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Walking on the Moon

New 85 degree Pentax XWs on the way


Highburymark
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It is of course the 14mm and 20mm EPs in the current range which show field curvature in many scopes. If the new XWs are up to the standards of the rest of the range, and I wouldn’t bet against it, then they are going to prove very popular. No news yet whether the 14mm and 20mm will be discontinued.

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Interesting! Yes hopefully they’ve addressed the common complaint about fc 

Mark

edit- of course they did :) 

“The new eyepieces feature a new optical system with 7 elements in 5 groups that surpasses the performance of the conventional XW series to obtain sharp star images all the way to the edge of the field of view.”

from the same press release they’re aiming squarely at us astro users too (rather than spotting scopes) This makes me happy as I feared Pentax (Ricoh) had abandoned us

“The new smc PENTAX XW16.5 and smc PENTAX XW23 deliver an apparent field of view of 85° -- the widest viewing angle in the XW series, suitable for observing nebulae and star clusters.“

They’re huge though- heaviest in the lineup but i guess that was to be expected.

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Edited by markse68
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Hopefully edge correction is better than in the 30mm and 40mm XWs.  The 30mm suffers from edge chromatic aberrations and the 40mm from edge astigmatism and field curvature, and they're only 70 degrees.  The 23mm appears to be almost identical in size to the 30mm while the 16.5mm will be a bit taller.

With MSRPs of $479.95 for the 16.5mm and $499.95 for the 23mm, I'd have to think long and hard about buying them since I already have the 17mm ES-92 and 17mm and 22mm Nagler T4s.  What I really want is for ES to release a 23mm to 26mm ES-92.

I'll take a wait and see attitude toward these new XWs for now.

Press release image:

spacer.png

Here's a couple of press releases I found about them.

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4 hours ago, Louis D said:

Hopefully edge correction is better than in the 30mm and 40mm XWs.  The 30mm suffers from edge chromatic aberrations and the 40mm from edge astigmatism and field curvature, and they're only 70 degrees.  The 23mm appears to be almost identical in size to the 30mm while the 16.5mm will be a bit taller.

With MSRPs of $479.95 for the 16.5mm and $499.95 for the 23mm, I'd have to think long and hard about buying them since I already have the 17mm ES-92 and 17mm and 22mm Nagler T4s.  What I really want is for ES to release a 23mm to 26mm ES-92.

I'll take a wait and see attitude toward these new XWs for now.

Press release image:

spacer.png

Here's a couple of press releases I found about them.

ES told me several years ago that 22mm was the maximum possible focal length for the 92° series, but that they were a bit scared to make it because it would be well over 3 lbs and physically larger than the 17mm.

They thought that 2 shorter (than 12mm) focal lengths would come first.  Then came slowdowns in production at JOC, then CoVid and then supply chain shortages.  

It seems to me that the 92° eyepieces have priced themselves out of the market in the US, though prices are more reasonable in the UK and EU.

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Ricoh told me they have no intention to discontinue the 14mm and 20mm 70° XW.

The XW85 will be a new series.  If successful, and I think they will be, it is likely these will only be the first focal lengths in the series.

More of concern is that though they give a 20mm eye relief from the glass, they are stating only a 12mm eye relief from the rubber eyecup, ruling out glasses use.

If there is a way to modify the top and change the eyecup to yield more eye relief, then they would be sold to glasses wearers.

As soon as I get my hands on them, I will investigate this.

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4 hours ago, Louis D said:

Hopefully edge correction is better than in the 30mm and 40mm XWs.  The 30mm suffers from edge chromatic aberrations and the 40mm from edge astigmatism and field curvature, and they're only 70 degrees.  The 23mm appears to be almost identical in size to the 30mm while the 16.5mm will be a bit taller.

 

Interesting - I see some colour with the 5mm too, the only XW I own, but not that it would diminish my enjoyment of the eyepiece.

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2 minutes ago, Don Pensack said:

Ricoh told me they have no intention to discontinue the 14mm and 20mm 70° XW.

The XW85 will be a new series.  If successful, and I think they will be, it is likely these will only be the first focal lengths in the series.

More of concern is that though they give a 20mm eye relief from the glass, they are stating only a 12mm eye relief from the rubber eyecup, ruling out glasses use.

If there is a way to modify the top and change the eyecup to yield more eye relief, then they would be sold to glasses wearers.

As soon as I get my hands on them, I will investigate this.

Good info Don. Presume the 14mm and 20mm still sell well with spotting scope users - popular focal lengths for daytime observing

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29 minutes ago, Don Pensack said:

More of concern is that though they give a 20mm eye relief from the glass, they are stating only a 12mm eye relief from the rubber eyecup, ruling out glasses use.

If there is a way to modify the top and change the eyecup to yield more eye relief, then they would be sold to glasses wearers.

They look like they will have the same removeable top section as the other XWs so probably have the 43mm thread that a TV Dioptrix could be mounted to? 

Mark

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7 hours ago, markse68 said:

They’re huge though- heaviest in the lineup but i guess that was to be expected.

They're only about the same weight as, or a little over, the XW30, and compared to my Axiom LX 23mm and 31mm (both 82 degrees) they are lightweights..

I'd be more concerned about  field curvature and edge sharpness..the FC in my former XW14 and 20 was bad enough at F8 to prompt me to change them, the 14mm for a Morpheus 14 and the 20mm for a Vixen LVW 22 which I found better in every respect but fov size.

Then, last year I bought an XW 30mm in the FLO sale and when I compared it to my Axiom 31mm the latter beat it comprehensively in my FS128, so it went back.. I was very disappointed with the XW30, especially given the sky high used prices the old XW30s went for before the relaunch.

I really want Pentax to succeed in the longer focal lengths: their shorter 3.5 to 10mm focal lengths are superbly good (as are the older XL range)..if Ricoh have truly sorted out and eliminated the FC and edge sharpness issues at the new, longer focal lengths, they will I'm sure prove very successful.

But the market for UWA premium eyepieces is very competitive these days, so pricing will also be important.

I look forward to reading some reviews before long and wish Ricoh well with this initiative.

Thanks for sharing the news, Mark👍.

Dave

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1 hour ago, Highburymark said:

Interesting - I see some colour with the 5mm too, the only XW I own, but not that it would diminish my enjoyment of the eyepiece.

So does my 7mm XW at the edge.  My old 5.2mm XL does not.  I've never detected any aberrations edge to edge in it.

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1 hour ago, Don Pensack said:

ES told me several years ago that 22mm was the maximum possible focal length for the 92° series, but that they were a bit scared to make it because it would be well over 3 lbs and physically larger than the 17mm.

That seems odd.  They make a 25mm ES-100 (with a touch of vignetting).  It seems like 23mm to 26mm at 92 degree should be doable.

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1 hour ago, Don Pensack said:

More of concern is that though they give a 20mm eye relief from the glass, they are stating only a 12mm eye relief from the rubber eyecup, ruling out glasses use.

Missed that.  I'm out unless screwing off the upper ring restores most of that eye relief.  Despite my 40mm XW's eye lens being recessed 7.5mm, I still measure 17mm of usable eye relief rather than the 15mm quoted in the chart up above.  There is a threaded ~6mm tall metal lip above the glass.  I suppose you could machine it off if you didn't want to be able to thread on the eyecup any longer and get to about 22mm of eye relief.  Perhaps something like this could be done with the new XW85s.

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3 hours ago, markse68 said:

They look like they will have the same removeable top section as the other XWs so probably have the 43mm thread that a TV Dioptrix could be mounted to? 

Mark

Let's do the math.

A 20mm eye relief from the glass at 85° means the eye lens must be 36.7mm wide (exposed part).

I'll presume a 39mm lens diameter to the edge and a 1.5mm wall thickness of aluminum around the edge = 39mm + 3mm = 42mm.

So it is indeed possible there could be a 43mm thread under the eyecup, like the other XWs.

If so, a Baader Morpheus eyecup could be threaded on and, folded down, likely increase the effective eye relief enough to use glasses.

3 hours ago, Louis D said:

That seems odd.  They make a 25mm ES-100 (with a touch of vignetting).  It seems like 23mm to 26mm at 92 degree should be doable.

15mm of eye relief = smaller lenses. (100° and 15mm eye relief = 35.7mm exposed eye lens)

     all lenses below the eye lens can also be smaller.

20mm of eye relief = larger lenses (92° and 20mm eye relief = 41.4mm exposed eye lens)

 

To wit, the 25mm 100° weighs 1176g

The 17mm 92° weighs 1159g

A 22mm with the same characteristics could be 1450g (3.2 lbs).

I can see why they might hesitate.  Especially if it has to sell for ~$1000 in the US.

2 hours ago, Louis D said:

Missed that.  I'm out unless screwing off the upper ring restores most of that eye relief.  Despite my 40mm XW's eye lens being recessed 7.5mm, I still measure 17mm of usable eye relief rather than the 15mm quoted in the chart up above.  There is a threaded ~6mm tall metal lip above the glass.  I suppose you could machine it off if you didn't want to be able to thread on the eyecup any longer and get to about 22mm of eye relief.  Perhaps something like this could be done with the new XW85s.

Eye relief is measured from the glass, so whatever is above it, if machined off, will not increase the eye relief of the eyepiece.

It will, however, increase the effective eye relief for glasses wearers.

A Morpheus eyecup increases the effective eye relief on the 70° XW.  I'm hoping it will do the same for the 85° versions.

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I can use glasses with all the 70° XW eyepieces. According to the above chart the affective eye relief of the 70° XW is 15mm. The new  90° XW eyepieces have affective eye relief of 12mm, that's only 3mm shorter. It might be that it will be difficult to use glasses as the AFOV of 90° XW is wider then the 70° XW. It would be a disappointment for some of us if the  90° XW eyepieces can't be used with glasses, only because of the design, that's the rubber eye cup.

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Regarding eye-relief. If you wear eyeglasses to correct far-sighted or nearsightedness you can take them off when observing through a telescope. Simply adjust the focuser to sharpen the view. Eyeglasses are not required. 

If however you wear eyeglasses to correct astigmatism then you might need to wear them while observing (mostly when observing at lower magnifications). 

Regarding optimum eyepiece eye-relief for eyeglass wearers, this varies person-to-person but most find around 15-20mm works well.

We and most other specialist astronomy retailers will understand if you buy an eyepiece then choose to return it because it doesn't suit your eyesight / eyeglass requirements. It isn't a problem. 

HTH, 

Steve 

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14 minutes ago, markse68 said:

Hi Don, off topic sorry but is there a way to calculate the afov of an eyepiece given the field stop and focal length?

Mark

If there aren't too many distortions produced within the eyepiece then the following formula works well:

  field stop           180
-------------    x   -----   =   FOV
focal length           π

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25 minutes ago, globular said:

If there aren't too many distortions produced within the eyepiece then the following formula works well:

  field stop           180
-------------    x   -----   =   FOV
focal length           π

Thanks Glob, that seems to give realistic sounding values 👍

Mark

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