How to select an eyepiece ?

My selection (VII)

Arrived at that point, we can appreciate the various eyepieces. I selected brands or manufacturers from their ability to innovate, supply high quality accessories but also from users's opinions. These ones can be right or false, depending on your interpretation of facts. So never say to numbers and facts what they don't say explicitely. The best example is that a Plössl, famous for their high contrast and luminosity can yield excellent images in low f/ scopes and show aberrations or technical problems in fastest instruments.

A first buy

A young student and a casual adult observer may or not have similar interests. One cannot assimilate the first and the second for the unique reason they observe occasionally the starry sky. Many factors may influence their appreciation of what they consider as their "best choice", which include all the factors detailled on these pages. So I should define a "first buy" as the first acquisition in order to get a reasonable small set of quality eyepieces. According various appreciations and tests, such eyepieces are located in the mid-range of prices, between $80-150. In that range you are sure to buy quality eyepieces and to be satisfied to keep them for a decade or more observing both faint and bright celestial objects using fast scopes, reducer, diagonal or barlow's. For that price you can already buy superwide eyepieces or Plössl's. One condition to meet : for each eyepiece appreciate each factor we reviewed.

The range of eyepieces is very wide, from the simple Huygens to Nagler. Prices begin around $12 but have no limit. Documents Edmund Optics and Jodrell Bank modified by the author.

What eyepieces to choose for a first buy ? For an amateur instrument from 60 to 300 mm of aperture used with a f/ratio between f/4-15, I suggest you to begin with a set of 4 eyepieces of 30 mm, 25 mm, 20 mm, 8 mm and a 2x Barlow. This range allow you to cover all discrete focals of 30, 25, 20, 15, 12.5, 10, 8 and 4 mm. A zoom eyepiece of 8-24 mm is also a solution (without Barlow) if you do not want to bring with you too many accessories. The other solution is to evaluate your needs according your subjects of observation and the quality you desire. You will probably select more expensive optics, like a Powermate 2.5x in to replace the Barlow 2x and somehigh-ends eyepieces.

In all cases when you will have more experience, maybe a larger scope and a more accurate idea of what are your specific interests, you could select high-ends eyepieces, models than may cost over $300 each from Leitz, Takahashi or Tele Vue to name a few. Then you will probably keep some of your old eyepieces for public star parties where there is always a potential risk of damage by the youngest observers. It is a good idea to preserve your most expensive eyepieces from the visitors's curiosity.

My selections are presented in the next tables. I have weighted advantages and disavantages of eyepieces in various conditions of use and scopes. These selections use only discrete eyepieces without taking account the potentiel use of a Barlow/Powermate.

I have taken care to select eyepieces in progressive power and reduction of the true field of view. When I had the choice I selected the shortest focal to gain more faint stars. As these tables are mutually exclusive, the best choice in each of them was not always optimized. The first table is my master choice among all high-ends eyepieces without upper price limit. But as they are quality competitors and other eyepieces that yield tremendous view too, a second choice was included, each of them suited for 2" and 1.25" barrels. The third  table concerns medium prices eyepieces below ~$150 which price excludes quality 2". The fourth table list the users choice. In each table I calculated the true field of the eyepiece for a 200 mm (8") f/10 scope.

For the amateurs whishing to spare some money, there is always the possibility to use these eyepieces in combination with a 2.5x Powermate or a 0.63x focal reducer. But I suggest you to keep your fixed focals eyepieces if you benefit regularly of an exceptional seeing.

In the field appreciation

In the next list I have summarized the appreciations of experienced amateurs about some of the most used eyepieces. Their appreciation does not always mention the conditions of use, the f/ratio for example or the use or not of a barlow, a diagonal or if there was a long in-travel or other minors problems. So their appreciation has to be consider as it and cannot necessary be applied to your specific needs. Consider these comments as a first indication of the factors to take in account and to check if you are interested in these optics. This list is not exhaustive and comments about others eyepieces are available in this Excel sheet (653 KB) regularly updated.

 - 55 mm Tele Vue Plössl : one of the best eyepiece in its category, sharp to the edge with a clear image. Much more confortable than 56 mm Meade. View easy to find due to huge eye relief.

- 40 mm Konig MK-70 University Optics : not sharp at the edges, less good than Meade Super Plössl 4000, for some less good than 32mm SWA from Meade. At f/10 Pentax XL has a better contrast and a bit sharper. In f/6 can be better than 35 mm Panoptic. Others consider it as a premium eyepiece.

- 35 mm Eudiascopic Baader : Best in its category. In the range 35-40 mm this Plössl yields the largest true field. It comes with a large winged eyeguard. Yields crisp image and comfortable. Its brightness similar to Tele Vue 40 mm Plössl. 35 mm TV Panoptic provides a wider field but not as clear due to its different design.

- 32 mm SWA Plössl serie 4000 Meade : some blackout due to huge relief, edge out-of-focus of fast scopes and SCT, better than 40 SWA, below 35 mm Tele Vue Panoptic or 40mm Pentax (Kellner), less pincushion than 35 mm Panoptic. Note that competitors use a different design and are not good examples.

- 31 mm Nagler type V Tele Vue : sharp on-axis performance, some lateral color like in other Nagler's, but not  important, sharpness quite good but suffers a bit on SCT f/10 at edges (similar to 22 mm Nagler type IV), almost no pincushion, kidney bean, no slide up/down eyecup but instadjust eyeguard, ideal for fast scopes due to exit pupil, heavy eyepiece. Can be selected over the 35 mm Panoptic from Tele Vue for contrast and AFOV but 31 mm is heavier and bulkier. Its adds.power will help resolving DSO on fast f/ scopes, similar to Leica 30 mm but heavier.

- 30 mm Widescan Leitz : wonderful eyepiece, high contrast, very sharp, some distorsions at edge on f/6.8 APO, eye relief and exit pupil not too large, very little pincushion. On f/4.5 newtonian the center is nice and tight but less crisp at 40% off axis with astigmatism/coma. According APM this Leitz is built by Kokusai Kohki. Same as 30 mm Apogee. Both built at Kowa of Japan.

- 30 mm Plössl Clavé : Best in its category. Rigid eyecap but old design. True field 7% wider than expected.

- 30 mm Ultima Celestron : Plössl enhanced, better contrast than 32 mm Tele Vue Plössl, crisper than 32 mm Super Plössl from Meade or 30 mm Orion Ultrascopic, better than 32mm Konig from UO, winged eyeguard.

- 26 mm Super Plössl serie 4000 Meade : as good as 25 mm Tele Vue Plössl, similar to 32 mm SWA from Meade. True field 6% shorter than expected.

- 26 mm Eudiascopic Baader : One of the best in its category, field larger than expected. Excellent image, edges of field, contrast and luminosity. Plössl modified, same as Ultima Celestron.

- 25 mm Ortho Carl Zeiss : HFT multicoated, superior color correction and design

- 24 mm LE ED Takahashi : Plössl design. As good as Nagler's but shorter AFOV. Medium contrast but fine edges of field, luminous and crisp image. No field curvature.

- 22 mm Nagler type IV Tele Vue : widest field, not as sharp as 17 mm Nagler type IV according some users, better contrast than 20 mm Nagler but this last is sharpest. Even at daytime as sharp as Radian to the edges, image below 22 mm Leitz, but contrasty, comfortable with instadjust eyecup, better than 22 mm Panoptic even on 18" f/4.2 Starmaster, minor pincushion despite sharp view, no ghosting, a bit of kidney bean.

- 21 mm SMC XL Pentax : ED glass, excellent but below Leica 22 mm, flatter field and eye relief superior to 22 mm Tele Vue Panoptic, 19 mm Tele Vue Panoptic is sharper even at edges (smaller and lighter), eyecup adjustable. For some better than 19 mm Panoptic due to larger relief and less distorsion.

- 19 mm Panoptic Tele Vue : Sharpest but some coma on fastest scopes (then use Paracorr), pincushion, ideal for Tele Vue Binovue, can be barlowed without vignetting. For many this eyepiece is superior to 22 mm Tele Vue Panoptic. 21mm Pentax SMC XL has a better relief and less distorsion

- 17 mm Nagler type IV : as sharp or sharper than 22 mm Nagler type IV, quasi as good as Radian's at 95% of FOV but with less contrast. Less distorsion, sharper and more contrasty than Panoptics, less ghosting than 9 mm or 7 mm Nagler, eyecup to loose for some.

- 14 mm Leica Leitz : One of the best in its category, better than Radian, Pentax or 15 mm Panoptic. Color-free and no ghost throught the entire field, some scatter around planets, excellent on-axis resolution may be a bit below Radian but FOV larger, relief and eyeguard fabulous ideal for eyeglass wearers, no kidney bean nor pincushion, lot of in-travel (not easy with all reflector).

- 14 mm Radian Tele Vue : distortion less and higher contrast, no pincushion, some kidney bean, better stars image than with Meade 14 mm UWA.

- 14 mm UWA Plössl Meade : for wider field deep-sky work, the 14mm Ultrawide (83° AFOV) is an ideal eyepiece and yields larger fields than the superwides.  Its performance is quite good and even for some planetary use, it performs fairly well.  It does not suffer from the extremely bad astigmatism in the outer portions of the field like more simple eyepiece designs do, and has decent performance even down to f/4.8. It yields a bit of kidney bean distortion (barely notic.at night) and pincushion and some lateral colors. The 14 mm Radian has clearly a better contrast. This UWA is more ergonomic than the 12 mm Nagler type IV when "eye-walks" around, and also better than this latter for eyewearers. It is a wide-field eyepiece by "design", so it may be outdone to a small degree for planetary use by some other designs like TV Radian's, but for wide field moderate power work, it is a great performer.

- 12 mm Nagler type IV Tele Vue : Combination of 13 mm Nagler and 12 mm Radian, tremendous view, superb, 14 mm Radian is a bit more contrasty (M13, Mars) and quasi similar AFOV, kidney bean as on Nagler 13 mm and more pronounced than on Radian, exceptionnal clear edges of field (no loss across the field) even at f/7 but with pincushion, pupil guide but not as secure as Radian instadjust, some do not like its instajust.

- 10.5 mm SMC XL Pentax : ED glass, sharp to the edges, excellent in its category, eyecup adjustable

- 10 mm Ortho Carl Zeiss : HFT multicoated, superior color correction and design (.965" has limited FOV, short relief)

- 9.7 mm Speer-Waler Antares : resolution sharp even at f/4.6, on par with 19 mm Tele Vue Panoptic barlowed x2., residual lateral color, some dust lodged inside the eyepiece, focus a bit inside of most eyepieces such as Celestron Ultima, slight kidney bean effect, no pincushion. Quasi similar and cheaper than 9 mm Tele Vue Nagler, ideal day-time eyepiece, also good for binoviewers.

- 8 mm Radian Tele Vue : maybe more contrasty on planets than the 7 mm Tele Vue Nagler. Maybe more detailled image than 6 mm Radian on TV-85 refractor.

- 7.5, 5 mm LE ED Takahashi : ED glass, as good as Nagler's even a brighter image, sharp field, but short eye relief and true field, very small eyepiece.

- 6, 5 mm Radian Tele Vue : excellent for planetary viewings as all Radian's

- 5 mm Lanthanum Superwide Vixen : may be sharper than 4.8 mm Nagler

- 2.5 Lanthanum LV Celestron/Vixen : sharp to the edges down to f/6, dark (8 el.), very slight chromatic aberration on planets.

By way of conclusion

After have understood how difficult can be the selection of an eyepiece, my best advice should be to say that if you want to buy new eyepieces get involve in a local astronomy club or visit astronomy conventions and other star parties to speak with amateurs having the chance of using some high-tech eyepieces and accessories in order to compare their respective qualities. According the weather conditions, the seeing, the scope f/ratio used and the others parameters we reviewed in these pages you will learn the plus and minus of each model.

Take some time to appreciate an eyepiece in the field prior any buy, specially if you want to use it in a fast scope where aberrations are more pronounced.

If the dealer does not accept to rent you his most expensive eyepiece for a test, contact a club or request for comments on newsgroups - S.A.A. is perfect - in order to get a complete appreciation from amateurs having used that item in the field. At the price reached by most of eyepieces, a bad investment is like buying a ring unsuited. It will go by its life in its box.

Theoretically an eyepiece must be tested in situ. You will quickly recognize that this attitude is very instructive and you will learn much more this way than readings pages of test reports in magazines. Better you will get a chance to look through oculars of your dreams, from the thiny Tak's to the monster Nagler's and check them in situation. On the other side I also know advanced astrophotographers, having an experience on the field over 40 years buying all their Nagler's and super wides oculars only readings test-reports in magazines. Both attitudes are not incompatibles. But remember well the sentence of Jack Marling : "The eyepiece represents the half of your scope". Nowit's up to you to confirm in situ what I have written.

I thank participants of SAA newsgroup for their support during the writing of this report.

For more information

List of eyepieces (.xls file)

So Whats in Your Eyepiece Case, Cloudy Nights (threads post between 2005-2008)

All about eyepiece designs, Dr. Marcus E. Hennecke

Eyepiece Report, Cloudy Nights

Tele Vue

Albert Nagler Plossl Eyepiece Patent (1984)

Albert Nagler Ultra Wide Angle Eyepiece Patent (1981)

Ludwig Bertele Wide Angle Eyepiece Patent (1951)

Telescopes, Eyepieces, and Astrographs, Gregory Smith, Roger Ceragioli et Richard Berry, Willman-Bell, 2012

Telescope Optics, evaluation and design, H.Rutten et M.van Venrooij, Willman-Bell, 1992

Star Testing Astronomical Telescope, H.R.Suiter, Willmann-Bell, 1994/2009

How to correct coma ? (sur ce site)

ATMOS (logiciel)

Edmund Industrial Optics.

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