28mm WO UWAN

iceman (Mike) · #1 29-05-2006, 10:45 AM

This eyepiece was suggested as a low power, widefield eyepiece for my 10" f/5 newt.

I had the opportunity to test this eyepiece at Kulnura on Saturday night, thanks to Joe (astropolak) who owns one and let me borrow it for a little while.

First impressions - the eyepiece is HUGE! It's a 2-inch (only) barrel, and the body of the eyepiece is massive. The eye lens is quite large.

It felt quite comfortable to use, the eye relief felt about 15mm, and upon looking at the specs just then, it's quoted at 18mm so I was close

The field of view felt large, the specs say 82 degrees and I'd guess this is right.

Unfortunately I don't have any more good things to say about it.. the eyepiece has shocking field curvature in my scope. The outer 30-40% of the field is not in focus when the centre is in focus, and if I focus for the outside, the inside goes out of focus.

When the stars were in focus, they were quite crisp and sharp and there was little evidence of astigmatism at the edge of the field.

However the field curvature is terrible and I just could not use this eyepiece on a regular basis in my scope. It was really distracting and a big put-off.

I did look through it again later in Joe's 8" f/10 LX90, and the field curvature was still there, but only in the outer 5-8% and was certainly not nearly as distracting.

At US$400 it's not cheap, and I would not recommend this eyepiece to anyone with a fast scope.

matt · #2 29-05-2006, 11:11 AM

Good to know, Mike.

But how about that 22mm LVW eh?...eh?

janoskiss (Steve H) · #3 29-05-2006, 11:23 AM

Thanks for the report, Mike. Is the FC much worse than in the XW 14mm?

iceman (Mike) · #4 29-05-2006, 11:24 AM

Yes, considerably.

xstream (John) · #5 29-05-2006, 11:24 AM

I felt the same way about it at Wiruna.
Joe was looking at it then and wanted to try it out in Anna's LX90.
Certainly not worth the US$400 but it is a massive eyepiece.

ving (David) · #6 29-05-2006, 11:28 AM

I still recon the EP for you is a siebert optics observatory class in say 34mm or 36mm. aparently they are designed for fast scopes and are only $200 US. they are 70 deg and some compare them to panos.
heres a cn review fer ya!
http://www.cloudynights.com/item.php?item_id=1416
and a 2" shoot out:
http://www.cloudynights.com/item.php?item_id=1451

just goes to show that you have to pick what evils you are willing to live with in this field.

astropolak (Joe) · #7 29-05-2006, 12:43 PM

This is why I have posted in the past my thoughts on Field curvature of certain types of telescopes. I would not mind checking this eyepiece in a fast 4.5 Newtonian of different make to confirm the existence of field curvature problems. If there is a serious field curvature problem with this eyepiece then I would have to claim that the recent review of this eyepiece on Cloudynights.com is full of !@#!$!@#$

Joe

janoskiss (Steve H) · #8 29-05-2006, 12:48 PM

Ving, you just want someone to be guinnea pig for those sieberts, don't you?

On the subject of reviews on CN, one by Tom Trusock notes coma as being the biggest issue with UWANs in fast scopes, and writes:

"The 28, 7 and 4 were extremely competitive eyepieces even in the fast (f4.5) Obsession with edge sharpness on a par with the Naglers ... I did note a minor amount of field curvature, perhaps most noticeable in the 28mm, but I suspect most individuals' eyes will probably accommodate it with few problems."

So either Mike and John both have very unaccommodating eyes, or Tom Trusock really wanted to like this eyepiece.

... no matter what the reviews say, you won't know till you try... And I believe this guy TT is one of the more experienced people on CN.

ving (David) · #9 29-05-2006, 01:07 PM

Quote:

Originally Posted by janoskiss

Ving, you just want someone to be guinnea pig for those sieberts, don't you?

.

pretty much steve

I'll end up buying one but I am short on $$$ atm and have to many other things to buy

square_peg114GT · #10 29-05-2006, 01:10 PM

Quote:

Originally Posted by ving

I still recon the EP for you is a siebert optics observatory class in say 34mm or 36mm. aparently they are designed for fast scopes and are only $200 US. they are 70 deg and some compare them to panos.
heres a cn review fer ya!
http://www.cloudynights.com/item.php?item_id=1416
and a 2" shoot out:
http://www.cloudynights.com/item.php?item_id=1451

just goes to show that you have to pick what evils you are willing to live with in this field.

I found the Stratus prototype to be remarkably better corrected for astigmatism in fast scopes than the Siebert. Given that the Stratus will sell for the same $200 US, I'd wait another month for it (unless I had balance issues, then I might reconsider the Siebert).

iceman (Mike) · #11 29-05-2006, 01:11 PM

Quote:

Originally Posted by janoskiss

So either Mike and John both have very unaccommodating eyes

I am very critical of edge performance.. both astigmatism and field curvature. For other people they may be able to "accomodate" it but I just can't look past it. Which is a shame, because it means expensive taste in eyepieces!

Maybe I should get an f/10 scope then

Tom Trusock is very experienced, he's one of the admins at CN.

ving (David) · #12 29-05-2006, 01:13 PM

thanks square peg. i have well over a month of wait time so i miay go down that road

your review?

square_peg114GT · #13 29-05-2006, 01:14 PM

Quote:

Originally Posted by ving

thanks square peg. i have well over a month of wait time so i miay go down that road

your review?

Yep. The 2" shootout, that is.

xstream (John) · #14 29-05-2006, 01:45 PM

Quote:

Originally Posted by janoskiss

So either Mike and John both have very unaccommodating eyes

I could probably live with it Steve, but even in a f/10 when I asked Joe what the price was I would of expected a lot more for my dollar.

scumbag1010 · #15 30-05-2006, 12:00 PM

Hi all,

I spent some time with Joe at SPSP with his telescope and one of my eyepiece cases. We compared the 25mm TAL, 28mm UWAN, 35mm Panoptic, 27mm Panotpic, 22mm Panoptic and finally 20mm Nagler Type 2. as well as UHC and OIII filters.

I am sure that he saw some difference between that lot. The last four of the above eyepiece didn't show the curvature that the 28 UWAN did. His impression was that the 20mm Nagler was the best followed by the 27mm Panoptic. I concur that was also my opinion.

As someone in the trade I would leave it at that so I don't appear to be biased.

Don
Bintel

astropolak (Joe) · #16 30-05-2006, 01:00 PM

Don
It is nice to hear from you.
No, you are not biased. I saw field curvature in all of the eyepieces, but the UWAN had more than others (except the TAL). Considering the other eyepieces in the "shootout" it (28mm UWAN) did not perform too badly. I liked the 20 mm T2 Nagler a lot and the Pan 27mm.
For now I am sticking with my 28mm UWAN.
Thank you very much for the eye opening experience at SPSP.

RGDS Joe

astropolak (Joe) · #17 27-06-2006, 07:49 PM

Extra info that I thought may be of some assistance to potential purchasers.
In talking to John (Ausastronomer) and other people it would appear that matching field curvature of eyepiece to field curvature of telescope is important.
I have tested the Uwan 28 in Tak 130 (thanks Rocket Boy) and Discovery 12.5 Dob (thanks Wavelandscott), the results - hardly any curvature at all. I would say that the eyepiece has in fact flat focal plane (this is on the assumption that the TAK has very flat focal plane as well).
I have not yet seen 70+ deg eyepiece (FL >14 mm) that does not show a field curvature in my 8" LX-90.
I know for sure that the Uwan does not work well in GSO 10 Dob and its fairly reasonable in my LX90.
It also works well in a large number of Dobs as tested by CN users.
I wish manufacturers (of both telescopes and eyepieces) would publish field curvature plots for their products - why do we have to find it out only after the purchase? Pentax does publish it but I do not read Japanese.
Joe

janoskiss (Steve H) · #18 27-06-2006, 09:46 PM

Newts of same focal ratio will have the same field curvature, i.e., the FC of the parabolic mirror. So I find it puzzling that in one brand of Dob (Discovery) the EP displays no FC while in another brand (GSO) it shows a severe case of it.

I would still like to see one of these EPs for myself...

Edit: Above I wrote: "Newts of same focal ratio will have the same field curvature". INCORRECT! Newts of equal focal length have the same FC. Focal ratio has no bearing on FC for a given focal length.

wavelandscott (Scott) · #19 27-06-2006, 10:01 PM

I would second Astropolak's comments about this eyepiece...in my scope it looked pretty good to me and not nearly as bad as the experience others seem to have had with it in their scopes....but as they say YMMV (your mileage may vary)

After hearing Joe's comments on the night about other people's experiences I then went and read the review on CN. Based on my brief look in my scope I thought Tom Trusock represented what I saw...(in my own technical terms) a decent wide field eyepiece.

Although I did not spend a lot of time with the eyepiece, I did not see anything other than the pure size and weight that I found truly objectionable.

With respect to size and weight it was heavy and did unbalance my scope...easy enough to fix if I was so inclined.

Were I interested in having an eyepiece of that magnification...based on my look through of that eyepiece in my scope (on that night) and the "few" looks I have had through other people's scopes and 31 MM Terminaglers I don't recall a great deal of differences...heretical I hear you say...maybe so.

Just another reason to "try before you buy" if you can...

Warf · #20 29-06-2006, 06:45 AM

Could it be that this eyepiece was designed and optimized for use with refractors since that is what William Optics focuses on (no pun intended)? I don't own this eyepiece but I have used it in my WO ZS80 and I found it to be a very excellent eyepiece and I didn't notice any curvature. I may have to borrow it again and try it in my NS11 and see what happens.