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CN Report: Panoptics, Naglers and Paragons

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#1 Tom T

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Posted 18 July 2007 - 11:30 AM

CN Report: Panoptics and Naglers and Paragons - Oh My!

#2 hoof

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Posted 18 July 2007 - 12:13 PM

Nice report. Incidentally, I now know you're nearsighted, with a -4 to -6 diopter correction, and you observe w/o glasses. How do I know this? Because I, too, see dust on the field lens of my paragon, and I have a -5 diopter nearsightedness. When I observed with corrected vision (with my glasses on), all dust went away and were completely invisible.

This tells me that the focal plane as designed (for 20/20 eyes) is not on the field lens, but it nearby. Our nearsightedness moves the effective focal plane to the field lens surface.

I'm wondering if nearsightedness's effect on the effective focal plane could have an effect upon perceived eyepiece astigmatism. My paragon focuses to pinpoints to about 90-95% of the field of view, when adjusting for the eyepiece's field curvature. OTOH, I have observed several TV eyepieces (Nagler 20mm T2, Nagler 20mmT5, Panoptic 19mm, Nagler 17mmT4) all to have a slight touch of astigmatism near the edge. If my eye's nearsightedness is adjusting the focal plane, that could be introducing astigmatism on the TV eyepieces, and correcting it on the Paragon. OTOH, the fact that you too see the field lens dust suggests similar nearsightedness, so maybe I'm wrong.

The focal plane adjustment can be verified by the fact that we need to move the eyepiece close (farther?) to adjust for nearsightedness/farsightedness, yet the 'scope's focal plane isn't changing. This has to affect the eyepiece in some way.

Next time I'm under the stars, I'll try testing my theory. I'll look at several of my long-focal-length eyepieces with and without glasses, and see if the edge-of-field astigmatism changes.

#3 Daniel Mounsey

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Posted 18 July 2007 - 12:18 PM

Nice review Tom,
BUT where's my darn Pentax XW's? aaaaaarrrrggggggghhhhhhh! :troll: I concur with your conclusions although I do have a couple of comments. You noted some minor loss of edge illumination in the 41 Panoptic. Any comments on why this was more noticible at twilight? Also, I agree with you and I have no real complaints about lateral color in the 41 Pan either.

:goodjob: and I'll forgive you this time on the XW's :grin:

#4 Tom T

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Posted 18 July 2007 - 12:20 PM

Nice report. Incidentally, I now know you're nearsighted, with a -4 to -6 diopter correction, and you observe w/o glasses.


Uh, sorry.

Nope.

I'm not near sighted or farsighted. (Although I have been accused of being FarSIDED, but that's a different story... :grin:)

In fact, I'm 20/13 in one eye, 20/15 in the other with less than .25 diopters of astigmatism.

I do not wear glasses - except good ole sunglasses that is. :grin:

#5 timmbottoni

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Posted 18 July 2007 - 12:22 PM

Excellent Review Tom!

I really have learned a lot from your reviews, both the content you have delivered, and the methodology that you have used.

I really appreciate all you do for the amateur astronomy community.

Timm

#6 Tom T

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Posted 18 July 2007 - 12:24 PM

Nice review Tom,
BUT where's my darn Pentax XW's? aaaaaarrrrggggggghhhhhhh! :troll: I concur with your conclusions although I do have a couple of comments. You noted some minor loss of edge illumination in the 41 Panoptic. Any comments on why this was more noticible at twilight? Also, I agree with you and I have no real complaints about lateral color in the 41 Pan either.

:goodjob: and I'll forgive you this time on the XW's :grin:


Hi Daniel,

I can only do what I've got access to.

:shrug:

If someone sent me the line of XW's, I'd be more than happy to include them.

:whistle:

:grin:

As per the illumination loss noticable at twilight and not as much during the day - I suspect it's because during the day because things are so inherently bright, a small change isn't that detectable.

T

#7 Olivier Biot

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Posted 18 July 2007 - 12:25 PM

Interesting review, Tom! I concur with the bit of astigmatism visible at the outermost portions of the Paragon (it doesn't bother me at all), but I never witnessed seeing the dust on the field lens though (which would have bothered me).

Cheers :waytogo:

Olivier

#8 Tom T

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Posted 18 July 2007 - 12:29 PM

Interesting review, Tom! I concur with the bit of astigmatism visible at the outermost portions of the Paragon (it doesn't bother me at all), but I never witnessed seeing the dust on the field lens though (which would have bothered me).

Cheers :waytogo:

Olivier


Thanks Olivier. Most likely I wouldn't have noticed it myself if I hadn't had some get on there. Good news is, it cleans easy, and since this eyepiece is mainly used for deep sky anyway, is pretty much a non-issue. It's just something I observed.

#9 hoof

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Posted 18 July 2007 - 12:29 PM

Nice report. Incidentally, I now know you're nearsighted, with a -4 to -6 diopter correction, and you observe w/o glasses.


Uh, sorry.

Nope.

I'm not near sighted or farsighted. (Although I have been accused of being FarSIDED, but that's a different story... :grin:)

In fact, I'm 20/13 in one eye, 20/15 in the other with less than .25 diopters of astigmatism.

I do not wear glasses - except good ole sunglasses that is. :grin:


Well, that blows that theory out of the water :)

OTOH, it means that my astigmatism idea might actually have a chance now. I'll report on my results when I get a chance.

#10 Tom T

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Posted 18 July 2007 - 12:30 PM

Excellent Review Tom!

I really have learned a lot from your reviews, both the content you have delivered, and the methodology that you have used.

I really appreciate all you do for the amateur astronomy community.

Timm


Thank you Timm, that's a very nice thing to say, and I appreciate it.

T

#11 Tom T

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Posted 18 July 2007 - 12:35 PM

OTOH, it means that my astigmatism idea might actually have a chance now. I'll report on my results when I get a chance.


FWIW, I'm more inclined to think that it's astigmatism inherent in your own eyes (or telescope) that you're seeing in the TV's, and further that at the low magnification of the 40, the spot/cross size may just be too small for you to notice in the paragon.

T

#12 hoof

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Posted 18 July 2007 - 12:48 PM


OTOH, it means that my astigmatism idea might actually have a chance now. I'll report on my results when I get a chance.


FWIW, I'm more inclined to think that it's astigmatism inherent in your own eyes (or telescope) that you're seeing in the TV's, and further that at the low magnification of the 40, the spot/cross size may just be too small for you to notice in the paragon.

T


I've explored that theory on several occasions. I've ruled that out because on-axis is pinpoint, and the "+" of the astigmatism is always aimed to the center of the eyepiece view, and is unaffected by my eye's motion, and is matched for each of my eyes. If it was my eyes, I'd expect it to be uniform across the view and the "+" oriented the same regardless of where I was looking.

OTOH, the idea of the 'scope might be valid, in which case, I've looked through the only NP101 I know of with axial-based astimatism :) Plus, it's rather consistent on other non-NP101 'scopes too.

#13 claytonjandl11

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Posted 18 July 2007 - 01:53 PM

Hi Tom,

Great review! I have both the Paragon and the Nagler 31mm. I've had the nagler for 4 years and the Paragon for about a year. The nagler hasn't been used (much) sinced I got the Paragon. Don't get me wrong the nagler is a great EP, but I prefer the Paragon. I really haven't seen any astigmatism you mentioned in the Paragon or any of the other issues you brought up, maybe someone would have to point them out to me. I don't wear glasses and acording to my doctor my eyesite is very good. What I find that I like better in the Paragon is, at least to my eyes is that the image looks brighter, whiter, slightly sharper contrast, colors seem to be more vibrant in colored stars. All this with a fairly flat field. Also it's light weight compared to the Nagler, and cost almost half the price of the Nagler. The Paragon is the only EP in my EP collection that isn't a Tele Vue EP, I have Naglers, Radians,Panoptics, and Plossls, and wouldn't trade them for anything, except with Nagler 31mm. I feel the that the Paragon edges out the Nagler by a nose in performance and if you factor in price and weight savings the Paragon IMHO is the winner. I don't have a 41mm Panoptic so I don't know how it would compare with the Pargon. Just my 2 cents.

Nick T.

#14 Randy Roy

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Posted 18 July 2007 - 02:20 PM

Excellent report Tom. I use the Paragon in my C14 and am delighted with it.

Randy

#15 gordon

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Posted 18 July 2007 - 03:16 PM

Therefore, I'm betting you really want to know who the winner is here, right?

It's simple really.

We are.

Kudos to both TMB and Tele Vue. We're a long way from Erfles and Konigs. It's a good time to be an amateur astronomer.
-----------------------------------------------------------
The above quote should be used in all reviews. :bow:

#16 naglertized

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Posted 18 July 2007 - 04:00 PM

Thank you for your report Tom. If I ever move to darker skies I think I will pick-up the Panoptic. I have a feeling that that astigmatism in the Paragon would just gnaw at me and make me want to sell it. I've seen them for as low as $400 used.

#17 Tom T

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Posted 18 July 2007 - 04:55 PM

Hi Tom,

Great review! I have both the Paragon and the Nagler 31mm. I've had the nagler for 4 years and the Paragon for about a year. The nagler hasn't been used (much) sinced I got the Paragon. Don't get me wrong the nagler is a great EP, but I prefer the Paragon. I really haven't seen any astigmatism you mentioned in the Paragon or any of the other issues you brought up, maybe someone would have to point them out to me. I don't wear glasses and acording to my doctor my eyesite is very good. What I find that I like better in the Paragon is, at least to my eyes is that the image looks brighter, whiter, slightly sharper contrast, colors seem to be more vibrant in colored stars. All this with a fairly flat field. Also it's light weight compared to the Nagler, and cost almost half the price of the Nagler. The Paragon is the only EP in my EP collection that isn't a Tele Vue EP, I have Naglers, Radians,Panoptics, and Plossls, and wouldn't trade them for anything, except with Nagler 31mm. I feel the that the Paragon edges out the Nagler by a nose in performance and if you factor in price and weight savings the Paragon IMHO is the winner. I don't have a 41mm Panoptic so I don't know how it would compare with the Pargon. Just my 2 cents.

Nick T.


Hi Nick,

Some great comments. I agree, and would only point out that I felt the brightness difference between the 40 paragon and 31 nagler is due to the difference in focal length - and thus magnification.

Thanks!

T

#18 Tom T

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Posted 18 July 2007 - 05:16 PM


OTOH, it means that my astigmatism idea might actually have a chance now. I'll report on my results when I get a chance.


FWIW, I'm more inclined to think that it's astigmatism inherent in your own eyes (or telescope) that you're seeing in the TV's, and further that at the low magnification of the 40, the spot/cross size may just be too small for you to notice in the paragon.

T


I've explored that theory on several occasions. I've ruled that out because on-axis is pinpoint, and the "+" of the astigmatism is always aimed to the center of the eyepiece view, and is unaffected by my eye's motion, and is matched for each of my eyes.

<snip>


To the best of my knowledge focus shift won't cancel astigmatism (this was just verified via e-mail thru someone with more optical knowledge than myself). Given what you've told me, outside of what I've already pointed out, I don't really understand how to account for what you're seeing - at least at the moment. But it's given me something to wonder about.

As to the disappearing dust - have you considered that you may have less accommodation with your glasses on? If the focus isn't exactly at the field lens, but rather close too it, it may simply lie out of range of your visual accommodation when you're wearing your glasses. This would also account for why some people do not seem to see dust on the field lens, and others do.

T

#19 Tom T

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Posted 18 July 2007 - 05:18 PM

Thanks for the comments folks - they are appreciated!

#20 Olivier Biot

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Posted 18 July 2007 - 06:11 PM

Hi Tom,

I have been observing Luna around sunset tonight with the 40mm Paragon, and I can confirm the sighting of dust on the field lens.

Living in a major 1,000,000 inhabitants city, close to heavily used highways and an international airport, there's a lot of dust in the air in my area. Just leaving an eyepiece in one of the 2" holes of my mount's spreader plate will already cover all its lenses with sticky goo (no, it are not grass pollen).

Cheers!

Olivier

#21 J_D_Metzger

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Posted 18 July 2007 - 07:00 PM

Hi Tom,

Terrific article! Very timely for me, too. I just bought an NP-127, and still have to make up my mind about a low-power ep. I have a partial set of Pentax XWs (up to and including the 20mm), and have been considering either the 30mm XW or the 35mm Panoptic. I didn't think about the 40's because I figured the exit pupil would be way too big. Your article put that myth to rest.

So that means I now have to consider the 30mm AND 40mm XWs, the 35Pan AND the 41Pan!! Arrgh... :foreheadslap:

Again, great review! :bow:

#22 Tom T

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Posted 18 July 2007 - 07:13 PM

Hey JD,

Thanks!

For the 127, the only reason that I'd consider any exit pupil too large would be if it's larger than your personal biology supports. For many folks, large exit pupils expose aberrations in their own eyes.

Al Nagler comments on this in his Common Telescope Myths article - you'll probably be specifically interested in myth's 1 and 2

http://www.televue.c...page.asp?ID=141

I'm almost certain you've seen that before, but just on the off chance you haven't it's a really good read.

T

#23 J_D_Metzger

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Posted 18 July 2007 - 07:29 PM

I have mild astigmatism (.5 diopter), which I correct with a Dioptrx on the 14mm and 20mm XWs (yes, it does fit). I need the Dioptrx with any ep that has an exit pupil of 2.0mm or greater. I'm not sure what my dilated pupil size is, but since I'm 61, I assume it is in the range of 5-6mm.

I don't wear glasses except to read (I'm FARsighted), so I expect that an ep in the 40mm range would work OK, but when I think about it, the smaller exit pupil of a 30-35mm would probably make more sense for me... If that's true, then I'm really back to the 30XW or the 35Pan. I'm leaning toward the 30XW, if for no other reason than it would match my current set, but I've owned the 35Pan several times over the last few years, and I've never been disappointed by it.

#24 Tom T

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Posted 18 July 2007 - 08:13 PM

Hi Tom,

I have been observing Luna around sunset tonight with the 40mm Paragon, and I can confirm the sighting of dust on the field lens.

Living in a major 1,000,000 inhabitants city, close to heavily used highways and an international airport, there's a lot of dust in the air in my area. Just leaving an eyepiece in one of the 2" holes of my mount's spreader plate will already cover all its lenses with sticky goo (no, it are not grass pollen).

Cheers!

Olivier


Owch! For just this reason (although it sounds you've got it worse than I do), I keep the endcaps on all my eyepieces when they aren't in use.

#25 Tom T

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Posted 18 July 2007 - 08:15 PM

I have mild astigmatism (.5 diopter), which I correct with a Dioptrx on the 14mm and 20mm XWs (yes, it does fit). I need the Dioptrx with any ep that has an exit pupil of 2.0mm or greater. I'm not sure what my dilated pupil size is, but since I'm 61, I assume it is in the range of 5-6mm.

I don't wear glasses except to read (I'm FARsighted), so I expect that an ep in the 40mm range would work OK, but when I think about it, the smaller exit pupil of a 30-35mm would probably make more sense for me... If that's true, then I'm really back to the 30XW or the 35Pan. I'm leaning toward the 30XW, if for no other reason than it would match my current set, but I've owned the 35Pan several times over the last few years, and I've never been disappointed by it.


I really like the 35 pan - but I also like to try eyepieces I've not used.

That's a tough choice - but a fun one.

:grin:


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