Pentax XW vs Vixen LVW

[janoskiss]

Has anyone had a chance to compare Vixen LVW and Pentax XW eyepieces of similar focal lengths? Are the Pentaxes considerably better? Is it just the obvious differences, i.e., 5 degrees extra AFOV & twist eyecup, or are they clearly superior optically? Any comments most welcome, thanks.

ps: I saw what could be very good deals on Vixen LVW and Pentax XW eyepieces, but I haven't followed them up yet. Just dreaming at this stage.

[davidpretorius]

sorry mate, all i can say is that i really like asimovs 5mm lv. talking to astroshop, he actually uses the lvw's and loves them

[matt]

I have the 6mm LV which I use with my 8" f5 and it's very nice.

I've had a look at the 13mm LVW and that's a serious lookin' bit o' gear!!! Big and lots of glass:lol:

It's the next EP on my shopping list and will work nicely with both the 8" and my Celestron 9.25.

[Starkler]

John B should have an answer to this.

I have the 10.5 and 14mm XL's and havent seen an eyepiece yet that I'd trade them for :whistle:

[janoskiss]

XWs maybe, Geoff? The XWs are 1.5x the cost of LVWs. Just wondering why when the specs are so similar and they are both meant to be "premium" EPs.

[ausastronomer]

Well I pretty much agree with Geoff. I have the 7mm,10mm,14mm and 20mm Pentax XW's and I won't be trading them on anything either. The 7mm and 10mm are about as good an eyepiece as I have ever used in these focal lengths and that includes everything uncle Al has ever made. The 14mm has a little bit of field curvature and the 20mm has slightly more field curvature in faster scopes. However, this is a necessary compromise to achieve 20mm of eye-relief and 70 deg AFOV at these focal lengths with this design. It is not obtrusive and you don't notice it in general observing, you can detect it if you specifically look for it. It causes stars in the outer 10% to 15% of the FOV to "bloat" in size by about 5% from best focus. They stay perfectly round and DO NOT become elongated astigmatic slits that are commonplace in $50 eyepieces. The upside is that on axis sharpness, contrast and light transmission are superb and superior to any premium widefield eyepiece I have used.

That having been said the Vixen LVW are also a superb eyepiece. Clearly superior to the LV's that others have mentioned as being great. They are also a completely different design to the LV's FWIW. Any observer would also be very happy to have a box full of Vixen LVW's in his observing kit.

In conclusion I possibly rate the 22mm Vixen LVW as superior to the 20mm Pentax XW. In all of the shorter focal lengths I think the Pentax XW's are about as good as it gets and superior to anything you care to throw at them. I rate them above the Nagler T6's and Radians also by a very small margin.

Whichever you choose between the Pentax XW's and Vixen LVW's you will end up with an excellent eyepiece. So don't get involved too deep in "paralysis by analsysis". If you can afford the shorter focal length Pentax XW's grab 'em, if not take comfort from the fact that the Vixen LVW's are also superb. Something else that may be important to you depending on the scopes you own is that the LVW's all have the dual 1.25"/2" barrel and fit either size focuser. This is no benefit to me but may be relevant to you.

CS-John B

[janoskiss]

Thanks heaps, John. Re the dual 1.25"/2" barrel size, don't the XWs have the same thing? I always thought they did. :shrug:

[Starkler]

Nope they dont in the shorter focal lengths, 1.25" only, and the 30mm up are 2" only.

Dual 1.25/2" configuration eyepieces can be a pain depending on focus point and travel of your focuser. If forced to use the 1.25" part in a barlow, it can be hard to get a firm mechanical coupling with the 2" section in the way also.

Well maybe I'd possibly swap for an XW, but I havent looked through any myself. DanielSun has a 22mm LVW that I looked through at the star camp, and that seemed very nice.

For those brave enough to buy second hand via astromart, I think the Pentax XL's are still a good bargain.

[ausastronomer]

Steve,

The Pentax XW's "look like" they do because of the step in the body but in fact they don't, the 2nd step is slightly smaller than 2".

CS-John B

[mental4astro]

Came across this old thread. So, replying to Steve's original post, I thought I'd share some of my own experiences with some of these eyepieces.

LVW: These are probably the most forgiving eyepieces I know. Forgiving in that they can be used in just about ANY telescope design and perform very well in all of them across their whole range of focal lengths, with the 30mm being the odd man out. I've used them in my fast Newtonians, in fast refractors and slow SCTs and Maks, and the only major change is a slight eye relief change with some. To ask an eyepiece to perform exactly the same way in a fast Newtonian to an SCT, to a Mak and to a fast refractor is a big ask. Very, very few eyepieces can do this and do it well, and even fewer across their whole focal length range. The 30mm is the weakest member, and this is also noted by Vixen with its different appearance despite the "LVW" label - it does not perform well in fast Newtonians.

XW: These are much more varied in their performance as they are very much telescope design sensitive. They do no all perform the same as the LVW's in different scopes. As an example, the 10mm XW is fantastic in fast Newtonians, but its performance in an SCT is no where as good - eye placement becomes much more critical and difficult. The 14mm shows significant field curvature in fast Newtonians, but it is a better optical match in slower Maks and SCTs [a coma corrector will improve the 14mm in a fast Newt, but the need for a coma corrector to improve field curvature in this eyepiece/scope combo shows a deficiency in the eyepiece/scope match]. One or two other XW's also show eyepiece/scope design optical mismatch. But when there is an optical match, damn they are good!

Which gives the better image? This is very subjective, but I would say there really isn't anything much between them as they are all stonking great (setting aside any optical mismatches). For me to split hairs is just too subjective for this post.

Which to get? Well, my cop-out phrase here is 'it is upto you'. Performance wise I would say the LVW's are stronger as they perform well in different scope designs. The XW's have a wider AFOV, but are more scope sensitive for which you need to figure out which is best for your scope/s.

[janoskiss]

Hi Alex,

As you resurrected this very old thread I started, let me share my experiences of the past 6 or so years.

I ended up owning and using both types of EPs. Generally I prefer XW's, except for the 22mm LVW, which I prefer to the 20mm XW. The 22mm is definitely the queen of the LVWs; 10mm of the XWs.

But I no longer own any XWs or LVWs. I got sick of heavy and bulky EPs. My EPs now are the two Pentax XFs 12 & 8.5 mm & a couple of Masuyama style plossls. I also have a generic ultra-wide 30mm which is crappy on its own, but very good in a long barlow & very versatile for public astro events. The XFs are the best EPs for me: small, light, good FOV, outstanding optics, great ergonomics.

[Kunama]

Holy Thread-resurrection Batman ...........

Now that it has surfaced, I find it interesting to see that the old Vixen LVWs are still up there as far as quality of views is concerned.
I now have the full set and can see no reason to look elsewhere, I think the difference between these and the Pentax XWs is so small that I would not bother mixing and matching brands. The LVWs for me are the perfect amount of eye-relief, nicely parfocal, all fit into a 2" diagonal (or a 1.25" bar the 42mm). They do have a little bit of warm colour out at the very edge of view but are very sharp across the view.

Although when they were introduced they were 'heavyweights' the more modern TVs et al have taken over for their mass. I have not tried the XFs but hope to in the near future.
At the moment the 13mm and the 22mm are getting most use. The seeing hasn't supported the 5 and 3.5 lately even in my little 900mm Tak.

[janoskiss]

Hi Matt! What ausastronomer (John Bambury) said above over 7 years ago took me around 5 years to confirm - and he was spot on. I never met John - he is just a bunch of informative posts to me - but my long term experience seems to show that everything he says about visual astronomy is always correct. LVWs are excellent EPs indeed! Forgot to mention that 13mm LVW is also preferable to 14mm XW for my eyes.

The main weakness of the LVW series is the gap between the 13 and 8mm, where having a 10mm XW alongside the LVWs is well justified if you own an f/5-ish instrument.

[Kunama]

I agree Steve, a 10mm LVW would be nice to have.
I agree also about John (ausastronomer), when I came back to this obsession, after a long sabbatical, I spoke to John at length as all the gear that is now available at a modest price was just a pipedream 20+ years ago, what a very helpful pleasant fellow he is. I must get down to Kiama and buy him the beer I promised !!!

I recently bought the 42mm LVW, a beautiful piece of glass for low power viewing. I know there are eyepieces in the top-tier like the Ethos line that are better but for my money, I shall stick with these LVWs.

[David Niven]

I have the XF12 and 8.5 and they are really superb Pentaxes, very sharp on and off axis and cost considerably less than the XW.
They are my favorites ep.

[PlanetMan]

Some may disagree but the feedback I have generally received over the years is that the pick of the Vixen LVW range is actually the 22mm.

This being the case I would be very curious to know what are everyones views in terms of what might be a better option between a Vixen LVW 22mm or a Televue Panoptic 24mm.

I don't think the 2mm difference between them is a significant issue and both are said to have flat fields without curvature on fast scopes (unlike what is supposedly encountered in the Pentax 20mm) consequently if you had to pick between the two which way would you lean and why?

All thoughts, opinions, perspectives would be most welcome.

[Kunama]

I can't find any difference in the quality of views between the 13mm, 17mm or the 22mm other than the level of magnification. In my 900mm f/l scope the 8, 13 & 17 get the most use.
Hoping for some clear sky tonight to really try out the 42mm.

Can't compare to the Pan24 though, but can't fault the 22mm LVW. I'm not an eyepiece junkie so am happy to stick with the one brand (they look so nice all together in the case too ..... ;)

[brian nordstrom]

:) I had a full set of Vixen LV's and I found the 20mm was as good as my 19mm Panoptic except the TV pan had a larger field of view that I liked .
The smaller focal length LV's were almost identical to my Radians , but I like the softer views the Radians give on the moon and planets , especially in my Tak M210 .
Its really down to personal choice , I found the Vixens excellent in all ways .
I would have kept the Vixen's in a heart beat but I decided my TV's were the ones to keep , my personal choice .
Brian.

[FlashDrive]

Show off....:lol:
But seriously....I just bought a Vixen LVW 22mm from OPT for $209.00 + Postage.... discounted from $269.00......there has been such a ' rave ' about this particular eyepiece...I wanted to find out myself...;)
Should go very well with my new Vixen NA140....left Japan last Friday...wooohoooo....!!!! :thumbsup:

Flash............

[janoskiss]

Re Pano24 vs LVW22. They are both great EPs in pretty much any scope. The Pano is smaller and lighter, nice traveller EP with slightly greater TFOV. Eyeglass wearers will likely prefer the LVW. The Pano has more pincushion distortion. They are different animals and you have to take them both for a walk to decide for yourself. There is no point telling you which one I prefer, because this is really a personal preference thing (like say pasta or risotto) & depends on scope/focusser you have also. I let go of my LVW22 because of its bulk and weight; let go of my Pano24 cos I needed money at the time & it was not getting used often enough to justify having it in my EP case. I got the most use out of the Pano while travelling around Eastern Europe with my 8" f/4 truss Dob.

If you're unsure, toss a coin and get either one. You'll be happy.

[Kunama]

Just a little update to this thread, I finally got a chance to try out the Pentax XF 8.5 and 12mm eyepieces this evening and as expected they are incredibly sharp. I compared them to the LVW 8 and 13mm in both the FS60CB and the TSA120.

I found the XFs are very sharp on axis and more neutral in tone. The LVWs have a warmer tone especially at the edge of field but the difference was minimal. On the trap stars in M42 the XF8.5 was better than the 8LVW.

The 8.5mm is the better of the 2 XFs being sharp across the full view, the 12 shows noticeable curvature in the FS60CB, less so in the TSA120. The LVWs are like the XF8.5, sharp from edge to edge.

I certainly would not rush into selling any of my LVWs but if there were more of these compact little XFs about I would love to build a set for the FS60.

[casstony]

The curvature evident in the XF12, XW14 and XW20 is a known issue with many scopes.

[janoskiss]

The XF-12 does indeed exhibit more field curvature than the XF-8.5 but it is nowhere near as much as the XW-14 or the XW-20. The XF-8.5 is a gem and the XF-12 is also a very usable and pleasing EP in pretty much any scope (to my eyes). Cannot say the same for the XW-14 or XW-20. The two XFs are essentially the same eyepiece with a more powerful barlow group in the XF-8.5. In a long barlow (Orion ultrascopic) the XF-12 is flawless in any scope from f/4 up. I tend to use it barlowed on planets and it's just gorgeous.

The XF-12 is also ideal for deep sky observing in f/6 scopes (which for most people means 8" dobs).

[mental4astro]

Like I mentioned earlier, the XW's for being a "premium" line are VERY scope design sensitive. What works in a Newtonian isn't the best in an SCT or Mak, & vise versa. Very few lines do well with all scope designs. By the sounds of it so too does the XF line struggle.

The LVW's are one that do well in all scopes, with the exception being the 30mm. And Vixen themselves acknowledge this by the different appearance of the 30mm.

[Allan]

Anyone looking at buying into this class of eyepiece would be well advised to consider the Delos. While I can't comment on the Vixens, the Delos are a little better optically than the Pentax, at least in the shorter focal lengths I have used. The Delos have performed well in any telescope I have put them in.

[brunono2]

I don't agree. Pentax are one of the best eyepieces for planetary viewing on short focal length refractors- I having been using them for many years and they are superior to most others including Televue eyepieces

regards

Bruno

[mental4astro]

Bruno, no one is disputing their image quality. The only thing that is being said is they are better in some scopes than in others. When there is an optical match, bugger all touches them.

There have been a couple of Pentax lines mentioned. Which line are you referring to, and which focal lengths do you have? It would be good to know which particular Pentax EPs are best in a fast refractor. I to have a fast refractor, an achromat, not best for high power, but would be good to know what works best with one.

[Profiler]

I have done side by side comparisons with a number of XWs with Delos on a few refractors and optically couldn't discern any difference between them.

I also took some measurements and was amazed to see that while the housings were slightly different the optical elements appeared to be virtually identical.

However, I did find that the comparative size and weight of the XW to be smaller, lighter and "very subjectively" felt far more sturdier. I "personally" thought the adjustable eye-cup design on the Delos as something that would be prone to break if twisted the wrong way/over twisted and/or after prolonged use. I also found it quite inferior in terms of ease of use in comparison to the very simple twist top design on the XW.

Finally, before this triggers any howls of protest and indignation from Delos fans I do have quite a few of the very big ticket Televue eyepieces which are great as well but from "my" experiences and preferences I personally think the XWs are a better eyepiece to the Delos (only) for a variety of reasons in the scopes I have tested them both upon. Thus, when I want 100' fov then Ethos has no rival and a low power flat field the Terminagler still reigns supreme in my view.

So, as many have commented before there is no one holy grail in eyepiece lines that is perfect in all circumstances and they all have strengths and weakness in terms of what some can do better than others and most importantly there is a personal taste element to all of them.

[brunono2]

As far as Pentax eyepieces are concerned which I use for short focal length refractors -I have various - XL, Zoom XL + Zoom XF. When seeing is excellent I use a 2.25 times baader barlow which screws into the bottom of the eyepiece -last week I pushed my 4 inch F5 and 5 inch F5 scopes up to 80 per inch on Jupiter - using the baader as well- the views were fantastic on the Pentax eyepieces I preferred the views to on these versus other eyepieces -Tak + Televue radians which I have

To be fair I don't have eg Ethos eyepieces so I cannot compare to eyepieces such as these but I am extremely satisfied with Pentax

[Camelopardalis]

The Baader 2.25x Barlow is excellent IMO I've used it with my Panoptic and Nagler to great effect in my travel scope.

I find the XW10 tricky in my C8 but when I can manage to keep my head still it's a wonderful view. Haven't tried an LVW yet, but sounds like I should :D

[AG Hybrid]

I've been looking at this thread on and off for what seems like forever. I'd like to contribute but I'm not really sure what to say. I have a 10XW. The views are brilliant in my 4", my 12" and every other telescope I've looked through with it.
Every LVW I've looked through gave brilliant views as well. Both are very comfortable to view through, absurdly sharp, excellent light scatter control and have a nice neutral tone. It has been well document that the >14mm XW's don't perform well in fast newtonians due to their lens design and they introduce extra field curvature in the image. A paracorr will fix that up I'm told.
No really issues like noted in the Vixen LVW range, except maybe the 30mm.
I'd recommend people just buy whatever they can afford and whatever is in stock with suppliers.

Can always sell them if you don't like it.

Personally though, I prefer the Delos line myself.

[Wavytone]

Bruno there's a good reason why - the curvature of the focal plane in refractors (and SCT's) is usually convex towards the eyepiece. In newtonians it's concave. Then there's coma, which fast newtonians have. This makes a huge difference as to how eyepieces perform in different scopes.

There is no such thing as an eyepiece that is excellent in all scopes - for that to be true, all scopes would have to produce effectively no aberrations, which simply isn't the case.

Some eyepieces work as well as they do in fast (f/4) Newtonians because to some extent they have a modest amount of negative coma and a curved field to match. This appears to be the case with the Explore Scientific eyepieces, the TV Naglers, Delos and Ethos.

I've only had one occasion to briefly try a Pentax XW20mm and 10mm, which at the time seemed excellent edge-to-edge but I wasn't looking at them critically. Unfortunately I don't know anyone with a set to allow a bake-off with my LVW set.

My only gripe would be the "safety groove", which IMHO is utterly annoying, as one who has never dropped an eyepiece in 40 years.

[Camelopardalis]

Remind me the next time you're heading for the mountains...I've got the 7 and upwards but I don't always carry them.

[gb_astro]

Anything is possible of course but I think Televue would be more concerned with optimising their eyepieces for their own line of refractors.
I really can't see them reversing curvature and adding coma to match third party newtonians.

gb.

[Wavytone]

Actually I'm sure they do, but it's complicated and only evident if you do some ray tracing of a Newtonian or refractor, and the eyepiece. The usual criterion used is the diameter of the "circle of confusion" containing 90% of the incoming energy.

Basically, while the curvature of a refractor is of the opposite sign, most serious refractors are f/7-f/9. Most dobs are around f/4-f/5. What this means is that an eyepiece design with a curved focal plane with a curvature (1/R) half that of the dob focal plane produces about the same size circle of confusion in both a dob and a refractor - the net aberration is about the same in magnitude, but of opposite sign.

Similarly, building in some negative coma in the design produces an eyepiece that performs exceptionally well in a fast Newtonian, yet is still quite acceptable in refractors, maks and SCT's.

You could design an eyepiece fully corrected for coma and curvature, resulting in an even smaller circle of confusion over a wide field for a fast Newtonian - as someone did (the Klee "Pretoria" eyepieces) with really superb results, however if used in a refractor or SCT the result will be very poor indeed.

This unfortunately was the undoing of the Pretoria eyepiece as many buyers at the time simply didn't understand it was totally unsuited to their Celestrons and achro refractors. The result was it got a bad name.

Another eyepiece that performed very badly in sone types of scope was the Koenig - though I never figured out what sort of scope it was supposed to match. Field curvature was always a huge problem with these ep's.

[Astromelb]

Dear I In S'ers

Great thread guys, on two wonderful series of Ep's.

Having a full set of both options, I find the performance is dependent on which scope they are being used in.

The Pentax's are wonderful, but sadly the recently new owners of Pentax, Hoya Corp of Japan decided in their wisdom to delete the astronomy gear from the Pentax range, very sad.

The Vixen LVW are excellent eyepieces, and as they are current production and available from the Oz agent for Vixen - My Astro Shop in Queensland, so they are a terrific buy.

If you are prepared to do work on the web pages globally - such as CN & Astronomy Buy Sell UK you can find Pentax XW's fairly 2nd hand reasonably regularly, but usually need to be very very quick to secure them.

The large 2 inch Pentax XW's (30mm and 40mm) are very very hard to get and you need to move fast as they sell very very fast.

All this said I do find that different telescopes perform differently with different eyepieces, so it is always a matter when I get a new telescope to test which eyepieces suit that particular telescope the best, which is always a test and trial process.

Eyepieces are absolutely critical, as I find so many people with a telescope that is most capable, but get eyepieces that are simply not good enough. The eyepiece is located at the focal point, this is the location where the image is produced, making the eyepiece the most important part of the system :)

Clear skies.

[janoskiss]

Wow, this thread just refuses to die! No more XWs for me. Also had my XFs stolen (in two separate incidents). I repurchased them last year after a few years of making do with plossls and a no-name 30mm UWA. That's how much I love those XFs. But I'm getting too old and lazy for the heavy and bulky XWs. No more awkward questions: 'Is that a Pentax in your pocket ...?'

[bytor666]

I've used a lot of XW's in a lot of scopes from Newts, to 'Fractors to SCT's and they are all excellent in all scopes, except for a slight bit of FC coming from the 14mm and 20mm XW's in Newtonians.

None of the FC can be seen in the SCT's from the 14mm or 20mm XW's.

Cheers!