If I were to chop my Pentax XW 10mmm.......gasps heard...

[martinl]

1 hour ago, Alan White said:

As an update, it was a terrible, terrible mistake!
I have kept the 22mm LVW and added a 13mm and now an 8mm.

Gosh! Someone on the interwebs admitting to having made a mistake! That has got to be a first!

The upside of staying within one line of EPs is parfocality (assuming they’re all the same generation of LVWs) and similarity of presentation.  I very nearly got a full set of LVWs at end-of-sale prices when I remodelled my EP kit and sometimes regret I didn’t. Enjoy!

[scarp15]

53 minutes ago, 25585 said:

Ditto the Vixen LVW 5mm. Pentax slightly more refined, but at my max mag of 100x, nothing between them optically.

Can only compare with my Delite and Delos, I like the cool colour tone of the XW for lunar observing. 

[Alan White]

8 hours ago, martinl said:

Gosh! Someone on the interwebs admitting to having made a mistake! That has got to be a first!

The upside of staying within one line of EPs is parfocality (assuming they’re all the same generation of LVWs) and similarity of presentation.  I very nearly got a full set of LVWs at end-of-sale prices when I remodelled my EP kit and sometimes regret I didn’t. Enjoy!

Folks only gushing about how good everything is and then ending selling it soon after show on many internet sites,
My view is put a journey online, then report on the WHOLE journey, however painful that is.
Keeps things informative and accurate.

Parfocal is good, but I am not worried about a mixed bag, just must have some parfocal within a range of steps.
 

 

[25585]

Smaller your TFOV, the more important parfocal is. For hand guided high magnifications a zoom is a good compromise. 

[John]

1 hour ago, 25585 said:

Smaller your TFOV, the more important parfocal is. For hand guided high magnifications a zoom is a good compromise. 

I've noticed that even zooms are not entirely par-focal. You do need to adjust the focus slightly after altering the focal length.

 

[Timebandit]

1 hour ago, 25585 said:

Smaller your TFOV, the more important parfocal is. 

 

48 minutes ago, John said:

I've noticed that even zooms are not entirely par-focal. You do need to adjust the focus slightly after altering the focal length.

 

 

I'm not particularly worried about eyepieces being parfocal. And a bit of adjustment if needed just does not concern me(as long as it is not over the top). Maybe I am a bit strange like that? 

My main attributes I want is that the eyepiece to produce a sharp crisp image across fov. To have a fov that frames the target nice. And will work well in all my scopes ranging from reflector and refractor at f/4.5 to f/ 7.6. The Pentax XW has done that . So in my opinion a "complete eyepiece" for my needs.

 

 

 

[25585]

I think the best newest ep out to that end is the Baader Morpheus 17.5mm. It is their finest optic IMHO. 

[michael.h.f.wilkinson]

They can take my three XWs (5, 7, and 10 mm) out of my cold, dead hands! I have a Delos 8 and 6mm with parfocalizer rings in between: planetary observing heaven. For light-weight travel, I have a brace of Vixen SLVs: 5, 9, and 15mm: very, very close to XW performance, in all except FOV, very nice and light.

[25585]

1 hour ago, michael.h.f.wilkinson said:

They can take my three XWs (5, 7, and 10 mm) out of my cold, dead hands! I have a Delos 8 and 6mm with parfocalizer rings in between: planetary observing heaven. For light-weight travel, I have a brace of Vixen SLVs: 5, 9, and 15mm: very, very close to XW performance, in all except FOV, very nice and light.

The original LVs, which are becoming scarcer on the pre-owned market, are more compact still. Almost collectible these days; 5, 10, 18, 20s & zooms have their own niche in my collection. 

[Louis D]

15 hours ago, martinl said:

The upside of staying within one line of EPs is parfocality

Except for the TV Ethos.  Take a look at column F of the Televue eyepiece specs page which lists the offset of the focal plane from the eyepiece shoulder.  They're all over the place.  I assume their users parfocalize them in some manner to make them more usable.

[michael.h.f.wilkinson]

1 hour ago, 25585 said:

The original LVs, which are becoming scarcer on the pre-owned market, are more compact still. Almost collectible these days; 5, 10, 18, 20s & zooms have their own niche in my collection. 

I had two LVs: the 7 and 9 mm. Optically they were fine, but I hated their stiff rubber eye-cup. You couldn't put a cap on them when folded back, and I could use them when they were not folded back. The 7mm had a bit of a warm tone, whereas the 9 was more neutral. I replaced them with the 8 and 10 mm Radians (similar warm tone to the LV 7, slightly better off-axis performance), which were in turn replaced by XWs (distinctly more neutral, better wide-field performance, more comfy). I can only compare the SLV 5 with the XW 5 directly, but the performances are very, very similar, apart from FOV. My impression is that they are very neutral in tone, and slightly sharper than the original LVs. I also much prefer their eye-cup design

[John]

1 hour ago, Louis D said:

Except for the TV Ethos.  Take a look at column F of the Televue eyepiece specs page which lists the offset of the focal plane from the eyepiece shoulder.  They're all over the place.  I assume their users parfocalize them in some manner to make them more usable.

I use Baader Fine Tuning Rings on the 13mm, 8mm and 6mm Ethos, which helps, but there is still some re-focussing required. The 8 and 6 are par-focal though. The 21 is par-focal with the 31mm Nagler so it's the 13mm that needs the most tweaking.

I've owned and used a few of the original Vixen LV's. They were very good eyepieces 2 decades ago and are still comfortable and reasonably sharp but their light transmission is noticably lower than, say, the SLV's with their more moden glass and coatings technologies.

 

[25585]

2 hours ago, John said:

I've owned and used a few of the original Vixen LV's. They were very good eyepieces 2 decades ago and are still comfortable and reasonably sharp but their light transmission is noticably lower than, say, the SLV's with their more moden glass and coatings technologies.

 

I have noticed this, even on the 2 inch models. 

[Louis D]

I'm wondering if it's the Lanthanum glass causing this.  TV Radians also used Lanthanum and some folks have reported either a darkened view or a coffee tone added to the view.  More recent designs have ditched rare earth glasses because their prices have shot up since the Chinese cornered the market on rare earths.  Without rare earth glasses, I've noticed recent designs don't use as radically curved surfaces as some earlier designs.  I think that's because rare earth glasses had a high index of refraction allowing for these radical curves.

[25585]

18 minutes ago, Louis D said:

I'm wondering if it's the Lanthanum glass causing this.  TV Radians also used Lanthanum and some folks have reported either a darkened view or a coffee tone added to the view.  More recent designs have ditched rare earth glasses because their prices have shot up since the Chinese cornered the market on rare earths.  Without rare earth glasses, I've noticed recent designs don't use as radically curved surfaces as some earlier designs.  I think that's because rare earth glasses had a high index of refraction allowing for these radical curves.

Vixen LVWs and Pentax XWs use earth glass but have bright images, so its not that IMO. The price has gone up, probably why Synta have dropped known types from their ED scopes such as the new 72 and 150 models.