Post by Chicago Astronomer - Astro Joe on Dec 6, 2010 18:23:16 GMT -6
56mm 2 Inch Eyepiece decision
Time for a new eyepiece to add to the Chicago Astronomer arsenal, but in the 2" barrel dimension.
I have a 40mm, 32mm & 26mm in 2" with a related 2x barlow - so I could go either way in millimeters. Should it be more power or a wider comfortable field.
I went with the wider field.
With my 40mm on the C11 (2800mm FL) I get 70x Magnification, (I can fit the full Moon nicely in the FOV), but with a 56mm, I'll enjoy a leisurely, easy and mild 50x. Great for comet hunting and M31.
There is a great wonderment scanning the skies under low wide field power - catching star clusters, nebulae and the Moon in their entirety. And I enjoy simply observing at random, grabbing on to the speed rails of the C11 and just slowly slew...stumbling upon objects.
But which one...more of a economics factor here.
This astronomer cannot justify spending hundreds of dollars on a single eyepiece. The house is paid for and I'm not shouldering a mortgage for a TeleVue.
I scour the web, lookin' to see what's available and came across two 56mm 2" eyepieces.
First is a Russell Optics eyepiece.
An Ebay find, R.O's are a great eyepiece with many loyal fans over the years and they are hand constructed here in the states.
Looks good and the price decent for this respectable eyepiece.
$67.77 + $6.88 = $74.65
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Then there is the Meade...
A amateur astronomer staple, the Meade 4000 series are at the door of serious type oculars. Some further descriptions:
The Meade 56mm Super Plossl is a super low power 2" eyepiece for under $100!
Great for SCT's and other scopes of f/8 and up for greatest possible field of view.
This 56mm Series 4000 eyepiece has a 52º apparent field of view and 21mm of eye relief.
Meade® Series 4000™ Eyepieces: The finest in premium telescope eyepieces. The world standard in telescope oculars, Meade Series 4000 eyepieces yield the widest possible fields of view, consistent with pinpoint edge-of-field sharpness and long eye relief—and yet with extremely low astigmatism, spherical aberration, and off-axis color.
Incorporating multicoated optics for optimum image contrast, these sophisticated 4- to 8-element designs permit levels of optical performance generally impossible to achieve with eyepieces of fewer elements.
All Series 4000 eyepieces include a soft rubber eye guard, custom fitted to each eyepiece with a bayonet mount. The eye guards fold down for eyeglass wearers, and in fact the folded eye guard shields eyeglasses from coming into contact with the metal eyepiece housings. Rubber grips are provided on all but the three shortest focal length Super Plössl eyepieces.
Super Plössls: Designed to utilize the very latest in optical glass types, Meade 4-element Super Plössls are excellent general-purpose eyepieces. For observing hairline lunar and planetary detail, splitting close double stars, or for resolving faint nebulosity in deep space, Meade Super Plössls optimize the performance of any telescope type, whether f/10 Schmidt- Cassegrain, f/16 refractor, or f/4 reflector. They also operate well in conjunction with the air-spaced design of the Meade #140 2x Apochromatic Barlow. All focal lengths through 32mm are parfocal. Each Series 4000 Super Plössl eyepiece is shipped in a dust-proof, threaded poly bottle for secure long-term storage.
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A world standard in telescope oculars, Meade Series 4000 Eyepieces yield wide viewing fields consistent with pinpoint edge-of-field sharpness, long eye relief, low astigmatism, low spherical aberration, and low off-axis coloration. With 7-layer multicoatings and edge-blackened optics, the sophisticated 4-element 56mm Super Plössl permits a level of optical performance generally impossible with eyepieces of fewer elements.
If you have a 2" focuser (or visual back) and desire viewing wide star fields without breaking the bank, this is an awesome choice; your exit pupil cannot be larger with f/10 Schmidt-Cassegrains. Let your vision become adapted to the darkness and try your hand at seeing a wide nebula remnant; you might be pleasantly surprised.
The Series 4000 56mm eyepiece includes a soft rubber eyeguard, custom fitted to the eyepiece with a bayonet mount. The eyeguard folds down for eyeglass wearers, shielding eyeglasses from coming into contact with the metal eyepiece housing. A rubber grip is provided.
The Meade 56mm Super Plössl eyepiece is only to be used with a 2" diagonal or visual back.
• Apparent field of view of 50°
• Eye relief of 21mm
• Excellent wide field eyepiece for observing clusters, galaxies, and constellations
• Accepts 48mm screw-in astronomy filters
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And good reviews on the 56mm - including:
A solid, recommendable set of quality eyepieces. They're parfocal with each
other, and offer clear, sharp views. Just get the focal length(s) you need;
there isn't one model that sticks out from the rest. As with any Plossl set,
the eye relief gets tight, and the lenses get "small" as you go down the range.
Everyone has their personal tolerance level, but I find these get "tiny" for me
around the 9.7 mm model. Your mileage will vary.
All of the models feature a generous 52 degree FOV, except the 40 mm, which
is a little narrow at 43 degrees. All Plossls have this issue; there is only so
much sky you can fit into a 1.25" barrel. If you do the math, the 40 mm winds
up showing you about the same amount of sky as the 32 mm. So I usually
recommend the 32 mm for low power fans. The 56 mm is in a 2" barrel only
and has long (maybe too long) eye relief. Some mind this, some don't. Try
before you buy.
One thing I like about the Series 4000 Plossls is the threaded poly bottle that
comes with every eyepiece (the #140 APO barlow, too). They're great for long
term storage and shows some thoughtfulness on the part of the designers.
More manufacturers should copy this.
Quibbles are minor. These don't have fully multi-coated optics (the lenses look
a little "bright" in daylight compared to the TeleVues, for example) but in
practice this is of little or no concern. Also, unlike TeleVue, Meade does not
(as of this writing) repair broken eyepieces. So be sure and take care of 'em.
I often get asked where these eyepieces stand, in the grand scheme of things.
Based on what I've seen, I'd say these are the beginning of the high-end for
eyepieces. Any gains past this point are incremental at best, and usually
are accompanied by large price increases. These 4000s deliver high quality
images at a still-reasonable cost. Warmly recommended.
www.scopereviews.com/page3.html
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Meade 56mm Plossl
1/4/2006
For faster scopes, a 32mm eyepiece is all you need to maximize your field of view, but for longer focal lengths, such as with Maks and SCTs, getting a the largest true field of view with GOOD QUALITY across the field can be a very EXPENSIVE challenge.
Many years ago, I bought a 35mm Panoptic, and it has been my workhorse eyepiece, being used in just about every scope I own. The 35mm Panoptic is priced well below the 31mm Nagler and 41mm Panoptic, and in terms of actual field, it gives up VERY little to either, and the performance is overall superb.
But there have been times where I could have used a bit of extra field. It was just very hard for me to justify the BIG dollars that it would take to improve on the 35mm Panoptic. I did try some inexpensive 40mm eyepieces, but found the edge of field performance to be less than great, and for 35mm Panoptic owners, well, you get spoiled.
This is my second 56mm Meade Plossl. I had one previously and wasn’t using it much after getting the 35mm Panoptic, so I sold it. Well, with a recent purchase of a Celestron CGE 1400 setup, the need to squeeze a bit more into the field became somewhat more imperative. While the 35mm Panoptic worked for me well in the 2800mm focal length NexStar 11, suddenly I found myself running out of space to cram large clusters into when using the 35mm Panoptic with the 3910mm (Stated, but I believe it is actually longer than this) focal length of the C14.
Some of the larger clusters like M37 become so large, that they overrun a 30 arc-minute field. In fact, in my newly acquired C14, M37 totally fills the 35mm Panoptic’s field of view. Almost all of the Messier clusters fit in the field, but BARELY. You can’t “Frame” some of these clusters easily though. By that I mean that it looks like you are just looking at a field full of stars. Many clusters change character when you put them in a field surrounded by contrasting background stars. So there are times when I want a bit more field of view. Enter the Meade 56mm Plossl.
Using the Meade 56mm, I get about seven or eight more arc-minutes of true field in the big SCT. Now this doesn’t sound like much of an improvement, but I find that this field is JUST enough to make enough difference to make the purchase price worth it. I didn’t feel that the cost of the 41mm Panoptic would be very easy to justify though, but the 56mm Plossl is by comparison a dirt cheap eyepiece.
So, is it any good?
Well, in fact, I find it to be a really fine eyepiece. Mine is the older style without the eye-guard. It is the second one I have owned, and performed identically to the first (Also an older one without the eye-guard).
It is hard to compare contrast to the 35mm Panoptic, because the lower power opens up so much more sky that background glow becomes a larger factor. If I compare them side by side, I can detect fainter stars in the Panoptic, but again, I think that this is very much a function of decreased background glow. I see the same effect when going from the 35mm Panoptic to the 22mm Nagler. Increases in magnification will pop in additional stars. So while I am not able to make an exact comparison (and that wasn’t really the intention), my observations indicate that the performance of the 56mm is at least as good as all of the inexpensive and mid-priced 40mm eyepieces I have used, and in fact, I would say better than most.
The field is quite sharp out to within a very few arc-minutes of the edge of field. Only in the last couple minutes toward the edge do I notice any optical degradation. This is VERY minor. In fact, I used the 56mm in my f/5.7, 140mm Vixen refractor (Totally on a whim, because this combination results in a 14.2x magnification and a 3.5 degree field but with a 10mm exit pupil!!!) Still, I was quite surprised to see that once again, the field seemed fairly sharp until the last few degrees before the edge.
Now one of the things that is important to me in terms of having a wide true field is to also have a sharp field. Having owned several other 2” low and mid-priced eyepieces longer than 32mm in focal length, only the Panoptic so far has given me the kind of across the field sharpness that really pleases me. I consider the 56mm to be the second best in this regard of the other 2” eyepieces that I have used past 32mm focal length, but being second to the 35mm Panoptic is not a bad thing. When I pull out the 35mm and put in the 56, I am aware of the difference in the apparent field field of view, but I don't feel like I am giving up any quality to get a bigger true field. And that was the whole idea… Get those extra few arc-minutes of field without spending lots of money.
There is one characteristic of this eyepiece that some people might not like. Eye relief is VERY long. You have to hold your head back away from the eyepiece quite far to see the full field. You have to back away o far in fact, that you see around the outside of the eyepiece with your peripheral vision. This lets ambient light enters, so if you observe in an environment with high ambient light (My backyard is not all that dark) this could be distracting.
Now I am not even remotely suggesting that you can match the performance of the most expensive premium wide-angle eyepieces with the Meade 56mm, but I am suggesting that given a field of “X” degrees, there is “Y” amount to see, and the 56mm seems capable of showing just as much, just about as sharply, for a quarter of the price of a premium, and half the price of a mid-priced wide-field eyepiece.
These eyepieces have been greatly reduced in the new selling price lately, and frankly, after trying a few other mid-priced 32mm+ wide-angle eyepieces and being less than satisfied with their edge performance, I think the Meade 56mm presents a VERY attractive alternative if your goal is to get the biggest field from a slower scope like an SCT or Mak Cass. SO, if biggest field/exit pupil in your long focal length scope is the REAL goal, the Meade 56mm eyepiece is a VERY good way to get there. Highly recommended…
www.astromart.com/articles/article.asp?article_id=356
Here is a great explanation and diagrams of the Meade 4000 Super Plossl series of eyepieces:
www.meade.com/catalog/meade_4000/meade_series_4000_01.htm
The weighing of specs....
The R.O. has a 5 element design - The Meade just 4
The R.O has a 30mm eye relief - The Meade at 21mm
The R.O eyepiece is rare - The Meade common
The R.O is more expensive - The Meade cheaper by $4.70
The argument on the eye relief is that as we get older, our pupils do not dilate as wide as they once did - 5/6 mm max....and that any claim to wide eye relief is wasted.
I don't care.
The portal views, in where one has to look around in the field of view is a great experience and well worth the extra mm's.
As of this posting...I have not decided yet, but will make a choice...probably in the wee hours of some upcoming morning.
