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Review of the Meade 18mm Ultra Wide Angle

Posted by Ed Moreno   11/05/2007 08:00AM

This is a review of the Meade 18mm Ultra Wide Angle eyepiece.

The sample I tested was bought used, but the seller said that it was basically in new condition, and indeed it arrived to my door in original packaging and in pristine condition.

Before the testing, let me tell you about why I wanted a Meade 18mm Ultra Wide Angle. About 2 months ago I acquired a used C5. I have since named it “Tiny Tiger” (I name my scopes… I call my Vixen 140 “Blade” because the wide field views are so sharp at the edge that you could cut yourself, I named my C8 “Gwen” after Gewn Stefani… Around 40 year old design that looks great in black and that you really want to spend the night with… LOL, and my C14, I call “Big Al”, after the giant roping horse that I ride at my cowboy friend’s ranch. Being on Big Al is like riding a horse standing on top of a small car. The other cowboys all have to look up to you. And big AL is a fine roping horse.. One of the best I have ever ridden.. IT seems appropriate homage to him to call the C14 Big Al because when I use it, I know I am using a seriously big telescope.

Anyway, Tiny Tiger has two design issues that one needs to consider when choosing eyepieces. First, like all SCTs currently made, SCTs hove copious amounts of field curvature built into the design. As you move further from the center of the field, stars become unfocused. There is also some coma, but the PRIMARY aberration in the design is field curvature.

Now field curvature is something that you learn to live with, just as coma is a built in aberration for Newtonians, and Astigmatism is present in many refractors (Inexpensive ED doublets usually have pretty serious amounts far off axis.) So pick your poison. Only the most expensive scopes can cope with off axis aberration well… AP Triplets, Maks, and Petzval scopes all deal with it rather well, but all have other tradeoffs.

Back to Tiny Tiger. The goal for Tiny Tiger was to get a bigger field of view than I was getting with the William Optics 20mm 66 degree apparent field eyepiece that I bought on Astromart. Now this is not a terrible eyepiece. It is actually fairly OK.. But it DOES show quite a bit of astigmatism at the edges of the field, and when you use this astigmatism to blur the already bloated stars (due to the telescopes field curvature), the edge of field doesn’t look so good. So my goal was to get a WIDER field, but with LESS eyepiece-introduced aberration. My eye can accommodate some of the miss-focus out, but you eye cannot cope with astigmatism from the eyepiece itself.

I like Televue products. Make no mistake; I consider them the benchmark for all other eyepiece products. Naturally, I considered buying a Televue brand eyepiece, but here was the problem. I was committed to staying with a 1.25” format eyepiece for Tiny Tiger because the small central baffle in a C5 means that if you use an eyepiece with a field stop larger than about 25mm, you will start to suffer from field illumination drop-off at the edge. Now I know that many people use 41mm Panoptics in C8s and will tell you that you can’t SEE vignetting, but the fact is that now you are taking an already out of focus star near the edge of the field that is already dim due to defocus and subtracting a half magnitude of brightness from it due to field illumination dropoff! So to me, it is better to match the eyepiece to the scope.

I considered the 24mm Panoptic. This eyepiece would give the widest fully illuminated TRUE field at about 1.25 degree. The field curvature of the scope is pretty bad, but due to low magnification, the blur would still be small enough that it would be inoffensive (for someone that has learned to accept field curvature).

The problem with this approach however is that using these kinds of larger exit pupils means that the sky brightness can cause faint stars to become invisible. I used to see this in my C14 when I would go from my 35mm Panoptic to my 56mm Plossl. The field was LARGER, but targets at the center were harder to pick out of the much brightened background (which is really foreground light pollution, yes?) Anyway, I would use the 56mm when I needed the absolute largest field, but the tradeoff was that the field would be more washed out than in the 35mm Panoptic.

Even when I received a 31mm Nagler as a birthday present, in comparison to the 35mm Panoptic, I was surprised to see that even 4mm of focal length worth of magnification improved the contrast of the view over the 35 Pan enough that it was CLEARLY noticeable. AND the field was BIGGER to BOOT!!! The lesson here is this. If you can get HIGHER MAGNFICIATION with a LARGER TRUE FIELD, the result is usually see more both in terms of the extra field area AND THE ENHANCED CONTRAST AT THE CENTER OF THE FIELD!

And THIS, my friends, is why you REALLY want to buy excellent wide field eyepieces. Don’t buy a Nagler or a Mead UWA for the “Spacewalk”. Buy it instead because it allows you to RAISE MAGNIFICATION TO IMPROVE CONTRAST while still preserving a large enough true field to frame your target! This is the WHOLE idea behind the new Ethos…

So, I was afraid that the 24mm Panoptic would simply provide too big an exit pupil and the resulting contrast loss would be a big step back from the WO, even though it would probably improve the “Quality” of the edge of field view.

I also considered the 16mm Nagler. Here, the field would be almost exactly the same the 20mm WO,, and while the QUALITY of the view might have been better, the goal was to also get a LARGER true field along with increased contrast.

So with the desire to stay with 1.25” format, RAISE magnification over the 20mm WO, and get the LARGEST well corrected field I could, then I was “Stuck” with one final option… That would be the Meade 18mm Ultra-wide angle.

Now I DO have experience with Meade Series 4000 UWAs. I have owned two 8.8 UWAs, and I will go on record as saying that they are every bit as sharp as Naglers. My concern was that with a lot of the competition and cost savings efforts today, the 18mm would not live up to it’s predecessor’s excellence. So when I say I was “Stuck” with the 18mm, I mean I was wary of purchasing an unproven design at a near premium price. Still, upon doing the math, I came up with about 70x and over 1.17 degree using the 18mm UWA, so this was “Enough” of an improvement over both the WO and the Nagler 16mm to make me say uncle and send the Paypal payment.

On to the eyepiece itself: First, up, the physical packaging of the eyepiece housing. Simply put, I don’t like it. When you look straight down on the eyepiece, the outer case of the lens housing has triangular-like shape. Well the LOBES of the triangle (they are squat and rounded so that they resemble the lobes of a cam) stick out quite a bit from the minimum dimension. The result is that the eyepiece is a lot squatter looking than it needs to be. Yes, this is esthetic only really, but it makes the eyepiece look UGLY when sitting on a diagonal. The proportion is just goofy. The lobes serve no purpose that I can discern, and they serve to make the eyepiece ungainly.

Next, there is the “Rotating Eye-guard.” It turns out that the Eye-guard itself doesn’t rotate exactly.. IN fact the ENTIRE OUTSIDE OF THE EYEPICE (the lobed housing) has to be rotated. For now, mine is very stiff, and I have to hold the focuser barrel to rotate the entire housing. Maybe it will loosen with usage, but the movement is very stiff as if there is some viscous grease inside. Not that it matters because I won’t use it. The eye-guard cup itself is harder rubber. In my T4 Nagler, the eye-guard is soft and I can fold up half of it to shield me from light source coming from one side. With the UWA, it is all or nothing. The guard doesn’t fold down. Rather it completely retracts so that the top is flush to the large metal ring around the eye lens. Also with the 18mm in particular (I don’t know about the rest), moving the eye-guard up even a tiny bit pushes your eye back from the eye lens enough that you can’t take in the full field. The Nagler eyepiece uses a very flexible rubber eye-guard that can be flipped up on one side. Also, it is simply less intrusive.

That naturally leads to the eye relief discussion. In the 18mm, things are tight. My eyelash has to touch the broad, flat ring around the eye lens to be able to get close enough to take in the entire field. Now at first, I though that it would be too close for me, but I am happy to report that after using the eyepiece for 20 or 30 minutes, I found it to have enough eye relief that I was more or less comfortable with it. Still, it is tight.

Ok. What you are really waiting on is the TEST, yes?

Comparison was done with my 17mm Nagler T4. The T4 is a MUCH more expensive eyepiece, and it has been DESIGNED to have better eye relief, and it does By comparison the 17mm Nagler is more comfortable to use. But again, it costs considerably and one of the design goals for the T4 line (Still my favorite eyepieces) was to have long eye relief. . So let’s get past that and chalk it up to comparing expensive apples to less expensive ones.

The focal length of the eyepieces is close enough to make the comparison valid. One could ask why I didn’t just use the T4 in Tiny Tiger and the answer is that it has a 2” barrel, and that it cost enough that I didn’t want to leave it outside in Tiny Tiger on the covered patio 24/7. I DID consider it, but in the end, decided that I truly did want to stay with 1.25. To use the 2” diagonal in Tiny Tiger would increase the focal length (because the mirror has to be moved for it to reach focus enough that you probably add 30mm or 40mm to the focal length). The effective in crease of the focal length would result in basically the same field as I would get using the 1.25” 16mm Nagler.

I did have experience have experience using the 17mm in Tiny Tiger enough to know that the field curvature of the SCT would show out of focus stars in the 18mm, even if the eyepiece was perfect. Field curvature in SCTs is progressive, so while the magnification would be lower resulting in slightly smaller blur circles in the field that was covered by both eyepieces, I assumed that the area NOT covered by the 17mm would show slightly more unfocused stars in the 18mm simply because once again, I would be seeing field not visible in the 17mm. And heck, I had already tried the 22mm Nagler. It too showed un-focused stars near the edge of the field that looked more or less the same as stars near the edge of the 17mm.. While the blur circles were less magnified, they were still almost as BIG as in the 17mm because I was showing field curvature from the extreme edge of the small mirror where field curvature is the worst.

So to do the comparisons for absolute sharpness, I didn’t even USE Tiny Tiger. Instead, I used the telescope that I use for all of my wide -field eyepiece testing… Blade, my favorite refractor.

The Vixen 140 is a 4 element ( 2 groups of 2 lenses) has an incredibly flat field. Like most refractors, as you move further off axis, the primary aberration is astigmatism. But you have to get really, really far off axis in the Vixen 140 before the aberration becomes significant enough to be intrusive. How far off? Try 31mm Nagler far off. Even in the 31mm Nagler, astigmatism from the telescope is only visible at the VERY VERY EDGE of the field. In literally the very last few arc SECONDS of the field, stars will show a tiny, faint “Seagull”. Go in a few arc-seconds from the edge, and the star will look pin-point. Not arc minute, but arc SECONDS. So the primary testing was with the Vixen 140.

First, I did baseline testing of the Nagler. Again, with the 17 Nagler, just as with the 31mm, only the TINIEST HINT of astigmatism was visible at the extreme edge of the field… “Hey Ed” you’re saying…. “Didn’t you just say that the Vixen 140mm was uber’flat?” If so, why are you seeing astigmatism????” Well, the astigmatism was THERE with the 31mm Nagler closer to the center of the field, but it simply wasn’t MAGNIFIED enough and that coupled with the lower contrast of the low power field simply makes it invisible. The fact is that almost ALL TELESCOPES star to show their PRIMARY aberration very close to the center of the field. A fast dob will have Coma outside of a 5 or 6 ARC MINUTE area at the center of the field. My C14 shows slight coma 10 arc minutes out from the center of the field, and as you progress further from the center of the field, stars become defocused due to field curvature of the design.

So, The 17mm Nagler showed very slight amounts of astigmatism that were no doubt coming from the telescope.. Now if I looked at the CENTER of the field, the aberration was invisible in my peripheral vision... On axis, stars were tack sharp, and the field was much darker and had much more contrast than the WO eyepiece did (which I also put in as a baseline). I had to move my eye to the edge of the field to see any astigmatism, and it was only noticeable in the very last few arc SECONDS of the field. It was RIGHT at the edge of the field. Everywhere else, the field was in almost perfect focus.

Flip to the 18mm, which I had in a 2” adapter. Get my eye in close… Slight re-focus… BANG, a practically IDENTICAL field. Dead sharp at the center, with only the faintest traces of telescope induced astigmatism at the edge of the field. In fact, the view was so similar that I wouldn’t have been able to tell the difference except for eye relief. The T4 Nagler was much more comfortable to use. There was clear separation between my eye and the top of the eyepiece. In the Meade 18mm UWA, my eye lash was touching the flat metal ring and the fatty-fatty body was along side of my fine, aquiline nose. On a cold night, I might not like that little hard metal or plastic body touching me….

But optically, there was little to differentiate the two. I did pass through focus and in fact, I felt that the 18mm was not exactly as sharp at the extreme edge of field. I think the Nagler MIGTH have edge it out, but remember, using the higher magnification of the Nagler over the UWA, I could have just as easily been seeing slightly more of the astigmatism from the Vixen refractor because I was showing parts of the field that weren’t visible in the Nagler due to its smaller true field.

I tested exhaustively making perhaps 10 or 15 comparisons on lots of stars of different brightness’s and the result was always the same. These two eyepieces are almost identical in on axis and off axis performance. In the Vixen 140, the difference in true field was only 1 tenth of a degree, and there was only 4x magnification difference, so in overall terms, the fields were mostly identical.

Next, I pulled out Gwen… Gwen is a sweetheart. She is without a doubt the best SCT I have ever owned from an optical quality standpoint. I would put her up against any 5” APO ever made and expect her to acquit herself well in terms of planetary performance. This telescope star tests as close to perfect as I have ever seen, and it is as sharp as they come. The ONLY smaller telescope that I have owned that could BEAT it on planets was my Meade 152ED. But the difference was hard to see. So both eyepieces went into Gewn for sharpness testing on Axis. While no planets were handy, I did use the moon and several doubles, and again, there was literally no difference between the two. I have used my 17mm Nagler in my C11 and my C14 on Planets and in spite of what people say regarding multiple element design eyepieces being grossly inferior on planets to simpler designs, I know that in reality, the difference is difficult to see. Only very slight differences in the faint glow around the planet will give away the fact that you are viewing in the 17mm Nagler vs a 17mm Televue Plossl… In THEORY, I know that this glow robs contrast. But in PRACTICE, the difference on planetary detail itself is almost impossible to see. Only the most critical observers will see it. In my testing, I used some bright stars to simulate the glow around planets and once again, the 18mm Meade showed just about identical sharpness and contrast to the Nagler. Again, only the eye relief (and the VERY slightly larger field of view) gave the 18mm away.

On another important observing consideration for wide field eyepieces, I think the Meade was better.. The UWA was NOT as susceptible to kidney-bean blackouts as the Nagler was. In fact, even in spite of the tight eye relief, I was growing MUCH more comfortable using the UWA. Now I have to say, SOME of this might be due to the fact that I was actually TOUCHING the barrel of the eyepiece with my head and maybe this actually helped me hold steady some. But overall, I felt that the 18mm was less inclined to show kidney-bean distortion. Again, the longer I used the 18mm, the more comfortable I became with it.

I had used the 17mm many times in the C5, so I knew that the outer edges of the field would be out of focus in the 18mm, and when I FINALLY got around to plugging the 18mm into Tiny Tiger, this is exactly what I did see. About 3/4ths of the way from center, the field curvature of the C5 started to introduce bloating in the stars. Now if you are older, your eye cannot “Accommodate” this as easily as when you are younger, but you can still accommodate SOME field curvature by refocusing… I chose to refocus the field so that those stars at about 75% out from center were as sharp as possible. Using this method, I could keep a little more of the field sharp because my eye could slightly refocus the center, so I extended the usefully sharp part of the field out to about 85%. And maybe even 90% of the field.

Now if I were to plug in a 24mm Panoptic, I doubt that I could do better in terms of overall field sharpness, so this was working actually BETTER than I had thought it might. I spent about 30 minutes with the 18mm in Tiny Tiger, and by the end of the session, I was feeling good about my decision to sacrifice a bit of true field to keep magnification (and CONTRAST) high. As I relaxed, I began to once again tune out the SCTs out of focus stars at the edge of the field, and soon the entire field became mostly “Sharp” to me. I find start that are simply a bit out of focus to be far less intrusive than stars that are out of focus and then SMEARED by astigmatism and the William Optics 66 degree eyepiece was not really making me happy in the C5 (and to be sure, astigmatism was easily observed when I tested that eyepiece in the Vixen). The 18mm was working well… For comparison, I put on the 2” diagonal and put the 17mm Nagler in. No doubt, the field was smaller and the magnification was noticeably higher. It was impossible to make accurate comparisons because I would have to remove the 2” diagonal to use the Meade (I could use a 2” adapter, but then the Meade would also loose field because of the extended focal length). So using the Meade in a 1.25” diagonal and comparing it to the 17mm Nagler in the 2” diagonal with the extended focal length made me very pleased about my decision to maximize the field of view by sticking to an 82 degree eyepiece in 1.25” format.

For my final test, I went to the Double Cluster… This is one of my FAVORITE objects. I put the 20mm eyepiece back in… Here was going to be the REAL question… Would the 18mm provide a substantially more rewarding wide field experience than the 20mm semi-wide field eyepiece did? With the 20mm, the field was slightly washed. I positioned the clusters in the field so that each cluster was about equidistant from the center of the field. Doing this, the “Edges” of each cluster were just crowding up against the edge of the field. In addition, the astigmatism in this eyepiece caused some of the brighter out-lying stars to steak very slightly over the top of the blur from the field curvature of the C5.. So while the view was nice, and someone that had never seen it before might have been very impressed, I KNEW that it could look better if it were framed better and if the astigmatism were removed from the picture.

I swapped to the 18mm… It made ALL the DIFFERENCE in the WORLD. Now, the edges of the clusters were well in from the edge of the field, even though the magnification was HIGHER. Everything seemed much BRIGHTER too… Some of the very tiny stars that form a tiny semi-circle at the center of NGC 884 (I THINK that is the one, but if not then it MUST be the other one… LOL). were barely pushing through the sky glow in the 20mm, but now the extra magnification and improved contrast made the little semi-circle QUITE evident. And the better corrected field meant that almost all of the stars in both clusters were sharp right out to their edges. Only a bright star at the VERY edge of the field was showing enough field curvature to intrude (and this is the case with field curvature.. You learn to somewhat ignore the brightest stars at the edge, and the medium bright stars don’t broadcast their bloating enough to distract from the view.) Now I didn’t buy the 18mm JUST for the double cluster, but this object was a PERFECT object to test out my justification, and I am DELIGHTED to say that, for me, I think the purchase was EXACTLY right for Tiny Tiger and my own preferences.

We will need to wait until after the year to see if the Televue price increase makes the Meade UWA line look more attractive from a cost benefit standpoint because right now, many people might be tempted to overlook them in favor of the Naglers (Unless they are looking for a SPECIFIC focal length or to solve an exact problem like I was). If Televue increases their prices quite a bit and Meade holds the line, I would say at that time that the Meade UWA line would make a compelling alternative to the Televue Naglers. Optically I consider the 18mm to be on par with the T4s in optical sharpness, and only the clunky packaging (lobes on housing and the hard rubber eye-guard) of the 18mm keep me from giving it my highest recommendation.

And if you WANT the biggest possible high contrast field using a 1.25” focuser format, for now it would seem that Meade has the best solution available. For you, I give the 18mm UWA a very high recommendation. If you were looking at a 24mm 1.25” eyepiece for your telescope, my own advice is to give very serious consideration to the 18mm Ultra Wide Angle eyepiece as a better way to get there because of the vastly improved contrast you will get over the much longer focal length 24mm. The tiny amount of absolute true field you leave on the table will easily be worth the improved contrast.

With the current (November/December ’07) Televue sale going on, you may prefer to ante up the small difference and go with Televue eyepieces. My 5mm T6 is very comfortable to use and I suspect that the Naglers are all this way as compared to the UWAs… After the first of the year, things will get interesting though. Televue will most likely increase prices, and if Meade holds their current pricing, I would say that for the first time in a long time, there will be a true marketplace competitor to the Televues in terms of QUALITY, at a price that might put more 82mm wide-field eyepieces into the hands of more and more observers.

So OPTICALLY, I give the 18mm UWA scoring equal to the Nagler T4 17mm. Put the 18mm on a slimming diet, and get rid of the funky hard rubber eye-guard in place of a more flexible fold-down style, charge 15 % less, and I would probably not hesitate to buy one over the corresponding Televue Nagler. But for now, considering ergonomics, Naglers still have it by a nose…. A big price increase by Televue might make the lobes and eye-guard less objectionable though… Stay tuned for 2008 price increases and it may be a different game.

Click here for more about this subject. -Ed.