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6mm Lunar/Planetary Eyepiece Comparison


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6 mm Lunar/Planetary Eyepiece Comparison

(As Viewed in a 4” APO and a 10” Dobsonian)

                By: Bill.Paolini (wapaolini@hotmail.com)

 

 

 

Televue Radian – TMB Planetary – Sterling Plossl – UO Ortho – Baader Genuine Ortho – TMB Supermono

Astro-Physics SPL – Zeiss ABBE Ortho I – Zeiss ABBE Ortho II – Brandon Ortho – Pentax SMC Ortho

 

I.          Introduction

 

The eyepieces selected for this competition represent a range of optical designs from simple ones with minimal elements to highly complex multi-element designs, and from the affordable to some of the most costly available.  In addition, many are classically considered, or generally marketed, as “planetary” eyepieces.  While each eyepiece’s performance was evaluated on a variety of celestial targets, including stars, doubles, clusters, bright nebula, and a bright galaxy, their performance on the moon and planets were given primary attention.  Since Saturn was the only planet in a most favorable position during the timeframe of this comparison, it is the only planet that is reported in detail.  Venus was also observed, but more to evaluate how well each eyepiece performed with a very bright planet in the field of view as opposed to how well the planet was rendered.  The moon however, was observed at various points and through all of its phases.

 

The primary goal of this competition was to determine how improved the view would be through what are generally considered the best-in-class planetary eyepieces (e.g., Zeiss ABBE Ortho, TMB Supermono, etc.) compared to a range of more affordable and more readily available contemporary planetary eyepieces (e.g., Televue Radian, TMB Planetary, Baader Genuine Ortho, University Optics Ortho, etc.).  As the observing sessions mounted, it was readily apparent that every eyepiece produced extremely detailed and very satisfying results – so all were excellent at the task.  However, there was a definite ranking in performance and the field quickly stratified into distinctive ranks when observing conditions were favorable.  This stratification into distinct performance ranks, also became more evident when either the target was sufficiently bright, or the aperture of the telescope was sufficiently large.  Therefore, while performance differences between the eyepieces were clearly obvious in a 4-inch telescope observing the moon, this was not the case on Saturn which needed a larger aperture telescope to reveal the several noteworthy distinctions between them.  It was also noted, that while some narrower apparent field of view (AFOV) eyepieces may have performed better for star fields, clusters, and nebula, this seemed of little consequence compared to the advantages of seeing more surrounding context or extent of the star fields, clusters, and nebula that the larger AFOV eyepieces afforded.  And when it came to lunar/planetary targets, which are typically very rich in fine details within a small area, just the opposite was true, and AFOV differences seemed to rarely matter -- if a narrower AFOV eyepiece performed more sharply or with more contrast, this was noted as a distinct advantage over AFOV advantages. 

 

As will be made clear in the details of which follow, from a planetary observing perspective this comparison clearly demonstrated two major themes to this observer: that AFOV size is virtually inconsequential compared to optical prowess on lunar/planetary targets (even at 200x in an un-driven telescope if the observer is adept at manual tracking), and that the trilogy of atmosphere, a thermally adjusted telescope, and aperture (or target brightness) seemed to be “the” key elements which allowed the best-in-class eyepieces to decidedly “strut their stuff,” and possibly also justify for the lunar/planetary aficionado the higher prices they command.

 

As a special note, much appreciation goes out to the several Cloudy Nights members (Steve Couture, Tamiji Homma, and Rolando Chavez) and AstromartTM members (Jim Curry, Sean Cunneen, and Eric Roel) who generously and graciously contributed some of these world-class eyepieces and permission to use their precision astro-photographs.  Without them this comparison would not have been possible.

 

II.     A Caution about Results

 

Before the detailed observations and results are reported for each eyepiece, a cautionary statement -- all observers should remember that no matter what the outcome of this or any other review, your individual results may vary and those variations may sometimes be significant.  Even if each of the eyepieces in this comparison only varied little from production unit to production unit (which one cannot guarantee), the seeing conditions we each have, our primary telescopes, our individual physiology, and our own unique psychology (i.e., likes, dislikes, expectations) introduce variables into the optical chain which can sway what you will see and your individual results.  Therefore, like any review or comparison you encounter, remember that it should be viewed only as a guideline which can indicate general likelihood of how similar equipment may perform for you.  So all things may *not* be equal when used by you in your equipment at your observing locations, many variations may exist due to the manufacturing process, if one focal length of a brand of eyepiece performs well this does not guarantee that different focal lengths of the same brand will perform similarly, and when reported results are close these rankings may change given your unique optical chain.

 

III.    Methodology and Results Reporting

 

The methodology used for this comparison was to have a single experienced observer evaluate all eyepieces during each observing session.  Each observing session used either one or two telescopes, and evaluated no more than two performance criteria on one or two celestial targets.  This approach, while greatly increasing the number of observing sessions required, also greatly reduced possibilities of both confusion and fatigue as each observing session then allowed concentration and focus on only a limited number of comparisons.

 

 

Observations for the comparisons were performed through both a 4-inch Takahashi TSA-102 f/8 APO and a 10-inch Orion XT10 f/4.7 Dobsonian.  Each instrument was thoroughly checked for proper collimation prior to each observing session, and was given several hours to reach thermal equilibrium to ensure peak optical performance.  Each instrument was equipped with fine-focusing capability to ensure critical focus was easily and fully achieved for each observation.  If a reported performance observation of an eyepiece altered when used between the TSA-102 versus the XT10, then this is annotated as such in the ranking tables and narrative text.  If there is no annotation of the telescope used, then this means the eyepiece performed similarly in both telescopes (see the footnotes under each table which explain how telescope differences are annotated).

 

The observations were conducted over approximately two months during many evenings and early mornings from a light-to-moderately light polluted suburban Virginia location west of Washington D.C. At this location the typical limiting magnitude varies between 3.5 and 5.0.  Seeing conditions for each recorded observation was never below Pickering 5 for stellar and/or deep space object performance rankings, and was never below Pickering 6 for any recorded lunar and/or planetary performance ranking.  All results were confirmed through repeated evaluations on multiple evenings – so in almost no case is a reported ranking or performance based solely on a single evening’s observation of a given target.

 

For this comparison, a ranking system was employed which indicates when performance differences are large and/or obvious (changing letters), and when performance differences are very close and/or subtle (changing numbers).  Within the tables listing performance outcomes, each eyepiece is therefore given a rank comprised of a single alpha character (e.g., A, B, C, etc.) or two alpha-numeric characters (e.g., A1, A2, B4, C3, etc.).  In this system, eyepieces which contain the same letter in the first position, indicates that these eyepieces performed equally or with subtle differences.  If subtle differences were observed, then this is indicated by the second position which is a number.  Therefore, if three eyepieces are ranked A1, A2, and B1, then this indicates that the A1 and A2 ranked eyepieces are very close in performance, and that A1 was judged subtly better than A2.  The eyepiece ranked B1 however, showed an obvious lesser performance from either the A1 or A2 eyepiece.  If no number appears after a letter, or if a same number appears after a same letter for multiple eyepieces (e.g., A & A, or A2 & A2), then this indicates these eyepieces performed equally.

 

The results of this comparison also categorize the observations which are intrinsically more static and objective (e.g., field stop, build quality, etc.), separate from those which are impacted by different telescope designs and/or focal ratios (e.g., off-axis performance, scatter, etc.), and separate again from those which can be highly variable and subjective (e.g., sharpness, contrast, color, etc.).  This has been done so the prospective observer who is considering any of these eyepieces can better assess which results may be more or less reliably transferable to their particular equipment, locations, observing habits, and preferences.

 

IV.    Considerations in Selecting a Planetary Eyepiece

 

While any eyepiece can serve as a “planetary” eyepiece, an eyepiece which is best able to perform on lunar or planetary targets should naturally optimize its performance around those attributes which are peculiar to the target being observed.  A planet as an observing target, when compared to the many other celestial targets available to the observer, has many attributes which are unique and can all occur simultaneously within the field of view.  Arguably, the resulting major attributes of the primary planets (i.e., Jupiter, Saturn, Mars, Venus), and the importance these attributes become relative to selecting a planetary eyepiece, can be summarized as follows:

1 – Very Bright

Becomes important for the eyepiece to control internal reflections, glare, flare, scatter, and lateral color as these problems are usually accentuated by a very bright object either in the field of view, or just outside the field of view.

2 – Small in Angular Size

Becomes important for the eyepiece to be available in short focal lengths so higher magnifications are available without adding more components like a Barlow which may not be to the optimum level as your planetary eyepiece.

3 – Rich in Both Very High Contrast & Very Low Contrast Features

Becomes important for the eyepiece to have excellent transmission and contrast with minimal scatter so low contrast features are more easily visible and high contrast features are more brilliantly defined to impart a well defined three dimensional effect.


4 – Has Colored Features which are Easily Observable

Becomes important for the eyepiece to have excellent transmission so sufficient light is available to activate the color receptors in your eyes and a neutral image tone to preserve the true colors.

5 – Has Satellites (i.e., moons)

Becomes important for the eyepiece to have high transmission to better see dim satellites, high contrast so satellite  shadows on a planet surface are more stark, and low scatter with a sharp field stop so dim moons are more easily detectable if you need to hide the planet behind the field stop and still have a field of view free from reflections and scatter in order to detect dim satellites close to the planet.

 

V.     The Eyepieces Being Compared

 

The field of competition for this comparison represents an incredible range in both price and availability, with street prices ranging between $40 to over $700, and several eyepieces being no longer in production and difficult to acquire on the used market.  All the eyepieces are fully multicoated on all air-to-glass surfaces with the exception of the University Optics and the Brandon.  The Brandon utilizes a single coat only as some planetary purists hold that this is superior for planetary observations due to a phenomenon called narrow-angle scatter which multicoatings can sometimes produce.  The University Optics uses single coatings on all air-to-glass surfaces and a multicoating on the top lens only to minimize external reflections.                                                                                  

 

Eyepiece

Price New
(2008)

Price Used
(2008)

Elements/
Groups

Marketed AFOV

Marketed Eye Relief

Back Row of 1st Page Picture (left-to-right)

TeleVue Radian                          

$250

~$175

7 / 5

60°

20 mm

TMB Planetary                           

$59

~$49

6 / ?

58°

12 mm

Sterling Plossl                               

$40

--

4 / 2

55°

3.6 mm

University Optics Ortho             

$59

~$45

4 / 2

43°

4.8 mm

Baader Genuine Ortho              

$99

~$85

4 / 2

40°-43°

Not Specified

TMB Supermono (1st Run)

Discontinued

~$185-$235

3 / 1

30°

5.1 mm

Front Row of 1st Page Picture (left-to-right)

Astro-Physics SPL                      

Discontinued

~$400-$450

3 / 2

42°

~8 mm

Zeiss ABBE Ortho v I
(ZAO-I)                                         

Discontinued

~$700-$800

4 / 2

45°

Not Specified

Zeiss ABBE Ortho v II
(ZAO-II)                                       

$600

(sold in sets only)

--

4 / 2

43°

Not Specified

Brandon Ortho                            

$235

~$85-$125

4 / 2

50°

Not Specified

Pentax SMC Ortho             

Discontinued

~$250-$375

4 / 2

40°

Not Specified

 

Close-ups of each eyepiece are pictured below for a detailed view of each eyepiece and its construction.  Each frame is a composite of close up photos of the eye lens (top), side housing (middle), and field lens (bottom).  These photos are not to scale.  Reference the Category-1 Results section which follows for the comparative sizing measures which were captured.

 

 

 

VI.    Comparison Outcomes

 

Comparison outcomes have been categorized into the following sections:

  1. Objective Measurements:

AFOV, Eye Relief, Eye Lens Size, Field Stop Definition, and Focus Travel

  1. Results may vary by personal expectation or habit:

Build Quality, Handling and Field Use Characteristics

  1. Results may vary by telescope / focal ratio / sometimes atmosphere:

Off-Axis Aberrations, Scatter, Light Control, and FOV Uniformity

  1. Results may be very subjective by observer, telescope, and atmosphere:

Resolution, Transmission, Contrast, Color Fidelity, and Image Warmth

  1. Anomalies and unanswered questions

 

Again, since some categories are by their nature more objective than others, this should allow the reader to more reliably determine which categories may be more or less transferable to their particular equipment, locations, observing habits, and preferences.

 

a)   Category-1 Results:  Objective Measurements

 

Criteria assessed: AFOV – Eye Relief – Eye Lens Size – Field Stop Definition –Focus Travel

 

Eyepiece

Measured AFOV

Measured Eye Relief (mm)
from housing surface

Measured Eye Relief (mm)
from lens surface

Measured Eye Lens Diameter
(mm)

Field
Stop
Definition

Out-Focus Required*
(mm)

Televue Radian

61°

17.4

17.7

21.1

Sharp

30

TMB Planetary

57°

11.7

12.3

20.7

Sharp

24

Sterling Plossl

56°

2.3

2.8

6.7

Sharp

14

University Optics Ortho

43°

3.2

4.3

5.3

Sharp

18

Baader Genuine Ortho

41°

3.5

4.9

5.5

Sharp

22

Pentax SMC Ortho

43°

3.0

4.3

5.5

Sharp

21

Zeiss ABBE Ortho v I

48°

3.6

5.2

5.1

Sharp

24

Zeiss ABBE Ortho v II

44°

5.1

5.4

5.8

Sharp

23

TMB Supermono

30°

3.5

4.4

3.9

Sharp

21

Astro-Physics SPL

39°

4.9

8.7

7.1

Sharp

25

Brandon Ortho

45°

2.6

3.6

6.4

Sharp

30

* Out-focus measured in millimeters on the TSA-102 with one 2” extension tube, 2” visual back, and 2” diagonal attached.

 

In all the eyepieces, the field stops were sharply defined when observing.  However, in practice I notice for those eyepieces with very tight eye relief that I would often not place my eye close enough in order to see the entire field of view and field stop due to reluctance to get too close to the eye lens and possibly contact it with my eyelashes.  These eyepieces in which the eye relief felt very tight were the Brandon, Sterling, and to a lesser extent the Pentax.  I would therefore rarely place my eye close enough to see their entire field stop while observing and instead choose to view with a smaller apparent field of view visible. 

 

The Baader, ZAO-I, ZAO-II, University Optics, and TMB Supermono, while also having relatively short eye relief, did not feel overly restrictive in use for me as a non-eyeglass wearer.  The TMB Supermono also stood out from this group in that the slightly upraised lip of the top housing make it quite easy to quickly find correct eye placement and not feel hesitant about getting too close to the eye lens.  This upraised ridge on the top housing therefore served as a kind of protection mechanism and I would always allow my forehead to lightly touch the edge of this ridge as a placement and centering technique which kept my eyelashes far from harms way to the eye lens.  Finally, the Astro-Physics SPL was noted as feeling fairly comfortable compared to most, while the Radian and TMB Planetary were a joy to use in comparison to all the others with their large eye lenses and generous 14mm - 20mm eye relief.

 

Of the two eyepieces with most generous eye relief, the Radian and the TMB Planetary, the TMB Planetary was comparatively easier than the Radian to find proper eye placement.  Neither of these eyepieces had blackout or kidney bean affects at any time during the observing sessions.  Both of these eyepieces employ adjustable eye guards to facilitate finding and maintaining proper eye position.  I found the eye guard on the TMB Planetary slightly more user-friendly as it rotated to adjust its height and would rarely change position like the push-pull eye guard on the Radian.

 

In assessing the apparent field of view (AFOV) of each eyepiece, the manufacturer claims were often close to actual measurements.  An exception was the ZAO-I which measured 48 degrees instead of the stated 45 degrees.  While only three degrees different, perceptually the impact was fairly significant and approaching a typical Plossl’s AFOV size.  To validate the measurement taken, I compared the AFOV visually by placing the ZAO-I up to one eye, and a TV Plossl with its 50 degree AFOV up to my other eye, and let the images merge to compare relative differences in both AFOV’s.  This test confirmed that my 48 degree measurement for the ZAO-I was accurate as the ZAO-I’s AFOV was only very slightly smaller than that of the TV Plossl.  Similarly, the TMB Planetary was visually validated as less than the Radian, and so forth for the remaining eyepieces.

 

Finally, the Category-1 table above also lists the relative “out-focus” required for each eyepiece.  The number shown is the distance in millimeters the focuser had to be extended from its full “in” position for each eyepiece to reach focus.  There was only a 16mm or 6/10th of an inch difference between the eyepiece needing the most in-focus, the Sterling, to the ones needing the most out-focus, the Brandon and Radian.

 

B)   Category-2 Results:  May Vary by Personal Expectation or Habit

 

Items assessed: Build Quality – Handling & Field Use Characteristics

 

Eyepiece

Build Quality

General
Handling

&

Field Use

Televue Radian

            A

A

TMB Planetary

            A*

A

Sterling Plossl

            A*

B

University Optics Ortho

            A

B

Baader Genuine Ortho

            A*

B

Pentax SMC Ortho

            A

C

Zeiss ABBE Ortho v I

            A*

B

Zeiss ABBE Ortho v II

            A*

B

TMB Supermono

            A

B

Astro-Physics SPL

            A

B

Brandon Ortho

            A

C

Note – Numbers indicate rankings (A is best); If a number is repeated for several eyepieces, then this means too close to call a difference with assurance; *=see narrative for explanation; If there are two sets of numbers, then the first set indicates ranking in the Takahashi TSA-102 APO, then the Orion XT10 Dobsonian.

 

After handling and examining all the eyepieces in this comparison, clearly each is well made.  Not one gave a build impression of anything less than being carefully designed, constructed, and well finished.  While some were made of lighter materials, such as lighter metals verses brass components on others, the use of heavier metals should not be taken as an indication of increased quality.  Instead, by my estimation, it is fit, finish, and attention to detail which better defines quality, and all of the eyepieces in this comparison met that criteria excellently.  As a side note, the eyepieces in the table which are shown with an asterisk (*) next to their ranking indicates that these eyepieces had portions or all of the lettering and graphics on the housing silk-screened and/or painted.  This of course will mean that over time one can expect the lettering to eventually wear off with repeated use and contact.  While I did not think this was sufficient to lessen their build quality rating, I thought it was valuable to note for prospective purchasers of these eyepieces as it may impact a personal preference.

 

While each eyepiece demonstrated a very good build quality, two eyepieces deserve special mention, the ZAO-II and the Astro-Physics.  The ZAO-II had a level of attention to the field-end of the unit more than any of the others.  In addition to having micro-baffles and an extremely flat black interior, it also had two larger baffles and then a deep, narrow and superbly blackened tube in front of the field lens as an additional shielding measure.  No other eyepiece showed this many methods employed within the barrel to control light and aid in contrast.  Second, the Astro-Physics employed several innovations which proved very effective, such as the Derlin housing which is resistant to cold to aid in reducing the possibility of eye lens fogging during cold weather.  During some very cold evening and morning observing sessions this improvement worked excellently as the Astro-Physics eyepiece did not fog whereas many of the others fell victim to this common cold weather issue.  In addition, I felt that constructing the barrel from stainless steel instead of chromed brass was also a notable improvement.  Using stainless steel, with a hardness rating similar to chrome, it has the additional advantage that any scratches over time can be buffed out without worrying about wearing off chrome and revealing brass.

 

In general handling, the larger Radian and TMB Planetary eyepieces were more confidently graspable due to their size.  Generally, even though much smaller most of the remaining eyepieces were similarly easy to handle and firmly grip.  The exceptions to this were the Brandon and the Pentax SMC Ortho.  Since the Pentax was a smaller .965 inch and not a 1.25” standard, handling was sometimes worrisome, particularly in the cold when fingers become stiff and touch is less sensitive.  The Brandon, while a 1.25” standard, is very light in weight which made handling in cold weather seemingly less secure.

 

In the field and at the telescope all the eyepieces were easy to use overall, with just a few exceptions.  The Brandon was difficult to remove from the focuser since the top lens housing was very thin.  If in cold weather, gloves had to be removed to effectively remove the Brandon from the focuser given how thin the top housing was on the 6mm unit.  To resolve this issue, I therefore only sat the Brandon half way into the focuser then locked it tight in this raised position.  The Radian, with its significant weight, tended to tilt just prior to insertion, so it always seemed to need a reposition to slide into the focuser smoothly.  Finally, all the eyepieces with safety undercuts on their barrels were a significant annoyance as they often hung on the compression ring during removal from the focuser.  The ZAO-I’s undercut in particular seemed to have this problem more than the others.  Removing the ZAO-II, Brandon, Astro-Physics, Pentax, University Optics, and Sterling from the focuser never encountered any issue due to their smooth or tapered barrels.

 

c)   Category-3 Results:  May Vary by Telescope / Focal Ratio / Sometimes Atmosphere

 

Items assessed: Off-Axis Aberrations – Scatter – Light Control – Field of View Uniformity                                                                             

 

Eyepiece

Off-Axis Sharpness

 

      TSA  -  XT10

Scatter

Light Control

Field of View

Background

Darkness

Uniformity

Televue Radian

A   -   A

D

A

A

TMB Planetary

A   -   C

D

A

B

Sterling Plossl

A   -   D

E

A

B

University Optics Ortho

A   -   B2

D

A

A

Baader Genuine Ortho

A   -   B2

D

A

A

Pentax SMC Ortho

A   -   B2

A

A

A

Zeiss ABBE Ortho v I

A   -   B2

B2

A

A

Zeiss ABBE Ortho v II

A   -   B1

B1

A

A

TMB Supermono

A   -   D

C

B1

A

Astro-Physics SPL

A   -   A

C

C

A

Brandon Ortho

A   -   C

C

B2

B

Note – Numbers indicate rankings (A is best); If a number is repeated for several eyepieces, then this means too close to call a difference with assurance; If there are two sets of numbers, then the first set indicates ranking in the Takahashi TSA-102 APO, then the Orion XT10 Dobsonian.

 

Off-Axis Sharpness

 

Performance off-axis varied as expected by telescope.  In the TSA-102 APO with its f/8 focal ratio, all the eyepieces performed excellently either to the field stop or very close to the field stop.  Turning to the Orion XT10, with its very fast f/4.7 focal ratio, many of the eyepieces were now greatly challenged off-axis.  Top performing off-axis in the XT10, were the Radian and the Astro-Physics (Rank-A).  Both of these maintained stars sharp to the very edge of field.  While the Radian does show a degree of chromatic aberration (CA) off-axis, it generally does not reach the moderate level until just prior to the field stop and is only noticeable on the brightest stars.  Therefore, for the vast majority of star fields, the CA is not of any impact.  After these two top performers, the Ortho eyepieces in the comparison (Rank-B) all performed quite similarly and next best, showing a sharp field of view until perhaps 5%-10% from the field stop where the star image deteriorated due to varying degrees of either field curvature, astigmatism, or both.  The two exceptions within the Ortho eyepieces were the Brandon (Rank-C) and the ZAO-II (Rank-B1).  The Brandon performed slightly less well off-axis than the other Orthos with the stars deteriorating a slightly further from the field stop than the rest of the Orthos, perhaps at 15% from the field stop. The ZAO-II was just opposite and remained sharp closer to the field stop than the typical Ortho, attesting to the marketing claim that the new ZAO-IIs have been designed to handle an f/4 light cone well.  The TMB Planetary put up an off-axis performance similar to the Brandon, and finally the TMB Supermono and the Sterling Plossl (Rank-D) both held only the central 50% of their field of views sharp.  This was expected from the TMB Supermono as the monocentric design is not designed to handle fast light cones well.  However, it was an unexpected result from the Sterling as Plossl designs typically do much better.  So the Sterling 6mm did not perform anywhere near as superbly off-axis as the Sterling’s line of other longer focal length Plossls have previously tested. 

 

It was noted that off-axis performance also varied significantly by target.  When viewing nebula, other extended non-lunar/planetary objects, or stars dimmer than magnitude two, these targets all tended to be very forgiving and it was difficult to notice any off-axis softness in the images.  Planets, while a little more sensitive, also performed surprisingly well off-axis.  Only the finest details on planets were obscured off-axis while the grosser and more prominent details remained well defined, even in eyepieces where the off-axis performance was not perfect.  The rich detail of the moon and bright stars were probably the harshest targets for the off-axis region of each eyepiece.  With either of these target types any off-axis aberration was immediately noticeable, with bright stars being the harshest target.  Therefore, depending on the targets an observer enjoys most, off-axis performance ranking may be judged differently.

 

Finally, although not conducted during this comparison, some observers find that using a close double star in which there is a very significant magnitude different between components as an excellent test for on-axis versus off-axis performance of an eyepiece.  In practice, this is an excellent test and one encouraged to conduct for reviews where off-axis performance is a focus of the evaluation.  However, since the primary focus of this comparison was to evaluate lunar/planetary performance, most effort was devoted to on-axis comparison.

 

Scatter

 

Three different approaches were used to evaluate scatter.  The first method was the traditional approach to estimate the extent of the glow around a bright star.  Magnitude zero Capella was used.  Using the Orion XT10 all the eyepieces showed obvious scatter to varying degrees with Capella.  I characterize the extent and brightness of the scatter for Rank-C and Rank-D eyepieces in the table above as moderate – plainly visible but not to the point where it was overly distracting or objectionable.  The Rank-E Sterling Plossl, I considered to be at the moderate level as it was sometimes distracting.  The three Rank-A and Rank-B eyepieces, the ZAO-I, ZAO-II, and Pentax Ortho, all showed noticeably less scatter than the rest of the eyepieces in the comparison.  Of these three top ranked eyepieces, the Pentax Ortho was judged a level better than either the ZAO-I or the ZAO-II, showing only very minor scatter which did not extend far from any star.  Still excellent, but a notch lower than the Pentax Ortho, the ZAO-I and ZAO-II showed very minimal scatter, and the newer ZAO-II performed subtly better showing slightly less scatter than the ZAO-I. 

 

For a second evaluation of scatter, I chose a brighter double star which had a very dim background field star closely positioned to the double, magnitudes 3.6 and 5.5 Lambda Orionis.  In the XT10 this double was generously split at 200x using the 6mm eyepieces.  In addition to the double star, there was also a line of three fainter stars in the field of view.  The one closest to the double was very faint and within the field of scatter of the double making it an excellent test.  For this test, instead of trying to measure the extent of the scatter, the faint star was viewed with direct vision and a comparison was made as to how strongly and distinctly this dim star could be viewed.  Using this test, the eyepieces ended up falling into their same categories of performance as was noted with the Capella test.  However, this test was more interesting in that it showed real impacts from scatter.  The eyepiece with the strongest scatter, the Rank-E Sterling, was unable to reliably maintain the dim star with direct vision.  Instead there would be moments when it would come into view within the brighter background of scatter, then disappear.  For those eyepieces grouped in Rank-C & D, the dim star was much easier to view.  Finally, for the grouped in Rank-A & B eyepieces, the Pentax Ortho and the ZAO-I and ZAO-II, the dim star stood out strong and clear against a nicely dark background largely unaffected by the scatter from the very close bright double.  Again, of these three top performers, the Pentax Ortho was significantly better with no scatter from the double impinging on the dim background star.  For the ZAOs, again the newer ZAO-II showed less scatter than its older ZAO-I brethren.

 

After these two tests, a variety of other doubles were viewed, including Beta Orionis (Rigel) magnitudes 0.1 and 6.8, Iota Orionis a 3rd and 7th magnitude double, and Theta 1 Orionis (components A-F of the Trapezium).  The results noted on Capella and Lambda Orionis held for these doubles as well with the Pentax Ortho clearly giving the best performance, followed by the ZAO-I and ZAO-II, with the remaining placing more distant 3rd, 4th, and 5th places.

 

A final “scatter-like” test was conducted by placing a bright planet, Venus, just outside of the field stop and judging residual glow from the planet that extended into the field of view.  It is probably arguable whether a test like this should be considered scatter or flare since the only artifact being noted is how much brightening of the immediate background or glow from the bright object makes its way into the field of view.  Nevertheless, the test was conducted for information purposes, but not included as part of the rankings for either scatter or light control.  Using the TSA-102, the TMB Supermono, ZAO-I, ZAO-II, and Pentax SMC all showed excellent control of stray light and the least amount of residual scatter extending into the field of view as this bright planet was positioned just outside the field stop.  The Baader Ortho (Rank-D for scatter), quite contrary to its final scatter ranking based on glow around stars, provided excellent performance relative to residual glow entering from outside the field stop, with only slightly more residual glow from outside the field stop than the Rank-A (for scatter) eyepieces showed.  The TMB Planetary, Radian, Astro-Physics, University Optics, and Brandon (Rank-C for scatter) also exhibited what I judged as good control of this glow, but a notch less than the BGO.  The Sterling showed a brightening glow extending from Venus when it was positioned just outside the field stop to a greater degree than any other eyepiece.

 

Light Control

 

Again, magnitude zero Capella was an excellent bright star for this test in the XT10, and only two eyepieces showed any ghosting/flare/reflections.  The Brandon showed a very dim ghost of Capella about half way across the field of view.  This ghost was very dim, pinpoint, and was rare and difficult to notice in any routine use.  The Astro-Physics was the other eyepiece showing any light control issues and they occurred frequently enough to be routinely noticeable during observations.  It showed oblong ghosts at multiple times during observing sessions, and flare/reflections at two distinct points when Capella crossed the field of view -- when Capella was positioned either half way across the field of view and a dim and small ghost appeared in the central region of the field of view, when it reached the field stop and a large moderately bright arc formed in the central region of the field of view, or at times when a line of light appeared from the field stop.  These minor-level light control issues in the Brandon, and the moderate-level light control issues in the Astro-Physics were repeated when Venus was observed.

 

In both the TSA-102 and the XT10 all eyepieces except the Astro-Physics handled the bright Moon very well.  Placing the moon’s limb just outside the field stop produced no flare, glare,  or other unwanted light control issue of any kind.  The Astro-Physics on several occasions did show an extremely faint and short arc of light about mid-field when the Moon was just outside the field stop, however it was very difficult to detect and not readily obvious.

 

Turning to Sirius using both the TSA-102 and XT10, the Astro-Physics showed strong multiple ghosts.  However, the Astro-Physics also had one of the cleaner looking star points for this very bright and difficult star.  In addition, the TMB Supermono for the first and only time during all observations showed a very faint and almost imperceptible ghost. 

 

Finally, most eyepieces exhibited the occasional reflection due to reflection off the eyeball back onto the top lens (i.e., eyeball glint).  This would occur at times for the brightest objects like Venus or Sirius, and at times from external sources like porch lamps.  A slight reposition of the eye, or shielding of the eyepiece from external sources, would easily eliminate these occurrences.

 

FOV Uniformity

 

The uniformity of background darkness across the field of view of an eyepiece is not a test which is often reported.  However, some eyepieces are known to exhibit a lightening near the field stop during normal observing and this has been reported for several popular wide fields and planetary eyepieces.  While this lightening can be caused by poor baffling, and has been corrected by some amateurs by correcting baffles in purchased eyepieces, it needs to be noted that stray light entering the front of a telescope can also be a cause.  Therefore, before determining the lightening near the field stop is a consequence of the eyepiece, it should be ensured that light entering the telescope is not the root cause.  During this comparison, both telescopes used exhibited this phenomenon for several of the eyepieces.  It was also observed consistently for these same eyepieces regardless of measures taken to further shield the telescopes from stray light.  The phenomenon was also slightly more pronounced on evenings when the observing skies were brighter and the limiting magnitude was only 3.5 or 4.0.  The ZAO-I, ZAO-II, Astro-Physics, Radian, TMB Supermono, Baader Ortho, University Optics, and Pentax Ortho were all nicely dark to the field stop during routine observing.  The Brandon showed a very faint lightening near the stop.  The TMB Planetary, and Sterling each showed a definite and stronger lightening near the stop.  In no case did this lightening affect apparent performance or the ability to accomplish any observing task.  For some observers this can be an annoying artifact, therefore important report.

 

d)   Category-4 Results:  May be Very Subjective by Observer, Telescope, and Atmosphere

 

Items assessed: Resolution – Transmission – Contrast – Color Fidelity – Image Warmth

 

Determining the exact reason why an image looks sharper or “better” in an eyepiece is highly debated, subjective, and difficult at best.  Therefore, the major attributes of sharpness or image crispness: resolution, contrast, and transmission, have been grouped into a single category of performance for this comparison.  In addition, this has been evaluated by observed object instead of generalizing the combination of these factors across all targets.  I feel this is a more balanced approach since one can never be sure when perceiving a view as being sharper, for example, that this is really due to better resolution, as opposed to some combination of improved contrast, transmission, scatter, or even tone of the eyepiece.  This approach therefore eliminates conjectures as to the root cause of these observed differences, and instead focuses on objectively documenting what visual impressions were observed by each celestial target type.

 

Eyepiece

Resolution/Contrast/Transmission

(overall performance on each target class)

Color Fidelity

Image Tone


(not a rating - FYI only)

Planets

Stars

Nebula

TSA-XT10

Luna

TSA-XT10

Televue Radian

C1

C

C  -  C1

C2 -  C2

A     (neutral)

neutral-warm

TMB Planetary

C2

D1

C  -  C2

C3 -  C3

B     (ruddier colors)

warm

Sterling Plossl

C3

C

C  -  D

D   -  D

A     (neutral)

neutral

University Optics Ortho

C4

D2

D  -  D

D   -  D

B     (ruddier colors)

neutral

Baader Genuine Ortho

B2

C

C  -  C2

C1 -  C1

A     (neutral)

neutral

Pentax SMC Ortho

B1

B

B  -  A3

B   -  B

A     (neutral)

neutral

Zeiss ABBE Ortho v I

A

B

B  -  A2

A   -  A2

A     (neutral)

neutral

Zeiss ABBE Ortho v II

A

A

A  -  A1

A   -  A1

A     (neutral)

neutral

TMB Supermono

A

A

B  -  A2

A   -  A2

A     (neutral)

neutral

Astro-Physics SPL

B1

B

B  -  B2

B   -  B

A     (neutral)

cool

Brandon Ortho

B2

C

A  -  B1

C1 -  C1

B     (less saturated)

neutral-cool

Note – Numbers indicate rankings (A is best); If a number is repeated for several eyepieces, then this means too close to call a difference with assurance; If there are two sets of numbers, then the first set indicates ranking in the Takahashi TSA-102 APO, then the Orion XT10 Dobsonian.

 

Planets - Resolution/Contrast/Transmission

 

On Saturn, the only planet high enough above the horizon to be free of most of the atmosphere’s turbulence during this comparison, three eyepieces consistently grouped highest, the ZAO-I, ZAO-II, and TMB Supermono.  The brightness, dimensionality, and level of detail these eyepieces revealed was clearly a notch above all others.  The photo of Saturn (see Saturn Simulation) demonstrates the differences in detail which was observed using these Rank-A eyepieces in the Orion XT10, versus the other eyepieces in this comparison.

 

SATURN SIMULATION: The base image taken on 12/08/2008, from which this simulation was based, courtesy of CN member Rolando Chavez (http://www.geocities.com/rolo0235/PlanetaryImagingbyRolandoChavez.html)

 

As can be seen from the Saturn photo simulation, the ZAO-I, ZAO-II, and TMB Supermono were the only eyepieces which showed an entire second band in the Northern Hemisphere, and in addition also showed structure within the larger band (most likely a storm).  In addition to these extra details, the diminishing in brightness of the rings where the Cassini division was located, as well as the shadow of the planet on the rings (pictured to left of orb in the simulation), was more starkly rendered in these Rank-A eyepieces.  Finally, the added brightness and the deeper blacks of the shadows in these eyepieces gave Saturn a decidedly three-dimensional appearance which none of the other eyepieces rendered as effectively.  There was also a very subtle difference amongst these three top performers on Saturn.  The TMB Supermono showed a cooler toned view and the atmospheric bands were not quite as dark -- there was not less detail visible, but the bands were not quite as dark of a ruddy orange-brown color as they were in the ZAO-I and the ZAO-II.  Finally, the ZAO-II showed a slightly brighter image and the atmospheric bands were slightly darker than through the ZAO-I.

 

Through the TSA-102, the differences on Saturn between the eyepieces were very much subdued, but the relative rankings remained the same.  In all the eyepieces in the comparison only the single larger band in the Northern Hemisphere was visible using the TSA-102.  At no time was structure within this band visible as this feature was angularly below the resolution limit of a 4-inch instrument.  The only real differences amongst the eyepieces when viewing Saturn through the smaller TSA-102, was the level of brightness and color tones on the planet.  The Rank-A ZAO-I, ZAO-II, and TMB Supermono presented a much brighter planet, followed by the Rank-B grouping which consisted of the Pentax SMC Ortho, Astro-Physics SPL, Brandon, and BGO. 

 

The tonal characteristics of the eyepieces also showed a performance difference on Saturn relative to colors, even in the smaller aperture TSA-102.  The TSA-102’s Rank-A and Rank-B eyepieces (i.e., TMB Supermono, ZAO-I, ZAO-II, Astro-Physics, Pentax Ortho, Brandon, and Baader Ortho) clearly showed the shadings on the Southern Polar region as a nice gradation of steel-blue hues.  In all other eyepieces this feature appeared as simply a neutral grey-scale.  The TMB Planetary was the warmest toned eyepiece of the group, but still showed as much detail as all others using the TSA-102.  The University Optics appeared similarly warm, but after much scrutiny I feel this impression has more to do with it showing a little less bright of an image than the rest of the eyepieces, rather than an actual tonal warmth.  Therefore, aside from slight brightness and coloration differences, unlike the varying levels of detail revealed when using the larger aperture XT10 Dob, through the smaller 4-inch TSA-102 all eyepieces revealed a very similar level of details on Saturn.

 

Stars - Resolution/Contrast/Transmission  

 

For the star test, I evaluated how well various stars presented themselves within the field of view.  By this I mean how easily a dim star could be seen, could it only be seen with adverted vision in one eyepiece but direct vision in another, did the star seem to stand out more prominently in one eyepiece then appear more subdued in another, etc.

 

For this test, the ZAO-II and the TMB Supermono ranked as Rank-A in both telescopes.  These two eyepieces regularly showed dimmer stars which were invisible in the other eyepieces.  At times these dimmer stars would be constantly visible with adverted vision, and at other times they would only periodically come into view.  In addition to dimmer stars being more visible, these two eyepieces also displayed stars with a level of presence and authority notably better than the other eyepieces.  So when viewing the Trapezium with these two eyepieces, component E was much stronger when using the TSA, and component F revealed itself more steadily and strongly when using the XT10.  And when viewing clusters like M35, M36, and NGC869, the brighter stars in these clusters appeared stronger, giving the cluster a more three-dimensional perspective.

 

In the Rank-B eyepieces (i.e., ZAO-I, Astro-Physics, and Pentax Ortho), the major difference was that stars appeared noticeably brighter than in the lower Rank-C eyepieces.  When comparing the views between the Rank-B and Rank-C eyepieces, the Rank-B eyepieces portrayed the Trapezium’s fainter components more strongly, and the M35, M36, and NGC869 clusters appeared brighter and with more dimensionality.

 

In each of the four rankings of eyepieces for star performance, there was not sufficient variation within each ranking to say that any single eyepiece within a rank performed any better than another eyepiece within the same rank.  The two Rank-D performers, the University Optics and the TMB Planetary, were ranked here solely because they did not show Trapezium-E in the TSA, or Trapezium-F in the XT10, when all others did during the evenings when the Trapezium was observed.  I also ranked the University Optics less well performing than the TMB Planetary as stars seemed a little dimmer in this eyepiece. 

 

As a final note, and one that cannot be stressed enough, even though technical performance of the Rank-A group evaluated as “best” in terms of the discrete test, the wider apparent field of view eyepieces (i.e., the Radian and the TMB Planetary) gave a more impressive view overall for stars and stellar objects.  Their views were more impressive not due to how much stronger the stars appeared, or how well formed the airy disks appeared, but simply due to being able to see more true field of view, resulting in a more interesting and rich field of view.  So depending on whether an observer desires larger and more feature filled fields of view, or if they desire the deepest penetration into a star field, the “best” performer in this category may differ substantially from individual to individual.  However, since the basis of this test was how well individual stars were rendered, this apparent field of view factor was not taken into account in the final ranking.

 

Nebula - Resolution/Contrast/Transmission

 

Through the TSA-102, performance on nebula was judged primarily on M42, M43, and M31 and the criteria was maximum brightness, extent, apparent contrast, and detail.  On these three targets all the eyepieces performed very similarly.  There was not much distinction to be seen between any of them with the exception of the ZAO-II and Brandon (Rank-A).  Both of these eyepieces showed an incredible amount of detail in the mottled structure of the M42 nebula compared to any of the other eyepieces.  The ZAO-II showed a brighter image and more extent to both M42, M43, and M31, with the core of M31 being much more pronounced than in the Brandon, however, the Brandon was ranked with the ZAO-II not because of brightness but because of the superb mottled detail of the nebula it was rendering.  The next best were the ZAO-I, Astro-Physics, Pentax, and TMB Supermono (Rank-B).  All of these were judged equal in their rendering of both M42, M43, and M31.  The remaining eyepieces (Rank-C & D) simply showed M42, M43, and M31 a little dimmer, a lesser extent to the nebula, and less details in the nebula’s mottled structure than the higher ranked eyepieces.

 

Moving to the XT10, there was more distinction evident between the eyepieces due to the larger aperture of this telescope.  The ZAO-I, ZAO-II, Astro-Physics, Pentax Ortho, and TMB Supermono (Rank-A) were the top performers in this telescope, all showing the greatest brightness, extent, and details within M42, M43, and M31.  It was odd that the groupings observed in the TSA-102 changed with some eyepieces moving lower to higher ranks and visa versa.  I have no explanation for this, but it was observed and repeated on multiple evenings.  Among the Rank-A group, the ZAO-II showed a slightly brighter and higher apparent contrast image of all the eyepieces.  As in the TSA-102, the remaining lower rankings of eyepieces in the XT10 simply rated lower because they showed an obvious less bright and less extended nebula or galaxy.  Like the Rank-A performers in the XT10, the Rank-B & C groups also had subtle variations noted between the eyepieces.  In these groups, the Brandon edged the Astro-Physics slightly in the details it was showing, and the Radian similarly showed a slightly better defined nebula than the rest of the Rank-Cs.

 

Again, as a similar final note as was given in the star comparison, even though the technical performance of the Rank-A group was definitely the best, the wider apparent field of view eyepieces (i.e., the Radian and the TMB Planetary) gave a more impressive and pleasing view overall due to their greater true field of view.  So depending on whether an observer prefers larger and more feature filled fields of view, or desires to maximize the brightness and detail within a nebula or galaxy, the “best” performer in this category may differ substantially from individual to individual.  Since the criteria of this test was maximum brightness, extent, apparent contrast, and detail rendered for nebula and galaxies, this apparent field of view factor was not taken into account in the final ranking.

 

Lunar - Resolution/Contrast/Transmission

 

During this comparison, the Moon more than any other target showed the greatest difference between the lowest and highest ranked eyepiece.  It didn’t matter whether the 10-inch or the 4-inch telescope was used, in either one there were spectacular differences between the highest ranked and lowest ranked eyepieces.

 

The first test was to conduct what I feel is the least pleasing high magnification lunar observation possible, viewing a flatly front lit full moon.  In the photo simulation, I turned to one of my favorite regions, the vicinity of Crater Clerke (see Crater Clerke / Apollo 17 picture).  This also happens to be the landing site of Apollo 17.  In this region, there is a cluster of dark shadings, which if you orient them correctly and use your imagination, looks somewhat like a short, stout goblin with both arms raised.  In the picture below the white arrow points to this feature and the dark shadings presenting the goblin feature are upside down.  During a full moon, since the Sun’s light is lighting the surface straight on as opposed to at an angle, this feature does not present significant contrast from its surroundings and overall appears lower in contrast than normal and very “flat.”  As can be seen from the views in the simulated pictures inset next to the larger picture, in the Rank-A eyepieces (i.e., TMB Supermono, the ZAO-I, and the ZAO-II), this feature still maintained surprisingly rich and deep contrast relative to its surroundings.  Never before have I viewed this feature during the full moon phase where it had such intensity and contrast.  In the TSA-102 the three Rank-A eyepieces all performed equally well, in the XT10 however there were definite subtle differences.  In the ZAO-II this feature was rendered with a greater register of contrast, and the very high albedo of crater Clerke appeared brighter and whiter.  Next, the TMB Supermono and the ZAO-I were tied, coming in a little less bright and with a little less apparent contrast than the ZAO-II.

 

The Crater Clerke / Apollo 17 Region (Photos: Full Moon – Eric Roel; Insets –  NASA #AS15-1113m)

 

After the top ranked grouping, next best were the Pentax Ortho and the Astro-Physics SPL (Rank-B), both tied in their performance on this goblin feature in the crater Clerke region.  They showed this feature and other lunar features as well, with an obvious notch less brightness and contrast than the Rank-A eyepieces, and an obvious notch better contrast than the Rank-C eyepieces.

 

The next group, the Brandon, Baader Ortho, Radian, and TMB Planetary (Rank-C), again showed this feature, and other lunar features, noticeably less well than the Rank-B group.  However, within the Rank-Cs there were subtle differences and I felt the Brandon and the Baader rendered a little crisper and brighter, followed by the Radian, then the TMB Planetary. 

 

In the final grouping, the University Optics and the Sterling Plossl, these placed last due to the poorer edge performance for the Sterling (particularly in the f/4.7 XT10), and for the apparent dimmer view rendered by the University Optics.  Again, while these eyepieces performed at varying levels on the moon, all were very sharp and rendered good, clean lunar images, with the TMB Planetary showing warmer tone.  Each eyepiece, standing on its own, I feel could be considered very capable for lunar observations.  However, when viewed side-by-side with some of the best eyepieces produced, differences can be seen.

 

As the phases of the Moon changed and I observed features during quarter, half, and three quarters phases, when lunar features have low angled light casting deep and long shadows, the views became breath-taking in the top ranked eyepieces compared to the other ranks.  Again, regardless of whether viewed through the TSA-102 or the XT10, lunar views in the ZAO-I, ZAO-II, and TMB Supermono were better than I had ever observed prior to this comparison.

 

In the photo simulation of the Crater Aristarchus region (see Aristarchus picture), the details were breath taking in the Rank-A TMB Supermono, ZAO-I, and ZAO-II.  This simulation actually does not do justice to how incredible the view appeared in these eyepieces. 

 

 

In addition to being both brighter and having a greater register of contrast (i.e., brightest parts were much brighter and darkest parts were much blacker), the region appeared incredibly three-dimensional and the darker material just outside the crater walls (see white arrows in top panel of Aristarchus picture) was so dark, granular, and detailed, that it appeared as soot or coal dust and prompted me to want to climb through the eyepiece to try and clean the area of this debris.  Again, the photo simulation to the right does not have sufficient detail to portray this effect, but it was dramatically different in the Rank-A eyepieces compared to the other ranks.  In short, I was treated to lunar views using these Rank-A eyepieces I have never experienced in my 40 years of observing.                                                                                     

 

The Rank-A eyepieces also demonstrated the ability to provide a three-dimensional perspective when observing the moon which was significantly more pronounced then any lower ranked eyepiece.  The Mare Crisium region of the moon provides a good example (see Mare Crisium picture).  In the simulation of the ridge of the Mare Crisium region in the photo to the left, the white arrow points to a mountain outcropping.  If you look at this feature in the top panel (see Mare Crisium picture) and compare it to the same feature in the bottom panel, you can begin to see the more dimensional impression in the top photo.  Again, this simulation does not fully portray the real visual impact while observing, but does begin to convey the difference an observer can expect on evenings of good seeing when lunar observing with these Rank-A eyepieces.

 

 

As final examples of the performance distinctions of the Rank-A eyepieces, the Crater Milichius and Sinus Iridium areas are excellent lunar regions to examine.  In the area of Crater Milichius, the region is rich in domes and broad raised landscapes.  In the TMB Supermono, ZAO-I, and ZAO-II, the 3-D dimensionality of the view was pronounced.  I could immediately “feel” the rolling nature of the terrain, and the relative sizes of the domes and broad rounded outcroppings very distinctly as I observed.  This experience did not occur nearly as strongly using any of the lower ranked eyepieces, and in the lowest rankings, while the dimensionality was still observed, it just did not convey quite the dramatic impression of relative sizes and variations in the sloping terrain anywhere near as well as in the Rank-A eyepieces. 

 

In addition to increased dimensionality, many of the small and tightly clustered mountain peaks in the area of Crater Milichius were more easily distinguishable as distinct peaks (see Crater Milichius picture).  In the eyepieces ranked lower than C1, while it was still easy to detect that these clustered outcroppings were multiple peaks, it was not possible to reliably count how many peaks comprised the cluster with any certainty.  In the Rank-A through C1 eyepieces, each peak was very clearly distinguishable (i.e., ZAO-I, ZAO-I, TMB Supermono, Pentax, Astro-Physics, Brandon, Baader). 

 

 

Finally, the Sinus Iridium area (see Sinus Iridium picture), the many rilles in this region were simply more sharply defined and showed starker gradations of black to grey in the Rank-A eyepieces than in any others.  The difference in sharpness, brightness, and contrast performance by the Rank-A eyepieces in this region, and in all other lunar regions, is perhaps best demonstrated by the simulations provided for Crater Clerke and Crater Aristarchus.  If you view the difference between the lowest and highest detail pictures in these two simulations they provide the best example of the actual difference in views when observing.

 

 

Finally, by no means were the views through any of the lower ranked eyepieces to be considered anything less than very pleasing.  Standing on their own, each eyepiece in the comparison provided very sharp and pleasing lunar views.  With any of these fine eyepieces one could easily look forward to endless evenings of very rewarding lunar observing. 

 

Color Fidelity

 

During the course of the comparison, I was surprised to notice comparatively little variation in color fidelity between these many eyepieces.  For an initial test I observed the very strongly colored Aldeberan through the XT10 (magnitude 0.84, color B-V 1.54).  Each eyepiece presented this star as an orange-to-burnt-yellow color and individual variation was slight.  The only notable difference was in the TMB Planetary and the University Optics where Aldeberan appeared slightly more “ruddy,” and in the Brandon where Aldeberan was definitely a more yellow-white color.  This appearance distinction of the TMB Planetary and the Brandon also held when viewing the yellow-orange star between two clusters of the Perseus Double Cluster, star TYC3694-1613-1 (magnitude 7.9, B-V Color 2.66).  This star appeared less pronounced as a colored star in both the TMB Planetary and the Brandon. 

 

Moving to the TSA-102, the colorful double star Gamma Andromeda was chosen (magnitude 2.3 and 5.5; separation 9.7”).  The brighter component is yellow-orange and the dimmer one is blue.  Most of the eyepieces rendered the colors of these stars equally well.  However, one eyepiece stood out showing noticeably stronger saturated colors, the Pentax SMC Ortho.  Through this eyepiece the primary was a brilliant orange-yellow and the secondary was a strong teal blue, a stronger color blue than any other eyepiece portrayed.  Not quite as strongly colored as in the Pentax, the Baader Ortho showed the blue component next best of all the eyepieces.  Aside from the Pentax at the top of the ranking, then followed by the Baader Ortho, in all others the colors were rendered equally well, showing a nice contrast between the components with a beautiful medium-blue secondary. 

 

Finally, there were two eyepieces which did seem to show the blue companion slightly washed out, the Brandon and the TMB Planetary.  While the secondary still showed a blue color, it was more of a weak blue-white than the stronger blue in the other eyepieces.  The performance of the Brandon and TMB Planetary in the TSA-102, confirmed what was observed through the XT10, both showing colors a little less saturated than the other eyepieces.  As a side note, comparing the ZAO-I & ZAO-II directly against each other, the ZAO-II showed the colors of Gamma Andromeda very minutely stronger.  Overall the newer ZAO-II has proven a worthy successor to the original ZAO-I.

 

Image Warmth

 

With all the attention many amateurs give to apparent visual impacts due to coating warmth, myself included, in these side-by-side comparisons I was surprised how uniformly image warmth or coolness appeared to be between all the eyepieces.  The eyepiece which struck me the most as showing a perceivable difference in warmth was the TMB Planetary as being warmer than the rest, and the Astro-Physics SPL being the coolest (actually most neutral) of the eyepieces in this comparison.  The side effect of the cooler tone of the Astro-Physics was that the view of the moon often seemed perceptually a little brighter.  However, no other advantage was noted in any test due to the cooler cast of the Astro-Physics.  Similarly, the warmer tone of the TMB Planetary caused a misperception when viewing the moon, making it seem not as bright at first glance.  It should also be noted that simply because a celestial object does not appear not quite as bright in any eyepiece, this does not necessarily mean that their transmission is any lower than any other eyepiece as the perception of brightness can be tied to multiple other factors as well (e.g., contrast, tone, sharpness, smoothness of polish, etc.).  Overall, however, throughout the course of this comparison an eyepiece’s coolness or warmth did not appear to have notable impacts on performance outside of rendering of colors cooler or warmer.

 

e)   Category-5 Results:  Anomalies and Unanswered Questions

 

Throughout the course of all the many observing sessions very few anomalies ever presented themselves.  All tests were repeated successfully on multiple evenings and between scopes with no re-ranking being necessary.  The one exception, which I did not report as a test, was focus snap.  The ability of one eyepiece to either snap to focus or to maintain a sharp focus varied significantly from evening to evening.  So on one evening eyepiece A would snap or maintain focus better than eyepiece B, then on another evening these results would reverse.  Due to this, I can make no conclusions regarding eyepiece focus snap.  I had expected the more highly touted ZAOs or those eyepieces with integrated Smyth/Barlow elements to be clear winners in this category, but they did not consistently show this characteristic.  However, although I was I unable to reliably repeat this performance, I was still generally left with a subjective impression that the ZAO-I, ZAO-II, Astro-Physics SPL, and Pentax SMC Ortho as a group provided the most authoritative focus snap.

 

VII.  Conclusions

 

As a set of general conclusions, considering the collective observation results I feel the following can be confidently asserted:

  1. Very good atmospheric seeing and transparency are required to bring out many of the rankings and differences noted.  On multiple evenings which did not prove good enough to conduct the evaluations, all eyepieces generally showed little difference between them.
  2. Regardless of an eyepiece’s ranking on any test, all the eyepieces produced very sharp, detailed views and every eyepiece served well in the role of lunar/planetary observation.
  3. Larger aperture instruments or brighter celestial objects are required to show significant differences between eyepieces.  Many observing sessions demonstrated this, as reported in results sections of this comparison.  This leads to the following sub-conclusions:
    1. Planetary observations can yield significantly improved details using the highest ranked eyepieces in larger aperture instruments.
    2. Lunar observations can yield significantly improved results using the highest ranked eyepieces even in moderate aperture instruments.
  4. The size of an eyepiece’s apparent field of view is fairly inconsequential for effective and pleasing lunar and planetary observing.  While larger apparent fields of view did make lunar observing more interesting at times, when the focus was on particular lunar features this advantage vanished.  This conclusion should be tempered by one’s equipment, whether high magnification tracking is manual or automated, and the observer’s skill at manual tracking.  If an observer does not enjoy manual tracking and they do not have automated tracking, then larger apparent field of views will be an advantage for high magnification lunar/planetary observing.
  5. The size of an eyepiece’s apparent field of view is an important consideration for viewing extended clusters, nebula, galaxies, and star fields.  As noted in the detailed reporting, when more surrounding context could be viewed for these targets, the observing experience was more dramatic, regardless of other optical considerations.

 

Finally, to supplement the more objective observed outcomes provided for the various tests in this comparison, I have also come away with distinct personal impressions related to each eyepiece.  These impressions are of course biased toward my own likes, dislikes, and individual observing habits, and should be expected to differ for other observers.  However, subjective impressions are important as they relate the more complete observing experience.  The final lists on the pages which follow therefore summarize my personal impressions and feelings as parting comments. 

 

In a way, this comparison can be characterized as having been a symphony in observing -- each eyepiece providing a richly individual view, and collectively providing a profoundly orchestrated view of the heavens.  Again, my personal thanks to all the many generous individuals who contributed their equipment, suggestions, encouraging words, peer review support, and their time.  Without them, this comparison and report would not have been possible.

 

The Subjective Results

 

While each test conducted and presented in the individual ranking tables should stand on its own to maintain an objective view of each eyepiece, tallies are often interesting and sometimes revealing.  The table below is a simple tally which summarizes the percentage of times each eyepiece attained each of the major ranks across all tests, with the Rank-A+B scores combined as an indication of overall top tier performance, then followed by the Rank-C+D+E scores combined as indicating overall second tier performance.

 

Eyepiece

(in rank order)

Ranking

A-B

C-D-E

Zeiss ABBE Ortho v I

100%

0%

Zeiss ABBE Ortho v II

100%

0%

Pentax SMC Ortho

92%

8%

TMB Supermono

86%

14%

Astro-Physics SPL

85%

15%

Baader Genuine Ortho

62%

38%

Brandon Ortho

62%

38%

University Optics Ortho

54%

46%

Televue Radian

54%

46%

TMB Planetary

46%

54%

Sterling Plossl

46%

54%

 

Obviously the weakness of the above table is that all weights are equal.  In reality some performance factors are more important than others and the weighting of the more important factors is relatively unique to each observer.  Therefore, leaving objectivity behind and focusing on what I personally felt were the most important factors for a lunar and planetary eyepiece, the eyepieces grouped as follows (and in the rank sub-order as listed within each place):

1st  Place:        The ZAO-II, TMB Supermono, and ZAO-I,

2nd Place:        The Pentax Ortho and Astro-Physics SPL, and

3rd Place:        Baader, Brandon, Radian, TMB Planetary, Sterling, University Optics.

The ZAO-II ranked highest because it performed every task not requiring a wider apparent field of view the absolute best – it showed the greatest apparent brightness, contrast, and sharpness of all eyepieces.  The TMB Supermono was preferred over the ZAO-I because it could pull as much planetary detail as the ZAO-I but would often pull a fainter stars.  It is also manufactured in 1mm increments which is a valued planetary preference.  The Pentax and Astro-Physics I considered second tier because they simply would not show as much detail on Saturn as the 1st Place group.  Of these two the Pentax was preferred as it controlled stray light and its scatter was significantly better.  In the final grouping, the Baader and Brandon were tied and ranked at the top of their placing because they were subtly sharper on both Saturn and the moon.  And as final words, each eyepiece was found to be special in its own way, and these impressions follow…

 

Zeiss ABBE Ortho v I

Time honored and worthy of its reputation.  Still representing perfection in the eyepiece makers art, but now surpassed by it successor in my opinion.

Zeiss ABBE Ortho v II

Seemingly extracts every last ounce possible out of the telescope and the target.  The ultimate in precision and perfection of the ABBE design.  The last word for precision observing.

TMB Supermono

Actually my personal choice among the contenders.  View was as pure as the ZAO-I, perhaps slightly better in terms of pulling the dimmest star, although not as good in terms of scatter.  I found the smaller AFOV a strength as it allowed attention to on-axis details without getting distracted by the off-axis.  As a planetary, prefer its availability in 1mm increments. 

Pentax SMC Ortho

I considered this eyepiece perfection for doubles, particularly for colorful ones.  Always a pleasurable view regardless of target.  Its lack of scatter and high color saturation view was unparalleled. 

Astro-Physics SPL

A very good all around performer and just shy of the top runners on Saturn.  Images were excellent and it rendered the prettiest star points.  Well thought out design with the Derlin housing for fog control and a durable stainless steel barrel.  Definite light control issues but these issues were never severe enough to harm the on-axis view.

Baader Genuine Ortho

Tries with all its heart to play with the best.  Neutral tone and bright – wonderful saturated view on colorful doubles and could easily pick up subtle colors on Saturn.  Well worth the investment giving memorable views in the classic style which only an Ortho can.  Plain and simple – a keeper.

Televue Radian

Great jack of all trades and my preferred wider field eyepiece due to its very precise field of view.  Background field of view nicely dark, uniform, and sharp to the edge even in fast scopes.  Wider AFOV and excellent high apparent contrast performance on stars and nebula makes it my preferred choice for DSO and any target needing a larger context.  Has some off-axis CA present on only brightest targets.

University Optics Ortho

The historic gold standard for everyday planetary.  Still a great performer that puts up a crisp view, but the updated UO HD and Baader versions have improved brightness for a small cost that is worth the minimal extra expense. 

Brandon Ortho

Love the view it provides, hate the short eye relief.  Intrinsically clean view.  Top notch detail on nebula, often crisper on lunar/planetary than complex designs.   Cooler tone is preferred.  A keeper.

TMB Planetary

View on DSO close to the Radian’s view at one third the cost.  Its price point places it in direct competition with the University Optics and the Sterling Plossl.  View doesn’t seem quite as crisp as others, but ergonomic plusses give it the edge of the three in its price class (i.e., much wider AFOV, adjustable eye guard, superb eye relief, large eye lens).

Sterling Plossl

Like the University Optics Ortho, puts up a crisp and sharp, but brighter view.  Extra AFOV a plus over standard Plossl, but eye relief is tight.  Easy handling size. 

 

For a formatted PDF version of this comparison, contact the author at wapaolini@hotmail.com.

 

~ end ~

 


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