easy and can be done in daylight or darkness. Your telescope’s optics were collimated at the factory, and should not need much adjustment unless the telescope was handled roughly in transit. To check collimation, remove the eyepiece and look down the focuser drawtube. You should see the secondary mirror centered in the drawtube, as well as the reflection of the primary mirror centered in the secondary mirror, and the reflection of the secondary mirror (and your eye) centered in the reflection of the primary mirror, as in Figure 8a. If anything is off-center, proceed with the following collimating procedure. Primary mirrorcenter markReflective surfaceof collimationcap drawtubeReflectionof primarymirror clip c. b. e. a. d. Figure 8. Collimating the optics. (a) When the mirrors are properly aligned, the view down the focuser drawtube should look like this. (b) With the collimation cap in place, if the optics are out of alignment, the view might look something like this. (c) Here, the secondary mirror is centered under the focuser, but it needs to be adjusted (tilted) so that the entire primary mirror is visible. (d) The secondary mirror is correctly aligned, but the primary mirror still needs adjustment. When the primary mirror is correctly aligned, the center “dot” of the collimation cap will be centered, as in (e). The Collimation Cap Your f/3.9 Newtonian Astrograph comes with a “quick collimation cap” (Figure 9). This is a simple cap that fits on the focuser drawtube like a dust cap, but has a tiny hole in the center and a reflective inner surface. The collimation cap helps center your eye over the focuser drawtube so that aligning the optical components is easier to achieve. The reflective surface provides a distinct visual reference that is helpful in centering the primary and secondary mirror reflections. Figures 8b through 8e assume that you have the collimation cap in place. We strongly recommend the use of a laser collimating tool such as the Orion LaserMate Deluxe or LaserMate Pro to aid in collimating the optics. A laser collimator will ensure a more precise collimation than you can usually achieve with the included collimation cap. With fast optics like those of the f/3.9 Newtonian Astrographs, getting a very precise collimation is critical for obtaining the sharpest, crispest images, so a laser collimator is a worthwhile (and small) investment. However, for the purposes of this instruction, we’ll assume that you don’t (yet) have a laser collimator, and that you’ll be using the supplied collimation cap. The Primary Mirror Center Mark You’ll notice that the primary mirror of your f/3.9 Newtonian Astrograph has a tiny ring (sticker) marking its center. This “center mark” allows you to achieve a very precise collimation of the primary mirror; you don’t have to guess where the exact center of the mirror is. NOTE: The center ring sticker need not ever be removed from the primary mirror. Because it lies directly in the shadow of the secondary mirror, its presence in no way adversely affects the optical performance of the telescope or the image quality. That might seem counterintuitive, but it’s true! Preparing the Telescope for Collimation Once you get the hang of collimating, you will be able to do it quickly even in the dark. If you’re new to It, it is best to collimate in daylight, preferably in a brightly lit room and with the scope aimed at a light-colored wall. It is recommended that the telescope tube be oriented horizontally. This will prevent any parts from the secondary mirror from falling down onto the primary mirror and causing damage if something comes loose while you are making adjustments. Place a sheet of white paper inside the optical tube directly opposite the focuser (Figure 10). The paper will provide a bright “background” when viewing into the focuser during collimation. Aligning the Secondary Mirror To adjust the secondary mirror collimation, you will need both a small and a large Phillips screwdriver. You will need to check, and adjust if necessary, four aspects of the secondary mirror’s alignment: 1. The secondary mirror’s axial position 2. The secondary mirror’s radial position 3. The secondary mirror’s rotational position 4. The secondary mirror’s tilt The first three will probably only need to be checked and (possibly) adjusted once. Chances are, however, that they are set correctly from the factory and will not need any adjusting. We recommend that you do not make the adjustments in 1 to 3 above unless you fir...

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