A telescope does not require high maintenance with ordinary usage, as long as it is reasonably looked after and carefully stored after each use. To keep the telescope in excellent working condition, the telescope's optical surfaces may need to be recoated eventually. Newtonian telescope mirrors may require occasional realignment as well. The optical elements of a telescope are its most delicate components, so these should be handled with extreme care.
Basic Care and Maintenance Tips
Telescopes are usually exposed to the elements, such as moisture from dew or frost and atmospheric temperature changes. Salty sea breezes can particularly harm the mirror and anti-reflective coatings, so it is vital to clean the device after exposure on the beach. Avoid leaving the telescope under direct sunlight, inside hot vehicles or in elevated temperature indoors to prevent heating up the optical tube interior and weakening the adhesives gluing the parts together. Do not keep a damp optical tube in its case; use desiccant sachets to absorb moisture.
As much as possible, do not touch the lens or mirrors to avoid leaving smudgy fingerprints from the skin's natural oils. A bit of dust does not have a major effect on the viewing experience, so it is better to reserve a thorough cleanup for seriously dirty optics. Gentle cleaning will do a more effective job of preventing any damage to the delicate optical surfaces and coatings. Scratched optical components cannot be repaired, but only replaced.
The fragility, precision, and special coatings of telescope lenses and mirrors require cautious handling. Follow the telescope manufacturer's instructions regarding suitable cleaning kits and supplies. Never use lens cleaning tissues, household cleaners, or abrasive pads on the optics. Avoid using compressed air to blow off dust because even trace amounts of the aerosol propellant can cause harm. Neither should dust be blown off with one's mouth to prevent moisture forming on the glass. Be careful with cleaning fluids which may damage the coating or leave a filmy residue. Do not use tap water since the mineral elements present in hard water may form rings or spots on the optical surface.
Below are the basic materials for safely cleaning a telescope.
Soft, fine brush (e.g., camel hair brush)
To gently sweep away specks of dust and dirt from lenses and mirrors
Blower brush or rubber bulb air blower
To blow away dust and grime particles
Cleaning liquid (e.g., plain distilled water or recommended cleaning solution of the telescope manufacturer)
To clean the optical components
New lens cleaning cloth; lint-free sterile cotton balls
To wipe dry the optical surfaces without leaving fuzz
Cleaning Techniques Based on Telescope Types
Variations in maintenance and cleaning techniques depend on the type of telescope. It is vital to perform the steps with utmost precaution to avoid degrading the scope's optical performance. Read the owner's manual for proper care and cleaning methods of a telescope.
Closed systems such as refractors, many reflectors and Cassegrain telescopes rarely require extensive cleaning of the interior lens surfaces. In ordinary circumstances, it may be enough to focus attention on the outer lens, the eyepiece and the tube. Unless absolutely necessary, it is best not to remove the lens from the tube when cleaning it. If it must be done, keep the lens retaining ring in place and avoid making adjustments.
Newtonian reflector telescopes are typically equipped with a modular mirror cell which can be taken out as a single piece from the mirror tube. This makes it somewhat easy to clean, but take note of the lens/mirror cell's orientation within the tube prior to removal. To retain its precise position, mark the meeting point of the tube and lens cell with a tiny dab of whiteout/correction fluid. Gently set down the mirror unit on a clean, well-padded surface in an upright position and without tilting or rotating the mirror. A separate section below provides the step-by-step procedure for cleaning the mirror.
For an air spaced reflector, follow the manufacturer's specific care and cleaning instructions. Rather than attempting to take out complex refractive lenses from their holder, let an expert with the right equipment handle it. The same warning applies to complex eyepieces.
Cleaning Optical Elements
A couple of signs indicate that a telescope's optical surfaces need to be cleaned, aside from a noticeably grimy appearance. One indicator is that stars that normally sparkle on a clear sky look unusually dim, blurry, or dull as observed through the telescope. On the other hand, when a glow, halo or glare seems to surround a celestial object, it may actually be an optical effect created from the scattering of light by the dirty telescopic mirror or lens.
Otherwise, there is no need to immediately clean precision optical surfaces if they are only a little dusty. Exercise extreme caution in cleaning them to avoid destroying their coatings and causing sleeks or tiny scratches on the surfaces. Take off jewelry from one's hands and arms to avoid accidentally scratching the delicate optics.
Lenses and Mirrors
Use a soft brush, blower brush, or bulb blower to lightly blow away loose dust particles. Wipe a dirty lens with a cleaning cloth or cotton ball dabbed in a little distilled water or mild cleaning solution recommended by the manufacturer. Ensure that the lens is tilted slightly downward so that water does not seep inside. Starting from the centre, work outwards with gentle circular motions and finish wiping with an upward lift to avoid leaving marks on the glass. Leave it for a few minutes to dry completely before putting back the dust covers.
Take out the reflector mirror from the scope, but if possible, do not remove it from the mirror cell. Work on a clean, softly padded surface. Follow the same steps as in cleaning the lens, carefully blot off the water droplets and allow the mirror to air dry.
A cloudy film can form on a telescope's optics due to moisture from dew or frost. Dewing occurs during humid nights or when a telescope is brought back indoors. When this happens, it is recommended that the lens be allowed to air dry uncovered in a warm room.
Although the interior of a closed system telescope may be well protected, it is not exactly airtight and may need cleaning, but this is seldom necessary. The extremely rare instances that require cleaning the corrector plate include a layer of dust or film on the internal surface or stains on the enclosed optical elements. Those who are not confident in removing the corrector plate should pass on the job to someone with experience.
Proper Storage of the Telescope
Wrap the telescope with a hood to protect it between uses or keep it in its case during longer periods of storage. Face the reflectors downwards to minimise accumulation of dust. The lens should always be covered with a snug-fitting cap when the telescope is not in use. However, the lens will usually dew up when it is brought back into the warmer air indoors, so allow it to air dry first before putting the cap back in place.
The storage area should be clean, dry and maintain normal room temperature to prevent the growth of mould and mildew. Use desiccant packs to help absorb moisture in highly humid environments. Store spare eyepieces, lenses and accessories in separate sealed containers to protect them from dust and damage. It is sound advice to use a telescope on a regular basis so that dust does not collect on different parts of the instrument.
Find Telescopes, Parts, and Accessories on eBay
For a general browsing of telescope listings on eBay, enter the keyword "telescope" in the search box. This brings up the Telescopes & Binoculars sub-category. Clicking on it leads to more specific results, including Telescopes and Telescope Parts & Accessories. Navigate to the Telescopes page to drill down to the types of telescopes, such as Refractor, Reflector/Newtonian and others. The selections can be further filtered by brand, lens coating, maximum magnification, mount type and other limiters.
If replacement parts are needed, go to the Telescope Parts & Accessories page. For cleaning supplies, type "cleaning telescopes" in the search field of the eBay homepage and choose the Telescopes & Binoculars sub-category.
Safe cleaning methods, maintaining the telescope in optimal condition and storing it with care are effective ways to keep it functioning properly and prevent major repairs in the long run. Owners who look after their telescopes well can expect to enjoy awesome stargazing for years to come.