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Meade 20mm 5000 Series Plossl

Posted by david elosser   04/23/2006 12:00AM

Meade 20mm 5000 Series Plossl
I am no expert in eyepiece design, but it is easy to see that the Meade 20mm 5000 series Plossl is a different breed of eyepiece. Although Meade calls this eyepiece a plossl, it has better eye relief and more true field of view than a typical plossl. Over the years I have (unintentionally) collected many 20mm eyepieces, so I have a number of benchmarks to compare the performance of this eyepiece. In the photo at the end of this article, from left to right, is the University Optics 20mm Super Erfle, the Meade 4000 series 20mm plossl, the Nagler 19mm Panoptic, and the Meade 5k 20mm.

First sight:
Construction of this eyepiece is excellent, but there are a few minor complaints. First, the eyepiece cap does not fit well (but what else is new with the 5k line?). Second, the chrome barrel is cheaply made (again, what else is new?). The barrel is sturdy enough, and has the standard set screw groove, but while adjusting the eyepiece cup I found myself accidentally unscrewing the barrel. Once I discovered this problem, I learned to “adjust my adjusting” technique. The cup itself is very well made and stays where you put it.

First light:
Orion was well placed in the sky, and the Orion Nebula was, of course, the first place to go. Even with my light polluted suburban skies, contrast was excellent and I could just make out some swirling in the brightest areas of the cloud. After some extended study with averted vision, I could begin to see the fainter areas extending far beyond the “wings” of the main nebula. The Trapezium, through my 102mm f/7.75, was small at 40x, but resolution was excellent and the eyepiece exhibited tiny, sharp pinpoints on the stars. I could see the entire Sword of Orion, from top to bottom, in the field of view. Another treat in Orion is the multiple star system Sigma Ori. All four A-B-C-D components were visible in my 102mm, and the nearby triple system Struve 761 is also easily resolved. Stars are definitely a bit soft at the margins, but not, in my opinion, objectionable for an eyepiece in this price range. What I really like about this eyepiece is the generous eye relief. I adjusted the eye cup up a bit to keep my eyeglasses from hitting the top glass, and I could still see nearly the entire field without moving around. (Your experience may vary depending on the type and size eye glasses you wear.) A star test on Sirius was excellent in my perfectly aligned Stellarvue 102ABV (considering the 40x magnification). Diffraction rings were well separated, but moving the star to the edge of the field showed some distortion. M45, the Pleiades, was a bit tight in the field of this eyepiece, but the superb contrast showed me some faint nebular glows around some of the stars. M104, the Sombrero Galaxy in Virgo, was easily visible and the “Stargate” was easily found in the same field of view. Other objects like M51 (Whirlpool Galaxy and companion), M81/82 pair, (all three in Ursa Major), galaxy NGC 2403 in Camelopardalis, and M78 diffuse nebula in Orion were easy targets in my light polluted skies, showing that this eyepiece has what it takes to hunt down dso’s. On the evening of April 9th, I was “picking up good librations” on the eastern limb of the waxing gibbous Moon. This eyepiece has excellent sharpness and contrast, with no detectable lateral color and very little flaring off axis when a neutral density filter was used. At 40x in my 102mm apo I was treated to a very sharp limb and I could see nearly all of Mare Smythii, right back to the far side mountain range. I could also count mountain peaks around Mare Humboldtianum to the north of Crisium. This is also a good eyepiece for solar observing. The power you get is a bit low, depending on the telescope you are using, and there is more lateral color off-axis than the Panoptic. But contrast is good enough to show me all of the features available with a Baader white light filter: spots, grain, faculae and plages.

Eye to eye versus the Meade 4000 series:
In my opinion the Meade 4000 series plossls are good eyepieces for the price range, giving good “typical” plossl quality images. The 5K plossl is, however, a more expensive eyepiece, and I would expect better performance over the 4K. This is definitely the case. In nearly every category: contrast, image brightness, field of view, eye relief, and edge of field performance, the Meade 5K wins hands down. The 5K is also a much better choice for eye glass wearers.

Eye to eye versus the 19mm Panoptic:
At first glances I could tell no discernable difference in image quality between these two eyepieces, other than a slightly brighter image with the Panoptic. A star test though, betrays the Meade’s inferiority. The diffraction rings were cleaner in the Panoptic, and showed little distortion at the edge of the field. The Pan has a much sharper image at the edge of the field, but this advantage is nearly negated by the fact that its eye relief is too tight for me to use with my eye glasses. This fact, and the much heftier price tag of the Panoptic, might make the Meade a better choice for many. Viewing the Sword of Orion, I discovered an interesting fact: the slightly smaller magnification and larger field stop diameter give the Meade a nearly identical true field of view as the Panoptic. (You might expect the opposite since the Panoptic is a 68* afov eyepiece and the Meade is rated at 60* afov, but it is the field stop diameter that determines the true field of view in any eyepiece.) So, does the Pan give you a smaller fov than it should, or does the Meade give you more than you ask for? I don’t know, but subjectively I do find that the Meade seems to be “too wide” and I usually end up adjusting the cup so that the edge is blocked a bit, partly because of the long eye relief.

Eye to eye versus the 20mm Erfle:
University Optics has a very popular line of fine quality orthoscopics and Konigs, and their 20mm Erfle is made to their same high standards. I made a visual comparison chart of the four eyepieces in this article and, a bit to my surprise, the Meade 5K performed slightly better than the Erfle in every category except color accuracy and sharpness, where I could not tell any discernable difference between the two. These two eyepieces are closest in overall performance to each other, but the Meade has the advantages of the adjustable eye cup (the Erfle does not come with any eye cup) and better eye relief. The Erfle lacks edge of field definition like the Meade, but its field stop diameter, and thus its true field of view, is smaller than the Meade’s.

The pros and cons of the Meade 20mm 5K plossl:

PROS: Moderate price tag
Excellent eye relief
Excellent image quality
CONS: Soft image at the edge of the field
Eye piece cap falls off too easily

In conclusion: of these four eyepieces, I would have to give the blue ribbon to the 19mm Panoptic. The Meade 5K is a respectable second place with the Erfle a very close third. Although the Meade 4K eyepiece does not live up to the standards of the other three, it does have very good sharpness and color correction and performs well for its price tag. Considering the Meade’s excellent performance and the much higher cost of the Panoptic, I think it would be fair to label the Meade 20mm 5000 Series Plossl as a “poor man’s Panoptic.”

David Elosser
Kernersville NC

Click here for more about this subject. -Ed.