OVERVIEW

Eyepieces come in all shapes and sizes with all sorts of lens arrangements. The most important feature of an eyepiece is its focal length, which is usually, etched on the eyepiece somewhere. The focal length of an eyepiece determines the magnification when used in a telescope. To calculate the power of a given eyepiece you will need to know your telescopes focal length in millimetres as well. The magnification is given by dividing the telescope's focal length by that of an eyepiece, eg. a 600mm focal length telescope when used with a 12mm focal length eyepiece, will give a magnification of 50X…. 600/12 = 50)

It might seem from this that one should buy a range of eyepieces with relatively short focal lengths as they will give better views because of the high power. However, before buying your eyepieces seek advice of other users. A 2mm eyepiece in a 600mm focal length telescope gives 300X, but there are problems here. A telescope has a maximum magnitude beyond which, although you can buy the eyepieces, it is useless to go. If you try to magnify beyond the practical limit of a telescope you will simply get poor images. To calculate the maximum magnification of your telescope multiply it's aperture in millimetres by two. For example a telescope with a 80mm aperture has a maximum useful magnification of 160X. There are several reasons why you can't use the theoretical limit of magnification for your telescope. Of these the unsteadiness of the night air (in astronomical terms “seeing") is the biggest problem. Too much power will cause objects to jump around in the eyepiece. Reducing magnification also reduces the effect so you can continue viewing. This unsteadiness in viewing is also evident when a warm telescope is taken outside on a cool night. It is particularly noticeable for owners of Newtonian telescopes as convection currents caused by heat radiating form the mirror spirals up the tube.

There is also a lower limit to the magnification you can use. It is calculated by dividing the aperture in millimetres by eight. The 80mm telescope above has a minimum magnification of about ten (80/8 = 10). If you try to use lower than the calculated minimum you will be wasting some of the light gathered by the telescope. You should calculate the maximum and minium magnification for your telescope and bear these in mind when choosing eyepieces. Three eyepieces will usually give you a good start. Choose one that is about 75% of the maximum magnitude, one that is about twice the minium magnification and the third halfway between the two.

The next most important feature of an eyepiece (after magnification) is Field of View (FOV). FOV describes the size of the circle you see when you look through the eyepiece. The larger the FOV of an eyepiece, the better is the view you will see. A large field of view makes viewing more interesting than a narrow one. Some eyepieces have an FOV as large as 70deg, although 40 - 50 is the norm.

Another consideration for an eyepiece is eye relief. This describes the distance you need to hold your eye from the eyepiece when viewing. This is important as it affects your comfort; holding your eye very close to the eyepiece for any length of time can be very tiring. Eyepieces with large eye relief that allow you to hold your head back are much better especially if you want to show the view to people who are not used to using a telescope. Generally low power eyepieces have better eye relief than high powers ones.

When choosing eyepieces always try to pick eyepieces that are coated. Anti-reflective coatings give superior viewing to uncoated optics, with fully coated, multi coated, and fully multi-coated indicating the increasing degree of coatings applied to eyepieces, and, increasing cost.

ED Eyepieces
Recently Orion Optical introduced a new range of budget priced eyepieces that have very good qualities and would normally cost considerably more . “ED” stands for “Extra-low Dispersion” optical glass, a special grade of glass that boasts superior refractive properties compared to standard optical glass. In fact, ED glass is the same type used in many expensive camera lenses and high-end refractor telescopes costing several thousand dollars!

ED 1.25" eyepieces feature a six-element lens design in which two of the elements are crafted from ED glass (hence, ED-2). This allows each eyepiece, from the 22mm down to the 3.7mm focal length, to provide a luxurious 20mm of eye relief with remarkably reduced chromatic aberration and excellent sharpness. Long eye relief means that even if you wear eyeglasses, you can take in the full, unconstricted field of view. Which is a generous 55°—a wider apparent field than that of Plössl eyepieces! Notice also that even the short-focal-length EDs sport nice, wide eye lenses—not small peep-holes! Another advantage of the EDs’ unique optical design is they are Fully Multi-Coated and Parfocal. ED-2 eyepieces are fully multi-coated (every air-to-glass lens surface is multi-coated) for maximum image brightness, and the lens edges are blackened for improved contrast. The series is parfocal, so little or no refocusing is needed when switching from one ED eyepiece to another. Currently these can be purchased from some Aussie suppliers for just $79 each.

Sizes
Three standard eyepiece diameters are available; they are 24.5mm/. 96ins, 31.8mm/1.25ins, and 52/ 2ins. Prices vary considerably depending on size, focal length, type, and manufacturing quality. Prices for mid quality, mid focal length range, .96 " eyepieces are generally between A$30 (modified Huyghenian) and A$80 (orthoscopic). For 1.25" eyepieces there is an enormous range of prices. They vary from $30 (Meade modified achromat [MA] and Kellners), and depending on quality, Plossles can range up to $100+. Orthoscopics can still be obtained from about $80 - $135 The general trend in 2" eyepieces is to produce as wide a FOV (65+deg) as is possible and therefore these are usually of more exotic multi element design. Prices can range from $280 (modified Konig) to the 31mmTeleview Nagler type 5 (82deg FOV) which is $900+.
EYEPIECE TYPES

Ramsden eyepiece
One of the earliest types of eyepieces invented was the Ramsden. These have a field of view of 35 deg, but suffer from Chromatic Aberration as they have only 2 lenses in them. In addition to these drawbacks drawbacks they also have poor eye relief. The only point in favour of the Ramsden the Ramsden eyepiece is that it is non-cemented making it suitable for solar solar work.

Huygens eyepiece
Last of the early types of eyepieces is the Huygens. This type is commonly included with small telescopes. It is usually not achromatic although it has some colour correction in it's design. It has very little eye relief and only a 20 deg FOV. It works reasonably well on long focus refractors, but image distortion through spherical aberration becomes apparent at short focal ratios.

Kellner eyepiece
An improvement on the Ramsden is the Kellner, which is a semi-achromatic 3 element eyepiece that has a wide flat field of about 45deg. It has better colour correction than the Ramsden, but it is haunted. That is to say, early Kellners could have a large number of ghost images in them, usually have little eye relief, and can be bought rather cheaply. Modern manufactured Kellners are generally regarded as a good all purpose eyepieces and are widely used

Orthoscopic eyepiece
The orthoscopic was invented to correct many of the problems of the earlier eyepieces. By using two pairs of cemented lenses, the orthoscopic is achromatic. It has a fairly wide field of view and moderate eye relief. They are relatively inexpensive and a set of "Orthos" is a good start for general viewing. A group of University Optic's Orthos is seen above right)..


Plossl eyepiece
In recent years a number of complicated designs have become available. Although more expensive these usually combine colour correction, wider fields and reasonable eye relief. The Plossl eyepiece is widely available. It uses a pair of achromatic doublet lenses to give a colour corrected 50 deg FOV..Eye relief is about 80% of the focal length so a 25mm eyepiece has some 20mm of eye relief. Some manufacturers produce modified Plossls by adding a fifth lens element. A group of 3 Meade Plossls is seen above left.

Erfle eyepiece
By using 3 sets of lenses instead of 2, opticians were able to design some spectacular eyepieces. The most common of these is the Erfle. Using 3 achromatic doublets, these eyepieces have a FOV of between 65 & 70 degs. When choosing an Erfle eyepiece it is very important to ensure they are coated, if not the ghosting and light loss will make them very difficult to use

More About Eyepieces
NOTE
The information below was gleaned from an excellent webpage designed by Bill Wiegert, which was part of the old “Belmont Society’ astronomical website. Unfortunately the page is no longer active on the net, and the redirect link is faulty. The information provided here is copied from the saved webpage, I downloaded some time ago – Mike Finn


Left, Orion Optical Plossls; rigtht, Meade new Plossls

An Introduction to Power

Prologue
The eyepiece that you use in your telescope determines what magnification (power) that you'll be observing with. Eyepieces (just like telescopes) are configured in short and long "focal lengths". A 5mm (five millimeter) eyepiece is an example of a SHORT focal length, and will deliver HIGH power. A 32mm eyepiece is a long focal length, and will render low power (L/L; Long=Low). Those two examples are the approximate extremes of both ends of the typical scale. There are shorter and longer of course, but for the most part you will encounter what lies between them. The typical eyepiece(s) that manufacturers include with a new telescope are likely to yield power in the moderate range of 40x to 100x. These will generally be about 25mm and 10mm respectively.

Power play
Most newcomers to astronomy make the assumption that all things are better viewed with high power. However, just the opposite is generally true. Views of dim objects (like many galaxies and nebulae) will tend to degrade dramatically under high power. There are exceptions, but high power will usually make them appear even dimmer.
Most general deep space observing is done in the neighborhood of 30 to 80 power (much lower for wide-field views). You will notice that 2-inch eyepieces are always configured in long focal lengths. This is to deliver wide panoramic views at low power. Panoramic views at high power would be an impractical and senseless contradiction. The simple reality (and the painful truth) is, if you want to see dimmer objects better — then get a bigger telescope.
There are situations however, where high power is mandatory - they require it. Planets like Jupiter and Saturn will tolerate high power. The moon will take as much as you've got, and many double stars will demand more than you have. In fact, "splitting" the components of some double stars can require as much power as the quality of your telescope's optics will endure. Upwards of 700 to 900 power is not unheard of with very good telescopes under very dark skies.

How much power will an eyepiece deliver?
You can calculate how much power an eyepiece will render by doing some simple math.
Determine the focal length of your telescope in MILLIMETERS (the entire length of the optical image-path between the objective lens - or primary mirror - and the eyepiece). For refractors, this is easy - it's basically the length of the tube. For Newtonians, Dobs and Cassegrains, you may have to consult the user's manual.
Determine the focal length of the eyepiece (easy - it's stamped on the barrel).
Divide the focal length of the eyepiece into the focal length of the telescope.
The answer you get is the power (magnification) if used in that particular telescope. For instance, if the telescope's focal length is 1000mm, and the eyepiece's focal length is 10mm, then the eyepiece would deliver 100 power in that telescope (200 power with a 2x Barlow). Using a 25mm eyepiece would deliver 40 power. Coupling a 2x Barlow to that 25mm eyepiece would get you 80 power.
Quality at a bargain?
The products recommended on this website are the result of personal use or by their reputation as quality items. We occasionally recommend products that we think are bargains because they exhibit excellent performance and bang for the buck, and NOT simply because they are affordable or cheap. Many beginning amateurs will buy the most expensive telescope they can afford, and then shop for bargains when looking for eyepieces. This is fine, if the bargain is genuine. There are many quality eyepieces available at comparatively low prices. But if you plan on obtaining an eyepiece simply because it's more affordable, without some knowledge of its performance, then you may be in for some disappointment.

A telescope will deliver an image that is no more and no less equal to the quality of its optics. An objective lens or a primary mirror of world class quality will NOT render a quality image if used in conjunction with an inferior eyepiece. This is analogous to a high-end stereo system that gets coupled to inefficient low quality speakers. Conversely, if you have a department store telescope, it would be a waste of time and money to purchase high-end eyepieces for it. In short, high quality eyepieces and telescopes will not make up for low quality in each other. And high quality optics will not compensate for polluted skies.
There are a staggering number of eyepiece manufacturers and distributors. The choices that are available to the amateur can be both tempting and mind boggling (especially for the newcomer). Is that Plossl advertised for $28 worth it? How about that 2-inch Erfle for $25? Would you know a bargain at a flea market? It depends. Many would not. Seasoned amateurs would recognize a popular brand, and can make a good decision based on what they hold in their hand. But to a newcomer, an eyepiece labeled "TeleVue - Panoptic" may seem no more or less important than one stamped "Acme - Pluto finder".
Most advertised eyepieces are legitimate examples of quality optics. Aside from what you may find in department stores and on a TV Shopping Network, they are all likely to be of excellent value, and well worth their price. There are websites devoted to reviewing eyepieces and telescopes, and some include discussion forums. We advise that before you purchase an eyepiece of unknown origin or manufacture, you at least seek one out to borrow at a star party, or consult these websites for reviews and recommendations. The chances are, if you can't find anybody who has one, it may not be worth having.

Note: The use of high power under poor conditions will render extremely poor images. Image quality will always suffer where there is light pollution or atmospheric turbulence regardless of what magnification you use. Higher power will amplify everything - even the problems.

Kellners
Kellners are a 3-element design. They yield a sharp and bright image at low and medium power, with small or medium apertures. Kellners have good eye relief, and about 40 degrees of apparent field. They are inexpensive, and far superior to Ramsden and Huygenian designs.
Types of eyepieces
Eyepieces are available in different basic designs. Some are suited for specific situations. Here are the most common types:

Erfles
Invented in the .1940's, the 5 or 6-element Erfle delivers a wide 60 to 70 degree apparent field of view. At low power they offer a "picture window" deep-sky experience. Erfles are mostly available in long focal length or in 2-inch configurations, as they aren't suitable for high power, where they tend to exhibit ghost images.

Plossls
By far the most popular modern design, the 4-element Plossl yields an excellent image, good eye relief, and about a 50 degree apparent field of view. Good Plossls exhibit high contrast and excellent sharpness. Good for general observing. Most telescope manufacturers include at least one Plossl in the box
Orthoscopics
Four-element "orthos" were once prized as the best all-around eyepiece, but they've lost ground among the amateur ranks because of a narrower field compared to other modern designs like Plossls. Orthos yield excellent sharpness, color fidelity, and contrast. They have longer eye relief than Kellners, though not as long as most Plossls. They are especially suited to planetary, lunar, and double star observing.

Ultrawides
To yield apparent fields up to a whopping 85 degrees, some manufacturers offer 6 to 8 element Superwide designs in various focal lengths. They can offer such a wide panoramic view that you have to move your eye around to take it all in. Depending on the view, it can seem as though you've stepped out into the blackness, or a spacewalk. Although brightness is slightly diminished, image quality is very high. So is the price!

Esoteric & High-end (expensive)
There are World Class, high-end eyepieces available which have earned a reputation for stunning images and performance. Most notable are the Panoptics and Naglers manufactured by Al Nagler (TeleVue). Almost every veteran amateur astronomer either has one, or wishes they did. Panoptics are a 6-element design, and exhibit a 68 degree field of view. Naglers are a 6 or 7-element design, and have an 82 degree field. Despite all that glass, these oculars render superb bright images, and their wide fields can invoke a "spacewalk" feeling at dark sites. Some of these beauties are very BIG. For instance, the 31mm Nagler Type 5 (pictured at left) weighs over two pounds!

TeleVue also offers their "Radian", a 6 or 7-element design, with 60 degree fields of view, all having 20mm eye-relief. Long eye-relief is important for eyeglass-wearers
A brief note about "optics":
Optics are of course why a telescope works, and we all know that good optics will deliver good results. So it quite naturally follows that poor optics will render poor images. The best images are ones with a high level of contrast and brightness.
One can refer to the parts of a telescope that transmit an image to the user's eye as an optical "train". The optical train consists of all the "glass" that reflects or transmits a viewable image. For instance, a refractor's optical train is all the glass in the objective lens cell, plus the diagonal mirror, plus the eyepiece. In a Newtonian reflector it includes the eyepiece, plus main and secondary mirrors.

Worth repeating:
A telescope will deliver an image that is no more and no less equal to the quality of its optics. An objective lens or mirror of world class quality will NOT render a quality image if used in conjunction with an inferior eyepiece. This is analogous to a high-end stereo system that gets coupled to inefficient low quality speakers. Conversely, if you have a department store telescope, it would be a waste of time and money to purchase high-end eyepieces for it. In short, high quality eyepieces and telescopes will not make up for low quality in each other. And high quality optics will not compensate for polluted skies.
Plossls and Orthos

Plossls:
Almost without exception, every major telescope manufacturer will include an eyepiece or two as standard equipment. In some rare cases you get their top-shelf oculars (i.e. - Meade's 4000 Series Plossls). Usually though, it'll be their mid-grade standard Plossl eyepieces in 10 and 25 millimeter focal lengths. These will render views of low and moderate power (the 25mm for low power, and the 10mm for moderately higher power). The design characteristics of Plossl eyepieces make them easy to manufacture. Thus, they are inexpensive, and because they are very efficient they're accordingly the most widely used eyepieces in the world.

In most cases, the standard Plossl eyepieces you get with your telescope will be of sufficient quality for most of your initial observing. After a while however, you may feel the need for more power, more "field", more contrast, or more quality. There are better eyepieces available that are not of the Plossl design, and which will cost more to obtain. Some can cost 10 times more! You will usually find that the best of anything is always the most expensive. There are however, a few fortunate exceptions. Some excellent eyepieces are available at surprisingly low prices. Eyepieces of the Orthoscopic design have enjoyed a quietly esoteric following among amateur ranks. They yield crisp and bright images, and most are comparatively inexpensive.

Orthos:
The Orthoscopic design was invented in 1880 by Ernst Abbe Orthos are not widely popular because of their relatively narrow field of view - between 42 and 45 degrees. Plossl eyepieces deliver a field of view of about 52 degrees, which is much better suited for views of popular deep space objects like galaxies and nebulae. However, the Ortho's narrow field of view is highly effective (and even desirable) when looking at narrow-field objects like double stars, planets, and globular clusters.
We have found that in general, Orthoscopics will deliver star and planetary images of unsurpassed clarity and color fidelity, and will render noticeably more contrast and brightness. And the best news? Orthos are (for the most part) comparatively cheap! You can get them from University Optics for about $55. Expensive, high-end Orthos were once made by Pentax (in .965 format). They are hard to find. Expect to pay $175 to $250 for one of these beauties.
Orthos do have a drawback: The shorter focal lengths are afflicted with an inherently short eye relief, so if you wear glasses you may encounter a problem with the higher magnification pieces.

What if you wear eyeglasses?
If you wear eyeglasses to observe, you may need eyepieces with a long eye-relief built in. Suitable minimum eye relief for eyeglass wearers is considered to be in the 15mm range. Eyepieces which offer suitable eye relief are available from several manufacturers, including TeleVue and Vixen.
TeleVue's Radians (pictured here at left) offer eye relief of 20 millimeters for all focal lengths (3, 4, 5, 6, 8, 10, 12, & 18mm). All have a wide 60 degree field of view. They are high grade, premium oculars, and are not cheap. They are all priced the same - $240.
Vixen Lanthanum eyepieces are sold by Orion and many other distributors around the world. Like Radians, they offer 20mm eye relief, and are of very high quality. They are priced at around $110 for the standard field, and about twice that for wide apparent fields of 65 degrees.

Also, take a look at what a Barlow can do for eyeglass wearers.

Bargains - Are expensive optics worth it?
The simple answer is, "Yes - when used in good equipment". High-dollar, premium optics will almost always outperform the rest. As an example, TeleVue manufacturers high-end, ultra-quality (and expensive) eyepieces. Their Panoptics and Naglers have earned a reputation for legendary performance and quality. They are examples of world class engineering, ISO production techniques, and extremely high quality standards. Such a caliber of manufacturing (especially where optical glass is concerned) will usually demand a premium price. We recommend these eyepieces for any good-quality telescope, and we can easily declare them to be worth every penny. Simply put... if you can afford one, get it. Pictured below-right is TeleVue's 27mm Panoptic. In our opinion this is one of the finest eyepieces ever manufactured. Retail price is US$330. Sadly, we've heard it is scheduled to be discontinued.

But there are genuine bargains!
Whereas the average affordable Plossl costs between $40 and $55, a high-grade, premium eyepiece could be priced anywhere from 2 to 10 times that amount. There are however, a few brands that offer premium performance at a bargain price.
Orion's Ultrascopics* are an excellent bargain. They are "ultra-multi coated", and of extremely high quality. They deliver bright, high contrast images of all objects — deep space and planetary — that rival any high-grade premium eyepiece on the market. Field of view is about 52 degrees. They are available in 5, 7.5, 10, 15, 20, 25, 30, & 35mm focal lengths. They range in price from $80 to $100, which is indeed a bargain for optics of this caliber. Meade's premium-grade Series 4000 eyepieces are also highly regarded. We believe that within this product line are the best Plossls available.
But remember: good eyepieces will deliver good images, only in good telescopes, and only on clear nights.
Another great bargain:
Oculars of very good quality are available from Hands on Optics. They offer the GTO line of eyepieces, and their Proxima Series includes an interesting 31mm super wide and a 2.5x 2-inch Barlow. Each is priced at $149, which is rather astounding. The Proxima 31 is a five-element design with a 71° field of view. It is not recommended for optical systems faster than F/5. It offers a comfortable 20mm of eye relief which is good for eyeglass wearers. Like all GTO products, it is shipped in a "StarDust" shock resistant case. The Proxima 1.5X 2-inch Barlow is multi-coated and a low profile design. It exhibits 42mm of clear aperture. Shipped in a StarDust case, it sells for $149.


Oculars - What does a Barlow do?
Plain and simple, a "2X" Barlow will double the power of any eyepiece (that's what the "2x" stands for). A "3x" Barlow will TRIPLE the power. Barlows can even be "stacked" at VERY DARK places, to multiply power to amazing levels provided you have a high quality telescope to handle it.
A 2x Barlow functions by dividing the focal length of any eyepiece by two. For instance, an eyepiece with a 20mm focal length becomes a 10mm eyepiece. A 3x Barlow divides it by three (20mm becomes approximately 6.7mm). If you have a Newtonian reflector or a Dobsonian telescope, just slip the Barlow into the focuser, and drop an eyepiece into the Barlow. With a refractor or SCT telescope, insert the Barlow into the mirror diagonal, and slide-in an eyepiece. If you install a 2x Barlow ahead of the diagonal, it will TRIPLE the power.

Like eyepieces, Barlows are available in economy, medium-grade and premium. In general, Barlows can cost anywhere from $30 to $300, depending on the brand and the quality of glass. A good quality 2-element Barlow will generally cost about $45. The 3-element variety sells for $65 and up. After that, esoteric brands and special configurations can approach the ridiculous. But then, so can any of several eyepieces on the market. Searching for higher power can be a choice of economics. One of the finest 2x Barlows available is Orion's Shorty Plus (pictured here). Priced at about $65, it's a 3-element design, which basically delivers better performance in good equipment.
Oculars - Eyeglass wearers: A Barlow's other benefit:
A Barlow is also an eye-relief saver. Those who wear eyeglasses to observe must use eyepieces with longer eye-relief (generally considered to be a minimum of 13 to 15mm). This can cause difficulty when higher power eyepieces are used, since eye relief is generally diminished as focal length is reduced. The use of a Barlow negates the effects of this problem, since it maintains the eye relief of the eyepiece it's coupled to. So instead of going from say, a 15mm to a 7.5mm eyepiece, just couple the 15mm to a Barlow, and enjoy the same eye relief.

The best eyepieces for Double Stars
Splitting doubles can be both fun and exasperating. Often, when viewing "close" doubles, the sky is not suitable because of turbulence or light-pollution Then too, even on clear nights, there can seem to be difficulty in discerning separate components which are close. This is sometimes due to contrast anomalies caused by the eyepiece itself. Many observers have found that Orthoscopics deliver the finest bright-object contrast of any ocular type. Without hesitation, we recommend Orthoscopics for viewing stars, doubles, open clusters, the moon and planets, and some of the brighter globulars. Good Orthos deliver high contrast images of superior quality and color fidelity. Excellent Abbe Orthoscopics are available from University Optics. They are available in 4, 5, 6, 7, 9, 12.5, 18, and 25mm focal lengths. They are priced from $56 to $60 (a definite bargain!). Orthos generally have poor eye relief however, so eyeglass wearers may have difficulty using focal lengths below 18mm.

Why use 2-inch eyepieces?
Looking at objects like dense open clusters or a field of stars with a standard eyepiece is thrilling, but nothing matches the thrill of a bright open cluster, or the carpet of the Milky Way, as seen through a large picture window! Viewing wide open clusters and expansive objects like the Veil Nebula or the stunning stellar carpet of the Milky Way can be much more pleasing with the large format of a 2-inch eyepiece. A "two-incher" can impart an astounding "panoramic" view, and actually make it seem as though you've stepped out into space. TeleVue Naglers and Panoptics are renown for their legendary panoramic images. They are very expensive, but it is generally agreed that they are worth every penny. Other manufacturers offer 2-inch eyepieces that are not so difficult to afford. For instance, Orion offers their "Optiluxe" 2-inch eyepieces for about one-third the cost of a Nagler.

It is quite an experience to just hold one of these grenades in your hand for the first time! In order to make use of a 2-inch eyepiece, your telescope must be equipped with a 2-inch focuser..

Siebert Optics
If you haven't seen the Siebert Optics line of products, you owe it to yourself to pay them a visit. They offer eyepieces in several grade levels (Standard, Premium, Ultra, & Ultra-Plus, and NEW Observatory Grade) besides an array of other optical numbers such as diagonals, finderscopes, etc. Each piece is handmade with high quality standards. Prices are very reasonable - much lower than you'd expect. For instance, their Ultra Plus series 2-inch 32mm (70 deg, FOV) has been compared to the 31mm Nagler in performance and without kidney-beaning or blackout. It sells for $189. Their Observatory Grade 2-inch 40mm (70 deg FOV) sells for $199. Their bino-viewer is one of the nicest pieces we've seen, and is similarly well priced. These optics have been engineered with reduced eye relief in the 20mm range to prevent blackout and eye movement.
T.M.B. Monocentric eyepieces
About a hundred years ago, Carl Zeiss adopted a "Monocentric" eyepiece design as the ultimate ocular for planetary and lunar observations. With only two air-to-glass surfaces, and a narrow 25 to 30-degree field of view, it was perfectly suited for those targets, and became the standard by which other eyepieces were judged for contrast and brightness. You would do well just to find one of these jewels today, as they are treasured by collectors.
TMB (Thomas M. Back) manufactures World Class APO refractor telescopes. They've recently introduced a series of eyepieces which they claim to be a duplicate of the original Zeiss Monocentric design. They describe the ocular as "Not ordinary", but one that is designed like an APO objective lens. Theoretically these eyepieces would be perfectly suited for lunar, double star and planetary observing because color-fidelity, brightness and contrast are usually enhanced and maximized with a minimum of glass. And their narrow field makes them a very desirable option for those targets. They are available in 4, 5, 6, 8, and 10mm focal lengths. Price is $200 each, which to a double star or planetary observer could be a genuine bargain. We would love the opportunity to test and review these oculars, as we are rabid enthusiasts of lunar and double star observing.


Care & Cleaning tips
The advice we always give when someone asks how they should clean their eyepieces is... Don’t! But if you absolutely MUST clean an eyepiece, you should USE EXTREME CARE.
Ever see someone use a shirt-tail to wipe the lenses of their eyeglasses, binoculars or Wal-Mart camera? Well, some folks do that to their eyepieces, and we cringe when we see it. Egad! If you could imagine what goes on (microscopically) when you use a cloth such as a shirt-tail to clean or wipe the glass of an eyepiece, you would likely never do it. Even when you use a supposedly "soft and clean" cloth, you are essentially grinding the lens-coatings with rocks and boulders.
There are procedures you can follow to clean your eyepieces safely. The one we prefer utilizes Dawn dish detergent, and sterile cotton balls and swabs.
• Add 2 drops of Dawn dish detergent (unscented plain original - it's BLUE!) to a quart of distilled water. Mix the two thoroughly.
• Soak a sterile cotton ball or swab with the solution; wipe the glass GENTLY in circular motions.
• Flush with liberal amounts of distilled water.
• Dry by wiping GENTLY with cotton balls or swabs.
• Gently "buff" with Kleenex "Softique" non-scented tissue.
NOTE: clean your filters the same way.
 

Return      Next