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Meade MWA 26mm Report


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With all the discussions about the Meade MWA 26mm being a possible 90° apparent field of view (AFOV) eyepiece with long eye relief, I thought it might be worth a try.  Despite the virus slowdowns in retailing, I was able to receive my new eyepiece within a week of ordering it.  It comes packed in a nice, large, black box with sturdy, closed cell foam cut/molded to fit the eyepiece.  The eyepiece itself comes in a zip-close bag with a microfiber cleaning cloth.  There are no printed inserts included in the box.

Exterior

The eyepiece itself is nice and hefty, but lighter than its bulk would belie at 786 grams or 27.7 ounces by my scale.  That makes it just slightly heavier than the much more compact Tele Vue Nagler T4 17mm.  The grip ring is nice and broad and makes the eyepiece easy to hold securely.  The top lens cap stays on securely due to the ribbing on the inside of the eye cup (which is on the outside when folded down to fit the lens cap on).  It comes off without a fuss when needed and has a small vent hole.  The bottom lens cap is very rubbery and almost has to be scraped off with fingernails to remove it.  It's super air tight and sometimes requires "burping" it to get the trapped air out so it doesn't bulge outward in storage.  The fairly short eye cup flips up and down easily but stays up when pressed around an eye socket.  Overall, I found the eyepiece quite handsome and functional.

The field lens is 10mm from the bottom edge of the lower barrel and slightly concave, so I've never worried about marring or damaging it because it is too close to the bottom.  I tried my only 2" filter, a 1990s Lumicon OIII, and it screwed into the bottom threads multiple turns until secure.  It came off just as easily.  The safety undercut on the black insertion barrel is fairly shallow.  No hang-up issues with focuser compression rings were noted over multiple nights with multiple focusers, coma correctors, and Barlows.

The eye lens is recessed about 4mm (more on this later) and is 35mm in diameter, about the same diameter as a Pentax XW for reference.  The multicoatings appear mostly greenish.  Lens and interior blackening and baffling appears to be good, but certainly not inky black great.

The following image shows the box exterior and interior, the eyepiece with caps and without caps with the eye cup flipped up, and the eye lens and field lens recessions.206069427_MeadeMWA26mmEyepiece.thumb.jpg.60dc5201de1b347552059d0d2521e0d5.jpg

 

Eye Relief

The manufacturer claims 25mm of eye relief.  I measured 10mm of usable eye relief (ER) where the exit pupil converges to the tightest circle via light projection, which is still pretty broad compared to competitive wide field designs.  If I measured when the inner white circle reached its smallest size before blurring out of existence (something I've only ever seen before on eyepieces with SAEP like the Meade 4000 UWA 14mm smoothie), it was 17mm of ER.  In use, to see most of the field easily, it felt closer to the 17mm ER value.  It is enough that I did not need to push my eyeglasses against the top to see the field.  Thus, given the relatively flat eye lens and 4mm recession of it, there's about 21mm of design eye relief for the easily viewed field.  That's not the advertised 25mm ER, but it's relatively close.

However, the entire apparent field of view cannot be seen at 17mm ER, but can be seen in peripheral vision at 10mm ER.  I had to remove my eyeglasses and press in really hard into the flipped up eye cup to perceive the field stop.  Based on this and the closeness of the camera lens to the top of the eyepiece to take in the entire field during my photographing of the AFOV, I feel confident that the actual usable eye relief is closer to 10mm to take in the entire field stop defined view all at once.  With eye lens recession, that works out to 14mm of design ER which is not at all close to the advertised 25mm ER.

SAEP

This large discrepancy in usable eye reliefs can probably be attributed to the eyepiece's greatest fault, massive spherical aberration of the exit pupil (SAEP) or kidney beaning.  If you keep your eye back at the 17mm or longer eye relief distance, it is fairly easy to deal with the SAEP, but the outer edge of the field is obscured.  If the user pushes in to take in the entire field, kidney beaning takes over the majority of the field of view obscuring all but a circle in the center and a ring around the edge if the eye is perfectly centered (see the MWA's full view in the images to see this effect).  If the eye is allowed to drift off center, various hemispheres of the view become visible while the opposite hemisphere goes black.  The effect is incredibly annoying and disappointing.  Even when fully dark adapted, there is no getting around this eyepiece's SAEP.

CAEP

I looked for chromatic aberration of the exit pupil (CAEP) which leads to the "ring of fire" as seen in the TV Nagler T5 31mm and ES-82 30mm eyepieces.  I could not detect any appreciable red-orange ring in the outer reaches of the FOV during daytime use.  I did see that the exit pupil was a blue edged circle further out from the tightest exit pupil circle and red edged on the other side of it.  The amount, though, was much less than in my ES-82 30mm.  Therefore, CAEP might be there in modest amounts that are difficult to detect visually.

AFOV

Next up is the controversial claim of a 100° AFOV by Meade.  On it's face, this usually refers to the field seen by the eye when looking into the eyepiece.  However, as has been reported elsewhere by others, the entire MWA line fails to deliver on this claim.  Most folks report an approximately 90° AFOV, which would still be quite respectable at this price point and eye relief amount.  I carefully measured the AFOV with projection and got a value of 83°.

When using photographic techniques to arrive at the AFOV, it is also 83° to the field stop with loads of SAEP.  There are only 79° of AFOV visible if the camera is positioned at the point at which SAEP starts to appear.  The true field stop has the characteristic blue ring of most modern wide field eyepieces.  The false field stop at 79° when the eye is pulled back to avoid SAEP is a very slightly fuzzy black ring.  The camera's "easy" view of 79° in the images pretty closely resembles what I see with my eye when SAEP starts to manifest itself, so I feel confident going with that value for the usable AFOV.  To see the true field stop, it feels like you have to peek under the ledge formed by the false field stop at 79°.  It's only 2° lost around the entire circumference, but it seems much larger and rather frustrating in practice.

This image compares the AFOVs of eyepieces with similar ultrawide angle (UWA) AFOVs from my eyepiece collection.962600011_MeadeMWA26mmAFOVComparisonEyepieces.thumb.jpg.30a80e2f84793e534149484d9941da1a.jpg1161623516_MeadeMWA26mmAFOVComparison.thumb.jpg.8e407655b5c665e3de19bd3492a186b8.jpg

Field Stop Diameter

I measured the effective field stop (FS) diameter and got a value of 41mm true FS to true FS.  It is about 38mm at the 79° easy viewing position.  If you back calculate AFOV using the 41mm FS value, you get an effective AFOV (eAFOV) of 90°.  This is due to edge compression cramming more into the edge of the AFOV than equal angular magnification would otherwise indicate (more on this later in the discussion section).  The eAFOV for the easily viewed 38mm FS value is 84°.

This image compares the field stop diameters of eyepieces with similar FSs from my eyepiece collection.36391348_MeadeMWA26mmFieldStopComparisonEyepieces.thumb.jpg.35b53e2d4761814567586e2b61572351.jpg590471839_MeadeMWA26mmFieldStopComparison.thumb.jpg.e189290e5badaa35cf95c0f782e8ea7e.jpg

Under the Stars

Enough about the eyepiece's specifications, how does it view the night sky in a telescope?  I spent several nights using the MWA in my 8" f/6 Dobsonian with a properly spaced GSO coma corrector and 90mm TS-Optics Photoline f/6.6 FPL53 Triplet APO with a properly spaced TSFLAT2 flattener.

In the central 30% of the MWA, the view was as good as through the best of my other eyepieces with these scopes.  On axis, this eyepiece provides a nice view of star fields with pinpoint stars and a dark background with no obnoxious pincushion distortion off axis to deal with during panning.  There is a slight compression of objects at the edge that is hard to perceive while looking at the center.  Beyond the central 30%, there is a noticeable blurring of stars and lunar details unless the eye is aligned to look straight at that part of the field of view.  In fact, if you can crank your head over far enough to just take in the edge in direct vision, it is nearly sharp to the FS while the rest of the field blacks out due to SAEP.  Only the last few degrees show trace astigmatism that is no worse than that at the edge of a TV Nagler T4 22mm

It has good control of stray light from bright objects inside and just outside of the FOV, and no visible chromatic aberration anywhere in the field other than the typical thin yellow/purple fringe on the edge of the moon seen in some of my best eyepieces as well.  It is also very close to being flat of field.  From 50% outward, a tiny bit of refocusing slightly improves the image.  It is flatter than the T4 Naglers, but not as flat as the ES-82 30mm, ES-92s and APM UFF 30mm.  I also could not perceive any edge of field brightening (EOFB) in either dark skies or with the moon in or near the FOV.

In the Dob, a coma corrector is necessary to yield a sharp field stop in the MWA.  Without it, the edge of field is blurry once you push far enough in to see it.  I've seen this in other eyepieces, although I can't remember which at the moment, so it's not unique to the MWA.

I did not measure focus point, but it came to focus relatively close to my other eyepieces that focus at or near the eyepiece's shoulder.  There was no need to massively refocus when using the MWA with other eyepieces, which is probably why I didn't think to measure it.

See my discussion section at the end for more thoughts/rants on viewing with this eyepiece.

Conclusion

As long as the observer keeps the object on axis and uses the rest of the field for context, this eyepiece easily keeps up with some of the best wide field eyepieces available today.  It's when the object is allowed to drift from edge to edge that the eyepiece's shortcomings due to SAEP become all too apparent.  The 4mm eye lens recession actually works to the eyeglass wearer's advantage because it keeps the user from drifting in too close and revealing the severe SAEP.  The raised eye cup works in a similar manner to maintain proper distancing for non-eyeglass wearers.

On net, this is a good eyepiece for eyeglass wearers who desire a UWA level experience in the 24mm to 27mm range and have the desire to simply scan star fields or strictly observe on axis and use the outer field simply for context in peripheral vision.  It is not a good choice for studying objects as they drift across the FOV in undriven scopes.  I would classify it somewhere close to a 79° Morpheus 26mm with minor SAEP but with the added outer field unsharpness issue unless the user precisely aligns their eye/head.  It is definitely not a 26mm ES-92 or Nagler T4 as some have wished for or hypothesized it to be.  For non-eyeglass wearers, there are probably better options out there such as the ES-100 25mm, Nagler T5 26mm, and ES-82 24mm.

Comparison Images

I have included three images for review (two were included earlier) along with a beauty pic for each group (top to bottom AFOVs correspond to left to right exterior views).  The third image included here compares the AFOVs of eyepieces in my collection having focal lengths similar to the MWA.

578339646_23mm-28mm2.thumb.jpg.f77e023a4bf75f823a79732e878b16b0.jpg1537884485_23mm-28mmAFOV2a.thumb.jpg.c95b4ccbeec2d7c0173289fcb5ca9ea2.jpg

 

All AFOV images were taken through an Astro Tech 72ED telescope with a properly spaced TSFLAT2 field flattener and then composited together in Photoshop.  The objective to target distance was approximately 35 feet for all images.  All sub-images in the first two images were taken with a superwide angle LG G5 phone camera.  All the sub-images except those marked "full" in the third image were taken with the narrower angle, but higher resolution, Samsung Galaxy S7 phone camera.  The "full" images in that third image were taken with the G5 and then scaled up to match the central image scale of the S7 images so the entire field of view can be compared for eyepieces exceeding the approximately 76° angle of view limit of the S7 (corner to corner).

The edge images were also taken with the S7 camera, but pointed straight at the edge to best capture the true edge sharpness that would be experienced by looking straight at the edge with the eye.  Notice that the edges of the MWA image seen while looking at the center (main middle image) is blurrier than the view when looking straight at the edges.  The exact same effect is seen with the eye as described earlier.

Discussion

It gets interesting when comparing this eyepiece to the ES-100 25mm eyepiece which has been measured by others to have a true AFOV of 103° and a claimed effective field stop diameter of 41mm by the manufacturer, which I have no reason to doubt.  Thus, I wonder if Meade reasoned that since this 26mm eyepiece has basically the same effective field stop diameter and thus same true field of view (TFOV) as the ES-100 25mm eyepiece, it must also be a 100° AFOV eyepiece.  However, the ES-100 25mm actually delivers a true 100° AFOV experience while this eyepiece does not.

How can we reconcile the Meade MWA 26mm and ES-100 25mm to have vastly different AFOVs and yet the same TFOV when they differ by only 1mm in focal length?  As mentioned earlier, AFOV edge magnification distortion is the reason.  The ES-100, like most Nagler and Ethos class eyepieces has increasing magnification as the edge is approached.  This stretches double stars apart and stretches the moon into an egg shape with the major axis aligned radially.  The Meade MWA has just the opposite, decreasing magnification as you approach the edge.  Double stars get closer together and the moon gets squashed into an oval shape with the major axis being tangentially aligned.  Thus, it compresses the ES-100 25mm's 100° AFOV into a mere 83°!  It's actually a pretty impressive feat when you think about it.  I've seen a similar effect with some fisheye lens attachments that favor the size of the image in the center by compressing the edges to continue to achieve a 180° image circle despite a lack of equal angular magnification across the field.

Despite all this comparative TFOV reasoning, I still won't let Meade off the hook on their 100° AFOV claim.  It's really only an 83° AFOV eyepiece at best, and more realistically, due to SAEP, a 79° AFOV eyepiece, putting it in the same league as Naglers, ES-82s, and other ultrawide angle (UWA) eyepieces.  In this respect, it competes more directly with the discontinued TV Nagler T5 26mm and the ES-82 24mm than with the ES-100 25mm.  The MWA does have more usable eye relief than any of these other eyepieces, but it has horrific amounts of SAEP that those others don't seem to have according to all the reports I've read on them.  It does have that wide effective field stop (FS) to it's credit, though, thanks to its decreasing magnification as the edge is approached.  In comparison, the Nagler 26mm has a 35mm FS while the ES-82 24mm has a 33.5mm FS.  Even the easy to take in 38mm FS at 79° is wider in the MWA 26mm than either of these two.

In use, the MWA shows a lot of the sky at once at a moderately higher power than in a 30mm to 40mm eyepiece with a similar FS diameter.  This was probably the greatest advantage of this eyepiece.  The MWA's eAFOV values of either 90° or 84° are actually quite respectable compared to the NT5 26mm's 77° eAFOV and the ES-100 25mm's 94° eAFOV.

This might be the only saving grace of this eyepiece.  It does deliver a wide TFOV at 26mm, rivaling that of the ES-100 25mm, but with enough eye relief for eyeglass wearers to comfortably enjoy the view.  Is this enough to forgive Meade's dubious AFOV claim?  I don't think so.  They hurt themselves by making these claims that simply can't be backed up by measurements.  Too many purchasers rightfully expect an Ethos or ES-100 level experience when Meade claims a 100° AFOV in their advertising only to be disappointed that they're actually getting a UWA level experience.  It's still an impressive experience, but definitely not in the same league.

The level of edge to edge correction would be quite an achievement were it not for the head/eye acrobatics necessary to take in such a sharp view.  In contrast, the 72° AFOV of the APM Ultra Flat Field 30mm is sharp edge to edge while looking at the center.  Looking directly at any point in the field shows no quirky blurriness that only careful eye positioning can eliminate as in the MWA.  The same is true with the ES-92 17mm.  It's all good, all the time, everywhere.  All I can figure is that due to the MWA's massive SAEP, not all ray bundles come in at the same angle as you scan across the field, necessitating realigning the head/eye combination to correctly admit them into the eye's entrance pupil.

This is not that big of a deal when viewing star fields while keeping the observer's attention in the center.  The blurriness is mostly in peripheral vision, so it is hard to perceive.  However, watching the moon drift across the FOV in an undriven 8" f/6 Dob is tiring and almost headache inducing trying to find the best viewing angle at each point in the journey.  This is especially problematic because the moon is wide enough that the edge closest to the FS and the edge closest to the axis require different eye/head positioning than the central part of the moon for best sharpness.  Thus, the entire moon cannot be seen sharply all at once anywhere except on axis.  As such, this eyepiece cannot be recommended for lunar observing in undriven scopes.  I would stick with the APM UFF 30mm, NT4 22mm, or ES-92 17mm if longer eye relief and a wide AFOV is desired.  Even the 63° AFOV of the 24mm APM UFF was far more enjoyable than the MWA's 79° easily usable AFOV when viewing the moon in the Dob with eyeglasses.

Am I happy with my purchase?  I would have to answer with a qualified yes.  The 79° "easy to view" field is eminently usable with eyeglasses and the view in the central 30% is among the sharpest I've seen in any wide field eyepiece.  However, the SAEP and quirky eye/head alignment issues make it tiring to use off axis for anything longer than a brief look.  It's a bit overpriced by about 30% right now for what it is.

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Great report Thank you for posting. I very much enjoyed the read with my tea & toast this morning. I'm a real Meade EP fan and have been really interested in MWA, so this really helps me.

As soon as funds allow I'll be looking to grab one I think.

Best wishes

Rob

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That is one Full report Louis.

Unfortunately I have not been a big fan of Meade generally . I think it was because I compared  Meade eyepieces to that of the likes of Televue and Pentax . And Meade always seemed to be runner up. The one Meade that did leave a positive impression was the Meade Research Grade Ortho. Still got the Research grade , but the likes of Televue and Pentax really do take some beating IMO

 

 

 

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Very interesting report Louis, thanks for compiling it and posting it here. I know how much thought and effort goes into these things :thumbright:

One line in your report jumped out at me:

"....It is not a good choice for studying objects as they drift across the FOV in undriven scopes....."

I would have thought that the above would be exactly the sort of use that a 26mm "100" degree eyepiece should be aimed at. Whatever it's other strengths it seems a great shame if they cannot deliver in that sector.

For all of that, your report was very comprehensive and an interesting read. Thanks again :smiley:

 

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  • 2 weeks later...

I was out with the 8" Dob last night and tried the Meade MWA 26mm again with and without the GSO coma corrector.  It turns out there's surprisingly little difference other than the fuzzy true field stop without the CC that I mentioned above.  It's so difficult to use the outer field, that any significant difference is just too difficult to tease out.  I would say the biggest benefit of the CC was the field flattening effect.  Even with the CC, there is still slight field curvature in the MWA.

CC or not, it was tiresome trying to keep the blackouts at bay while scanning star fields, even at the "easy view" distance with eyeglasses.  I could always see an incipient shadow ready to rear its ugly head as my head/eyepiece alignment varied during scanning.  It displays a pleasingly sharp and false-color free view in the central region, but the always imminent SAEP is really a bummer.

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  • 6 months later...

I just discovered that Ernest in Russia tested this eyepiece back in late September.  My report was even mentioned up above.  Ernest panned my report as being methodically flawed, though he didn't expound on this point very much other than mention unknown distances from ruler to exit pupil.  The distance from ruler to focal plane is fixed, though, as the tripod and ruler never moved.  Regardless, my numbers for the field stop, apparent field of view, effective field of view, and eye relief if you use my value to see the field stop are all pretty close to his.  He didn't even bother trying to quantify as I did the usable field that is mostly SAEP free.

I do disagree with his assessment that SAEP is not an issue at night.  Under my light polluted skies, my pupils will not dilate far enough to cope with the extreme SAEP (largest he has ever measured!).  Maybe at a dark sky site, but not in my backyard.

He also fails to mention that the 25mm ES-100 has a 94 degree eAFOV as well due to rectilinear distortion, so neither is a "true" 100 degree eyepiece.  Each eyepiece comes at the same eAFOV from two different directions distortion wise (angular vs rectilinear).  He also arrives at the 90 degree eAFOV value by plugging the claimed 26mm FL rather than the measured 25mm FL.  Since both are the same for FL and field stop diameter, they have the same eAFOV.

I was surprised that he measured the MWA to have a 25mm focal length instead of 26mm.  I did a pixel count of the center section where distortion is lowest and did a comparative analysis against known good eyepieces to arrive at a measured FL value of 25mm as well.  I don't know how Ernest measures it, but I'm glad he does because I don't normally check this.  I'll have to amend my value for eAFOV as a result to 94 degrees now.

Edited by Louis D
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