Pentax - Naglers shootout

[Pathan07]

Pentax vs Naglers which one Rulz???

[koputai]

I suspect the one that's Phat will beat the one that's Fully Sick.

[MikeyB]

We have a winner! :lol:

[wavelandscott]

How deep is a hole?

Holden or Ford... Coke or Pepsi...

Each has their merits depending upon intended use and personal preferences...

Are you an eyeglass wearer?
Focal Length you are intersted in?
Scope?

Both brands are top shelf and depending on you and your preferences you may prefer one brand or the other...I have some of both and I like them all.

[brian nordstrom]

:) dont forget the biggy , How deep are your pockets ?
Brian.

[Poita]

Explore Scientific are fully sick!

Well, fully sealed at least. I love the wide views, the eye relief and the fact that they are waterproof and seemingly indestructible.

I finally got a look through two Nagler eyepieces on my scope, and the ES held its own on my gear. Other gear probably would give a different result, but it quenched my desire to spend any more $$ on eyepieces.

[JethroB76]

Lolz
It used to (roughly) be Pentax for 10mm and less and Naglers above that (at least between those two lines of EPs).
Obviously specific personal needs (long ER for eyeglass wearers etc) and other developments within the industry (the Explore Scientific lines, Delos, Docter, Nikons) muddy the waters a little

[Rodstar]

Earth to Ausastronomer, come in Ausastronomer......

[ausastronomer]

Ausastronomer .... is all posted out until Saturday because he has his butt draggin along the ground trying to get a Board report ready for tomorrow afternoon :help:

I will post my 2 cents worth on Saturday when I have adequate time to to go to the necessary depths to resolve this extremely important matter:rofl:

Cheers,
John B

[Rodstar]

Glad to hear that John....this thread was made for you, mate!

[Suzy]

.. . gets the popcorn and bags the front row seat. :D :lol:
I'm staying out of this one. :P

[ausastronomer]

Good Morning all,

I hope you didn't run out of popcorn Suzy, or fall asleep in the front stalls :)

Let me say there is always a lot of hype about Televue eyepieces and justifiably so; they are very good. Being a US grown product they have a proliferation in the US astronomy market and community, which is easily the biggest in the world. Televue also spend an enormous amount of money advertising in the astronomy magazines and always have a personal presence at the major US star parties. This up front marketing ensures their market domination in the USA. That doesn’t mean they are the best and the only top quality eyepieces available, although many posters on US dominated forums, would have you believe that and in fact think that themselves. In the widefield eyepiece market some of the other top brands include Pentax, Nikon, Vixen and Docter; and a few others. Not all of these companies specialise in Astronomy equipment and in fact astronomy equipment manufacture is only a very small part of their business. Televue only makes astronomy equipment and a fairly limited range of astronomy equipment at that, essentially they only make refractors, eyepieces and optical accessories. Pick up any Sky and Telescope magazine from the past 10 years and you will find a Televue advertisement for their eyepieces and equipment. Pick up those same magazines and see how many advertisements you will find for Pentax or Nikon eyepieces. Not too many, if any. It doesn’t mean the product isn’t as good, or in some cases better.

At the end of the day Pentax XW’s and Televue eyepieces (most breeds including Naglers), are excellent eyepieces. It comes down to which eyepiece performance criteria are most important to you. You need to determine this before making your purchase decision. In many cases a mix of both might be the best long term option. They each excel in some performance criteria and have some faults in others. In some cases they have been designed to optimise different performance criteria. Further, they are not “scaled designs” which means different focal lengths have different lens configerations and do not necessarily perform the same, although in some cases they do. In the attached diagram you can see all of the different lens configurations and design differences for the entire Pentax XW range.

http://pentaxplus.jp/archives/tech/xo-xw/61.html

This is borne out when comparing the short focal length XW's with the longer focal length XW's. If you look at the attached graph you can see that the Pentax XW’s with a focal length of 40mm to 14mm have different Field Curvature characteristics to the eyepieces with a focal length of 10mm to 3.5mm.

http://pentaxplus.jp/archives/tech/xo-xw/64.html

The longer focal length eyepieces have positive field curvature, the shorter focal length eyepieces have negative field curvature. This gets further complicated when the field curvature characteristics of the eyepieces need to be “matched” to the field curvature characteristics of the telescope. For instance a Newtonian reflector which has positive field curvature when used with the short focal length Pentax XW’s, which have negative field curvature, work very well because the two field curvatures cancel each other out. When the positive field curvature of the longer focal length Pentax XW’s is combined with the positive field curvature of a fast Newtonian reflector, the observed field curvature is compounded. When used with a paracorr which has inherent negative field curvature, the longer focal length Pentax XW’s work very well.

Just about all of the major eyepiece lines and types have these different performace characteristics across types and focal lengths. Pentax however is one of the few companies that makes these graphs and diagrams available

There are many different types of Naglers and also ETHOS and DELOS. Those currently available include the Type 4’s (12mm,17mm and 22mm), Type 5’s (16mm,20mm,26mm and 31mm) and the type 6’s (2.5mm to 13mm). They differ greatly in many respects and have different design objectives. The type 4’s have long eye relief in all focal lengths but have inferior edge of field (EOF) performance to the T5’s and T6’s, which have shorter eye relief. The 17mm and 22mm T4’s IMO need a paracorr to deliver top quality images in a Newtonian. When combined with a paracorr they work exceptionally well and are very comfortable to use. The eye relief on the T6’s and most of the T5’s is too short for eyeglass wearers (The 31mm T5 being the exception). The design goal with most of the Nagler’s (except the T4’s) was to have sharp stars at the EOF. They do this very well.

For a good comparison you need to consider the strong points and weaknesses of each type and design and weigh up what are the most important criteria to you. To do the comparison properly one needs to look at the Pentax XW’s 3.5mm to 10mm and then over 14mm and over. Similarly one needs to consider the different design criteria from the T4 Nagler's to the others.

Pentax XW 3.5mm to 10mm (inclusive) strong points
• Very sharp on axis
• Very sharp at EOF
• Very high light transmission
• Excellent Contrast
• Excellent eye relief and suitable for eyeglass wearers
• Very comfortable to use for long viewing sessions
• Very resistant to dewing and fogging and getting eyelash oil on the lenses
• Excellent cool neutral (white) colour reproduction
• Waterproof and a have a lifetime warranty
• Excellent construction quality and durability
• Excellent for daytime use in a refractor

Pentax XW 3.5mm to 10mm (inclusive) weaknesses
• Field of view (FOV) is limited to 70 degrees. Many people however find this to be ideal, me included
• Expensive

Pentax XW 14mm to 40mm (inclusive) strong points
• Very sharp on axis.
• Very high light transmission
• Excellent Contrast
• Excellent eye relief and suitable for eyeglass wearers
• Very comfortable to use for long viewing sessions
• Very resistant to dewing and fogging and getting eyelash oil on the lenses
• Excellent cool neutral (white) colour reproduction
• Waterproof and a have a lifetime warranty
• Excellent construction quality and durability
• Excellent for daytime use in a refractor

Pentax XW 14mm to 40mm (inclusive) weaknesses
• Field of view (FOV) is limited to 70 degrees. Many people however find this to be ideal, me included
• EOF can be a little soft on some telescopes, particularly fast newtonians. This is corrected by using a paracorr with a newtonian
• Expensive

Nagler T4’s strong points
• Sharp on axis
• Good light transmission
• Good Contrast
• 82 deg FOV
• Excellent eye relief and suitable for eyeglass wearers
• Very comfortable to use for long viewing sessions
• Very resistant to dewing and fogging and getting eyelash oil on the lenses
• Excellent construction quality and durability
• Excellent for daytime use in a refractor

Nagler T4’s weaknesses
• EOF can be a little soft on some telescopes, particularly fast newtonians. This is corrected by using a paracorr with a newtonian
• Warmer colour tones
• Expensive

Nagler T5 strong points
• Very sharp on axis
• Very sharp at EOF
• Good light transmission
• Good Contrast
• Excellent construction quality and durability

Nagler T5 weaknesses
• Eye relief except the 31mm is inadequate for eyeglass wearers. Some people can use the 26mm with their eyeglasses on, some cannot.
• Eye lenses prone to fogging and dewing and contamination from eyelash oil
• Warmer colour tones
• Not ideal for daytime use in a refractor
• Expensive

Nagler T6 strong points
• Very sharp on axis
• Very sharp at EOF
• Good light transmission
• Good Contrast
• Excellent construction quality and durability

Nagler T6 weaknesses
• Eye relief is inadequate for eyeglass wearers. Eye lenses prone to fogging and dewing and contamination from eyelash oil
• Warmer colour tones
• Not ideal for daytime use in a refractor

Now, let’s see where all the above gets us. My current telescopes are a 10”/F5 newtonian, a 14”/F4.5 newtonian and an 18”/F4.5 newtonian. The eyepieces which I currently have to use in these scopes are:-

5mm Pentax XW
5mm UO HD orthoscopic
6mm UO HD orthoscopic
7mm Pentax XW
7mm UO HD orthoscopic
8mm Televue Radian
8.5mm Pentax XF
9mm UO HD orthoscopic
10mm Pentax XW
12mm Televue Nagler T4
12mm UO HD orthoscopic
13mm Televue ETHOS
14mm Pentax XW
17mm Televue Nagler T4
18mm UO HD orthoscopic
20mm Pentax XW
22mm Televue Nagler T4
27mm Televue Panoptic
31mm Televue Nagler T5

I also have a Televue Paracorr

I am an eyeglass wearer and my preference is to observe with my eyeglasses on using long eye relief eyepieces. If I was to start over again I would build the following eyepiece collection for use in these scopes

5mm Pentax XW
7mm Pentax XW
10mm Pentax XW,
12.5mm Nikon NAV HW (or 12.5mm Docter)
17mm Nikon NAV HW
22mm Nagler T4
31mm Nagler T5

Televue Paracorr

If I was a young bloke and didn’t need eye glasses I would build the following eyepiece collection

5mm Pentax XW
7mm Pentax XW
10mm Pentax XW,
12.5mm Nikon NAV HW (or 12.5mm Docter)
17mm Nikon NAV HW
20mm Nagler T5
26mm Nagler T5
31mm Nagler T5

The above of course all assumes cost isn’t a factor.

Base your decision on what things are the most important to you in terms of performance criteria, there is no right or wrong answer and neither rulz :)

Cheers,
John B

[wavelandscott]

Well written John!

[Rodstar]

Ahhhh, that's better! Hats off to you John, great info.

It is refreshing to hear such balanced thoughts from someone who owns BOTH XWs and Naglers.

[mercedes_sl1970]

A very nice summary. Interesting to see how this post would go down on one of the US sites...!

Thanks for taking the time.

Andrew

[bytor666]

That pretty much sums it up wonderfully John!

cheers,

[clive milne]

Excellent write up John, if I were to add my 2c it would be to clarify a point you made. A coma corrector will (or should) have negative field curvature... but when you place it in the focuser of a Newtonian, the resulting image plane should ideally have zero field curvature. Also, it probably deserves mentioning that different eyepiece configurations have their own peculiar sensitivity to the f/ratio of the light cone irrespective of of how well controlled the 5 primary Seidel aberrations are at the focal plane.

One thing the Naglers (and their derivatives) do very well, is control (or rather not introduce excessive amounts of) astigmatism as the speed of the primary gets above /6. This more than anything is the reason they can extend the field out to the silly territories we see today.


Anyway,
It has been a long time since I last had a peek through an XW, I seem to remember thinking that they would be an eyepiece I would be more than happy to live with. Another good series is the old classic Masuyama... the FOV would be challenging to my tastes though.

best
~c

[gb_astro]

Don't forget the new Delos line at the short end.
A few posts over at Cloudy Nights have been placing these just ahead of some Naglers and XWs.

gb.

[Auditor]

Hey, Ausastronomer, AKA John, I have the following question regarding your great write up. Is the Televue Paracorr needed with the 5mm Pentax XW, 7mm Pentax XW, and or 10mm Pentax XW? Maybe needed is not the right wording to use. Therefore, put another way does the Paracorr improve the views in the above listed eyepieces?

[MattT]

Suzy, put down the popcorn and jump in.... also hoping Cloudy Nights XW Buddha will make a special guest apperance to guide all to the path of visual lightness.
:D Matt

[ausastronomer]

Hi,

Let me answer by saying that my 2 larger newtonains (14" and 18") are both F4.5 focal ratio telescopes and I do not use the paracorr when I use the 5mm, 7mm and 10mm Pentax XW's in those scopes. Any eyepiece be it a Nagler, ETHOS, DELOS or Pentax XW, in my opinion benefits when used with a paracorr in telescopes faster than F4.5

The 14mm and 20mm Pentax XW's benefit from a paracorr when used in any newtonian telescope.

Let me explain a little bit about the optical theory on why this is. The two predominant aberrations from using a fast newtonian are field curvature and coma. This comes from the telescope itself. An eyepiece can also introduce additional field curvature and off axis astigmatism. The astigmatism gets worse as you go further off axis. Top quality widefield eyepieces like Pentax XW's and Naglers generally have minimal astigmatism. A newtonian telescope has inherent positive field curvature. The amount is solely dependent on the focal length of the primamry mirror. The shorter the focal length the more field curvature. It has NOTHING to do with the F-ratio of the telescope which is solely a function of the focal length and the aperture. I have attached a graph showing the field curvature of all the Pentax XW eyepieces. As you can see the 3.5mm, 5mm, 7mm and 10mm Pentax XW's have inherent negative field curvature. When used in a newtonian the +ve field curvature of the telescope cancels out with the -ve field curvature of the eyepiece and you get a flat field view. The 14mm to 40mm Pentax XW's have inherent +ve field curvature and when used in a newtonian both field curvatures compound and the field curvature is noticeable to many people. Some peoples eyes have a better capacity to accomodate and adjust for field curvature so it will appear more noticeable to some people than others. Enter the paracorr. The paracorr does two things. It's main goal is to correct for coma. However, in order to achieve this, it necessarily has to flatten the field of a newtonian telescope. It does this by having inherent -ve field curvature built in, which cancels out the +ve field curvature of the telescope. Consequently when an eyepiece is used in combination with a newtonian telescope and a paracorr you are only left with the inherent field curvature of the eyepiece itself, which is usually very small and hardly noticeable. The compounding effect of two field curvatures in the same direction is eliminated.

I hope this explains the benefits of the paracorr and the Pentax XW's a little.

Cheers,
John B

[OICURMT]

John:

Might I suggest that you bundle your posts into an article. I think Mike (and the rest of us) would appreciate it should we require it for reference (instead of searching the forum archives).

OIC!

[sally1jack]

Good info , thankyou John
Phil

[Auditor]

John,

Thanks for the info regarding the Paracorr and the Pentax 5 - 10 XW's.

[Nico13]

Thank you John, :thumbsup:
I have been considering another EP to add to my humble set but wanted a quality piece of glass this time and was wondering how this info relates to Refractors and SCT's as these are the types of scope I have.
A Meade 8"SCT and SW ED80.
One that would cross between the two around the 10-20mm, higher power on one while lower on the other, a dual purpose EP for want of a better description.
And the other question is "Where do ya get em" Pentax that is as I'm a bit of a Pentax fan.
Thanks for any info.

[MattT]

Ken I have the XW 10mm which is the best eyepiece I have ever looked through by a long shot. In my 100ED f9 frac I also like the ES 82 degree series, specially the 6.7. I got the Pentax from OPT in the US. Astronomics is a bit cheaper too, give them a try.
Matt

[bratislav]

A lot of wishful thinking in that statement.

The cancellation would only occur at one single telescope's focal length (about 500mm judging by those graphs); and only for ONE Petzval curve (saggital and meridional curves are quite a bit apart, indicating eyepiece's residual astigmatism).

In my experience, no Pentax eyepiece gives sharper images at any given distance off axis than a corresponding Nagler. Naglers are significantly wider, sharper off axis, smaller (type 5 and 6), work better at fast f-ratios and can completely take care of residual astigmatism of the observer's eye via Dioptrix, if needed (eliminating the need to wear glasses while observing). I can see people liking Pentax eyepieces, but for me they hold no interest whatsoever. They may be a smidge more neutral in tone, but that is about it.

BTW, Newtonian's field curvature is rather unimportant (unless you use 8" f/4 or shorter as your main scope). At 14" (or 18") at f/4.5 telescope's curvature is negligible (10mm off axis, the curvature would amount to about 30 microns, worst case. At that amount, defocus blur is barely larger than Airy disc, and is completely swamped by coma).

I think a lot of people prefer large eyelens because they use eyepiece as a screen (to look AT, as opposed to THROUGH). I actually find huge eyelenses annoying and rather distracting.

[AstralTraveller]

At the risk of wandering too far off the original topic, I notice you have a pretty complete set of UO HD orthoscopics. Any comments on them??

[ausastronomer]

Hi David,

I have the full set of UO HD orthos (5mm,6mm,7mm,9mm,12mm and 18mm). The Baader Genuine Orthos (BGO) are the same eyepiece with possibly slightly different coating specifications. For all practical purposes the two perform the same. The original UO volcano top orthos came in extra focal lengths (4mm, 5mm, 6mm, 7mm, 9mm, 12.5mm, 18mm and 25mm). Because of the top design the old volcano tops were slightly easier to use, but slightly inferior optically. The HD's (and BGO's) go a bit deeper and have better scatter and internal reflection control.

Like all orthoscopics, the UO HD's have a narrow FOV and short eye relief, which gets shorter as the focal length gets shorter. I have no problems using any of them with my glasses off. Optically they are very good. They offer 90% to 95% of the performance of the premium orthos like the Zeiss Abbe II's and the Pentax XO's, at a greatly reduced cost. They are a clear notch ahead of the cheaper Chinese/Taiwanese orthos and plossls. I would rate them as about the equal of Televue Plossls and maybe a touch ahead of the Takahashi LE's. They are much cooler in their colour tone than Televue Plossls. They "were" made in Japan and build quality on them was typical of all Japanese manufactured optics, very good. I believe they are no longer made following the Tsunami in Japan and any new items you might find, will be shelf stock. Over time you should be able to put together a set 2nd hand. They are certainly worth getting if you can find them and can't afford the very top end orthos, for lunar/planetary viewing etc, or can't afford premium widefields.

Cheers,
John B

[bytor666]

Bratislav,

You can sit here and type whatever math you like, but the eyes do not lie. I have used Naglers and Pentax eyepieces for years. The off axis distortion in the Naglers I tried in my 10" f/4.7 was all too evident as compared to a 10mm, 7mm, 5mm and 3.5mm XW. The same goes for the Pentax XL eyepieces in those focal lengths, I am not talking coma here, I am talking AMD and RD. Off axis, these Pentax eyepieces show a lot less distortion than the Naglers I have tried.....which were 9mm and 7mm T1 and T6. I see ZERO distortion in any of these I just mentioned. The Naglers have a lot of rectilinear distortion and AMD off axis. The Pentax eyepieces I mentioned showed ZERO RD or AMD.

FYI, Field curvature is there in my 10" f/4.7 scope in case you were wondering, but I see NONE in the 10mm, 7mm, 5mm or 3.5mm XW's or 10.5mm, 7mm 5.2mm XL's.

Don't get me wrong, Naglers are fine eyepieces indeed in certain focal lengths, but what you said above was completely wrong.

Just sayin'

[glenc]

A Pentax XW 10mm EP is available for U$280 + U$39 shipping from http://www.bhphotovideo.com/c/product/321665-REG/Pentax_70514_SMC_XW_10mm_Wide.html
That is about A$307 including shipping.

[Tom Hancock]

The Pentaxes are superb, probably the benchmark and they are not overtly expensive.
My Pentex 10mm XW has pride of place in my limited ep set.
But other ep like the ES are no push over and they provide excellent value.
My favorite ES is the 8.8mm 82d and you can pick it up at VTI yourself now, if you are in Melbourne for a miserly $149!

[brian nordstrom]

;) I have the same set in Orthoscopics and they are awsome in my long focal length Zeiss refractor . very good luna , planetary and double star eyepieces ,
I have 3 Naglers ( 13mm 17mm 20mm ) and love them all .
Brian.

[Profiler]

Would any of the 82' ES owners be able to say where these EPs are made? Akin to their Televue progenitors do they have any letters in fine print stamped on their sides such as 'Japan' or 'Taiwan ROC' by any chance?

[brian nordstrom]

:) You are right thers Profiler , my 13mm T1 and 17mm T4 are 'Taiwan ROC ' and my 20mm T2 is ' Japan ' .
I cant see any differance in the build quality and views , both are of very high quality , good QA I suppose ?.
Brian.

[MattT]

My 82 and 68's all made in China...

[Waxing_Gibbous]

Having used both the Pentax XWs and T5 & 6 Naglers (side by side for 10/11mm, 13/14mm and 5mm) I can only agree with John's excellent post, particularly his comments on colour fidelity and sharpness.

I would add only one other factor: the Naglers are more forgiving with eye relief IMO. While the Naglers 'allow' up to about 15-20mm, the Pentax EPs positively require it. I found 'kidney-beaning' and blackout to be major issues with the XW, unless my eye was perfectly placed. This I found pretty uncomfortable and so settled on Naglers.

I can't however fault the actual view with the Pentax XW series - beautifully crisp across the field and very neutral colour.

[Tom Hancock]

Since my last entry, it seems VTI has knocked the price of their 8.8m ES to $99.95!
A ES at less then a hundred dollar,if you pick up, is indeed a milestone in Australia?

[Suzy]

Hi Peter :hi:
From my experience I think it depends on the eyepiece.

With the Nagler type 1, I found eye placement very difficult each time I tried it out. I hear kidney beaning was particularly inherent in this eyepiece tho. Yet for the owner, it's not an issue.
The Nagler 17mm (type6 I think), I had no problem.

The Pentax 10mmXW (a workhorse) I have no problem with eye placement (If I did in the beginning, I can't remember). Yet I find the 7mm XW trickier. It doesn't get a whole lot of use so perhaps that's why and I do notice if I use it for a long session I'm fine with it.

And here's the weirdest one of the whole lot... The Denkenmeir 14mm was really bad on my first use. Someone else got theirs the same time as me and sent me a pm of how hard the eye placement was on the first use. A message from him the next day told me it wasn't a problem anymore & had now become his favorite ep. Exactly the same thing happened to me- the second night I didn't know what all the fuss was about- eye to eyepiece and off I went straight away, just like him. :shrug:

Dare I say, eye placement is just a matter of getting used to I think. :question:.

[ausastronomer]

Hi Suzy,

I think some of your following comments, which I have quoted, indicate that the individual observers physiology has a lot to do with things as well as the eyepiece itself



Could not agree more. I have problems with blackouts on a a lot of the type 1 Naglers and the 16mm T2 Nagler. I find the 35mm Panoptic (which others have no issues with) absolutely horrendous.



One of the easiest eyepieces to use from a comfort viewpoint that I have used, outside my Pentax XW's. My 17mm Nagler T4 sees a lot of focuser time, as it hits the sweetspot in the 18" for a lot of DSO's. It does need a paracorr to give a good view across the entire FOV in a fast newtonian but works beautifully when combined with a paracorr. As does the 22mm Nagler T4.



Never had a problem with this one either.



Here's where it comes down to the individual user. This is my absolute favourite high power eyepiece for lunar/planetary in both my 18" (300X) and my 14" (230X) and I have never experienced a blackout or kidney bean with it, and I have owned it for 10 years :shrug:



I know you spent your very hard earned dollars on the 14mm Denkmeier based on my recommendation, a year or more ago. Me recommending the 14mm Denk was pretty funny in itself on the basis that I own a 12mm UO HD ortho, 12mm Nagler T4, a 13mm ETHOS, a 14mm Pentax XW and don't own a 14mm Denk :lol: I also know that you initially had some reservations with the 14mm Denk. Am I correct in assuming that on the basis you still own and use the 14mm Denk, you are happy with it? While I don't own the 14mm Denk I rate it as optically the best eyepiece around this focal length outside the 12.5mm Docter and the 12mm Nikon NAV HW which are a serious amount of coin, and a major waste of $$$$ on my old burned out retinas.



Of equal importance to eye placement is the ability to keep your head/eye still while you observe. If you move your head around like "Noddy the Clown" you will have a lot of difficulty with a lot of eyepieces. The ability to "find" the exit pupil and then hold your head still is of critical importance.

Cheers,
John B

[PlanetMan]

Austrastromer (John)

As the resident expert of Pentax XWs I would be very grateful to hear and be appreciative if you could share your thoughts on the specific merits of the Pentax XW 30mm versus the 31mm Nagler?

[casstony]

I recall John expressing a preference for the 31 Nagler at this focal length to maximise FOV. Having owned both the Nagler and 30mm ES 82 degree eyepieces, I'd suggest you look at the ES since it's almost as good as the Nagler for nearly one third of the price.

[ausastronomer]

Tony is 100% correct.

With the scopes I own ranging from a 10"/F5 newtonian to an 18"/F4.5 newtonian, a ~30mm eyepiece is essentially a low power widefield eyepiece and about as long a focal length eyepiece as I like to use, based on fairly fast F-ratio scopes and liking to keep the exit pupil < 7mm or thereabouts.

The strong points of the 31mm Nagler are widest FOV at this focal length (outside of the 30mm 88 deg Leitz, which is very expensive) and sharp to the EOF in fast f-ratio scopes. The strong points of the 30mm Pentax XW are slightly higher contrast, light throughput and on axis sharpness. However for my purposes these are less important criteria than maximising FOV at the longer focal length end of things. If one of my scopes was a 16"/F20 Classical Cassegrian having a focal length of 8.1 metres, things would be entirely different. In such a scope the ~30mm eyepiece would give 270X and generally be used for high power observations where light transmission, on axis sharpness and contrast are more important considerations than FOV IMO. In addition the cooler colour tone of the 30mm XW would be an important consideration as it would see use for lunar/planetary viewing as well, in such a scope. The 30mm XW is smaller and lighter than the 31mm Nagler, by a reasonable amount. The 31mm Nagler can unbalance a lot of dobsonian scopes under 14" aperture, that are undriven. The 30mm XW can also exhbit some field curvature with some scopes and some observers. The 31mm Nagler on the other hand will give a flat field view right across the FOV in just about any telescope. I own the 31mm Nagler and have never really wanted to change it for a 30mm Pentax XW, notwithstanding the 30mm XW ticks a lot of boxes.

I haven't used any of the Explore Scientific 82 degree eyepieces so I can't comment on those from first hand experience. The feedback I have seen indicates they perform to a different standard in different focal lengths, some very good, some not to the standard of the premium eyepieces, but reasonable for the price. I don't know which are good and which are not so good. What you need to remember is that "some" of these "cheaper" eyepieces perform very well in long focal length and focal ratio scopes like SCT's, but their performance deteriorates by comparison to the premium eyepieces, in faster F-Ratio telescopes, like newtonians.

I did use a prototype of the Explore Scientific 14mm 100 degree eyepiece before it hit the streets for sale and was very impressed with it. It was very good optically, pretty close to my 13mm ETHOS when used in the 18"/F4.5 Obsession, at a lot lower price than the 13mm ETHOS. However you can't assume that because one eyepiece from company "A" is good, then all eyepieces from company "A" are good.

If you plan to use the eyepiece for lower power widefield astronomical views and your scope(s) handle the size and weight of the 31mm Nagler it is IMO the best choice at this focal length.

Hmmmm :eyepop: I never thought I would see the day where I recommended a Nagler over a Pentax XW :lol:

Cheers,
John B

[casstony]

I'd like to add that I've used the ES30mm in a 16" Lightbridge and, while I was too busy enjoying the views to examine the edge of field, the eyepiece performed quite nicely in general.

Certain ES eyepieces are so close in performance to Televue that there's no point spending 3x the cash. Televue must be feeling the pinch and I'm looking forward to their 30% discount sale (:D) to pick up a Delos or two.

ES quality control is definitely not as good as Televue and I won't risk any further overseas purchases now that there are competitive local suppliers.

[David Niven]

I wish there are more ES dealers but it seems, there is only one VTI Optics in Melbourne that is actually selling.
The others being thrown around are just mere promises till the day they actually have any items to sell.
I could be wrong and stands to be corrected!
Hope VTI will build up their product range and I would prefers to buy from an Authorized Distributor then just any ordinary retailers, that's for sure.

[Suzy]

Crickey John,:lol: when I saw my post being chopped into quotes, I felt the sweat trickling off my otherwise chilly body.:eyepop: And then I read on, Phew...! :lol:

Interesting point you made on the XW7 :thumbsup:

Regarding the Denkenemier 14mm...
When or when will I finally get around to putting my review of it on that thread- note to self- asap! :lol: I get a few pm's asking about it from people who've seen the thread and want to buy one.

I love it!!!!! :love:
The stars aren't as pin point as my XW or LVW- could it be the astigmatism it's picking up from my eyes that my other eyepieces don't?- I don't know. But that's okay- because everything else about it I absolutely love!!!! Nice black background- amazing contrast! It seems to have a slightly darker background than my XW10mm. It has a shallow cup and with that 20 degree eye relief, it means you can see the entire fov without having to get that close into the ep. Comfort wise, personally, I rate this even more comfy than the XW (in itself a very comfy ep). Seems to suffer the effects of dew a lot quicker than my XW's or LVW though- I wonder if this is because it has a very short eye cup :question:.
You steered me (yet again!) very well John in pointing me towards this ep.
Oh, I nearly forget- the advertised fov is supposed to be 65deg- I would say it leans more towards 68 deg. :question:

After saying all that, I just realised this would make a good review for that thread, so I've copied & pasted from here to there.:D
Help Choosing a Premium 14mm Eye Piece. (http://www.iceinspace.com.au/forum/newreply.php?do=postreply&t=71653)

[moonunit]

Bought a 26mm Nagler based on this thread, it superceded my original GSO 26mm, I had first light last night and it blew me away, could not believe the clarity, no blurring towards the edge of the eyepiece, cost me a weeks wages but it has given my 10" dob a much longer life.

[Larryp]

I have a 26mm Nagler too-absolutely superb!

[Tom Hancock]

My most used ep is the Pentax XF8.5
Fantastic performer and one that will stays by my side as long as my eyes are capable.