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John

Vixen SSW Ultra Wide Angle Eyepieces: Review

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Paul73    2,365

An interesting read John (as always).

Sounds like they are nearly there. Maybe they should have stuck with 70° ish. There would have been a market for a light weight Delos alternative (for those not burdened with glasses). These could have out gunned the narrower field DeLites???

Interesting that they stop at 14mm...

Paul

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JeremyS    341

>> The other thing for me would be the undercuts. Why did Vixen do this when the excellent SLVs have smooth sides? Anyone who owns a Takahashi prism will know why I say this. 

don't follow you about the Tak prism. ​What do you mean, Roy?  

Jeremy

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Roy Challen    624

The Tak prism uses a twist-lock to clamp the EP rather than a screw/compression ring. The plastic collar that does the clamping often gets stuck on undercuts, at least that's what happened to me. Tapered EPs are better, but require lots of twisting before they feel properly secure. The Baader click-lock doesn't have this problem at all, and is the best EP securing system out there IMO.

Sorry for going off topic.

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F15Rules    1,564

The Tak prism uses a twist-lock to clamp the EP rather than a screw/compression ring. The plastic collar that does the clamping often gets stuck on undercuts, at least that's what happened to me. Tapered EPs are better, but require lots of twisting before they feel properly secure. The Baader click-lock doesn't have this problem at all, and is the best EP securing system out there IMO.

Sorry for going off topic.

+1 for smooth barrels, not undercuts. I see no useful purpose in undercuts and much prefer smooth or tapered barrels. They don't just get caught in Tak prisms (IMO one of the best value 1.25" diagonals available), but also in standard ones too. I have Meade and no-name generic 2" diagonals with which I use good quality Baader 2" to 1.25" adapters and the few undercut equipped 1.25" eps I have do still get caught in them now and again - it's most infuriating for me when you have your drive switched on to track at higher power, then you want to switch to a different (but also high power), eg 8mm to 5mm, then in the process of removing the 8mm undercut ep it catches on the compression ring and "tugs" or resists removal just enough to nudge the object out of the field of view....aaaaaarrgh!!

That's better, I feel calm again now. And I am slowly ridding myself of undercut eps...trouble is, my Nagler 13mm T6 is SO sweet.... :grin:  :grin:  - but my Meade 4000 UWA 14mm has 2" and 1.25" barrels, is just as sweet and has no undercut, so the Nag had better watch out... :evil:  :evil:

Dave

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John    16,324

This was hardly a major talking point of my review but I just don't get it about these undercuts :icon_scratch:

I've owned and used dozens of different eyepieces during my years in the hobby and owned 25+ scopes to use them with. Most of the eyepieces have had an undercut of one sort or another but, apart from the odd wriggle now and then, I've rarely had any sort of problem getting them in and out of scopes. I don't even think about it really.

I realise that from what I read on this and other forums that I seem to be in a minority of one but thats just how I've found things.

I'd certainly never consider moving on a top performing eyepiece just because it had an undercut :undecided:

They obviously do cause others great consternation though so I'll stop there.

NB: I'll happily give premium eyepieces with undercuts a good home if you are desparate to be rid of them. Tele Vue, Pentax, TMB Supermono's, I'm not fussy :smiley:

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JeremyS    341

I am still confused. Is an "undercut" a groove in the eyepiece barrel? I use a Tak prism diagonal and have never had a problem. My Tak eyepieces are smooth-sided, whereas my Pentax ones have grooves (undercuts). All all fine. Or have I missed something?

Jeremy

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John    16,324

I am still confused. Is an "undercut" a groove in the eyepiece barrel? I use a Tak prism diagonal and have never had a problem. My Tak eyepieces are smooth-sided, whereas my Pentax ones have grooves (undercuts). All all fine. Or have I missed something?

Jeremy

I think you've got it Jeremy.

Roy Challen has started a new thread on this so folks can have a vigourous discussion on the topic :smiley: :

http://stargazerslounge.com/topic/255334-undercuts-love-or-loathe/#entry2786578

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F15Rules    1,564

This was hardly a major talking point of my review but I just don't get it about these undercuts :icon_scratch:

I've owned and used dozens of different eyepieces during my years in the hobby and owned 25+ scopes to use them with. Most of the eyepieces have had an undercut of one sort or another but, apart from the odd wriggle now and then, I've rarely had any sort of problem getting them in and out of scopes. I don't even think about it really.

I realise that from what I read on this and other forums that I seem to be in a minority of one but thats just how I've found things.

I'd certainly never consider moving on a top performing eyepiece just because it had an undercut :undecided:

They obviously do cause others great consternation though so I'll stop there.

NB: I'll happily give premium eyepieces with undercuts a good home if you are desparate to be rid of them. Tele Vue, Pentax, TMB Supermono's, I'm not fussy :smiley:

Hi John,

Well, I confess there was an element of "tongue in cheek" about my post, but I do genuinely really dislike them. I was brought up (showing my age) on smooth barrels and apart from the obvious caution about making sure the diagonal screws were fully secure (and of course in the old days they did mark the eyepiece barrel), I never came close to losing an eyepiece apart from once, when using a large 2" ep which I stupidly popped into the diagonal without tightening up for a few seconds, and of course that was the one time that the nosepiece on the diagonal chose to unscrew itself.

Of course, whether I would sell one just because of the undercut if it was otherwise superb (eg the Nagler) is unlikely :grin:  - unless the sale was unavoidable financially or there was an alternative that I really preferred. Interestingly, I will be having a shootout between the Nagler T6 13 and the Meade UWA 14mm when/if we ever get another clear night again, and it is unlikely I will keep both as their magnifications and FOV are so similar. We'll see..

The undercut has only really caused me problems at higher magnifications since low power eps can take a minor "nudge" without losing the object..but as one of my favourite areas of observing is double stars at fairly high power it does become irritating at times. But we're all different I guess in what "winds us up" and what doesn't :smiley: .

Dave

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John    16,324

Hi John,

....The undercut has only really caused me problems at higher magnifications since low power eps can take a minor "nudge" without losing the object..but as one of my favourite areas of observing is double stars at fairly high power it does become irritating at times. But we're all different I guess in what "winds us up" and what doesn't :smiley: .

Dave

Hi Dave,

Yes, different things annoy different people. I've been observing Neptune at very high powers recently, seeking out it's moon Triton with my 12" dob. Swapping between my Pentax 3.5mm XW (454x) and my Radian 3mm (530x) involves both a reduction in apparent and true fields and several mm outward focuser adjustment. I find those factors much more challenging that the undercuts in their barrels :rolleyes2:

Still, thats what you get when you use "ludicrously high" power with an undriven, alt-az mounted scope !

The reward when that little point of light pops into view makes it all worthwhile though :grin:

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Don Pensack    170

I concur with all the comments of the reviewer John(he was thorough).

The two downsides to the eyepieces are SAEP (spherical aberration of the exit pupil) which is the cause of his difficulty in eye placement,

and edge of field astigmatism (they are not free from it).

I'm a bit surprised at the safety undercut groove on these eyepieces, since their new SLV series has smooth barrels, and the SLVs came out first.

There are many more pluses to the eyepiece, including a great suppression of scattered light, but these two issues are especially noticeable when comparing them

to the TeleVue Nagler Type 6s, which have neither issue.

It's a good first try for Vixen in the ultra-wide market.

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Dave In Vermont    4,375

This very much reminds me of bicycle-mechanics and the recent innovation of making it harder to remove the front wheels by putting an extra-groove into the fork. This supposedly makes it so a wheel can't come off the bike if you forget to lock the quick-release mechanism in the first place. These defeat the entire reason for the quick-release altogether. And people have complained about these things until blue-in-the-face.

Us mechanics refer to these as "Lawyer-Lips." Their presence drives people crazy, while fixing a non-problem in the first place.

Pathetic,

Dave

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disciplus55    42

I just sold my Delite 7 mm because of the too narrow field of view on my 16" Dob. Now I am looking for another 7 mm, but I can't decide if I would prefer a Pentax XW 7 or a Vixen SSW 7 ... I have a XW 10 ans an SSW 14, so I know both lines of EP's, but I can't get decided on which one to buy for a 7 mm, and later a 5 mm. I tried to Barlow both the 10 and 14 and i liked both views... indeed the XW are a bit easier on eye positioning, but the FOV of the SSW is very nice... damn... can't get decided...

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Pig    4,723
2 hours ago, disciplus55 said:

I just sold my Delite 7 mm because of the too narrow field of view on my 16" Dob. Now I am looking for another 7 mm, but I can't decide if I would prefer a Pentax XW 7 or a Vixen SSW 7 ... I have a XW 10 ans an SSW 14, so I know both lines of EP's, but I can't get decided on which one to buy for a 7 mm, and later a 5 mm. I tried to Barlow both the 10 and 14 and i liked both views... indeed the XW are a bit easier on eye positioning, but the FOV of the SSW is very nice... damn... can't get decided...

There is little difference between the XW and the Delite, thus out of the two choices the SSW would give a wider field.... 

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John    16,324

In case you have not read my review at the start of this thread, I liked the Vixen SSW's but I had 2 reservations about them:

- I found eye placement a bit too fussy.

- There was some astigmatism (as well as the expected distortion) showing in the outer 10% of the field of view.

Other than that they are nice eyepieces :smiley:

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disciplus55    42

John, thanks a lot, yes indeed I have read your review. Eye placement is indeed more difficult than on the XW's, but on my 14 mm, I have found the sweet spot with eyeguard, so it's almost ok now.

astigmatism on the outer fov is perceivable only when moving the eyeglobe around, but the 83deg fov gives a great immersion feeling that the XW's are lacking. I loved the image of the Delite but 62deg fov is too narrow for me on my Dobsonians.

I may go for a XW 7 and an SSW 5.... or à SSW 7 and and XW 5?... still hesitating...

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Pig    4,723
1 minute ago, disciplus55 said:

John, thanks a lot, yes indeed I have read your review. Eye placement is indeed more difficult than on the XW's, but on my 14 mm, I have found the sweet spot with eyeguard, so it's almost ok now.

astigmatism on the outer fov is perceivable only when moving the eyeglobe around, but the 83deg fov gives a great immersion feeling that the XW's are lacking. I loved the image of the Delite but 62deg fov is too narrow for me on my Dobsonians.

I may go for a XW 7 and an SSW 5.... or à SSW 7 and and XW 5?... still hesitating...

You will soon be sliding into Ethos territory :happy8:

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John    16,324
31 minutes ago, disciplus55 said:

I may go for a XW 7 and an SSW 5.... or à SSW 7 and and XW 5?... still hesitating...

For around a year I've been comparing the 5mm and 3.5mm XW's with a range of others of a similar focal length and in particular the Ethos SX 4.7 and 3.7. I'm a big fan of the Ethos but in the end I decided to let the 3.7 and 3.7 go. I just found the XW's a tiny bit sharper when viewing very fine lunar and planetary detail. It took me many months to come to this conclusion though - they were very close and the massive field of the Ethos SX's is very addictive :smiley:

Given the choice between the XW's and SSW's I think the viewing comfort would draw me to the Pentax's. But thats what my choice would be - you may well reach a different conclusion and I'm sure you will enjoy whatever you decide to go for :smiley:

 

 

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I must say my XW5, XW7 and XW10 all have superb viewing comfort and sharpness, and they are parfocal. I am not sure the Vixen SSWs will be parfocal with them (although my SLVs seem to be very very close to arfocal with the XWs).

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Don Pensack    170
On 10/17/2015 at 10:58, YKSE said:

Excellent review as always, John,

A couple of questions:

About "bright rim at field stop", is it the so-called "Ring of fire"? If so, what's the color of it? Is is visible in day time too?

And the"kidney bean" effect, do you see it in day time use too?

The term "ring of fire" was coined to describe a situation wherein a colored ring appears in the field of view near the edge.  I could be wrong,

but I believe it was first applied to the 31mm TeleVue Nagler.  In daytime use, the outer 5° of field is orange tinted in that eyepiece.  It is not visible at night

unless the Moon drifts into that part of the field.  It is caused by a chromatic aberration of the exit pupil (CAEP) and it is found in several widefield and ultrawidefield

eyepieces.

Nearly all widefield eyepieces have a very thin ring of color at the very field stop.  It can be blue or red or green or yellow--it depends on the coatings used.

That is not what "ring of fire" refers to.

The issue called EOFB, or Edge of Field Brightening, is a recent phenomenon, and the cause is not completely known.  In fact, there may be several causes.

It makes the background appear slightly brighter as you near the field stop.  It sometimes appears as if you are viewing a circular nebula and the center of the field in the eyepiece

is inside the nebula, so appears darker than the outer field.  Its extent and brightness seem to be related to the f/ratio of the scope.  Some have taken to blackening barrel interiors, filter threads,

lens edges, and even adding an iris-like stop to the bottom of the eyepiece, and these all reduce, but do not eliminate the EOFB.  Some have noted the effect is worse when the air is hazy

or a tiny bit of dew is appearing on the optics.  As I said, the complete set of parameters that cause it are not well known, and so its elimination is yet to come once all optical designers

know what causes it.

The "kidney bean" shaped blackouts are caused by spherical aberration of the exit pupil.  You can read about it here: https://www.handprint.com/ASTRO/ae4.html#SAEP

Note that many eyepieces have this, but on short focal lengths it is usually invisible.  You can see how it shows up in the exit pupil by looking at the line(s) represented by the exit pupil

in the bottom cross-section eyepiece diagrams here: http://www.telescope-optics.net/eyepiece_aberration_2.htm

If the exit pupil is not a single line, there is SAEP.

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YKSE    1,999
41 minutes ago, Don Pensack said:

The "kidney bean" shaped blackouts are caused by spherical aberration of the exit pupil.  You can read about it here: https://www.handprint.com/ASTRO/ae4.html#SAEP

Note that many eyepieces have this, but on short focal lengths it is usually invisible.  You can see how it shows up in the exit pupil by looking at the line(s) represented by the exit pupil

in the bottom cross-section eyepiece diagrams here: http://www.telescope-optics.net/eyepiece_aberration_2.htm

If the exit pupil is not a single line, there is SAEP.

Don,

Thanks for reminding me the second link, I'm under the impression that my post 

https://www.cloudynights.com/topic/547588-say-it-aint-so-26mm-nagler-is-out/page-3

a year ago is one of the first (if not the first) to use that link for explaining that SAEP exist  in many EPs, when some persisted in no SAEP in new Naglers.:smiley:

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Don Pensack    170

Yes, the question is more "how much is visible?" versus "does any exist?".

If the amount is small enough no one sees it and no ones notices, then you might as well say the eyepiece has none, like the Plössl in the link.

This is probably the case with most short focal length eyepieces.

I'm sure there is a variation among individuals as to sensitivity to this issue, but it's quite possible for the value to be opposite

the curvature that would be noticeable and, hence, not visible, just as field curvature in an eyepiece can cancel or add to the field curvature in a scope.

It's been stated the 13mm original Nagler had just about the worst SAEP of any eyepiece, but, surprisingly, there were a lot of observers

that never had any issues with that in the eyepiece.  Compared to that one, SAEP is pretty much minimal in modern Naglers.

I'm afraid I don't know what characteristic of the eye relates to the obtrusiveness of SAEP.  It might just be a "threshold" phenomenon, like the visibility of astigmatism in an image.

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YKSE    1,999
6 hours ago, Don Pensack said:

Yes, the question is more "how much is visible?" versus "does any exist?".

If the amount is small enough no one sees it and no ones notices, then you might as well say the eyepiece has none, like the Plössl in the link.

Yes, when no one sees it, it's all right to say it has none. But, when someone sees it but I don't, then it is "to my eye" or IME, calling it has none is plainly wrong.

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