How Important Is Lens Coating When Buying a Telescope?

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How Important Is Lens Coating When Buying a Telescope?

Lens coatings are used on telescopes to increase the transmission of light and to provide low, flat reflectance over the visible spectrum. Some telescopes do not use a coating at all but rather rely on the quality of the material and production of the glass used in the lens; however, the majority of modern telescopes do use some form of coating, and most users prefer a coating and may even replace an existing lens with an upgrade that has a higher-quality coating. Recoating services are also available although the quality and cost can vary greatly.

Types of Lens Coatings

Lens coatings can be described and applied in a number of ways. The poorest quality, seldom found in modern telescopes, is the dip and bake method. This method usually uses aluminium oxide or magnesium fluoride. The problem with dip and bake coatings is they usually do not last more than a year or two and sometimes will even wipe off and quickly need replacing. Other methods ensure the coating stays on the lens. The term fully coated means that both sides of the lens have been coated as opposed to just one side. The methods and materials used in these coatings will vary from manufacturer to manufacturer. The most often used materials include aluminium oxide, titanium oxide, magnesium fluoride, and anti-reflective coatings made up of silicon dioxide. Similar materials will be used in multi-coated lenses. As the name suggests, this involves building up layers of materials to give high performance and durability. Fully coated and multi coated lenses are what will most commonly be listed on a telescope or lenses features. Other terms and specific methods, such as phase coated, air space coated, and ultra-high transmission coatings, will also sometimes be described by different brands and manufacturers. These methods can usually be found described on the manufacturer's website. It should be noted that advancements to coated telescopes are being developed all the time.

Types of Telescopes and Lenses

Telescopes can loosely be described in a number of categories. The quality and price will vary within each type. Astronomical telescopes are designed for sky watching and therefore require quality lenses with adequate magnification and viewing clarity. The lens coating can help enhance the performance of any astronomy telescope. Hand held and portable monocular telescopes are sometimes used for astronomy viewing but are as likely to be carried by backpackers and bird watchers. Selections can be made depending on the level of magnification and focus the user feels will be required on a regular basis. Many modern telescopes are also designed to be used for either sky or land viewing. Photographic telescopes are designed to attach to a camera and may be found under the general term of telescopic lenses or specifically as a telescope. Lens coatings are particularly important in photographic telescopes in order to produce not only excellent viewing, but excellent result in shots as well. Telescope lenses or eye-pieces are often purchased separately to attach to an existing telescope. As a general rule, when any type of telescope or lens has a high-quality coating, this will be noted among its features or technical specifications although this is not always the case, and some further research may be needed.

Astronomy Telescopes

From relatively cheap models designed for the novice sky watcher to highly technical astronomy telescopes that offer the clearest of night vision and superb magnification, a range of models are readily available. As well as looking at all the various features and benefits included when selecting an astronomical telescope, it is wise to glean information on the type of lens coating that has been used.


Used telescopes

Vary in price and quality. Lenses and lens coatings will probably vary greatly depending on age and quality of manufacture. Some vintage telescopes may in fact be of better quality than brand new models that are poorly made or designed. If lens quality is lacking, it may be possible to replace the lens or have it professionally coated.

Tripod mounted telescopes

Useful for setting up and providing stability. Sizes, magnification, lenses, lens coatings, and other features will vary. Select the best quality possible within budget. Small telescopes or tripods may be more suitable for portability and versatility but may not offer some of the benefits of a larger, semi-permanent setup.

Telescope with recording capabilities

Many modern telescopes are set up to enable capturing video or still shots to be transferred directly to a computer, camera, or mobile device. While this is a useful feature, it is advisable to check that the qualities of other areas of the unit have not been sacrificed.

Beginner or children hobby telescope set

Suitable for the purpose and a good way to encourage interest. Quality varies, but it is unlikely that lens coatings will be of a highly professional standard.

Dual astronomy and wildlife telescopes

Offer versatility. Size and quality will vary. Check especially for lens and lens coatings among other features. While top models are certainly available, some qualities may fall short to accommodate for versatility and budget. Potential purchasers are advised to look carefully.

Hand-Held Monocular Telescopes

Technology has moved a long way from the old spy glass of old although, surprisingly, replicas of such models are still available, usually with updated lens and coating to give real viewing clarity and pleasure. Modern hand-held telescopes offer all the advantages of portability, sturdiness, durability, and accuracy to suit both land and sky viewing. Some models also have the option of being mounted to a tripod for added stability.

 

Used telescope

Available from vintage and antique to contemporary models. Depending on intended use, it is advisable to check for quality features, including lens coating.

Brass or other material spyglass type telescope

May be designed simply as a toy or ornament or fully functional to high specifications. Variable quality. Select for desired purpose.

Functional hand-held telescope

Often available with strap. Function, design, and quality vary between brands and models.

Photographic Telescopes

Designed to fit onto, usually, modern cameras. Telescopes for cameras usually come complete with a mount or adapter mount to fit a particular brand of camera. Adapter mounts can also be purchased separately to fit the telescope and camera model. Some models may be small enough to be hand-held, but for the best quality shots, it is usually advisable to use a tripod or other support. The camera telescope is slightly different to a general telescopic lens, usually providing greater magnification. It is essential that the lens is of high quality, and therefore, top quality coatings are usually applied. A photographic telescope can be used for astronomy purposes as well as wildlife or general land photography.


Mount supplied for specific brand and/or model

Can sometimes be purchased with a particular camera but more often sold separately. Check for compatibility and quality.

Adapters for telescopes

Available to fit a variety of brand and models of camera. Quality of the camera, telescope, and adapter are all important to get the most out of this option.

Telescope Lens or Eyepiece

A telescope lens or eyepiece is used to replace or add to an existing telescope, usually the monocular type. This can be an efficient way to update a telescope with a compatible lens with a quality lens coating to obtain better performance. Eyepieces come in many known styles such as Barlow, Plossl, Kellner, and Orthoscopic. It is worth researching which style or make is preferred. Importance should be placed on quality of materials used in the lens and coating as well as appropriate fit for the telescope. A multitude of lenses and eyepieces are available to suit almost any brand and type of telescope.


Eyepiece sets

Available to suit a variety of telescopes, offering a range of options. Check for coating type and quality.

Multi fitting eyepiece/lens

Suitable for many telescopes. Can be particularly useful for upgrading performance of older telescopes. Check for coating type and quality.
 

Finding Telescopes on eBay

eBay is one of the easiest places to find both new and used telescopes and telescope lenses. From the eBay homepage, hover over the Electronics tab on the left hand side of the screen, and click on Cameras & Photography. Next click on Telescopes & Binoculars and use either the advanced search to type in requirements or the left hand column to narrow the search for particular models or types of telescope. Both general and highly specific browsing can bring up results to suit. Lens coatings are not always mentioned in auctions, so it can be useful to use the question option for individual listings.

Conclusion

When selecting a telescope, or a telescope eyepiece, many features are important. It can be easy to get absorbed by bells and whistles on some telescopes, so it is up to the individual to do a little research and decide just which features are the most important for intended use and value for money. Lens coating is definitely one important feature that should never be overlooked.

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