Orion #8296 10" F/3.9, #8297 8" F/3.9 instruction manual Cleaning Mirrors

Out of collimation Collimated

Figure 15. A star test will determine if the telescope’s optics are properly collimated. A defocused view of a bright star through the eyepiece should appear as illustrated on the right if the optics are perfectly collimated. If the circle is unsymmetrical, as illustrated on the left, the optics need alignment.

cap on the eyepiece opening. Keep the telescope inside the hard storage carrying case when not in use. Store it indoors or in a dry garage. Do not leave the telescope outside except when using it. The optical tube is aluminum and has a smooth anodized surface that should resist scratches and smudges. If a scratch does appear on the tube, it will not harm the tele- scope. Smudges on the tube can be wiped off with standard household cleaners such as Windex or Formula 409.

Cleaning Mirrors

In general, your telescope’s mirrors will only need to be cleaned very infrequently, if ever. Covering the front opening of the telescope with the dust cover when it is not in use will prevent dust from accumulating on the mirrors. Keeping the dust cap on the focuser’s 1.25" opening is also a good idea. Improper cleaning can scratch the mirror coatings, so the fewer times you have to clean the mirrors, the better. Small specks of dust or flecks of paint have virtually no effect on the visual or imaging performance of the telescope.

The large primary mirror and the elliptical secondary mirror of your telescope are front-surface aluminized and over-coated with hard silicon dioxide, which prevents the aluminum from oxidizing. These coatings normally last through many years of use before requiring re-coating.

To clean the secondary mirror, first remove it from the tele- scope. Do this by keeping the secondary mirror holder sta- tionary while completely unthreading the Phillips-head screw in the center hub of the spider vane assembly (see Figure 11). Do not touch the mirror surface when doing this. Once the Phillips-head screw is unthreaded, the secondary mirror and its holder can be removed from the telescope. The sec- ondary mirror does not need to be removed from its holder for cleaning. Then follow the same procedure described below for cleaning the primary mirror.

To clean the primary mirror, first carefully remove the mirror cell from the telescope. To do so you must remove the screws that attach the primary mirror cell and end ring to the tube (Figure 16). Then pull the cell away from the tube. You will notice the primary mirror is held in the mirror cell with three clips held by two screws each. Loosen the screws and remove the clips.

Figure 16. To clean the primary mirror, it must first be removed from the telescope tube. To do so, remove the Phillips-head screws that fasten the rear cell and end ring to the telescope tube. Then separate the cell from the tube.

You may now remove the primary mirror from its cell. Do not touch the surface of the mirror with your fingers. Lift the mirror carefully by the edges. Set the mirror on a clean soft towel. Fill a clean sink or large bucket with room temperature water, a few drops of liquid dishwashing detergent, and if possible, a capful of 100% isopropyl alcohol. Submerge the mirror (alu- minized surface facing up) in the water and let it soak for a few minutes (or hours if it’s a very dirty mirror). Wipe the mir- ror under water with clean cotton balls, using extremely light pressure and stroking in straight lines across the mirror sur- face. Use one ball for each wipe across the mirror. Then rinse the mirror under a stream of lukewarm water. Any particles on the surface can be swabbed gently with a series of cotton balls, each used just one time. Dry the mirror surface with a stream of air (a “blower bulb” works great). Cover the mirror surface with tissue, and leave the mirror in a warm area until it is completely dry before replacing it in the mirror cell. Then reinstall the mirror cell in the telescope optical tube with the six screws.

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