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Thread: wide-field vs plossl EP for planetary viewing

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    Default wide-field vs plossl EP for planetary viewing



    I read somewhere that widefiled eyepieces such as Naglers and Meade UWA 5000s dont fare as well on the planets as a good plossl or more narrow FOV eyepiece does. Is this true, and if so - why?
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    Planets are SMALL.... absolutely no need to have a wide field of view. to view a small object...

    Kind of like taking a nickel and placing it in the palm of your hand vs looking at it if it was on the floor... The nickle will appear much smaller on the floor then it does in you hand...

    This is not saying that you can't use as wide angle eyepiece .. 200x is 200x ... but will the planet will "appear smaller" in the eyepiece with a wide angle eyepiece because you have a larger background

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    Thank you for the responce. I see your point about the relative space around the planet, but I was referring more to the actual glass differences between the two styles of eyepieces. Do high quality plossls bring out more detail in planets than something like a nagler?
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    A standard Plossl eyepiece uses a two-group, four element design that provides a 50-degree FOV. The front element group is composed of a plano-concave extra-dense flint glass element and a light flint convex element. This group forms the eye lens of the eyepiece. The second group, forming the field lens uses a larger diameter convex element followed by a concave element made of double-dense flint glass. The two groups use an air-space of varying dimensions based on the eyepiece focal length.

    A Nagler Type I uses a four-group, seven element design, and provides a 82-degree FOV. The front element group is composed of a concave-convex element pair of light flint and extra-dense flint glass. Air-space separates the first and second group, a convex/concave-convex element pair of light flint and extra-dense flint glass respectively. A second air-space separates the third element, a single convex-concave corrector of light flint, followed by an air-space and the fourth group, a concave-plano-convex pair of light flint and extra-dense flint glass.

    The Type II Naglar uses a five-group, eight element design, with also with a 84-degree FOV. The front element group uses a concave-plano-convex element of extra-dense and light flint glass. After an air-space, the second group uses a single element plano-convex light flint glass component. Following a second air-space, the third group uses a light flint glass asymmetric convex element and double-dense flint glass concave-convex element to provide field-flattening. The fourth group uses additional air-space on either side, and is another asymmetric convex light flint glass element. The fifth and final group is a two element light flint glass concave, and a double-dense flint glass plano-convex element that provides correction and magnification at the exit pupil. In effect, the Type II has a "built-in barlow".

    The original Nagler/TeleVue eyepieces use barium flint glass in place of extra-dense flint glass elements.

    A Plossl is relatively wide-field eyepiece, and because it contains fewer elements, it will lose less light, on average than a Naglar of equivalent focal length. For planetary viewing, this will in general result in slightly brighter, higher image contrast.

    The Naglars are very wide-field, but due to the slightly higher absorption, related to the number of elements in the lens, they'll produce slightly less bright, slightly reduced image contrast for planetary viewing. Combined with the wider field of view, you're not getting much, if any benefit by using a Naglar against a Plossl of equivalent focal length for planetary work.

    The best eyepiece design for planetary observation is the Orthoscopic. These are relatively short focal length, high magnification eyepieces. They use a two-group, four element design. The first group, forming the field lens uses a triplet composed of an asymmetric convex element made of crown glass, a concave element made of extra-dense flint glass, and a final asymmetric convex element, also of crown glass. The second group forms the eye lens, and uses a single asymmetric convex element of light flint glass. Most Orthoscopic designs have a 45-degree FOV.

    The relatively low number of lens elements, highly transmissive lighter glasses in each element, along with a narrower FOV produce a higher contrast, brighter exit pupil image than either the Plossl or Nagler.
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    Excellent write up.
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    AustinPSD your posts are always so informative, thank you. I heard that Celestron Ultima LX eyepieces are very good planetary eyepieces. Have you had any experience with these 70 dgr EPs?

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    Quote Originally Posted by JoeThePro View Post
    AustinPSD your posts are always so informative, thank you. I heard that Celestron Ultima LX eyepieces are very good planetary eyepieces. Have you had any experience with these 70 dgr EPs?

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    I don't have any direct experience with, nor do I own any of the Ultima LX series...

    They're based on the "Wild" design, using two additional elements to allow all the eyepieces in the series to be parfocal.

    That's about all I can tell you - Celestron hasn't published much detail on this particular design, and I have none in my collection for comparative purposes.
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    A good planetary epeyepice, I would'nt restrict myself to wide vs. narrow or Plossel vs WA/SWA/UWA or edge on or radian or orthoscopic... or...'planetary' (purely a marketing term and I find the TMB planetary ep's 'poor' at best)

    There are a lot of myths out there about good planetary eps - I think mainly because so few ep's are 'great' planetary ep's. Few are great, some are good, many more are downright not-so-good.

    I'm a bit of a planetary fanatic. So aside from all ep discussion treat each planet as it's it's own. Neptune is nothing like Jupiter to me Venus?.... ummm boring... Mars is a constant source of frustration but sometimes rewards. Jupiter and Saturn... the king and queen. And our moon, after all these yesrs I'm still enjoying it.

    Planets like Jup, Mars, Venus are very bright and the contrast/color gradients are taxing on most ep's - pose their own problems... ghosting, light 'splash' or wash, internal reflections(within the ep itself), reflection from your own eye on the lens, 'lightning stirke', er blackout... list goes on and on. A lot has to do with the lens grouping and coatings (yes! coatings scatter light! but they also mitigate reflections...) and edge blackening and baffleing and field stop and exit pupil. It's unfortunately easy to do a lot of things right and get it wrong for a great planetary ep. (may work nice on everything else) You wont notice a lot of these issues looking at 'reatively dim / lower surface brightness' stuff normally up there on the same ep in most cases.

    I am NOT a fan of the green letters for planetary at all (TV eyepieces) outside possibly the plossels. (I no longer own any other than an ethos or two) I think most of the TV ep's inluding -but to a less degree- the Ethos - give a slight 'coffee tint'.

    Great planetary ep's are coveted and have high resale. I don't know of any inexpensive ones that wont show a little anomoly. TMB planetary ep's, edge-on, radian... all on blacklist. Also less than impressed by the Tak ep's (love their scopes) - I've read were folks liked them more with a quartz diagonal vs. mirrored - but I can't speak to that - nowhere near what i expected - sold...

    If you can come by a reasonable priced used TMB - SMC(supermonocentric) they are a winner. Pentax XO or XW also very nice but $$. Much less expensive and have some anomoly are Baader genuine orthos and UO orthos (in most low mm fl's the eye relief is too tight for many), or the uo 'volcano-top' orthos (the volcano top design helps mitigate er tightness for some). Somewhat in the middle are the VS Brandons - which I really like, possibly the most underrated ep design out there (orice new abt$200, used I've seen abt $125). I've also been impressed with the old Meade 4000 plossels as an inexpensive planetary ep - sure they have anomoly but are generally crisp and as low cost as most orthos.

    ------------------------

    So what am I currently using(and to be accurate that is in my 'f8' refractors /Tak FS-128 and TEC160ed)? Each of these eyepieces is a different design grouping and coating scenario but got it right in my book.

    ZAOII's (Zeiss Abbe Ortho, gen 2 - the original are also quite good)used only and rare and very $$ (cheapest I've seen is about $550!!) but worth every cent if your a fanatic like me. Nothing magic, flawless execution, anomoly free. There a sort of gold standard for me to test other planetary ep's against. Eye relief can be tight - but the view is "10".

    TMB SuperMonoCentric - supermono's - they were quite affordable when new and sold out - now used are fetching mid $200's, still at that price a fantastic ep. I'd give a 9.

    Ethos 8 (the 6mm eye relief wasnt enjoyable but I think it has to do with the exit pupil on my f8's) Ethos are very $$ but I have been consistently impressed with their performance on everything. IMO dispel the less glass is better myth along with the Pentax XW's. I think they are a great planetary ep just because they don't show anomoly. There were a few night this summer where I was able to see I think Uranus or Neptune in same view as Jupiter in the Ethos and that was exceptional. I'd also give these a 8-9.

    Pentax XW's I only have the 5,7,10 - the eye relief on these as well as all other aspects is wonderful. I give these a 9-10.

    VernonScope Brandons - a bit tight er, but barlowed these are extraordinary ep's and rate even very near my ZAOII's tested on Saturn. I'd give these a 7-9.

    ---------
    For many years my planetary ep's of choice were 'orthos' (I give a solid 7-8)- so I keep some old v-top and Baaders and 400 Plossels around for comparison purposes. You can find the Baader and UO's $40-70 a pop on the used market, I've seen the meade4000's for as low as $20 (these I give a 6-7).

    Sure you don't 'need' a wide FOV to view planets, but if that wide FOV gives an anomoly free view, doesn't give false color and shows the subtle changes in hue along with great contrast - I'm a happy camper. Like all viewing patience at the ep rewards, so I value the comfort factor highly. That is entirely subjective - my eyes are aren't same as yours and what I find comfortable may be very different. I have pretty good vision for my +50 yrs, and so things like exit pupil and eye relief are something I can still contend with - but comfort can just mean I've gotten used to certain things over the years too.

    Sure the scope optics are important and I dont want to get into that other than to say 2 years ago I changed my principal scope to a reliable color free variant and so re-evaluated all my ep's. The ep's I give top tier marks work same in my apochromatic refractors as they did in my 10-11-12" SCT's (when sky conditions, cooling and collimation, mags allowed).

    Sorry about rambling post, hope it helps. I'm no 'expert' and it's just another post/opinion.
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    Thanks for the great writeup and info. Ill definitely keep all of this in mind when I go shopping!
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    Very nice posts Austin and klatuu!! I've been looking for some detailed information on the best eyepieces for planetary viewing and there ya went and did it for me. Thanks gentlemen!

    P.S. Any views on the Baader Hyperion 8-24mm zoom? (Hopefully not bad since I already ordered it, but I can always send it back )
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