that you find an observing site well away from light pollution. Take plenty of time to let your eyes adjust to the darkness. As you become more experienced and your observing skills get sharper, you will be able to ferret out more and more subtle details and structure from these fascinating objects.
Beginners are often surprised to discover that the deep sky objects they see through the eyepiece of a telescope are mostly grayish, not colorful like those you see in long-expo- sure astro-images. The reason is that our eyes are not sensi- tive to color in faint light. Still, there is something very special about seeing an astronomical object in real time with your own eyes – “live,” if not in living color.
Note About Astro-imaging
The SkyQuest XTg GoTo Dobsonian is designed for visual, not imaging, use. With that in mind, however, it is possible to do some simple lunar and planetary astro-imaging with the XTg. With the use of afocal imaging techniques (where the camera is simply put right up to the eyepiece to take a picture) and digital cameras, it is possible to capture images of bright objects. Certain imaging accessories, such as the Orion SteadyPix, can help in obtaining images by the afocal method.
Deep-sky photography is not recommended with the SkyQyest XTg Dobs. For the longer exposures required for deep-sky photography, an equatorial mount is needed, or an altazimuth mount equipped with a field rotator.
11. Care and Maintenance
If you give your telescope reasonable care, it will last a life- time. Store it in a clean, dry, dust-free place, safe from rapid changes in temperature and humidity. Do not store the tele- scope outdoors, although storage in a garage or shed is OK. Be sure to keep the dust cover on the telescope when not in use.
Your SkyQuest XTg requires very little mechanical mainte- nance. The optical tube is steel and has painted finish that is fairly scratch-resistant. If a scratch does appear on the tube, it will not harm the telescope. Smudges on the tube or base can be wiped off with a soft cloth and household cleaning fluid.
Cleaning Eyepiece Lenses
Any quality optical lens cleaning tissue and optical lens clean- ing fluid specifically designed for multi-coated optics can be used to clean the exposed lenses of your eyepieces or find- er scope. Never use regular glass cleaner or cleaning fluid designed for eyeglasses. Before cleaning with fluid and tissue, however, blow any loose particles off the lens with a blower bulb or compressed air. Then apply some cleaning fluid to a tissue, never directly on the optics. Wipe the lens gently in a circular motion, then remove any excess fluid with a fresh lens tissue. Oily fingerprints and smudges may be removed
using this method. Use caution; rubbing too hard may scratch the lens. On larger lenses, clean only a small area at a time, using a fresh lens tissue on each area. Never reuse tissues.
Cleaning Mirrors
You should not have to clean the telescope’s mirrors very often; normally once every few years or so. Covering the tele- scope with the dust cover when it is not in use will prevent dust from accumulating on the mirrors. Improper cleaning can scratch 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 adverse effect on the visual performance of the telescope. The large primary mirror and the elliptical sec- ondary 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 (which is easily done).
To clean the secondary mirror, you will need to remove it from the telescope. Before doing so, remove the upper tube section from the assembled telescope. Hold the secondary mirror sta- tionary while loosening the center Phillips-head screw. Handle the mirror by its edge; avoid touching the mirror surface itself. Once the mirror (still in its holder) is removed from the tube, follow the same procedure described below for cleaning the primary mirror. You do not need to remove the secondary mir- ror from its holder when cleaning.
To clean the primary mirror, you must carefully remove the mirror cell from the telescope. To do this remove the screws on the side of the tube near the rear end ring.You do not need to remove the collimation screws on the bottom of the mir- ror cell. Remove the entire mirror cell from the tube. You will notice the primary mirror is held down with clips, each one fastened by two screws. Loosen the screws and remove the clips. You may now remove the mirror from the mirror cell. Do not touch the surface of the mirror with your fingers; lift it care- fully by the edge.
Set the mirror, aluminized face up, on a clean, soft towel. Fill a clean sink free of abrasive cleanser with room-temperature water, a few drops of liquid dishwashing detergent, and if possible a capful of 100% isopropyl alcohol. Submerge the mirror (aluminized face 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 a straight line across the mirror. Use one ball for each wipe across the mirror. Then rinse the mirror under a stream of lukewarm water. Any particles on the sur- face can be swabbed gently with a series of cotton balls, each used just one time. Dry the mirror in a stream of air (a “blower bulb” works great), or remove any stray drops of water with the corner of a paper towel. Water will run off a clean surface. Cover the mirror surface with a tissue, and leave the mirror in a warm area until it is completely dry before reassembling the telescope.
