Baader Hyperion Aspheric 36mm VS TS-Optics Paracor UFL 35mm

[PeterC65]

I bought the Baader Hyperion Aspheric 36mm in the recent FLO sale as I've been looking for a widefield 2" eyepiece for a while. I use it with the Explorer 150PDS (F5.0) to get a wide field of view (3.44°) and with a 2" diagonal with the Photoline 72 (F6.0, 72mm) to get a very wide field of view (5.97°). It sees more use with the Explorer 150PDS.

The BHA 36mm does the job but I have noticed star distortion around the edges which makes the stars seagull shaped. Sometimes this isn't an issue if the target is towards the centre of the field of view and my objective is to view it in context (with dark sky around it), but it's quite noticeable when viewing wide star fields.

There has been much discussion about the StellaLyra UFF 30mm with many people enthusing about its flat field. I have considered this eyepiece but at 30mm it is just a bit too close to my ES68° 24mm with a field of view noticeably smaller than with the BHA 36mm. So I have been considering the TS-Optics Paracor UFL 35mm which I understand is a clone of the AeroED 35mm.

How much improvement could I expect from the TS 35mm compared with the BHA 36mm?

I would be particularly interested to hear from people who have experience with the TS-Optics eyepiece rather than the AeroED. I think they are the same but am not certain. The AeroED 35mm isn't available anymore and they don't seem to come up second hand (which suggests they are a great eyepiece!).

 

[michael.h.f.wilkinson]

I have had a chance to look through a Baader Hyperion Aspheric 36 mm in an F/8 scope, and the TMB Paragon 40 mm I had at the time (of which the Aero 40 mm is a clone), and the edge performance was noticeably better in the latter, even at F/8. I have used the Paragon 40 at F/6 and that worked fine. Having said that, the Paragon 40 mm is reported to be better than the 35 mm, so it is hard to be sure about the 35 mm vs the Baader 36 mm. I must say I was a bit underwhelmed at the performance of the Baader 36.

[Louis D]

I have both the 35mm Aero ED and the 40mm Lacerta ED.  The 40mm is noticeably better corrected than the 35mm.  However, the 35mm has a noticeably wider AFOV and nearly the same TFOV thanks to its 44.4mm field stop diameter.  If I had to guess, the 35 ED is probably a bit better than the 36mm BHA, but not substantially better.  It will probably have a significantly wider TFOV.

The old, massive 35mm Baader Scopos Extreme that was replaced by the 36mm BHA is sharp edge to edge at f/6 and probably close to that at f/5 being a massive negative/positive design not much affected by fast f-ratios.

Take a look at my Lacerta ED 40mm write-up.  I think I have an image showing all three FOVs for comparison somewhere in it.

I've never been even remotely interested in the 36mm BHA due to poor correction reports and high price, so I cannot directly comment on how it compares.

[PeterC65]

9 hours ago, Louis D said:

I have both the 35mm Aero ED and the 40mm Lacerta ED.  The 40mm is noticeably better corrected than the 35mm.  However, the 35mm has a noticeably wider AFOV and nearly the same TFOV thanks to its 44.4mm field stop diameter.  If I had to guess, the 35 ED is probably a bit better than the 36mm BHA, but not substantially better.  It will probably have a significantly wider TFOV.

The old, massive 35mm Baader Scopos Extreme that was replaced by the 36mm BHA is sharp edge to edge at f/6 and probably close to that at f/5 being a massive negative/positive design not much affected by fast f-ratios.

Take a look at my Lacerta ED 40mm write-up.  I think I have an image showing all three FOVs for comparison somewhere in it.

I've never been even remotely interested in the 36mm BHA due to poor correction reports and high price, so I cannot directly comment on how it compares.

I've read your review of the Lacerta ED 40mm a few times and it's very helpful. This eyepiece will mostly see use with the Explorer 150PDS with which the 40mm gives an 8mm exit pupil, so I'm favouring something closer to 35mm.

It's useful to know that the field stop of the Aero ED 35mm is wider than might be expected (from its specified AFoV). I checked the TS-Optics Paracor UFL 35mm and it has a specified field stop of 44mm, further evidence that it is an Aero ED clone and that it will also have a better than expected TFoV. Interestingly the StellaLyra UFF 30mm has a specified field stop of only 30.4mm which should mean a smaller than expected TFoV, putting me off this possible contender.

I've seen several positive reviews of the Aero ED 35mm which is what brought it to my attention, but your guess is that it may only be a bit better than the BHA 36mm. Given that you don't rate the BHA 36mm this is not a great endorsement of the Aero ED 35mm either! Yet you do have the Aero ED 35mm.

I'm trying to decide whether the TS-Optics Paracor UFL 35mm is worth a punt (about £130, which is above my usual punt territory).

 

[Louis D]

56 minutes ago, PeterC65 said:

I've seen several positive reviews of the Aero ED 35mm which is what brought it to my attention, but your guess is that it may only be a bit better than the BHA 36mm. Given that you don't rate the BHA 36mm this is not a great endorsement of the Aero ED 35mm either! Yet you do have the Aero ED 35mm.

I'm trying to decide whether the TS-Optics Paracor UFL 35mm is worth a punt (about £130, which is above my usual punt territory).

The ED 35mm is going to be slightly better than the BHA 36mm, but not head and shoulders better.

Here are Ernests tests of the BHA 36mm, ED 35mm, and Panoptic 35mm for comparison.

Here are the entries from his index of tests below:

	FL	AFOV	F4	F4	F4	F10	F10	F10	rest
Eyepiece	mm	°/deg.	axis	zone	edge	axis	zone	edge	aberrations

Baader, Hyperion Aspheric

36

70

3

30

60

3

15

25

Ast.,FC +3%

Levenhuk Ra, ED

35

70

>5

>20

>35

4

12

20

Ast.,FC

TeleVue, Panoptic

35

67

<2

8.5

13

<2

3

6

Ast. +15%

As you can see, the ED is slightly better than the BHA at the edge, but not hugely better and certainly not at Panoptic level correction.

Edited February 12, 2023 by Louis D

[badhex]

Basically, what @Louis D said. I also have both the 35mm TS-Optics and 40mm Lacerta. The 40mm is better, so get that if you can. It also affords you approximately the largest FOV possible in a 2" barrel, and will give you a bit more of a difference to your 24mm.

Only downside is that the larger exit pupil of the 40mm could be a bit of an issue in very fast scopes. 

[PeterC65]

1 hour ago, Louis D said:

Here are the entries from his index of tests below:

That's very helpful!

I'd seen Ernest mentioned but hadn't previously found his reviews. The index table, when converted to Excel to allow sorting, is very instructive.

The StellaLyra UFF 30mm has the best astigmatism performance of any 30mm to 40mm eyepiece. I can see now why people rave about it!

The BHA 36mm is in the bottom 25% (just), the Aero ED 35mm is in the middle, and the Lacerta ED 40mm is in the top 25% (just).

The TV Panoptic 35mm is the best of the 35mm FL eyepieces, and third in the list (of 30mm to 40mm FL eyepieces).

My favoured eyepieces, Explore Scientific 68° and 82° do well I'm pleased to say, and the ES 68° 34mm is on a par with the Aero ED 35mm.

Lots of food for thought ...

 

[Ricochet]

1 hour ago, PeterC65 said:

best astigmatism performance

I believe that the numbers represent the sum distortion size of all aberrations, not just astigmatism. Given the excellent numbers for the 30mm UFF I suggest that you would be better off buying that rather than buying a wider eye piece where aberrations mean that the extra field is actually unuseable. The other alternative that you might want to consider is the TS 28mm UWA available in the classifieds. 

[PeterC65]

2 minutes ago, Ricochet said:

I believe that the numbers represent the sum distortion size of all aberrations, not just astigmatism. Given the excellent numbers for the 30mm UFF I suggest that you would be better off buying that rather than buying a wider eye piece where aberrations mean that the extra field is actually unuseable. The other alternative that you might want to consider is the TS 28mm UWA available in the classifieds. 

My existing ES 68° 24mm gives me a 2.1° TFoV with the Explorer 150PDS. Unfortunately the 30mm UFF only increases that to 2.3°.

 

[Don Pensack]

5 hours ago, PeterC65 said:

I've read your review of the Lacerta ED 40mm a few times and it's very helpful. This eyepiece will mostly see use with the Explorer 150PDS with which the 40mm gives an 8mm exit pupil, so I'm favouring something closer to 35mm.

It's useful to know that the field stop of the Aero ED 35mm is wider than might be expected (from its specified AFoV). I checked the TS-Optics Paracor UFL 35mm and it has a specified field stop of 44mm, further evidence that it is an Aero ED clone and that it will also have a better than expected TFoV. Interestingly the StellaLyra UFF 30mm has a specified field stop of only 30.4mm which should mean a smaller than expected TFoV, putting me off this possible contender.

I've seen several positive reviews of the Aero ED 35mm which is what brought it to my attention, but your guess is that it may only be a bit better than the BHA 36mm. Given that you don't rate the BHA 36mm this is not a great endorsement of the Aero ED 35mm either! Yet you do have the Aero ED 35mm.

I'm trying to decide whether the TS-Optics Paracor UFL 35mm is worth a punt (about £130, which is above my usual punt territory).

 

You should know the factory field stop dimensions on the Ultra Flat Field eyepieces are the actual physical field stops, not the virtual field stops that you see in the eyepiece.

Without another repeat of a long-winded explanation, these are the actual field stops you see in the Ultra Flat Field eyepieces:

30mm --36.3  That is 33.5% wider than the 24mm ES 24x68 (2.1° becomes 2.8°)

24mm --27.5

18mm --21.7

15mm --18.2

10mm --11.2

The 30mm is narrower than the Aero ED, but not that narrow.  It's a real 70°.

 

By the way, there is a way to tell whether an eyepiece has pincushion distortion or barrel distortion at the edge.

If you calculate a field stop assuming 0% distortion,  it is = (apparent field ÷ 57.2958) x FL.

1) Example:  the 24mm TeleVue Panoptic.  A calculated field stop based on 68° is 28.5mm.  Its actual field stop is 27.0mm.

That means the 68° apparent field is created by stretching the field stop radially by 5.6% to yield a larger apparent field, so the eyepiece has pincushion distortion.

If the calculated field stop had been smaller than the actual field stop, it would mean the edge of the field was compressed to yield a smaller apparent field than the field stop implied.

2) Example: 12.5mm Docter/Noblex 84° eyepiece with a calculated field stop of 18.3mm and an actual field stop of 19.2mm.

That means the edge is compressed by 4.7% to yield only an 84° field, so the eyepiece has barrel distortion.

 

The 30mm UFF 70° eyepiece has a calculated field stop of 36.65mm and an actual field stop of 36.3mm.  That's pincushion distortion.  The field stop is stretched by ~1% to yield the apparent field measured.

That is very low distortion.

Edited February 12, 2023 by Don Pensack

[Littleguy80]

I use the Aero 40mm with my 80mm F6 frac for maximising FOV. I often look around at the other 40mm options. The 41mm Panoptic may well have the best performance but is also super heavy compared to the Aero. I can’t find anything that seems to match the Aero for performance at the size. It’s also incredibly good value.

As a side note, I have the APM UFF 30mm (Same as the Stellalyra) which is superb. I tend to go to this before the 40mm due to the improved contrast. The 40mm only being selected when I need a bigger FOV. Not that often for my observing habits. 

[PeterC65]

13 minutes ago, Don Pensack said:

You should know the factory field stop dimensions on the Ultra Flat Field eyepieces are the actual physical field stops, not the virtual field stops that you see in the eyepiece.

Without another repat of a long-winded explanation, these are the actual field stops you see in the Ultra Flat Field eyepieces:

30mm --36.3  That is 33.5% wider than the 24mm ES 24x68 (2.1° becomes 2.8°)

Thanks for pointing this out. It makes quite a difference!

 

[Louis D]

2 hours ago, PeterC65 said:

My existing ES 68° 24mm gives me a 2.1° TFoV with the Explorer 150PDS. Unfortunately the 30mm UFF only increases that to 2.3°.

2 hours ago, Don Pensack said:

30mm --36.3  That is 33.5% wider than the 24mm ES 24x68 (2.1° becomes 2.8°)

I composited together the 24mm APM UFF (which has about the same TFOV and correction level as the 24mm ES-68) with the 30mm APM UFF to show the difference in TFOV, AFOV, and magnification:

You get a nice 33.3% increase in linear field of view with the 30mm over the 24mm APM UFF with much better edge correction and a wider AFOV.

[PeterC65]

Thanks to all those who have commented.

My conclusion is that to get an eyepiece that is substantially better than the BHZ 36mm (i.e. worth the punt) I need to accept a smaller field of view and get the StellaLyra UFF 30mm.

While the Lacerta ED 40mm may also be substantially better, the exit pupil size with the Explorer 150PDS would be too big.

There is some merit in going for a slightly shorter focal length eyepiece as I'm finding the 36mm just a bit too low magnification / widefield when used with the Photoline 72.

 

[badhex]

54 minutes ago, PeterC65 said:

There is some merit in going for a slightly shorter focal length eyepiece as I'm finding the 36mm just a bit too low magnification / widefield when used with the Photoline 72.

Good shout. I have a ZS73 and I will most likely get a 30mm UFF eventually for similar reasons, since the 24mm is so good. 

[PeterC65]

I did some testing of the BHA 36mm last night ...

With a target like M45 which sits in the centre of the field of view, the star cluster looks OK, with just a bit of sparkle in the stars.

When looking at a wider starfield such as the one around Aldebaran (Hyades), the distortion of stars is quite noticeable. As Aldebaran is slewed from the axis to the edge of the field of view it acquires lines pointing towards the edge and as it approaches the edge the length and number of lines increases. Even on the axis Aldebaran appeared to sparkle a little, at 50% of the way to the edge it was three times the size, at 70% of the way it was six times the size. At the edge there were six or more lines dancing around as I moved my eye even very slightly.

The issue seems to be that these distorted edge stars are so elongated that they no longer look like star points of light, and they dance around with tiny movements of the eye. Both things make them very distracting.

Comparing with the ES68 24mm, there was similar distortion but much less than with the BHA 36mm making it less noticeable. Right at the edge I would say that stars are four times the size they are at the centre (the lines are shorter and there are fewer of them) but they remain sharp until 70% of the way to the edge from the axis.

 

[Louis D]

At large exit pupils, make sure you're not seeing eye astigmatism on axis and assigning it to the eyepiece.  With a star on axis, rotate your whole head around to make sure the lines of sparkle don't follow your eye's orientation.

The increase in distortion center to edge can safely be 100% assigned to the eyepiece, though.  What you're describing sounds a lot like a traditional Erfle eyepiece.  It's appalling Baader charges so much for these BHA eyepieces.

To confirm eyepiece astigmatism, rack focus inside and outside of best focus.  The lines should swap between radial and tangential forming a small cross at best focus.  If there is a fan pointing away from the cross toward the edge, that is coma and/or chromatic aberration depending on whether it is gray or rainbow colored.

[Don Pensack]

Louis makes a point.  I was unimpressed with the quality of the star images in the APM 30mm Ultra Flat Field when I first reviewed one several years ago.

A couple years later, I decided to try wearing my glasses at the eyepiece because it was obvious I needed them to see naked eye stars as points instead of little stick men.

Eureka! Tiny pinpoint star images from edge to edge in the 30mm.  Why I hadn't realized it was in my eye was because the star images in the center of the field were no worse

than the 36mm or 31mm Baader Hyperions and I just figured it was the same level of eyepiece quality as the Hyperions. 

Nope.  I went back to wearing glasses and tried the two Hyperions again--still bad.  But the 30mm APM became world class.

[PeterC65]

9 minutes ago, Louis D said:

If there is a fan pointing away from the cross toward the edge, that is coma and/or chromatic aberration depending on whether it is gray or rainbow colored.

What I was seeing with both the BHA 36mm and the ES68 24mm (to a much lesser degree) was a fan of lines pointing towards the edge of field. The fan lines got longer and more numerous as the star was slewed to the edge. I'd say with the BHA 36mm there was colour in the fan, but that was with Aldebaran which is very bright and quite yellow.

I should probably test with the refractor before doing anything rash!

Maybe I need a coma corrector for the Explorer 150PDS, but for visual that seems overkill.

[PeterC65]

5 minutes ago, Don Pensack said:

Louis makes a point.  I was unimpressed with the quality of the star images in the APM 30mm Ultra Flat Field when I first reviewed one several years ago.

A couple years later, I decided to try wearing my glasses at the eyepiece because it was obvious I needed them to see naked eye stars as points instead of little stick men.

Eureka! Tiny pinpoint star images from edge to edge in the 30mm.  Why I hadn't realized it was in my eye was because the star images in the center of the field were no worse than the 36mm or 31mm Baader Hyperions and I just figured it was the same level of eyepiece quality as the Hyperions. 

Nope.  I went back to wearing glasses and tried the two Hyperions again--still bad.  But the 30mm APM became world class.

I only need glasses for reading but I can sense my eye's are aging when I try to see detail, even in bright daylight. At the last optician visit the astigmatism part of my prescription was -0.25 which is quite good as far as I understand?

This may be a daft question but do people treat observing as they do reading, so use reading glasses if they need them when reading a book?

 

[Louis D]

28 minutes ago, PeterC65 said:

I only need glasses for reading but I can sense my eye's are aging when I try to see detail, even in bright daylight. At the last optician visit the astigmatism part of my prescription was -0.25 which is quite good as far as I understand?

0.25 diopters of astigmatism might cause some of the sparkle you saw on axis.  Try looking at stars naked eye and see if they also sparkle similarly.  Overall, that is a very low level of astigmatism.

29 minutes ago, PeterC65 said:

This may be a daft question but do people treat observing as they do reading, so use reading glasses if they need them when reading a book?

I use distance-only single vision glasses when observing.  That keeps the focus plane close to the eyepiece design focus plane so the field stop should be sharp.  It also makes looking up to the sky for object acquisition easier.

I could see using readers if you were referencing a detailed star chart when trying to locate Pluto or an asteroid, though.  That way, you could go back and forth quickly without any fussing putting glasses on and taking them off again.

[LDW1]

On 14/02/2023 at 14:41, PeterC65 said:

I did some testing of the BHA 36mm last night ...

With a target like M45 which sits in the centre of the field of view, the star cluster looks OK, with just a bit of sparkle in the stars.

When looking at a wider starfield such as the one around Aldebaran (Hyades), the distortion of stars is quite noticeable. As Aldebaran is slewed from the axis to the edge of the field of view it acquires lines pointing towards the edge and as it approaches the edge the length and number of lines increases. Even on the axis Aldebaran appeared to sparkle a little, at 50% of the way to the edge it was three times the size, at 70% of the way it was six times the size. At the edge there were six or more lines dancing around as I moved my eye even very slightly.

The issue seems to be that these distorted edge stars are so elongated that they no longer look like star points of light, and they dance around with tiny movements of the eye. Both things make them very distracting.

Comparing with the ES68 24mm, there was similar distortion but much less than with the BHA 36mm making it less noticeable. Right at the edge I would say that stars are four times the size they are at the centre (the lines are shorter and there are fewer of them) but they remain sharp until 70% of the way to the edge from the axis.

 

Wow, that sure would spoil an astronomers night of viewing !

[Don Pensack]

That is astigmatism, and it is inherent in the eyepiece.

The 31mm and 36mm Hyperions are best used at f/10 or longer focal ratios, and, even then, display residual astigmatism.

There are better-corrected eyepieces at those focal lengths.

[Louis D]

2 minutes ago, Don Pensack said:

There are better-corrected eyepieces at those focal lengths.

And prices.  It's absurd what Baader charges for the BHAs.