TS 30mm 2 inch UFF eyepiece.

[Carl Au]

A few weeks ago I decided to add a inexpensive 2 inch ep to my collection and after hunting around I found TS in Germany had their version of a Ultra Flat field eyepiece at 30mm. I lost track awhile ago of all the possible factories this ep might have come from, including United Optics and GSO. This ep appears to be very simular to the OVL/SW Aero 30mm. The build quality is very good, it looks a feels like a much more expensive ep, its also very light for a 2 incher. It comes well boxed indeed. The eye cup is rubber over a metal frame. I don't wear glassess when I observe but the eye relief is very comfy and stands at 16.5mm. The field of view is 69 degrees. I have looked through ep's with a wider field of view, they made me feel a little bit sick when I did, not sure what all that is about. What I do know that with a 100 degree field leaves me wondering where I should look, there is a lot to look ay and I find my eye ball endlessly wandering around, I never seem to settle. I have had 5 clear nights now to give my new toy a good try. The Double Cluster, Bee Hive and Pleiades easily, and with lots of room to spare in the field of view using my rather lovely Starwave 102ED-R which is fl7. I am looking forward to going into the Lincolnshire Wolds this summer (very dark sky) to spend sometime with the NA and Veil nebulars, should fit in nicely. Others would need to check out this ep in less forgiving  scopes, fl4.5 to fl6, but I have yet too see any sea gulls or any star which was not pin point. I have looked very hard at the outter 20% of the field of view and to my eyes at least I cannot tell any difference between the stars in the centre to the stars at the outter edge. Because it is so light it places little if any additional strain of the scope or mount.  I have to say that I love this ep, what a bargin. The coatings a lovely green colour that reminds me of a TAL refreactor I once owned. to date I have experinced no ghosting and no kidney beaning either. I am no abberations expert it has to be said, but I just can't find anything wrong it, which at £115 quid delivered seems remarkable. TS were their usual efficent selves. I ordered frist thing Monday morning, it arrived Wednesday at 12.30 lunchtime, amazing. If it is identical to the Aero, i.e. the same ep then It seems I could have gotten it a little cheaper in the UK, although it had been reduced from 169 euros which leaves me wondering if it is made to TS spec. I have heard so many stories about what is and what is not inside what appear to be identical ep bodies I have given up trying to work it all out. 

In short a very good quality ep piece for not very much money.

I need to run a blub blower over it now, there is some very fine fluff from somewhere judging my those photos

Edited March 4, 2021 by Carl Au

[John]

Good report !

That eyepiece looks identical in every respect to the Aero ED 30mm that I had recently. Including the lens coatings and the dust caps.

They are nice and light for 2 inch eyepieces and the one I had worked well at F/7.5 and slower I thought.

Edited March 4, 2021 by John

[Pixies]

Yep - looks identical to my OVL Aero ED 30mm.

I see some astigmatism at the outer 20% of the view - in an F6 dob. Now, that could be my eyes, as I suffer a little astigmatism and this EP has a 5mm exit pupil in an F6 scope.

[vlaiv]

48 minutes ago, Pixies said:

Yep - looks identical to my OVL Aero ED 30mm.

I see some astigmatism at the outer 20% of the view - in an F6 dob. Now, that could be my eyes, as I suffer a little astigmatism and this EP has a 5mm exit pupil in an F6 scope.

Your astigmatism is going to affect all stars in the field equally, so that is not it, but it can possibly be coma?

In F/6 scope - you don't see much of it and only time it can be seen is with wide field eyepieces with this one.

@Carl Au

Nice report. Any chance of field stop measurement?

[Carl Au]

24 minutes ago, vlaiv said:

 

Nice report. Any chance of field stop measurement?

This is where I start to fall down, I don't know to be honest, but it really is the most comfortable eyepiece to use. I would have no problem recommeding one of these to anyone. How they perform in a fl5 dob In have no idea, but they are a joy my fl7 refractor (a scope which I love just a little more everyday, I am soooooo glad I didn't buy that pretty little StellaMyra). I will have a dig and see what else I can find, re field stop. 

[Carl Au]

1 hour ago, John said:

Good report !

That eyepiece looks identical in every respect to the Aero ED 30mm that I had recently. Including the lens coatings and the dust caps.

They are nice and light for 2 inch eyepieces and the one I had worked well at F/7.5 and slower I thought.

I just found your review John, you did a far more though job of it than I did. You are right, that has to be the same ep. I am sure that I read somewhere it was made by the same crew that built my scope, Kumnings United Optics. If so maybe that's why it performs so well. It's a while now since I sold my last TV eyepiece, a 24 mmm Panoptic. This was probs the widest field I have owned (is the 32 mm TV Plossl any wider?) I don't remember the panoptic being optically any better that this one although the build quality was. Having said that they build quality is really good. I think it was John that said they look and feel like WO, I think that is spot on, and probs made in the same factory too. 

[vlaiv]

7 minutes ago, Carl Au said:

This is where I start to fall down, I don't know to be honest, but it really is the most comfortable eyepiece to use. I would have no problem recommeding one of these to anyone. How they perform in a fl5 dob In have no idea, but they are a joy my fl7 refractor (a scope which I love just a little more everyday, I am soooooo glad I didn't buy that pretty little StellaMyra). I will have a dig and see what else I can find, re field stop. 

It is not hard to measure if you can access inside of the barrel - just be careful not to scratch any elements.

Here are a few images to explain it:

You can use either calipers or ruler.

Ruler won't be as precise - but there is less chance for anything going wrong. You can put it against the barrel and eyeball field stop diameter against it.

 

 

[Carl Au]

I make it 26mm, does that sound about right? 

[vlaiv]

1 minute ago, Carl Au said:

I make it 26mm, does that sound about right? 

To be honest, it sounds too low. That is field stop of 32mm 52° plossl.

It should be closer to 36mm, maybe it is a typo in your post?

 

[Carl Au]

No, that's just my poor measuring. I think on reflection I might have read it was it was 39mm, but it looked wrong when I wrote it down. Like I say this is where I fall down, this kind of thing is not a strong point. And now to make myself look even stupid-er. How can it be 36 or 39 if it's only a 30mm ep? 

[vlaiv]

Just now, Carl Au said:

No, that's just my poor measuring. I think on reflection I might have read it was it was 39mm, but it looked wrong when I wrote it down. Like I say this is where I fall down, this kind of thing is not a strong point. And now to make myself look even stupid-er. How can it be 36 or 39 if it's only a 30mm ep? 

30mm is focal length of eyepiece, while field stop diameter - is well diameter of that "baffle" that limits how much of focal plane "eyepiece" sees.

Roughly, for astronomical eyepieces, following relationship holds: field_stop = focal_length * AFOV, where AFOV is expressed in radians.

For terrestrial eyepieces this has a bit different form: field_stop/2 = focal_length * tan(AFOV/2), again AFOV is in radians.

Although eyepiece is said to be 30mm and it is said to have 69° AFOV - these numbers might not be correct. Eyepiece can have FL of say 30.7mm and still be called 30mm EP, or could have 67.2° and still be said to have 69°.

This happens mostly due to marketing and "rounding" up - whole line is marketed as 69° eyepieces but in fact there is small variation in actual numbers.

In any case - field stop is true indicator of how much of true field of view in the sky you will see with particular telescope. For that reason it is good to know that value - but it is often not stated for eyepiece.

If, for example, I'm looking for eyepiece that will give me 4° TFOV in 600mm FL telescope, then I need eyepiece with 41.9mm or larger field stop - regardless of focal length and apparent field of view of eyepiece. Once I have narrowed my selection of EPs, then I can think about focal lengths, exit pupils, AFOV and all of that. That is one way of looking at it - not necessarily the best way, but it has its uses.

 

[Louis D]

Here's Ernest in Russia's review/test of the 30mm, 35mm, and 40mm versions of these eyepieces under the Levenhuk ED brand.  All versions are made by KUO and the 30mm and 40mm were originally designed by Thomas M Back as the TMB Paragon.

From his summary chart, the measured field of view is 66 degrees for the 30mm, so just slightly less than the claimed 69 degrees (the top row of the table needs shifted one column right):

FL	AFOV	F4	F4	F4	F10	F10	F10	List of
Eyepiece	mm	°/deg.	centre	zone	edge	centre	zone	edge	rest aberrations

United Optics, ED	40	64	5	18	25	<5	12	20	Ast.,FC
United Optics, ED	35	70	5	20	35	<4	12	20	Ast.,FC
United Optics, ED	30	66	5	20	40	<4	11	22	Ast.,FC

[vlaiv]

10 minutes ago, Louis D said:

Here's Ernest in Russia's review/test of the 30mm, 35mm, and 40mm versions of these eyepieces under the Levenhuk ED brand.  All versions are made by KUO and the 30mm and 40mm were originally designed by Thomas M Back as the TMB Paragon.

From his summary chart, the measured field of view is 66 degrees for the 30mm, so just slightly less than the claimed 69 degrees (the top row of the table needs shifted one column right):

FL	AFOV	F4	F4	F4	F10	F10	F10	List of
Eyepiece	mm	°/deg.	centre	zone	edge	centre	zone	edge	rest aberrations

United Optics, ED	40	64	5	18	25	<5	12	20	Ast.,FC
United Optics, ED	35	70	5	20	35	<4	12	20	Ast.,FC
United Optics, ED	30	66	5	20	40	<4	11	22	Ast.,FC

I wonder why 40mm one is no longer made.

It has best performance at the edge of the field of the three.

In any case, I can see 35mm having enough of field stop to give me 4° in ST120 (together with 7mm exit pupil) - good to know.

 

[Louis D]

1 hour ago, vlaiv said:

I wonder why 40mm one is no longer made.

It has best performance at the edge of the field of the three.

In any case, I can see 35mm having enough of field stop to give me 4° in ST120 (together with 7mm exit pupil) - good to know.

You would think TS-Optics could have had a production run made for them of the 40mm version since it is the most in demand worldwide.

The 35mm is going to struggle a bit at the edges in an ST120.  Here's how my 35mm OVL Aero ED looks at f/6 in my AT72ED:

[vlaiv]

29 minutes ago, Louis D said:

Here's how my 35mm OVL Aero ED looks at f/6 in my AT72ED

Is that flattened or regular AT72ED. It has rather short focal length - field curvature must be strong in the young one .

ST120 will have quite a bit larger radius of curvature if we take 1/3 of FL of each to be approximate radius of curvature. If above is flattened field then I can only expect worse from ST120 unless I have young eyes that compensate for FC (I'm starting to need reading glasses when working on computer - so that boat is probably about to set sail).

 

[Louis D]

1 hour ago, vlaiv said:

Is that flattened or regular AT72ED. It has rather short focal length - field curvature must be strong in the young one .

ST120 will have quite a bit larger radius of curvature if we take 1/3 of FL of each to be approximate radius of curvature. If above is flattened field then I can only expect worse from ST120 unless I have young eyes that compensate for FC (I'm starting to need reading glasses when working on computer - so that boat is probably about to set sail).

It is field flattened with a properly spaced TSFLAT2 ahead of a GSO dielectric diagonal.  Notice that the Meade 5000 SWA 40mm had no problem with the field.

The AT72ED has a 430mm focal length and 143mm RoC.  Your ST120 has a 600mm FL and 200mm RoC, so it will be less severe on eyepieces.  It might need about 15mm less TSFLAT2 spacing than my AT72ED.  However, I've found that the same spacing for my AT72ED works just fine with my TS-Optics Photoline 90mm FPL-53 Triplet APO which has the same FL as the ST120.  Shortening it didn't seem to improve things visually.

[ScouseSpaceCadet]

Nice eyepieces. My OVL ED30 presented a very pleasing image in the ST120. Edge correction and field curvature I can't comment on, being too busy making 'Wow' noises.

Almost as good as the more expensive Vixen NVLW lanthanum 30mm, which actually lost to the ED30 due to the uncomfortable eye cup.

[Don Pensack]

On 04/03/2021 at 10:24, vlaiv said:

Your astigmatism is going to affect all stars in the field equally, so that is not it, but it can possibly be coma?

In F/6 scope - you don't see much of it and only time it can be seen is with wide field eyepieces with this one.

@Carl Au

Nice report. Any chance of field stop measurement?

This eyepiece has residual lateral field astigmatism, so that is probably what he is seeing.

[Don Pensack]

I may not have pointed this out before, but the field stop diameter will equal the focal length (+/-) if the eyepiece has a 1 radian apparent field (57.3°)

and will be larger if the apparent field is larger and smaller if the apparent field is smaller.

Some examples:

18.2mm Delite, 62°, field stop 19.1mm.  Field stop is 0.9mm larger than the focal length, or 4.9% larger.  Apparent field is 8.2% larger than 1 radian.

20mm Plössl, 50°, field stop 17.1mm.  Field Stop is 2.9mm smaller than the focal length, or 14.5% smaller.  Apparent field is 14.6% smaller than 1 radian

21mm Ethos, 100°, field stop 36.2mm.  Field stop is 15.2mm larger than the focal length, 72.4% larger.  Apparent field is 74.5% larger than 1 radian.

Of the 3, the one with the largest discrepancy is the 18.2mm Delite.  Either its apparent field is wrong or the field stop is wrong.  I suspect it's 60° or a hair more.

 

 

[Louis D]

On 04/03/2021 at 11:29, Pixies said:

Yep - looks identical to my OVL Aero ED 30mm.

I see some astigmatism at the outer 20% of the view - in an F6 dob. Now, that could be my eyes, as I suffer a little astigmatism and this EP has a 5mm exit pupil in an F6 scope.

In my OVL Aero ED 35mm, I'd peg it at the outer 25% of the field of view at f/6.  Notice in my above image how fuzzy the marks get about 4.5 inches in from the edge?  That's 4.5/17=26% from edge to center.  I like to tell folks that the central 75% of the field of view is acceptably sharp based on this assessment.

[Carl Au]

11 hours ago, Louis D said:

In my OVL Aero ED 35mm, I'd peg it at the outer 25% of the field of view at f/6.  Notice in my above image how fuzzy the marks get about 4.5 inches in from the edge?  That's 4.5/17=26% from edge to center.  I like to tell folks that the central 75% of the field of view is acceptably sharp based on this assessment.

 I wonder how much difference using a refractor makes, that and a little longer fl at fl7, to me all the stars look pin point with the 30 ED.  I bought it to use for open clusters and so far have been delighted with it's performance, its really very good for the money. I think you can get one from FLO for 90 quid at the minute, amazing. I think I am right in saying the that both my Starwave 102 ED-R and ED30 eyepiece were made by KUO. I wonder if they were made in the same factory?

 

Edited March 6, 2021 by Carl Au

[Louis D]

4 hours ago, Carl Au said:

 I wonder how much difference using a refractor makes, that and a little longer fl at fl7, to me all the stars look pin point with the 30 ED.  I bought it to use for open clusters and so far have been delighted with it's performance, its really very good for the money. I think you can get one from FLO for 90 quid at the minute, amazing. I think I am right in saying the that both my Starwave 102 ED-R and ED30 eyepiece were made by KUO. I wonder if they were made in the same factory?

I was using an f/6 AT72ED refractor, so no difference there.  I could try my 35mm in my f6.6 APO to see if it makes any difference.

Understand, I'm being hypercritical when I'm looking for edge astigmatism.  I take as bright a star as I can find, focus it in the center, note the sharpness, move it toward the edge, refocusing it for the edge to eliminate field curvature issues as needed, and then note the sharpness in comparison.  I then rack the focus on either side of best focus to look for astigmatism in the form of radial or tangential lines instead of a nice, off center circle.  The 30mm APM UFF passes this test without any issues.

All that matters is that you really like the eyepiece in your scope, and it works extremely well for your needs.  How it performs under test bench conditions is irrelevant.

As for your scope, it does indeed appear to be KUO made.  As far as factories go, there's a good probability they were made in the same town, but possibly in two separate buildings dedicated to different optics.  As companies expand, it's typically easier to build a new building instead of expanding an existing one, so you end up with a collection of buildings on a campus or even spread around town.

I just realized they're based in Kunming (hence their name).  That was the terminus of "The Hump" US air supply route for the Chinese army of Chiang Kai-shek in WWII.  I also used to work for a guy born and raised in Kunming.  Really nice fellow.

Edited March 6, 2021 by Louis D