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Meade UWA and Explore Scientific 6.7mm 82 Degree Wide Field Eyepieces


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Twas some hours after nightfall, when all through the pack
Not a telescope was stirring, not even the Tak.
The stockings I hung by the chimney with care,
Ready for new eyepieces that Elves would put there.


Then out in the heavens, there arose such a clatter,
My eyes opened wide, to see what was the matter.
Away to the window I flew like The Flash,
Tore open the shutters and threw up the sash.


High in the heavens, with no Moon to be seen,
And the sky of black velvet, with stars shining keen.
Then what to my eyes should happen to appear,
But Jupiter and Saturn and Mars chiming clear.


With this motivation, moving lively and quick,
I knew in a moment, I’d be observing lickety-split.
More rapid than meteors the eyepieces they came,
And I whistled, and shouted, and called each by name!


"Now Mono! Now Ortho! Now Kellner and reversed one!
On Plossl! On Nagler! Ready spacewalk! Even more fun!
So out of your trays! Caps off bottom and top!
Dash away! Dash away! To my scopes dash non-stop!"

(St. EP Nick By Bill Paolini)

I. OVERVIEW

Dashing into the holiday season on October 14th, 2004 Meade introduced the then new Meade 5000 Ultra Wide Angle (UWA) eyepieces. Hallmarks of this line include: 82 degree Apparent Field of View (AFOV), premium grade optical glass including multiple types of exotic glass, individually tuned multi-layered coatings, lens edges and all internal metal surfaces fully blackened, parafocal, long eye relief, and adjustable twist-up rubber eye guard. Available focal lengths are: 4.7mm, 6.7mm, 8.8mm, 14mm, 18mm, 24mm, and 30mm with their optical designs ranging from 6 to 7 elements.

In late 2008, Explore Scientific also entered the ultra wide race with the Explore Scientific 82 Degree Series which then became available in the Spring of 2009. Hallmarks of this line include: 82 degree AFOV, advanced computer design, combinations of low dispersion and high refractive glass, multilayer deposition coatings, lens edges and all internal surfaces fully blackened, long eye relief, and adjustable twist-up eye guard. Available focal lengths are: 4.7mm, 6.7mm, 11mm, 14mm, 18mm, 24mm, and 30mm with their optical designs ranging from 6 elements in 4 groups to 7 elements in 4 groups.

This review focuses on the 6.7mm versions from both these lines. The eyepieces were tested over several weeks in a combination of three telescopes: a 10” Orion XT10 f/4.7 Dob, a 4” Takahashi TSA-102 f/8 Super APO, and a 3.1” APM 80mm f/6 Super APO. Given these are wide field eyepieces, the two refractor choices would reveal how well the off axis performed in fast refractors, and the Dob would challenge the off-axis with it’s very fast sub-f/5 light cone adding coma from the mirror into the mix. Unfortunately, the performance of each eyepiece with a Televue Paracorr coma corrector was not conducted as my Paracorr is on holiday in the colder climates for the winter.

The table below presents the basic stats for each eyepiece as given by the manufacturer, with several of the items direct measured for validation. I was pleased to see that the manufacturer’s eye relief listings were very close to actual from the lens surface. The Explore’s eye lens is inset slightly further into the housing than the Meade’s. Oddly however, even with the eye relief being approximately 2mm shorter on the Explore from the housing top, it gave no impression in use as feeling any tighter. While the AFOV measured at the bench as being slightly larger than 82 degrees, I estimate there is an accuracy of plus or minus 5% or so in the measuring process due to the sensitivity of some of the measures. In the field, the Explore did show a very slightly larger AFOV however, which is in line with how the bench measures indicated.

Attribute

Explore Scientific

Meade

Focal Length:

6.7mm

6.7mm

Optical Layout:

7 Elements
(4 Groups)

7 Elements
(grouping not specified)

Apparent Field of View:

82 degrees
(measure approx 83-86 deg)

82 degrees
(measure approx 82-85 deg)

Eye Relief:

14mm
(measured at
12.4mm from housing, 14.3mm from lens)

15.7mm
(measured at
14.1mm from housing, 15.3mm from lens)

Field Stop Diameter:

Not Specified

Not Specified

Eye Lens Diameter:

19.5mm (measured)

19.5mm (measured)

Height & Width:

3.5” h x 2.1" w (measured)

3.48” h x 2.1" w (measured)

Weight:

10.9 oz

8.8 oz

Barrel Diameter:

1.25"

1.25"


II. GENERAL CHARACTERISTICS


Fit, Finish, Handling - Overall, fit and finish was very good on each eyepiece, with the Meade coming in a very nice velvet lined box. Everything about each eyepiece looked and felt quality. However, the Explore’s outer metal shell was quite thick and gave the eyepiece a better heft and feel to it. The Meade’s on the other hand, had a nice broad rubberized section to its housing which made grip and handling feel very secure. While the Explore didn’t use any rubberized grip materials, it still however had good handling ergonomics because its shape was such that it would not easily slip from your grip as you would have to open your grip to quite a degree for that to happen. Lettering and graphics on both were excellent, being engraved into metal and paint filled, so nothing to rub off over time with handling. Finally, there is one odd feature of the Meade which I later discovered as being very useful – the main housing is not round but has three distinct lobes. The advantage I found is that when you lay the eyepiece on its side, it will not roll easily. A nice feature, and useful, for those who have scopes with flat trays under the tripod with no drilled holes for 1.25" or 2" eyepieces.



Moving Mechanicals - Moving to the eye guard mechanism, I felt both were very precise. As you moved the Explore’s to the full up position, there was an initial rough spot then the rotation became very smooth. After a few uses the rough spot disappeared and it remained smooth and positive in its motions. The Meade’s eye guard movement was smooth from the outset and remained so through all usage. The Meade’s also showed a thin layer of grease on the part of the housing exposed as the eye guard was rotated to the full up position. However, in normal use my fingers never contacted this section, and it could easily be wiped clean if one wanted to. The Explore showed so such grease on its exposed section.



Coatings – The coatings on each eyepiece were very different. The Explore had a typical rich green color that is often seen today, and the Meade had a rich aqua to blue coloration. When looking at the reflections off the lens surfaces, the Meade’s coatings appeared to be suppressing reflections slightly better as the reflections were not as bright. Even though the Meade’s coatings appeared as if they would do a more effective job, no advantage was seen for either coating type during the observational tests.



Optical Design – While both eyepieces are listed as seven element designs, there is discussion on the boards that these two eyepieces are optically the same and probably from the same original equipment manufacturer. Upon examination of the reflections, one can readily see that the optical designs are indeed not the same between these two eyepieces. As illustrated in the photo that follows, the reflection positions in the top elements of each eyepiece are identical. However, when you flip the eyepieces and look at the reflections in the lower elements contained in the barrel (commonly sometimes referred to as the Smyth grouping), one sees that one reflection is at a very different position relative to the same reflection in the other eyepiece. Not being a very confident “Reflectionologist” myself, I was hesitant to make a definitive judgment so I forwarded pictures to resident expert Mike Hosea (who insists that while he is not an expert, that he did stay in a Holiday Inn Express last night) -- thank you Mike. After his examination we agreed that the elements used in the barrel grouping are indeed a different design. Mike’s assessment was as follows: "I think the Smyth lenses differ at the cemented interface. Looks like the lowest reflection in bottoms.jpg [pic of the bottom field lenses] is the outer surface, the next one up (the faintest) is from the field lens (after the field stop), the next one (the reflection that moves) is the cemented interface of the Smyth lens, and the top one is from the inside surface of the field lens. If I'm right, it would appear that the ES has a thinner crown element. Maybe it's using a higher index material there." So at least for the 6.7mm versions of these two brands, the optical design is not identical. The difference in the design obviously also had an impact as these two eyepieces did not perform exactly the same on-axis as far as focus snap, and each had very different off-axis characteristics as well.



III. OPTICAL PERFORMANCE COMPARISON

#

Performance Area

Explore 82

Meade UWA

1

Image Crispness (On-Axis)

Tie

Tie

2

Image Crispness (Off-Axis)

--

>>> Preferred <<<

3

Transmission

Tie

Tie

4

Contrast

Tie

Tie

5

Scatter

Tie

Tie

6

Tone

Slight Warmth

Neutral

7

Light Control / Baffling

Tie

Tie

8

Focus Snap

>>> Preferred <<<

--

9

Eye Positioning

>>> Preferred <<<

--

10

Eye Relief

--

>>> More <<<

1. Image Crispness (On-Axis)

As a note, I generally refer to how sharp and eyepiece is as “crispness” as the perception is really impacted by a combination of the eyepiece’s resolution (i.e., sharpness), contrast, scatter, tone, and aberrations/distortions. Pleasantly, I found that both eyepieces showed equally crisp images across all targets, with a similar level of minimum scatter. Comparing the image of Jupiter to a 4-element Plossl of same focal length, the planetary picture looked equally detailed. The level of crisp detail that these two complex wide field eyepieces revealed on-axis was a much welcomed surprise, as to-date in my observing it has been rare that any complex wide field could approach so closely what a good 4-element Plossl or Ortho would produce. So both the Meade and the Explore I felt were very capable planetary tools offering performance nicely close to what one can expect with a quality Plossl or Ortho (and with more generous AFOV and eye relief). Where the simpler 4-element Plossl obviously excelled over the Explore and Meade was in showing a slightly greater contrast in features, particularly on Jupiter which has so many low-contrast variations. With the simpler 4-element eyepiece, as should be expected, the varying subtle features on Jupiter were displayed with a greater register of darks to lights, so finer features were easier to see, cloud bands were a little richer in color or a deeper dark, etc. I would also give the Explore a slight advantage over the Meade for planetary due to the better focus snap it exhibited. Its ability to more quickly and positively snap to best focus initially gave me the impression that the Explore was a little crisper and with slightly more contrast than the Meade. However, once the Meade was finessed into best focus it was obvious both eyepieces were just as sharp, crisp, and of high contrast, on planetary and across all targets.

2. Image Crispness (Off-Axis)

Off-axis performance is of course the most difficult challenge for any wide field eyepiece. In the off-axis, the Explore and the Meade performed very differently. Regardless of the scope I used, from the fast Dob to the slower APO, the Explore showed a small region of softness in the off-axis that was approximately 10% from the field stop. Using a bright star as a test, it was obvious that the softness was due to some mild astigmatism. Overall, given how well the Explore performed on-axis I felt this was of little detriment when the Explore was used in either the fast f/6 or slower f/8 APOs. When I moved to the f/4.7 Dob however, things changed rapidly for the Explore. In this fast Newtonian the Explore simply could not handle the fast light cone satisfactorily without Paracorr, and unfortunately my Paracorr was out on loan and not available during any testing. So in the XT10, the Explore’s off-axis became soft at approximately the 20% point from the field stop. The sequence for the off-axis in the XT10 with the Explore was that lateral color and impact from the mirror’s coma began at the 50% point from the field stop, then at the 20% point from the field stop astigmatism was further added as the coma’s impact progressed. At the very field stop a bright star was deformed as much as three star diameters from the combination of coma, lateral color, and astigmatism. The Explore therefore showed a strong preference for refractors as the combination of coma and a very fast light cone took its toll in the off-axis. Finally, rectilinear distortions in the Explore, like in the Meade, were less than what I felt was typical for other wide fields I have viewed through.

Moving to the Meade in the XT10, its off-axis performed quite admirably. The impact from the telescope mirror’s coma was only less than half as great as was revealed in the Explore. I therefore felt the view in the Meade was quite pleasing even without Paracorr all the way to the edge, with only slight coma, slight lateral color, and slight field curvature showing (an eighth turn or less of the fine focus knob would bring a star back to sharpest focus at the field stop). So overall, the Meade showed very strong off-axis performance, and I felt it was very much in step with how the Nagler T6 line performed off-axis in my XT10 (except with better lateral color control and less rectilinear distortion based on memory and observing notes from T6 use in the XT10 – however, a side by side test really should be done to validate this impression).

3. Transmission

Testing for transmission differences was done on several levels in the field, from rapid switching of eyepieces on bright lunar views to try and detect any change in apparent brightness, to viewing the dimmest visible extents of showcase nebula and galaxies like M42 and M31, to examining any difference in detecting faintest stars or stars just on the edge of adverted vision within the M42 cloud or clusters such as the Perseus Double, Stock 2, M34, M35, etc. In no case and on no target was it perceived that the transmission was any different between the two eyepieces, regardless of which telescope was being utilized. Transmission was therefore judged as equal.

4. Contrast

Testing for contrast differences was conducted using planetary observing, to using subtle shadings in Lunar Maria or ejecta material from craters, to observing for dust lane differences in M31 or the mottled structure of M42. Again, across all targets and in all scopes, the two eyepieces performed identically.

5. Scatter

Testing for scatted was conducted primarily on planetary targets and on brighter stars and doubles. Across these targets I felt the levels of scatter exhibited by both eyepieces was slightly less than what I am used to from complex designs like the Radians, and fairly equal between both of the eyepieces. Very good performance for both eyepieces.

6. Tone

I typically can determine tonal differences between eyepieces best on targets like Jupiter, the Moon, and on colorful stars (e.g., for me red stars appear more saturated in a warm toned eyepiece and blue stars usually appear less saturated in a warm toned eyepiece, and then this reverses when a cooler toned eyepiece is used). Again, both eyepieces in this performance category appeared identical for all targets excepting for the Moon using the largest of the telescopes, the Orion XT10. In the XT10 the Explore showed a slightly warmer tone than the Meade. The Moon appeared to have a slight coffee tinge. For this target this was an advantage as subtle shadings in Maria and brighter ejecta from craters appeared slightly more prominent and defined.

7. Light Control / Baffling

Both eyepieces appeared to be baffled to the same level. A good inside test for this is to simply hold both eyepieces at arms length and near to a bright light source like a table lamp. The light source should be tangential or to the side of the eyepiece’s barrel bottom (i.e., don’t point the barrel directly at the light source). Once the barrel bottoms are close to the light, any stray light, reflections, glare, etc. can be seen in and around the eye lens as you look at it from arms length. In the case of both the Explore and Meade, they showed the exact same patterns which indicated to me a similar level of light baffling and/or light suppression effectiveness. Both the Meade and the Explore did not show the exemplary performance in this inside test as is produced by more premium eyepieces like the TeleVue Radian (which shows almost no stray light), however both eyepieces performed more than adequately in the field showing only one instance of glare. Using any of the three telescopes, when the Moon was placed outside the field stop and slowly moved toward the field stop, a bright glow would temporarily appear opposite to where the Moon was about to enter the FOV just prior to its entry. Once in the FOV this brightening would vanish so there was no impact while any part of the lunar surface was actually in the FOV, showing all features crisply with excellent contrast and a jet black background around the lunar limb into the surrounding space. Therefore, while light baffling and control was comparatively not perfect in these eyepieces, it was in my opinion more than sufficient and allowed the eyepieces to perform excellently on all targets examined.

8. Focus Snap

As I use the term, focus snap is how easily and effectively it is to find best focus when using an eyepiece. Typically this is most noticeable in planetary observations when trying to get best focus on fine low contrast details of the atmospheric structures of a planet (which are many times not easily defined). Whether I used the Orion XT10 f/4.7 Dob, or my Takahashi TSA-102 f/8 APO, or my APM 80mm f/6 APO, it was readily apparent that the Explore was noticeably easier to get to best focus quickly. In use on planetary (Jupiter, Mars, and Saturn were all observed during testing), the Explore very authoritatively snapped to focus on-axis. Whether this was due to the different optical design of the elements in the barrel or from some other factor it is not known. Moving to the Meade, its focus snap reminded me very much of how my Radian’s behave, needing a small amount of futzing with the fine focus knob before I am sure I have optimum focus. Bottom line is that achieving critical focus was simply easier with the Explore and this ability should not be under stated as it often mistakenly gives one the perception that an eyepiece may be sharper or have more contrast -- a definite advantage for the planetary observer.

9. Eye Positioning

Eye placement was judged as easy for both eyepieces. Neither was very sensitive to eye placement, and blackouts or kidney bean rarely occurred. The Explore however did seem to have a more natural feel to it than the Meade. With the Explore, the moment your eye approached the eye lens the entire FOV tended to “pop” into view all the way to the field stop more quickly, whereas with the Meade this was less the case. I was not able to determine exactly why they behaved differently. Perhaps the larger flatter housing surface around the eye lens on the Explore contributed to zeroing in on best eye position easier? Whatever the reason, both eyepieces still showed much less sensitivity to eye position than I am used to from many other wide field designs, with the Explore’s being the slightest bit better than the Meade’s.


10. Eye Relief

Eye relief was comfortable and did not feel tight on either eyepiece as a non-eyeglass wearer. I found that for both eyepieces there was sufficient eye relief to keep the eye guard raised slightly, making viewing more comfortable as it blocked more stray light. Eye relief did not seem tighter or more generous on either eyepiece, even though the Meade advertises, and direct measures showed, a slightly longer eye relief for the Meade.

IV. SELECT OBSERVING LOG NOTES

On Mars many features were clearly visible using the TSA-102 with either eyepiece. For most detailed observations a 1.5x or 2.5x Barlow was used (183x and 304x). Clearly visible on Mars were the North Polar Cap, Mare Acidalium, western portions of Utopia, portions of Mare Erythraeum and Aurorae Sinus.

Turning to Saturn in the TSA-102, polar shading was well rendered in both eyepieces with one prominent band in the atmosphere visible, the rings clearly etched, the Cassini Division was easily evident at outer edges of the rings, the dark space inside the arc of the C-Ring was starkly rendered on each side of the planet as well as the shadow cast by the planet on the rings. The moons Titan and Rhea clearly also clearly seen with direct vision.

Overall in the TSA-102, the Explore had very excellent focus snap, better than the Meade. Off-axis however Saturn softened when it was positioned in the outer 10% of FOV and softened less so when the Barlows were used. Scatter around the planets were mild and equal between the two eyepieces Mild CA started in outer 20%-25% of FOV of the Explore (seen as a very slight purple and green hues on rim of Jupiter, slight purple with Saturn). With the Meade, focus snap was finicky, needing a little playing with the fine focuser to achieve best focus. Planetary images stayed sharp right to the very field stop both with and without Barlow using the Meade. Mild CA started at the same position in the Meade’s FOV as in the Explore’s, with similar colorations.

Using the Orion XT10 f/4.7 Dob, both eyepieces showed incredible detail on-axis for Jupiter -- four belts were steadily visible (NEB, SEB, NTeB, STeB) and occasionally NNTeb became visible, graduated shadings were seen on both poles, many detailed festoons particularly around NEB were visible, colors ranging from salmons to light chocolate browns were observed, and the four jovian moons were very prominent. In the Meade the only off-axis distortions visible were Lateral Color (opposite purple and green on Jupiter’s rim) and minor coma from the XT10’s fast mirror. Lateral Color was minor in the Meade as details within the planet remained sharp until 10% from the field stop where coma from the telescope took its toll. By contrast, the Explore could not handle the XT10’s fast focal ratio nearly as well as the Meade. In the Explore Lateral Color became easily noticeable as close as 50% from center and coma from that point outward progressively accentuated the Lateral Color off the rim of the planet until the outward pointing greenish/yellow Lateral Color blur extended past the planet perhaps one quarter or more of the planet’s diameter when placed at about 10% from the field stop. The Lateral Color blur from the Explore unfortunately obscured fine details within Jupiter when the planet was placed anywhere past the 50% mark from center. At no time did either eyepiece exhibit any light control issues when Jupiter was either in the FOV or just outside the FOV in the XT10. Given the difficulty of the Explore in handling the fast focal ratio and coma of the XT10, the Meade had a much better showing in this instrument. I felt the Paracorr may have cleaned up the off-axis performance of the Explore substantially, however it was not available during the testing.


Both eyepieces showed incredible detail on-axis in XT10 for the Moon with very sharp/crisp views. The Explore appeared to show the slightest bit of a warmer tone, very slightly coffee-toned. This warmth served to accentuate contrast in the Maria showing the varying shades and lighter streaks of ejecta from craters with slightly more authority. In the Meade the image was sharp to about 5% from the field stop and at the field stop was only the slightest bit soft from the mirror’s coma. In the Explore the image was soft at 20% from the edge. Adding a 1.5x Barlow to the optical train (268x) both eyepieces continued to provide a crisp and detailed picture. With the Barlow in place both eyepieces showed a crisp image to the edge of the field. Again, the Meade showed a slight bit of temperament with its focus snap whereas the Explore found best focus easily and quickly.


  • Through the TSA-102 the colors for Albiero, Castor, Mizar, Aldebaran, and Polaris were rendered equally well. The Meade seemed to have slightly less Lateral Color off-axis through the TSA, but it was difficult to quantify the level of difference. The Meade was sharp to the field stop with bright stars whereas the Explore showed some astigmatism in outer 10% of field of view.


  • In the XT10 both eyepieces showed the colorful double Albiero with equal rich saturation. Scatter appeared equal. Moving these bright stars to the edge of the field it was apparent that the Meade handled the mirror’s fast focal ratio and coma much more effectively than the Explore. Star points remained nicely round across most of the field of view with the Meade, and as a star approached far off-axis and near the field stop, only minimal deformation from coma and lateral color was apparent. At the field stop, coma from the XT10’s mirror extended the star image in the characteristic fan shape approximately 1.5x the star diameter – very minor considering not using a Paracorr. By comparison in the Explore, when the stars were only 50% from center the stars were deformed in the coma fan shape as much as they were at the field stop for the Meade. At the field stop the stars in the Explore were deformed by coma and some astigmatism resulting in the star point being as much or more than three star diameters larger. Compared to the Meade, the Explore could not handle the fast focal ratio of the XT10 well.


In the XT10 the Perseus Double (NGC869/884), M34, M35, and Stock 2 were rendered beautifully in both eyepieces, with the Meade excelling over the Explore due to the better controlled off-axis. Transmission was judged equal in each eyepiece. Contrast, background field darkness and uniformity looked equal between the two. Pushed to extreme magnification with a 2.5x Barlow (448x), both eyepieces performed wonderfully showing nicely tight star points within a jet-black field of view. Stars were sharp to the edge in both eyepieces under Barlow. AFOV size seemed unaffected by the Barlow (which was not a telecentric but a standard doublet).


V. CONCLUSION

Both the Explore Scientific and Meade 5000 Ultra Wide Angle eyepieces showed a quality build. The Explore, even with its minor off-axis astigmatism in the refractors, I felt was a slightly stronger eyepiece given its very authoritative focus snap and the slightly more positive feel related to eye positioning. If the primary use would be in a refractor, and planetary performance was a strong consideration, then I felt the Explore had the edge of the two. In contrast, if the primary or most frequent use of these eyepieces would be in fast focal ratio Newtonians, then the Meade was the definite choice of the two.

Overall the Meade showed itself to be a stronger generalist, like premium-level wide fields, performing admirably in all telescopes regardless of optical design or focal ratio. Its excellent control of lateral color, field curvature, and rectilinear distortion off-axis were impressive. This, together with its excellent on-axis showing planetary just as sharply and with only slightly less contrast than a good 4 element Plossl, its small size, and nice ergonomics makes the 6.7mm Meade 5000 UWA a very grand all-around performer.


Happy Holidays & Wishing New Eyepieces for Everyone!




All graphics and images by the author. For a PDF version of this review email wapaolini@hotmail.com.

No eyepieces were harmed during the making of this review.








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