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Pentax XW versus DeLite

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#1 Heywood

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Posted 30 June 2020 - 04:14 PM

How do the Pentaxes compare to the DeLites, in terms of ease of viewing? About the same?

Do the Pentax XW's have a full 20mm of effective eye relief?

Edited by Heywood, 30 June 2020 - 04:22 PM.


#2 Deep13

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Posted 30 June 2020 - 05:02 PM

Pentax XWs each have 20mm of eye relief. They also have a 70 deg. AFOV.

#3 Starman1

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Posted 30 June 2020 - 05:20 PM

How do the Pentaxes compare to the DeLites, in terms of ease of viewing? About the same?

Do the Pentax XW's have a full 20mm of effective eye relief?

No.  More like 17mm effective eye relief on the Pentax due to the inset.

It's 20mm from the glass.


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#4 StarDust1

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Posted 30 June 2020 - 05:33 PM

I use both Pentax XW and Delite with glasses without issue. Though I do have issues with glasses with other eyepieces that have 16-17mm eye relief.



#5 russell23

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Posted 30 June 2020 - 05:35 PM

I’ve never had an issue using glasses with the Pentax XW. 



#6 Heywood

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Posted 30 June 2020 - 06:40 PM

No.  More like 17mm effective eye relief on the Pentax due to the inset.

It's 20mm from the glass.

 

Very interesting!!!  How about the effective eye relief of the DeLites and Deloses?



#7 25585

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Posted 30 June 2020 - 07:04 PM

No.  More like 17mm effective eye relief on the Pentax due to the inset.

It's 20mm from the glass.

For 3.5, 5 & 7mm, the 62° Delites are easier viewing, better exit pupil behaviour, closer to Vixen LVWs and Pentax XLs in those focal lengths, both of which were 65°, both discontinued.  

 

But for 10mm & longer, Pentax XWs are more comfortable I find.

 

Perhaps the steadiness of small exit pupils that short FL eyepieces have, present too much design optical challenge for longer eye relief and AFOVs of 70° & more?


Edited by 25585, 30 June 2020 - 07:06 PM.

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#8 Miranda2525

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Posted 30 June 2020 - 07:51 PM

How do the Pentaxes compare to the DeLites, in terms of ease of viewing? About the same?

Do the Pentax XW's have a full 20mm of effective eye relief?

XW's have very good eye relief. I can wear my glasses while using them. They are both good.


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#9 Miranda2525

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Posted 30 June 2020 - 07:52 PM

For 3.5, 5 & 7mm, the 62° Delites are easier viewing, better exit pupil behaviour, closer to Vixen LVWs and Pentax XLs in those focal lengths, both of which were 65°, both discontinued.  

 

But for 10mm & longer, Pentax XWs are more comfortable I find.

 

Perhaps the steadiness of small exit pupils that short FL eyepieces have, present too much design optical challenge for longer eye relief and AFOVs of 70° & more?

I own a 5mm and 7mm XW and both are as comfortable as the others.


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#10 Miranda2525

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Posted 30 June 2020 - 07:53 PM

Very interesting!!!  How about the effective eye relief of the DeLites and Deloses?

Effective eye relief of these are a bit better than the XW's. You have more "breathing room" with the Delites and Delos compared to the XW's.



#11 213Cobra

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Posted 30 June 2020 - 08:51 PM

I have all the Pentax 1.25" XWs and the full set of DeLites. DioptRx can be installed on both, though better on the DeLites, at focal lengths necessary (10mm and longer for me). Nevertheless, I would use the preferred set, either way.

 

Both are serious glass. I'll just say that the Pentax XW have been relegated to the role of guest eyepieces only. I use DeLites routinely and they earned that place in my rotations.

 

Phil



#12 Heywood

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Posted 30 June 2020 - 10:46 PM

No.  More like 17mm effective eye relief on the Pentax due to the inset.

It's 20mm from the glass.

 

Can you tell me the effective eye relief of the DeLites?  Deloses?

 

Thank you!



#13 Starman1

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Posted 01 July 2020 - 12:35 AM

Don't know. However, of the 3: XW, Delite, Delos, the XW seems to have the least effective eye relief. Still, they're usable by many glasses wearers.

#14 25585

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Posted 01 July 2020 - 07:06 AM

The Delites I own have no eye placement issues in respect of exit pupil steadiness, while Delos & some XWs are more bothersome.

 

For out of the box user-friendliness, Delites are the winners.



#15 Heywood

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Posted 01 July 2020 - 07:22 AM

Don't know. However, of the 3: XW, Delite, Delos, the XW seems to have the least effective eye relief. Still, they're usable by many glasses wearers.

That is very good to know.  Thank you!



#16 BillP

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Posted 01 July 2020 - 06:04 PM

No.  More like 17mm effective eye relief on the Pentax due to the inset.

It's 20mm from the glass.

Just for jollies, I just measured the ER of my 14XW.  Optical ER from the center of the eye lens surface was 22mm (1).  The eye lens is inset into the housing 5mm, making the usable ER with the top rubber guard unscrewed 17mm (2).  The top rubber guard protrudes another 3mm when it is installed making the usable ER 15mm (3).

 

(1) multiple measures an always the same, 22mm

(2) confirmed by both measuring the ER from that point and measuring the inset depth of eye lens

(3) confirmed by both measuring the ER from that point and measuring the inset depth of eye lens

 

So usable ER on the 14XW was either 15mm or 17mm if you removed the top rubber guard.


Edited by BillP, 01 July 2020 - 06:11 PM.

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#17 25585

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Posted 02 July 2020 - 10:09 AM

Just for jollies, I just measured the ER of my 14XW.  Optical ER from the center of the eye lens surface was 22mm (1).  The eye lens is inset into the housing 5mm, making the usable ER with the top rubber guard unscrewed 17mm (2).  The top rubber guard protrudes another 3mm when it is installed making the usable ER 15mm (3).

 

(1) multiple measures an always the same, 22mm

(2) confirmed by both measuring the ER from that point and measuring the inset depth of eye lens

(3) confirmed by both measuring the ER from that point and measuring the inset depth of eye lens

 

So usable ER on the 14XW was either 15mm or 17mm if you removed the top rubber guard.

That's less than my XL14mm (which can be fully decloaked as well), and Vixen LVW 13mm with cup its cup flat. Both are full FoV wearing glasses.

 

https://astromart.co...nd-xw-eyepieces


Edited by 25585, 02 July 2020 - 10:10 AM.


#18 gnowellsct

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Posted 02 July 2020 - 11:09 PM

I have an aversion to products that incorporate "lite" into their name.


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#19 25585

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Posted Yesterday, 04:28 AM

I have an aversion to products that incorporate "lite" into their name.

The "lite" part of Delite is AFOV, only 62°. Did TV really have to drop that low to design an eyepiece range with long eye relief & good exit pupil behaviour? Design or designer limits?



#20 j.gardavsky

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Posted Yesterday, 05:41 AM

I have an aversion to products that incorporate "lite" into their name.

... yes,

especially when it is about the drinks,

JG


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#21 j.gardavsky

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Posted Yesterday, 05:47 AM

The "lite" part of Delite is AFOV, only 62°. Did TV really have to drop that low to design an eyepiece range with long eye relief & good exit pupil behaviour? Design or designer limits?

For the wide field, long ER, and good EP behaviour you need some glass materials which have both the high refractive index and a lower dispersion.

The Corning optical glass is expensive, that's the answer.

 

Best,

JG



#22 25585

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Posted Yesterday, 06:25 AM

For the wide field, long ER, and good EP behaviour you need some glass materials which have both the high refractive index and a lower dispersion.

The Corning optical glass is expensive, that's the answer.

 

Best,

JG

Interesting. I don't remember reading about Corning glass on CN before.

 

Maybe Delites were designed to a price bracket (& Delos too), hence their small AFOV, size and top FL limits. 


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#23 gnowellsct

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Posted Yesterday, 06:39 AM

Interesting. I don't remember reading about Corning glass on CN before.

Maybe Delites were designed to a price bracket (& Delos too), hence their small AFOV, size and top FL limits.


Sort of. The ZAO II oculars were $600 apiece and you had to buy a set of 4. They featured 25% less afov and half the eye relief.

A Camry offers a nice comfortable ride and dependability for $25000. For four times as much you can have a Porsche that carries fewer passengers and transfers every crack in the road direct to your butt and reliably breaks down every 10k miles.
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#24 j.gardavsky

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Posted Yesterday, 01:18 PM

Interesting. I don't remember reading about Corning glass on CN before.

 

Maybe Delites were designed to a price bracket (& Delos too), hence their small AFOV, size and top FL limits. 

Most of the optics is designed on its purpose (typical use), according to a list of specifications, and for a price tag.

 

In 1989, Leitz has transferred manufacturing of its 30 proprietary glass materials to Corning,

1 Leitz proprietary ED glass has been transferred to Schott. So far the published announcements from those times.

 

Every designer and manufacturing can order the expensive glass materials from whatever source,

but it is much cheaper to avoid them, taking the CDGM glass from China.

 

Best,

JG


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#25 Starman1

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Posted Yesterday, 03:20 PM

Interesting. I don't remember reading about Corning glass on CN before.

 

Maybe Delites were designed to a price bracket (& Delos too), hence their small AFOV, size and top FL limits. 

TeleVue uses Japanese glass in all their eyepieces.  It is known.

 

Delites are 62° because:

--the series replaces the long unavailable Radian line

--a less expensive eyepiece was desired

--a long eye relief was desired, but in a smaller, more binoviewer-friendly structure.

--it's a logical line to have between 50° and 72° when you already have 82° and 100° lines.

 

What should be next is a long eye relief replacement line for the Plössls that runs from 3mm to 32mm and costs, perhaps, 70% of the Delite price.

But, the market really thinks of 50° eyepieces as cheap, so they'd be harder to sell than a 62° line.

Plus, what would you get with 52° that you don't already get with 62°, except a lower price.

And the miserable sales of Vixen SLVs, a premium long eye relief 50° line says TeleVue might be right in avoiding such a line altogether.


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