[lachlustre]

Well... thanks for all the responses! A couple of follow-ups:

It seems that everyone would strongly recommend the xw line of eyepieces for making the scope field-proof. This was a bit disappointing: I was hoping that, magically, waterproofing was somehow less important for the eyepiece than the body, but what you all said sounds eminently sensible.

However, my first thought is that using the xw line (partially) negates many of the advantages of the Pentax in general, especially with regard to price! Instead of the Pentax being around 50% of the price of the Zeiss Diascope, It will come out around 70%, in my estimation (850 Euro versus 1230 Euro). Second, the Pentax SMC/XW zoom weighs about 50% more than the Zeiss one. Henry Link's tests find that optically the Pentax zoom is somewhat inferior to the competitors. I also read an astronomical review where the pentax zoom lens wasn't rated especially highly, in use, compared to much cheaper alternatives: http://www.jimrichberg.com/astronomy...lar_review.htm. On the other hand, BetterViewDesired discussed the large zoom lens in its review of the Pentax 80 scope (http://betterviewdesired.com/Pentax/index.html), and came up with a glowing assessment, and SoutFork suggested that it was as good as anything else available. I don't think I've read about any owner of the XW zoom lens who loves it, which is interesting contrast to the number of people who proclaim how happy they are with the XW fixed length scope.

Putting this all together: is the Pentax such a good deal after all? One possibility, that I haven't actually heard expressed directly, is that birding with the Pentax + xw fixed eyepiece is actually superior to using the Zeiss 65mm. Any takers? A lot of you are suggesting/hinting that zoom lenses are not worth it anyway. As a novice, I like the general idea of a zoom, for finding birds, and for experimenting with different magnifications. Maybe the best combination is: Pentax body + cheap-ish zoom (pick one from this thread) PLUS XW 14 fixed lens. The fixed lens would then be my primary birding equipment. On the 7 days a year it is dry here, and when I'm on vacation somewhere dry, I can play with the zoom. How does that sound for a scoping experience? Better than a Zeiss? Equal to a Zeiss? Inferior enough that I should suck it up and pay the extra money.

Wow, another long post. And not even any coffee to blame...

[lachlustre]

Henry,

I suppose what I am looking for really is for the scope to be generally usable in fairly poor weather conditions. I googled the JIS scale, and the web page I found (and if its on the web, it must be accurate) says that JIS 4 is splash proof; JIS 6 is water-tight - meaning that "direct jets of water from any direction would not enter the enclosure" (Birding relevance: getting splashed by a surprise large wave standing at the coast, perhaps?). JIS 8 is the mark for continuous submerged usage. I would guess from that that JIS 4 would be adequate for my needs, with a bit of caution. Would you agree?

Rob

[henry link]

Rob,

Under the poor weather conditions you describe fogproof may be as important as waterproof. I don't think "splash proof" to JIS 4 could be counted on to prevent eventual moisture penetration and internal fogging of the Pentax XW eyepieces. It might not happen, but they are not sealed to a standard that guarantees it won't. Zeiss claim water and fogproofing for their scopes conforms to ISO standard 9022-8. That is probably at least as good as JIS 6.

As always with scopes, the optical quality of the particular specimen you buy is as important as the brand you choose. I've seen both bad and good samples of Zeiss and Pentax scopes.

Henry

[devouges]

Hi,
I have a CP4500 and the XW14 with a 28-43 stepup ring. I find that it has a lot of vignetting. Does the XW20 have a lot of vignetting ?
Thanks
gary

Originally Posted by mmdnje

I have a pentax XW20mm, Orion stratus 13mm and DCL-28(24mm). For general birding I prefer the XW20. For handheld digiscoping I'm using the orion 13mm with a fuji S5100 (no vignetting at wide angle). The DCL-28 is great for digiscoping with my CP4500 although sometimes the magnification is not enough.
If I had to choose one to keep, I'll keep the XW20 to wich I can also attach the CP4500 with a step-up ring as it has a 43mm thread. Jose Navarrete

[mmdnje]

Hi devouges. No, there is not a lot of vignetting. Just a little in the corners. I'll post later an uncropped picture taken with CP4500 and XW20 using a 28-43mm step ring. I've got to finish something now but look for the pic in this thread later. Jose
OK, I edited the post. Here is the pic 100% crop and resized. I have a 13mm 68degrees of FOV and do not get any vignetting using the CP. I onla have used handheld. In my gallery there is a picture posted yesterday using the CP4500 and the 13mm eyepiece that should have similar performance compared to thje pentax XW14. Let me know what your conclusions are. Jose

[Sout Fork]

For some time now I have had what I consider a big hole in my EP collection.

Because I do a lot of long distance field surveys I have felt the need
for a really high quality 50X plus fixed EP.

I could use my Zoom but it really didn't cut it. Too dark and narrow and a bit soft.
It's not the fault of the zoom. I have used and/or borrowed practically
every combination of scope brand and zoom and in my opinion they all are
unacceptable at much over 40x on a 80mm at distances over half a mile.
Of course that mile or so of air between the bird and your objective is
also part of the optical system but I can't do anything about that.

So after much research and thought I bit the bullet and bought a Pentax
XW 10mm (52X).

Have had only one dark over-cast day to use it looking at the feeder
birds but a few first impressions...

Looking through it rather than at it...
Compared to the only other EP close to it the Stratus 13mm (40X). Given
the difference in power the Pentax obviously has greater contrast and
light transmission. Obviously sharp right out to the edges. In fact it
feels as though the field stop is just a mask and that the sharpness
continues under the field stop. Also the the FOV seems greater than the
2 degree difference would seem to indicate.

My big concern was brightness at this power. While not as bright as the
40X Stratus the difference is not nearly as much as it would be using
the zoom at 52X.

Have not been able to use it as I intend to but next week I'm scheduled
to be down on the river bottoms again with the same Fish and Wildlife
employee I mentioned in a previous post. I happen to know he has a 11mm
Nagler so perhaps I can make a direct comparison on my scope. If so
I'll let you know how it goes.

Take care all

[henry link]

I think you will find that the best zooms have light transmission and center sharpness as good or better than complex wide field eyepieces like the Pentax XW or TV Naglers, Radians and Panoptics. Most of them, zoom or wide field, have 8 or 10 glass to air surfaces and usually have transmission percentages from the upper 80's to the lower 90's. The highest transmission eyepieces are the simple ones like Plossls and Orthoscopics. The best of those can have peak transmission between 98 and 99%. The trade off at short focal lengths is short eye relief and narrow fields. Even the highest transmission eyepieces can't brighten the image but so much at high magnification. Changing from an 90% eyepiece to a 95% eyepiece has about the same effect on brightness as changing the scope aperture from 80mm to 82mm.

I've tried nearly every eyepiece out there that looked promising. I've found that almost all premium quality eyepieces, simple or complex, have about the same center sharpness. At high magnification the scope objective is the limiting factor for resolution, not the eyepiece. That's true even if the scope objective is essentially perfect. In spotting scopes the situation is worse. Except for the rare cherry specimen, the build up of wave front error has already compromised the image before the light ever reaches the eyepiece. The eyepiece just magnifies the aberrations that are present at the focal plane of the objective. The noticeable differences in eyepieces are in edge performance, brightness and contrast. The brightness and contrast of the Pentax XW's stands up well among the complex eyepieces, better than the TeleVues. The TV Naglers and Panoptics are quite sharp at the edge, but have huge amounts of pincushion distortion which the Pentax XW's don't have. The very highest transmission complex eyepieces I've seen are the Swarovski and Nikon spotting scope eyepieces. I would estimate their transmission is perhaps 94 to 97%. Curiously, the Swarovski and Nikon zooms are the very brightest. The Nikon zoom is a real stand out, with brightness and contrast nearly as high as a Zeiss Abbe Orthoscopic.

[Sout Fork]

Originally Posted by henry link

I think you will find that the best zooms have light transmission and center sharpness as good or better than complex wide field eyepieces like the Pentax XW or TV Naglers, Radians and Panoptics. Most of them, zoom or wide field, have 8 or 10 glass to air surfaces and usually have transmission percentages from the upper 80's to the lower 90's. The highest transmission eyepieces are the simple ones like Plossls and Orthoscopics. The best of those can have peak transmission between 98 and 99%. The trade off at short focal lengths is short eye relief and narrow fields. Even the highest transmission eyepieces can't brighten the image but so much at high magnification. Changing from an 90% eyepiece to a 95% eyepiece has about the same effect on brightness as changing the scope aperture from 80mm to 82mm.

I've tried nearly every eyepiece out there that looked promising. I've found that almost all premium quality eyepieces, simple or complex, have about the same center sharpness. At high magnification the scope objective is the limiting factor for resolution, not the eyepiece. That's true even if the scope objective is essentially perfect. In spotting scopes the situation is worse. Except for the rare cherry specimen, the build up of wave front error has already compromised the image before the light ever reaches the eyepiece. The eyepiece just magnifies the aberrations that are present at the focal plane of the objective. The noticeable differences in eyepieces are in edge performance, brightness and contrast. The brightness and contrast of the Pentax XW's stands up well among the complex eyepieces, better than the TeleVues. The TV Naglers and Panoptics are quite sharp at the edge, but have huge amounts of pincushion distortion which the Pentax XW's don't have. The very highest transmission complex eyepieces I've seen are the Swarovski and Nikon spotting scope eyepieces. I would estimate their transmission is perhaps 94 to 97%. Curiously, the Swarovski and Nikon zooms are the very brightest. The Nikon zoom is a real stand out, with brightness and contrast nearly as high as a Zeiss Abbe Orthoscopic.

Thats is exactly what I have not found to be true-in actual field use I have noted no stunning difference between the various high end Zooms as high power EPs. For instance I had the exclusive use of the Zeiss 85mm with Zoom for over two months recently and out there in the rain and fog and sleet I don't see any big difference one way or the other between the Zeiss and my present setup. Sure there is some difference but I'm not going to lose any sleep over it.

I think you might find this interesting-it was packed with the Pentax ep.

"Description Pentax XW 10
Field of View 70° FOV
Coatings Internal and external patented SMC coatings
Design Lanthanum/crown/flint, 7 Lenses in 4 groups
Construction weather proof
Average Light Transmission 98.37 %* in visible wavelengths
Eye relief 20 mm, all models

*Bench test using Carl Zeiss* Z1 Spectrometer.
*Carl Zeiss Optronics GmbH
Carl-Zeiss-Str, 22
73447 Oberkochen Germany

Signed:Fumio Ondo
PENTAX Sapporo Bldg. 4f, 18-36 kita,-Jujo Hokkaido."

I don't at all disagree with you about the limiting factor being the objective when it comes to high power ep's.
Given I only had 80mm to work with it made sense to buy the most light efficent ep I could find as well as other factors. At the present state of the art 80mm is about all I'm willing to lug around.

Next week I'll put it to the test against these other zooms you mention. Most of them will be there and I can at least eye ball them and see for myself.

Good Birding

[henry link]

Sout Fork,

The information packed with your eyepiece is very odd. It's not what came with my 14mm and appears to contradict the specs on the Japanese Pentax website here: http://www.pentax.co.jp/english/prod...ugan/scope/xw/

Its very strange that the number of groups in the eyepiece design is given as 4 rather than 6. I hate to argue with a machine, but average transmission above 98% in a complex eyepiece is hard to believe. My 14mm certainly doesn't have that kind of transmission. It has obviously lower transmission than the Swarovski and especially the Nikon zooms set to 14mm and the Nikon zoom is visually a little dimmer than a 16mm Zeiss Abbe which I have seen measured at about 98.5%. Even a single peak of 96% in such a complex eyepiece is, to quote the Pentax website, astonishing. Could the design of these eyepieces have been changed recently?

I compare zoom eyepieces on the same scope with 2" adapters, usually a 92mm Astro-Physics Stowaway, sometimes a Takahashi Sky 90 or FS-78. When the zooms are evaluated on their own different scopes it isn't really possible to separate the performance of the eyepiece alone from the eyepiece and scope in combination.

I doubt that you will be dissappointed in how your Pentax compares to a Nagler Type 6. I think the Pentax is superior in almost every way.

Regards,

Henry

[Sout Fork]

Originally Posted by henry link

Sout Fork,

I doubt that you will be dissappointed in how your Pentax compares to a Nagler Type 6. I think the Pentax is superior in almost every way.

Regards,

Henry

I remember my first view through a Nagler. I knew more or less nothing about televue products one way or the other.

Anyway this Nagler was in some short FL wide field astro scope. It was daylight and we were looking over the valley from someone's porch. It was a little afternoon cocktail party.

The eye lens was small there was no eye relief to speak of and it took forever to find the sweet spot. In addition pan across the landscape and you could see all this field distortion at the edges. Also move your eye to see the edges and it blacked out.

Not knowing Televue from Chevy I just assumed it was some cheap throw-away ep that came with the scope. Not unlike the "Super Wide Field" 11.5 degree plastic binos that Walmart sells for 50 bucks.

While the Naglers may have their place in the astro community that is exactly where they should stay. The Pans may be a better choice for the birder but why bother? No short focal lengths and inferior to the Pentax in most every way.

My opinion.

BTW- I agree. 98 percent of ANYTHING is awfully large. I'm sceptical.
I did try it again compared to the 13mm during the middle of the day when things were very bright. There was practically no difference between the two under these conditions. Perhaps the 10mm is one of the cherries in the XW line? I suppose given the lighting conditions my eye pupil was stopped down in any case. I did try the zoom at this time and sure enough it was darker than both the 13mm and the 10mm.

Another thought: All else being equal a complex 8 element ep will be less efficent at light transmission than a simple 4 element ep. However given the price of the XW line perhaps all else is not equal. Perhaps it's possible to get comparable light transmission to an ordinary Plossel given the difference in quality? I really don't know.

Anyway so far it's a keeper.

Just got hit by 12 iinchs of snow and they are predicting 20 below tonight. Have to fire up the tractor and plow our steep 800 foot driveway-one the joys of remote rural life.

Talk to you later.

PS- got a stunning view of a Sharp-Shinned Hawk through one sheet of window glass using the Pentax ep. It was about 40 mins before sunset and quite dark out and the bird was maybe 50 yds away. That bugger was checking out my late feeding Cardinals at the feeder. Good detail and could clearly make out eye color under these conditions (Red).

At the end of the day perhaps the only specification that really matters is does it work for you?

[smonrad]

Having had a straight Pentax 80 w/the big expensive zoom and now a Pentax angled 65, forget the zoom and the cheap eyepieces. The XW14 is the best eyepiece, the 65 is just as good as the 80, MUCH lighter and cheaper. Stick with the waterproof combo, save the money with the smaller scope and get a higher power XW eyepiece plus the XW14 if you need the maginification.

[henry link]

For those interested in the Pentax XW eyepieces there is very detailed and complete information in this technical report at the Pentax Japanese website. http://www.pentax.co.jp/japan/tech/xo-xw/6.html

Unfortunately the text is only in Japanese, but if you scroll down the subheadings under XW you will find cutaway views of the optical formulas, a graph of light transmission curves and a set of graphs I'm uncertain about. Do they show tangential and sagittal astigmatism or possibly astigmatism vs field curvature or distortion?. Can any Japanese speakers help out?