Pentax XW 16.5mm and 23mm 85 degree eyepieces

[John]

Apologies if I have missed some discussion on these but I wonder if anyone has them and, if so, what they think of them ?

I'm just "tyre kicking" really - pondering the option to move from my current mixed collection of Tele Vue and Pentax eyepieces to a simplified all Pentax line up of:

23mm, 16.5mm, 10mm, 7mm, 5mm and 3.5mm. I already have the 4 shorter focal lengths in the series.

Each time I think about "rationalising" my eyepieces I seem to talk myself out of it but I'm feeling a stronger will to actually make some moves now and a Pentax XW set, although not perfect (of course) would seem to be a pretty good compromise to happily live with based on my experiences with the XW's that I currently own.

I suppose the main thrust of my question is to find out if the new 85 degree Pentax's have any major issues that I ought to be aware of. I don't wear glasses when observing 

Thanks in advance for any feedback 🙂

 

Edited March 24, 2023 by John

[Alan White]

Hi John

@HollyHound has the 16.5 at least a very early adopter and has posted on the forum.
As has @Don Pensack in an initial review.

I believe they have shorter eyerelief if you wear glasses than the 70 degree XW line.
A reason I have bypassed them myself sadly.

[John]

2 hours ago, Alan White said:

Hi John

@HollyHound has the 16.5 at least a very early adopter and has posted on the forum.
As has @Don Pensack in an initial review.

I believe they have shorter eyerelief if you wear glasses than the 70 degree XW line.
A reason I have bypassed them myself sadly.

Thanks Alan. I'll use the forum search facility and see if I can find some reports.

I don't wear glasses when observing and find 12mm and upwards eye relief fine but I can understand that more than that is required if you do wear glasses.

[globular]

Hi John, 
I have the 16.5mm.  Unfortunately I haven't had enough quality time with it to post a review yet (and in my F/10.5 you might not be that interested in my findings anyway). But I would say after the brief testing I've done that I love it. Everything is sharp across the FOV with nice even illumination and no obvious distortions as things drift from one edge to the other.  It sits lovely with my other XWs, N22T4 and ES92/12.

Hi Alan,  
My wife and I share our EPs... she wears glasses and I don't.  With our XW7,10 & 40 I wind the eyecup nearly fully out and she uses them fully in. Doing the same with the 16.5 we can both see the full FOV. Everyone's face shape and glasses distances are different - but you might want to try one yourself before giving up on them for eye relief reasons. I think it is fair to describe them as glasses friendly - although while the 70 degree ones will typically work for all glasses users, the 85 degree ones will probably work for some and not for others.  If you're ever up near Shropshire, pop in and try mine.

[HollyHound]

11 hours ago, John said:

Apologies if I have missed some discussion on these but I wonder if anyone has them and, if so, what they think of them ?

I'm just "tyre kicking" really - pondering the option to move from my current mixed collection of Tele Vue and Pentax eyepieces to a simplified all Pentax line up of:

23mm, 16.5mm, 10mm, 7mm, 5mm and 3.5mm. I already have the 4 shorter focal lengths in the series.

Each time I think about "rationalising" my eyepieces I seem to talk myself out of it but I'm feeling a stronger will to actually make some moves now and a Pentax XW set, although not perfect (of course) would seem to be a pretty good compromise to happily live with based on my experiences with the XW's that I currently own.

I suppose the main thrust of my question is to find out if the new 85 degree Pentax's have any major issues that I ought to be aware of. I don't wear glasses when observing 

Thanks in advance for any feedback 🙂

 

I have the XW16.5, and will be getting an XW23 very soon.... I've not used the XW16.5 as much as I'd like (in fact been super busy with work for months, so very little astronomy 😬).

My earlier (initial) report on the 16.5 is here... 

On the basis of using this eyepiece, I have already sold my XW14, XW20 and XW30, and have consolidated my eyepiece as follows XW40, XW16.5, XW10, XW7, XW5, XW3.5... the XW23 will be slotted in there as well and then I think I have just about the perfect primary set of eyepieces (for me) 😀

I've had TeleVue (of all types), Masuyama and loads of others, but for me, the XW range just seem to work perfectly. I wouldn't say their image rendition is any better than those, but the ergonomics (eye relief, comfort, physical handling of the eyepiece) just work perfectly for my needs 👍

 

[Don Pensack]

14 hours ago, John said:

Apologies if I have missed some discussion on these but I wonder if anyone has them and, if so, what they think of them ?

I'm just "tyre kicking" really - pondering the option to move from my current mixed collection of Tele Vue and Pentax eyepieces to a simplified all Pentax line up of:

23mm, 16.5mm, 10mm, 7mm, 5mm and 3.5mm. I already have the 4 shorter focal lengths in the series.

Each time I think about "rationalising" my eyepieces I seem to talk myself out of it but I'm feeling a stronger will to actually make some moves now and a Pentax XW set, although not perfect (of course) would seem to be a pretty good compromise to happily live with based on my experiences with the XW's that I currently own.

I suppose the main thrust of my question is to find out if the new 85 degree Pentax's have any major issues that I ought to be aware of. I don't wear glasses when observing 

Thanks in advance for any feedback 🙂

 

https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/?p=12369694

https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/?p=12369699

https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/?p=12369736

 

By the way, that thread has 602 posts, and it is only 1 of over 200 threads containing posts about the eyepieces.

[Steve]

21 minutes ago, Don Pensack said:

By the way, that thread has 602 posts, and it is only 1 of over 200 threads containing posts about the eyepieces.

Don, @John is a moderator for Cloudy Nights, so he is familiar with your posts there 🙂

I think John is looking for opinions from UK/SGL owners. 

[Louis D]

9 minutes ago, Steve said:

Don, @John is a moderator for Cloudy Nights, so he is familiar with your posts there 🙂

I think John is looking for opinions from UK/SGL owners. 

Although I wonder how much effect observing locale or clientele has on the optical properties of a widely available eyepiece.  I could see where power supply impressions might vary greatly between US/UK given the power grid differences.

[John]

2 hours ago, Steve said:

Don, @John is a moderator for Cloudy Nights, so he is familiar with your posts there 🙂

I think John is looking for opinions from UK/SGL owners. 

Thanks Steve. Just for clarity, I am not a moderator on CN although I do frequent the forum quite often. I will search there for feedback on these eyepieces as well.

I was seeking SGL feedback specifically with this post 🙂

Many thanks for the responses so far 👍

 

 

Edited March 24, 2023 by John

[Highburymark]

So you’d get rid of your Ethos John? At current prices they would be very expensive to reacquire if you missed them.

[Deadlake]

On 24/03/2023 at 01:11, John said:

Apologies if I have missed some discussion on these but I wonder if anyone has them and, if so, what they think of them ?

I'm just "tyre kicking" really - pondering the option to move from my current mixed collection of Tele Vue and Pentax eyepieces to a simplified all Pentax line up of:

23mm, 16.5mm, 10mm, 7mm, 5mm and 3.5mm. I already have the 4 shorter focal lengths in the series.

Each time I think about "rationalising" my eyepieces I seem to talk myself out of it but I'm feeling a stronger will to actually make some moves now and a Pentax XW set, although not perfect (of course) would seem to be a pretty good compromise to happily live with based on my experiences with the XW's that I currently own.

I suppose the main thrust of my question is to find out if the new 85 degree Pentax's have any major issues that I ought to be aware of. I don't wear glasses when observing 

Thanks in advance for any feedback 🙂

 

Interested in why you would move from TeleVue to Pentax and not the other way around. 

You've had your TeleVue from some years not, why the Pentax EP's?

All the best, Martin

[Louis D]

Having owned some Tele Vue eyepieces, I can attest that they are not perfect and can be improved upon.  I retired my 27mm Panoptic in favor of my 30mm APM UFF, my 12mm NT4 for my 12.5mm APM Hi-FW and 12mm ES-92, and my 17mm NT4 for my 17mm ES-92.  I'm on the hunt for a 22mm NT4 replacement with greater eye relief and/or AFOV while being at least as sharp across the field with less SAEP.  The 23mm Pentax XW 85° might be that eyepiece.  I'm just not willing to drop $500 on one until I know for certain it is comfortable to use with eyeglasses (at least 17mm of usable eye relief in my case).  It seems to tick the other criteria (greater AFOV, sharp across the field, and less SAEP).

[Don Pensack]

2 hours ago, Louis D said:

Having owned some Tele Vue eyepieces, I can attest that they are not perfect and can be improved upon.  I retired my 27mm Panoptic in favor of my 30mm APM UFF, my 12mm NT4 for my 12.5mm APM Hi-FW and 12mm ES-92, and my 17mm NT4 for my 17mm ES-92.  I'm on the hunt for a 22mm NT4 replacement with greater eye relief and/or AFOV while being at least as sharp across the field with less SAEP.  The 23mm Pentax XW 85° might be that eyepiece.  I'm just not willing to drop $500 on one until I know for certain it is comfortable to use with eyeglasses (at least 17mm of usable eye relief in my case).  It seems to tick the other criteria (greater AFOV, sharp across the field, and less SAEP).

Forget the Pentax 23mm, Louis.  It has only 12mm of eye relief from the eyecup up.

You MIGHT be able to use that, but I had to press my glasses into my eye socket until my eyelashes brushed the glasses in order to see the field edge.

That was not comfortable.

The suitability for glasses would mean you have shallow eyes and small glasses that sit well within the eye socket.

There is no eyecup out there that will help, because there is a section of eyepiece several mm above the eye lens protruding from the body of the eyepiece that you cannot remove.

I tried a Morpheus eyecup and a simple stretch-on rubber eyecup, and all of them yielded about the same depth to the eye lens, which is strongly concave, as the original eyecup.

It is not, alas, a substitute for the 22mm T4.

The Long Perng 20mm 80° could be if the eyecup is removed and a simple stretch-on eyecup is used and folded down as a replacement.

Good luck finding a 50mm rubber eyecup to fit it, though.

Edited March 26, 2023 by Don Pensack

[John]

11 hours ago, Deadlake said:

Interested in why you would move from TeleVue to Pentax and not the other way around. 

You've had your TeleVue from some years not, why the Pentax EP's?

All the best, Martin

Fair question Martin. I'm not decided by any means on this  or any other eyepiece path, which is why I used the term "tyre kicking". I have owned Ethos and XW eyepieces for around a decade, perhaps a little more so I feel that I know both types quite well.

I have also owned the ES 92's that @Louis D mentions and the 22mm T4 Nagler. 

If I move away from Ethos I will almost certainly miss them at times and likewise with the Pentax XW's. I'm trapped by excellence !!!!

Oddly, for a Tele Vue enthusiast, I don't feel quite the same about the Delos. I had the 17.3 and 14 Delos for a while and both were excellent performers and comfortable to use but somehow I didn't grow as fond of them as I have the Ethos and XW's. I still have the 14mm Delos (the 17.3 was not a focal length that I used much) but I don't feel similar pangs about the thought of letting it go, if that is where my path leads me 🙄

 

 

 

 

 

 

 

 

Edited March 26, 2023 by John

[Louis D]

On 26/03/2023 at 10:09, Don Pensack said:

Forget the Pentax 23mm, Louis.  It has only 12mm of eye relief from the eyecup up.

You MIGHT be able to use that, but I had to press my glasses into my eye socket until my eyelashes brushed the glasses in order to see the field edge.

That was not comfortable.

Has anyone posted a 3/4 image of the top of the 23mm Pentax XW to any thread anywhere?  I can't find one.  I'm just curious how much the eye lens is recessed from the top of the metal barrel.

I've measured my 40mm Pentax XW-R to have at least 7mm of eye lens recession from the lip of the exposed metal barrel once the eye cup is screwed off.  Have you measured the eye lens recession with the toothpick method on the 23mm XW?  It would be a shame if Pentax did the same with it and wasted 7mm of usable eye relief for no particular reason.

[globular]

I've just measured my XW40 (to make sure we're measuring the same thing). 
I agree your figure of 7mm recession at the edge.  The top lens is convex on this EP, and the recession is 4.5mm at the centre.

On my XW16.5 it's recessed 4.5mm at the edge.  The top lens is concave on this EP, and it's 7mm recessed at the centre.

 

Edited May 9, 2023 by globular

[Louis D]

Thanks so much.  Yes, I was measuring at the edge.  That might explain the 20mm/12mm eye relief difference for the XW-85s if the 20mm refers to the design eye relief which will be ~8mm more than the usable eye relief (12mm).

[John]

On 26/03/2023 at 00:41, Highburymark said:

So you’d get rid of your Ethos John? At current prices they would be very expensive to reacquire if you missed them.

This post caused me to pause and I'm still paused.

I did grab a TOE 4mm though 🙂

With the weather we have had in the my part of the UK since I started this thread, the contents of my eyepiece case seems somewhat academic 😒

[Louis D]

You could do like me and start playing with them indoors taking pictures of standardized targets through them. 😁

[globular]

6 hours ago, Louis D said:

Thanks so much.  Yes, I was measuring at the edge.  That might explain the 20mm/12mm eye relief difference for the XW-85s if the 20mm refers to the design eye relief which will be ~8mm more than the usable eye relief (12mm).

The 70 degree versions claim 20mm/15mm eye relief and the 85s claim 20mm/12mm.

The 20mm is measured from the centre of the top face of the top lens.  And the 15mm & 12mm are from the top of the rubber eye guard.

The eye guards are the same for both eyepieces so they sit the same distance above the outside edge of the lens housings.

You can see from my measurements that the centre of the glass to the top of the eye guard differs by 7 - 4.5 = 2.5 mm between the two EPs.  

This is close to the 3mm difference in usable eye relief claimed - so I think their figures are pretty good / my measurements are fairly accurate - although my wife says they feel closer to each other in use to her bespectacled eyes.

How much wiggle room do you have when using the XW40 @Louis D?
You could try winding it out 2.5mm from the fully in position on your XW40 and that might give you an idea of how the 85 degree versions will behave. 

[Louis D]

10 hours ago, globular said:

How much wiggle room do you have when using the XW40 @Louis D?

I can't quite remember if I need to be resting my glasses on the eye guard or hovering just above it.  I'll have to check sometime.  On my 40mm Lacerta ED, I know have to have my glass resting on the retracted eye cup to see the entire view.  I might even need to push in a bit.  The 35mm Aero ED requires me to mash my glasses into the eye cup to see the entire field.  At the other extreme, my decloaked 40mm Meade 5000 SWA allows me to hover well above the eyepiece in relaxed comfort with 24mm of usable eye relief.  It also has better edge to edge correction and field flatness as compared to the Pentax XW-R 40mm, but it is more massive.

[Highburymark]

15 hours ago, Louis D said:

You could do like me and start playing with them indoors taking pictures of standardized targets through them. 😁

Alongside my artificial star and squared paper targets I have pieces of tree bark and (Moroccan) banknotes, which are a useful way to compare contrast and sharpness.
If you really want to make it exciting, you can hunt for tiny, deliberate misprints on banknotes which are often used to discourage forgeries.
Just remember, the weather here in the UK is often very bad for long periods - we need these little diversions.

[Don Pensack]

22 hours ago, Louis D said:

Thanks so much.  Yes, I was measuring at the edge.  That might explain the 20mm/12mm eye relief difference for the XW-85s if the 20mm refers to the design eye relief which will be ~8mm more than the usable eye relief (12mm).

I measured the depth and assumed the eye relief from the glass was 20mm.

The depth of the lens below the rubber eyecup was exactly 8mm.

[Don Pensack]

15 hours ago, globular said:

The 70 degree versions claim 20mm/15mm eye relief and the 85s claim 20mm/12mm.

The 20mm is measured from the centre of the top face of the top lens.  And the 15mm & 12mm are from the top of the rubber eye guard.

The eye guards are the same for both eyepieces so they sit the same distance above the outside edge of the lens housings.

You can see from my measurements that the centre of the glass to the top of the eye guard differs by 7 - 4.5 = 2.5 mm between the two EPs.  

This is close to the 3mm difference in usable eye relief claimed - so I think their figures are pretty good / my measurements are fairly accurate - although my wife says they feel closer to each other in use to her bespectacled eyes.

How much wiggle room do you have when using the XW40 @Louis D?
You could try winding it out 2.5mm from the fully in position on your XW40 and that might give you an idea of how the 85 degree versions will behave. 

I found the difference just enough that the 85° were a NO-GO with glasses, while the 70° are very comfortable.  I'm very sorry about that, because the optics in the 16.5mm are excellent.

[Louis D]

On 08/05/2023 at 12:13, globular said:

On my XW16.5 it's recessed 4.5mm at the edge.  The top lens is concave on this EP, and it's 7mm recessed at the centre.

If we assume that it's 20mm design ER from the center, and we machine off the top of the barrel to be flush with the eye lens's edge (ignoring for now that it will fall out if tipped too far), that saves 4.5mm of usable ER at most.  So 20 - 4.5 = 15.5mm maximum usable eye relief for eyeglass wearers if the eye lens could somehow be flush mounted to the very top of the barrel.  That's quite tight for most eyeglass wearers with deep set eyes like Don and me.  Subtract a mm or so to secure the eye lens, and now you've got 14.5mm of usable eye relief.  Perhaps a monocle is in order for these eyepieces even if redesigned? 😄