Pentax XW 16.5mm and 23mm 85 degree eyepieces

[John]

Now that these ultra-wide Pentax XW models have been around for a while I wonder if anybody has them and if so how they are finding them ?

I've managed to find very little feedback on these relatively new Pentax eyepieces. They seemed quite exciting when they were launched.

Edited December 4, 2023 by John

[HollyHound]

Hi John,

I've had the 16.5mm since it was launched, and although time for astronomy for me this year has been very limited, for the times I have used it, I can say that this eyepiece has been a superb replacement for it's predecessor in my set (the XW 14mm) 👍

There is very little field curvature (the 14mm suffered from this), contrast is excellent and I find that (for me) 70-85 degrees is the sweet spot for being able to take in all the field comfortably and not feeling constricted. You have XWs in the lower focal lengths so you will also know how comfortable the view is on these eyepieces, and the 16.5mm continues with that same comfort. I always find my eye feels relaxed when using any of the XW eyepieces 😀

Ergonomics and comfort are also up there with the 75 degree versions. Being able to set and fix eye relief, plus the rubber tops make them very usable.

In short, they continue the excellence of the original XWs, remove the FC issue from the 14 (and 20) and provide an additional useable field. Their only downside is cost, but then I would put them up against TeleVue anytime and these aren't exactly cheap either 😬

Now that I have a bit more time, and with darkness back again, I am about to order the matching 23mm this week, to complete the set again... which shows the confidence I have in these.

Hope that's been of some help...

[John]

41 minutes ago, HollyHound said:

...Hope that's been of some help...

Very much so. Thanks Gary 🙂

[Louis D]

@HollyHound Do you observe with eyeglasses at those focal lengths?  I have such strong astigmatism in my eyes that I need a minimum of 17mm of usable eye relief to comfortably see the entire field of view of an eyepiece.

My 12mm and 17mm ES-92s exactly tick that box, so I have no incentive to get the 16.5mm XW.  My XL, XW, Hi-FW, Delos, and Morpheus eyepieces all provide at least 18mm of usable eye relief, so are also quite comfortable to observe with.  I've held off purchasing the 23mm XW to replace my 22mm NT4 because I've read that the eye relief is marginal for eyeglass wearers.

[John]

I have owned and used the ES 92's so I know what those are like.

It is the Pentax XW 16.5mm and 23mm that I am enquiring about.

[HollyHound]

8 minutes ago, Louis D said:

@HollyHound Do you observe with eyeglasses at those focal lengths?  I have such strong astigmatism in my eyes that I need a minimum of 17mm of usable eye relief to comfortably see the entire field of view of an eyepiece.

My 12mm and 17mm ES-92s exactly tick that box, so I have no incentive to get the 16.5mm XW.  My XL, XW, Hi-FW, Delos, and Morpheus eyepieces all provide at least 18mm of usable eye relief, so are also quite comfortable to observe with.  I've held off purchasing the 23mm XW to replace my 22mm NT4 because I've read that the eye relief is marginal for eyeglass wearers.

I don't currently observe with glasses, although that may be around the corner one day 🤞

I note that both the 16.5 and 20mm XWs have a quoted eye relief of 20mm (as per the other XWs), but also noted that usable eye relief is 12mm from the eyecup, so seems that might be an issue indeed.

I do have some astigmatism, which shows itself on lower power eyepieces (20mm and up), but have solved that on my XW40, by installing a Dioptrx inside the eyecup of that eyepiece... quite an elegant solution, as I align the mark with the label on the eyepiece and just rotate it appropriately to set the correct position for correcting astigmatism 😀

More details here... 

 

[HollyHound]

15 minutes ago, Louis D said:

@HollyHound Do you observe with eyeglasses at those focal lengths?  I have such strong astigmatism in my eyes that I need a minimum of 17mm of usable eye relief to comfortably see the entire field of view of an eyepiece.

My 12mm and 17mm ES-92s exactly tick that box, so I have no incentive to get the 16.5mm XW.  My XL, XW, Hi-FW, Delos, and Morpheus eyepieces all provide at least 18mm of usable eye relief, so are also quite comfortable to observe with.  I've held off purchasing the 23mm XW to replace my 22mm NT4 because I've read that the eye relief is marginal for eyeglass wearers.

Hi again @Louis D... I see that you and @Don Pensack did discuss this here... so I've linked it in case any use to anyone 👍

 

 

[John]

3 hours ago, HollyHound said:

Hi again @Louis D... I see that you and @Don Pensack did discuss this here... so I've linked it in case any use to anyone 👍

 

 

I had completely forgotten that I started that thread back in March 🙄

I don't wear glasses when observing and find 10mm and upwards of eye relief fine. 

[Hans Joakim]

Anyone using the XW 85 with Dioptrx? Curious to hear if the resulting eye relief feel comfortable!

[Stu]

1 hour ago, John said:

I had completely forgotten that I started that thread back in March 🙄

I don't wear glasses when observing and find 10mm and upwards of eye relief fine. 

Have you seen any of the CN threads John? I suspect you have but I found this one for instance…

https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/page-14?hl= pentax 85

[John]

1 hour ago, Stu said:

Have you seen any of the CN threads John? I suspect you have but I found this one for instance…

https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/page-14?hl= pentax 85

Thanks Stu. I have seen those. I probably started one of them. I was looking for an SGL-slant on these eyepieces with this thread 🙂

[HollyHound]

3 hours ago, Hans Joakim said:

Anyone using the XW 85 with Dioptrx? Curious to hear if the resulting eye relief feel comfortable!

As mentioned in my post above, I have fitted a Dioptrx within the eyepiece of my XW40, which works perfectly. I’ve yet to try or need to do the same in my XW16.5, but will certainly try it when I get the XW23 🤔👍

[Don Pensack]

1) the 85° eyepieces are not compatible with glasses unless the distance from your eye to the lens is very very short.

I tried it, but I had to jam the glasses lens into my eye socket to the point my eyelashes brushed the eyeglasses every time I blinked and it made my glasses hurt.

So I don't regard them as eyeglasses compatible.  And I can use eyepieces with as little as 14.5mm from the rubber up at 85°.

 

2) They are not compatible with the DioptRx unless the DioptRx is somehow attached to the rubber eyecup.  I regard these eyepieces as incompatible with the DioptRx.

Since the eye relief is only 12mm from the rubber up and the DioptRx eats up about 8mm of eye relief, even if you could attached the DioptRx, you'd have almost no eye relief left.

 

3) the 16.5mm has a flat field, no vignetting, and sharp stars.  The 23mm had noticeable vignetting at the edge of the field, but I note that I used the eyepieces with a Paracorr so I would not

evaluate the edges of the field with coma present, and it is possible some of the vignetting is from the Paracorr.  I did not look to see if the vignetting disappeared without the Paracorr

because then nearly the entire field would have visible coma.  Even with vignetting, the edge of field was nice and sharp--not perfect on the 23mm, but very good.

 

So, I think these are very good eyepieces for an observer who does not wear glasses.  It would be a rare glasses-wearing observer who could use them with glasses.

Edited December 5, 2023 by Don Pensack

[michael.h.f.wilkinson]

Sounds I should stick to my ES 17mm 92 deg and Nagler 22 T4. Both work fine with glasses, and are very sharp across the field, even in my fastest scope (the Meade SN-6 6" F/5 Schmidt-Newton). The ES 12mm 92 deg is great as well. Much as I love my Pentax XWs at shorter focal lengths, I don't think I will try these 85 deg offerings.

[John]

So, as someone who does not wear glasses when observing, I can experience some 85 degree Pentax goodness if and when I feel the urge 😁

Many thanks for the feedback and your thoughts folks 👍

Next decision is whether these will run alongside my Ethos 21mm and 13mm or replace them 🤔

The prospect of an all Pentax line-up is quite tempting:

3.5mm - 5mm - 7mm- 10mm - 16.5mm - 23mm - 40mm

Edited December 5, 2023 by John

[globular]

I have the 7, 10, 16.5 and 40 XWs.  They are all fabulous.
I didn't get the 23 because I already have a very nice N22T4.
I haven't got the 3.5 and 5 (yet) because I don't (yet) have a scope that would make regular use of them.  I will get them when I do.

[michael.h.f.wilkinson]

I have the XW 5, 7 and 10 mm and they are absolutely great. I am sometimes tempted to get a 3.5mm which could be useful in the 6" F/5 Schmidt-Newton for planetary, but in my C8 (which is my main planetary scope) it would be essentially useless, and the 6" F/5 is really more of a wide-field performer (although it works well on planets and moon too).

[Elp]

Is the 5 or 7 worth getting if I already have a 10 and a 2.5x Powermate? Also already have an ES 6.7 but enjoy the LER comfort of the XWs.

[John]

I have the 3.5, 5 and 7 XW's. Can't fault them. Ethos performance, more eye relief, less AFoV. Much less £'s.

That's my summary 🙂

[Elp]

1 hour ago, John said:

I have the 3.5, 5 and 7 XW's. Can't fault them. Ethos performance, more eye relief, less AFoV. Much less £'s.

That's my summary 🙂

If you could only have one of them, which one?

[John]

6 minutes ago, Elp said:

If you could only have one of them, which one?

Well, the 5mm is probably the most used but the others are just as good in performance terms.

[michael.h.f.wilkinson]

1 hour ago, Elp said:

Is the 5 or 7 worth getting if I already have a 10 and a 2.5x Powermate? Also already have an ES 6.7 but enjoy the LER comfort of the XWs.

I like the fact that they are parfocal (and I made my Delos 8 and 6 mm parfocal with the XWs). Switching magnification to adjust to variable seeing is much easier this way than when I used a 2x TeleXtender or 2.5x PowerMate . The XW with a Meade TeleXtender (similar to a PowerMate) is fine, optically, but the position of focus shifts by a huge amount. I much prefer my current planetary set-up. BTW, the Vixen SLVs perform with near XW performance with a reduced FOV, and they are also parfocal with the XWs

[IB20]

I have the 3.5, 5, 7 & 10. They sit in my diagonal 99% of the time, I think they’re the bee’s knees and are incredibly comfortable. It’s a pleasure having extended sessions with them. Don't use 2” EPs but I’d be sniffing round these and the longer FL originals if I did!