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William Optics UWAN Eyepieces

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#1 asaint

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Posted 28 July 2006 - 01:36 PM

William Optics UWAN Eyepieces

#2 timmbottoni

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Posted 28 July 2006 - 03:18 PM

Hi,

Very good analysis and review!


Timm

#3 Daniel Mounsey

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Posted 28 July 2006 - 10:53 PM

Dr. Reese,

First of all, thank you for taking the time to write this review. I read it with interest. There are a couple of things that I would have liked a more definitive answer on. For example you mentioned that the contrast in the 8" F-5 between the eyepieces was hard to descern and that stuns me, particularly with the Meade being compared to the XW. I can not attest to the WO, but I certainly can with the others. The contrast bewteen even the Panoptic, Nagler and XW is unquestionably real, particularly on galaxies. I understand the concerns many observers have regarding edge sharpness, but observers should know that most eyepieces don't correct all of that. I've tested the XW's in two different F-5's and I think the views were absolutely breathtaking to trained eyes. I avoid Paracorr's when I can but if observers are that concerned about coma, then perhaps that's what they use. When I read many reviews, I notice a lot of emphesis on the over all field of view, but I sometimes have to ask observers what it is they are viewing.

It's almost as if they are not even scrutinizing or studying the object itself whether it's a planet or a deep sky object like a galaxy. I admit that I myself have criticized certain eyepieces because of light scatter or glow, but this has a direct effect on surface contrast and features. To me, the issue regarding light scatter on stars had its points, however I just think too many observers are not paying attention to the object they are observing. If you were observing the Lagoon nebula for example, was there enough difference between the eyepieces for you to see the dark lane a bit more definitively than with another eyepiece?

I recall one particular observation between a 20XW and a 19 Panoptic while viewing very faint galaxies in Draco in my 10" F-5. After switching back and forth, there were obvious differences. The galaxies were unquestionably more apparent and higher in contrast in the XW. Every time I went back to my 19 Panoptic, the image contrast appeared between 5% or 7% less and there was absolutely no doubt whatsoever about this. If anything, the contrast of the 19 should have been a notch above with the slight bump in extra magnification. To me, the XW was clean and not once did coma come into play and this goes back to what I said about observers being so obsessed with coma.

Thank you :smirk:

#4 David E

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Posted 29 July 2006 - 06:52 AM

Mr Reese,
Thank you for this review. It is very informative and well thought out. I would like to make one comment concerning the 7mm "family" of Pentax, Meade and WO. The true field of view of any eyepiece is determined by the field stop diameter (fsd), not the focal length (although shorter focal length eyepieces generally have smaller fsd's by design.) I measured my Meade 6.7mm UWA to have about an 11.5mm fsd (a bit difficult because the fsd is imbedded in the eyepiece barrel). This would agree with your observations that the WO 7mm has about 20% more tfov than the Meade 6.7mm, as the WO eyepiece has a 14mm fsd by your measurment. Since the eyepiece focal length does not factor at all in the formula for true field of view, I cannot conclude that the WO eyepiece is anything other than the stated 7mm focal length without data showing the measurments of its true magnification to be otherwise. The fact that you could not split Epsilon Lyrae 1-2 as easily with the WO as you could with the Meade or Pentax demonstrates less sharpness of this eyepiece rather than less magnification. The warmer tones that you noticed in this eyepiece might possibly make this a very good choice for planetary work, as (in my personal experience) any telescope or eyepiece that shows me a warmer tone presents colors better than the "pure white" look.

Again thank you for this review. It is an excellent one and gives the reader some valuable information for making pre-purchase comparisons.

David E

#5 RRaubach

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Posted 29 July 2006 - 02:04 PM

Dr. Reese;

Thank you for your review, which I read with interest. I personally own 2 of the 4 UWAN series, and to date I am completely satisfied with their performance. I own the 28 and 4, the extremes of the series.

I find that I now use my UWAN 28 in place of either my Panoptic 27 or Panoptic 35. It offers a significant improvement in contrast over the 35 mm, in particular.

I also own 2 Pentax XW series eyepieces, and they receive more use than almost any others in my set, so I appreciate the comparisons that you have made.

I would give the UWAN 28 a somewhat higher grade than you have given it. I agree with your assessment of the UWAN 4 completely.

#6 Cereso

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Posted 01 August 2006 - 03:54 AM

Thank you, Timm!

Carsten

#7 Cereso

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Posted 01 August 2006 - 04:10 AM

Hello David,

thank you for your reply.
The focal length issue on the 7mm is something I am quite sure about. You are right, just taking the field stop diameter will fit with the measurement on the true field of view - but you will not get any information about the focal length out of that. Comparing resolution/sharpness and true field of view will do so. However, I would like to have a direct measurement of the focal length. May be someone is able to do that and to tell us about. And I really would like to know why WO states 7mm for this eyepiece.

Clear skies,

Carsten

#8 Cereso

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Posted 01 August 2006 - 04:16 AM

Hi Rodger,

thank you for your feedback. The 4mm UWAN is really a nice eyepiece. I downgraded the 28mm a little bit just for the edge performance, which is good, but not perfect at F/5. This should not be an issue on slower telescopes.

Regards,

Carsten

#9 Cereso

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Posted 01 August 2006 - 04:36 AM

Hi Daniel,

I´ll take out the contrast issue of your reply. First, I would like to say that contrast comparison is a little bit personal to some extend. I found that differences in contrast are more prominent at shorter focal length, and that there is a clear difference between the Hyperion 3.5mm and the UWAN 4mm. The Nagler as well as the Panoptic eyepieces (of course I do not know all focal lengths) in my opinion are not the "contrast performers" at all. The Naglers are great for edge performance in fast telescopes, especially for medium and long focal length.
So, may be that somebody is able to see differences in contrast between the eyepieces I compared - I am not, at least not at my telescope.

Regards, and thanks for the reply,

Carsten

#10 timmbottoni

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Posted 01 August 2006 - 10:14 AM

Hello David,

thank you for your reply.
The focal length issue on the 7mm is something I am quite sure about. You are right, just taking the field stop diameter will fit with the measurement on the true field of view - but you will not get any information about the focal length out of that. Comparing resolution/sharpness and true field of view will do so. However, I would like to have a direct measurement of the focal length. May be someone is able to do that and to tell us about. And I really would like to know why WO states 7mm for this eyepiece.

Clear skies,

Carsten


Hi,

I have the UWAN 7mm and a TV plossl 8mm (which I will assume is an accurate 8mm), so if you can tell me some way to compare, calculate, measure, photograph, etc, the two focal lengths, let me know and I will tell you the results.

Thanks,

Timm

#11 LivingNDixie

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Posted 01 August 2006 - 10:21 AM

Nice write up!

#12 timmbottoni

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Posted 01 August 2006 - 11:08 AM

Hi again,

I'll see if I can try taking a digiscope picture through both my 7mm UWAN and my TV plossl 8mm and then bring them into Photoshop to compare them. If I keep the focal length on the camera the same for both shots, then the difference in image size should be exactly relative to the difference in the focal lengths. Assuming that the TV plossl 8mm is dead on, at 8mm, I should be able to easily see any difference in size between the two, and using Photoshop, do a transform to one of them and calculate the actual percentage difference to get them to be exacty the same size by overlaying them on top of each other in two layers.

Sorry about the computer geek talk, but I think this will work if I can get one of my digital camera's to focus this way with both eyepieces, and will completely ignore any human interpretation of the two views since they are such wildly differnt relative and real field of views.

I'll let you all know if this works, and post the results with photos in a followup.

Thanks,

Timm

#13 Cereso

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Posted 02 August 2006 - 01:19 AM

Hi Timm,

nice idea!
Some hints about this: If you use the camera without objective (eyepiece projection) you have to take into account the distance from the eyepiece to the CCD-Chip for the magnification factor. If this distance varies for the two eyepieces, the magnification factor will vary!
A far as I know there is no impact if you use the camera together with its objective. The magnification factor in this case just depends on the telescope focal length, the eyepiece focal length, and the camera objective focal length. Hope that I am right here.

Carsten

#14 timmbottoni

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Posted 02 August 2006 - 09:02 AM

Hi Timm,

nice idea!
Some hints about this: If you use the camera without objective (eyepiece projection) you have to take into account the distance from the eyepiece to the CCD-Chip for the magnification factor. If this distance varies for the two eyepieces, the magnification factor will vary!
A far as I know there is no impact if you use the camera together with its objective. The magnification factor in this case just depends on the telescope focal length, the eyepiece focal length, and the camera objective focal length. Hope that I am right here.

Carsten


Hmmm, yeah I was thinking about that too. I have to think about how to do this. I have a Canon 20D and a Canon A540, and for something like this, I might be better off with a clear daylight shot, and setting the A540 on a tripod, and focusing on something with the eyepiece, then with the camera on a tripod, bring it up to the eyepiece and fix focus manually. I could use the Canon 20D as well. I didn't get a chance to try yesterday, but hopefully today or maybe over the weekend since storms are expected today and tomorrow.

Thanks for the ideas on my idea.

Timm

#15 RRaubach

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Posted 03 August 2006 - 10:56 AM

I thought about that! (After I already opened my mouth and posted!). I was using my TMB 203 f/7 to make these observations, so that DID have a bearing on the outcome!

:tonofbricks:

#16 David E

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Posted 13 August 2006 - 07:07 PM

Timm, Carston, this thought just occured to me. You can use a binoviewer with the 7mm UWAN on one side any another 7mm ep in the other. You don't have to merge the images, just focus each eyepiece. I would try this during the day on a stationary target like a distant house. Use two small pieces of black cardboard just big enough to hold over the eyepieces and cover them. Alternately cover and uncover each one, back and forth, and look for any change in image size. If the UWAN is closer to 8mm as suspected, the 15% larger image should be obvious. If it is at, or nearly at, 7mm you should notice no change in image size.

David E

#17 timmbottoni

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Posted 14 August 2006 - 09:32 AM

Hi David,

Good idea on the binoviewer. I don't have one, and I haven't had time to successfully try the digital photo idea. At night, it is too hard to do, and we are swamped at home with kids activities, so I don't know when I will get to try a daytime test.

I tried to compare the 7mm UWAN to the 8mm TV Plossl, a number of times at night, and the field of view difference makes the perception of what my eye sees, just too dramatically different.

Thanks,

Timm

#18 RRaubach

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Posted 17 August 2006 - 11:17 AM

I finally had a chance to try the UWAN 28 in my new Discovery 12.5", which is f/5. I didn't notice any edge problems, only a trace of coma from the primary mirror.

#19 timmbottoni

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Posted 17 August 2006 - 02:02 PM

Hi,

I sold my TV plossls to finance a UWAN 16mm, so I will not have a chance to try my photo idea after all that would compare the 8mm plossl to the 7mm UWAN.

Sorry

Timm

#20 timmbottoni

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Posted 22 August 2006 - 11:57 AM

Hi,

I got the 16mm UWAN on Saturday and tried it out on Sunday night and am VERY pleased with it. To me, it is even better than the 7mm UWAN, but it's probably becuase it provides close to a 2mm exit pupil, and matches my scope and eyes ability to resolve objects.

Timm

#21 Arief

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Posted 04 September 2006 - 01:48 PM

I hope someone can do a review between 7mm UWAN and 7mm Nagler Type 1. Both is slightly less than $200 new.


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