Eyepiece Comparison 2019

Introduction | Comparisons in Daylight | Comparisons by Night | Conclusions | Links | Appendix: Brief Comparison of TSWA32 and TSED35 Eyepieces

On this page, I report on an informal eyepiece comparison that I did in November and December 2019. Primarily it was about using 2" eyepieces on my new Celestron C8 telescope. A starfriend lent me four of his 2" eyepieces because he did not need them for some time. In addition, there were two of my 2" eyepieces and some 1.25" eyepieces from my "collection" that matched some of the 2" eyepieces. Unfortunately, the sky was mostly cloudy at night or we were not at home. So I did a lot of the testing during the day, partly with my refractor PS 72/432, and also while traveling. The daytime comparisons with the C8 and PS 72/432 showed approximately the same results, so that I think that the use of the refractor in these comparisons is acceptable. Thereafter, I was able to carry out tests at night on the crescent and half moon.

I would like to emphasize that I consider myself as a layman in the evaluation of eyepieces and only report on my subjective impressions here.

Note: See also the appendix offering a Brief Comparison of TSWA32 and TSED35 Eyepieces.

 

Introduction

I used the following eyepieces for the comparison:

Photos of the Eyepieces

Photo: All eyepieces that were used in the comparison - TS 16 mm UWA, Explore Scientific 18 mm UWA, TeleVue 24 mm WA, Sky-Watcher 28 mm LET, 32 mm DigiScope Plössl, TSWA32 32 mm WA, TSWA38 38 mm WA, TSED35 35 mm WA, Omegon 56 mm Super Plössl

Photo: The eyepieces with a shorter focal length - TS 16 mm UWA, Explore Scientific 18 mm UWA, TeleVue 24 mm WA, Sky-Watcher 28 mm LET, 32 mm DigiScope Plössl (has about the same field of view as the 28 mm LET and the 24 mm TeleVue)

Photo: The eyepieces with a shorter focal length - 32 mm DigiScope Plössl, TSWA32 32 mm WA, TSED35 35 mm WA, TSWA38 38 mm WA, Omegon 56 mm Super Plössl

Visual Power (Magnification) and other Data for Different Focal Lengths of Eyepieces

Visual Power (Magnification) and other Data for Different Focal Lengths of Eyepieces

Note: These tables include the StarTravel 120 refractor*, a TSWA32 eyepiece (2", 32 mm focal length, 70° viewing angle) that I borrowed together with the StarTravel 120, a 18 mm eyepiece (2", 82° viewing angle), a 38 mm eyepiece (2", 70° viewing angle), and a 56 mm eyepiece (2", 52° viewing angle).

I did not include the Celestron 25 mm Plössl- eyepiece which is packaged with the C8, because I will probably give it away...

*) I had compared the TSWA32 and TSED35 eyepieces using this telescope in the fall of 2019; it was not involved in this comparison, because I had returned it already.

Telescope
Further Data
Focal Length of Eyepiece (mm)
Magnification
 
Focal Length of
Telescope (mm)
4
7
10
16
18
24
28
32
32
35
38
56
PS 72/432
432
108.00
61.71
43.20
27.00
24.00
18.00
15.43
13.50
13.50
12.34
11.37
7.71
ST120
600
150.00
85.71
60.00
37.50
33.33
25.00
21.43
18.75
18.75
17.14
15.79
10.71
PDS150
750
187.50
107.14
75.00
46.88
41.67
31.25
26.79
23.44
23.44
21.43
19.74
13.39
Skymax-127
1500
375.00
214.29
150.00
93.75
---
62.50
---
46.88
---
---
---
---
C8
2032
508.00
290.29
203.20
127.00
112.89
84.67
72.57
63.50
63.50
58.06
53.47
36.29
C8 (red.)
1280
320.00
182.86
128.00
80.00
---
53.33
---
40.00
---
---
---
---
 
True Field of View (°)
Apparent Field of View (°) >
82
82
72
82
82
65
56
52
70
69
70
52
 
Focal Length of
Telescope (mm)
4
7
10
16
18
24
28
32
32
35
38
56
PS 72/432
432
0.76
1.33
1.67
3.04
3.42
3.61
3.63
3.85
5.19
5.59
6.16
6.74
ST120
600
0.55
0.96
1.20
2.19
2.46
2.60
2.61
2.77
3.73
4.03
4.43
4.85
PDS150
750
0.44
0.77
0.96
1.75
1.97
2.08
2.09
2.22
2.99
3.22
3.55
3.88
Skymax-127
1500
0.22
0.38
0.48
0.87
---
1.04
---
1.11
---
---
---
---
C8
2032
0.16
0.28
0.35
0.65
0.73
0.77
0.77
0.82
1.10
1.19
1.31
1.43
C8 (Red.)
1280
0.26
0.45
0.63
1.03
---
1.22
---
1.30
---
---
---
---
 
Exit Pupil (mm)
 
Focal Ratio
4
7
10
16
18
24
28
32
32
35
38
56
PS 72/432
6
0.67
1.17
1.67
2.67
3.00
4.00
4.67
5.33
5.33
5.83
6.33
9.33
ST120
5
0.80
1.40
2.00
3.20
3.60
4.80
5.60
6.40
6.40
7.00
7.60
11.20
PDS150
5
0.80
1.40
2.00
3.20
3.60
4.80
5.60
6.40
6.40
7.00
7.60
11.20
Skymax-127
11.81
0.34
0.59
0.85
1.35
---
2.03
---
2.71
---
---
---
---
C8
10
0.40
0.70
1.00
1.60
1.80
2.40
2.80
3.20
3.20
3.50
3.80
5.60
C8 (red.)
6.3
0.63
1.11
1.59
2.54
---
3.81
---
5.08
---
---
---
---

Blue: Equipment that I borrowed for comparison purposes; violet: borrowed and bought; italic 2" eyepiece

Magnification: Yellow: low (30-50 x); magenta: medium (80-100 x); violet: high (150-200 x - and more); red: beyond maximum usable magnification.
Exit pupil: Values in magenta cells are either too small (< 1 mm) or too large (> 6.4/7 mm); yellow background: best for galaxies (about 2-3 mm).

 

Comparisons in Daylight

I describe the following comparisons in "telegram style." I did not take any photos of what I saw in the eyepieces, describe my subjective qualitative impressions only with words.

Comparisons Using the Omegon PS 72/432

On November 21, 2019, I compared the eyepieces presented above using my Omegon PS 72/432 refractor.

TS UWA 16 mm (1.25") versus Explore Scientific 18 mm Wide Angle (2") - About the Same Magnification/Field of View

TeleVue WA 24 mm (1,25") versus Sky-Watcher LET 28 mm (2") - Identical Field of View

Omegon Super Plössl 56 mm (2")

DigiScope Plössl 32 mm (1,25") versus TSWA32 32 mm (2") - Two 32 mm Eyepieces

TSWA32 (32 mm, 2") versus TSED35 (35 mm, 2") versus TSWA38 (38 mm, 2") - the Long Ones...

Brief Conclusion

After this first daylight test, the 56 mm eyepiece did not recommend itself for me, and the 35 ED was in my opinion superior to the two TSWA eyepieces (32/38 mm). Only the AP is better on the 32 when observing with the ST120 and the Explorer 150PDS. I did not like at all the 18 mm eyepiece from Explore Scientific when observing in daylight and got a very short eye relief, even though the advertising states otherwise.

Comparisons Using the Celestron C8

On November 22, 2019, I compared the eyepieces presented above with the Celestron C8. Due to the long focal length of the C8 the field of view is much smaller and the magnification much higher than on the PS 72/432.

TS UWA 16 mm (1,25") versus Explore Scientific 18 mm (2") - About the Same Magnification/Field of View

TeleVue WA 24 mm (1,25") versus Sky-Watcher LET 28 mm (2") - Identical Field of View

Omegon Super Plössl 56 mm (2")

DigiScope Plössl 32 mm (1,25") versus TSWA32 32 mm (2") - Two 32 mm Eyepieces

TSWA32 (32 mm, 2") versus TSED35 (35 mm, 2") versus TSWA38 (38 mm, 2") - the Long Ones...

Brief Conclusions

The results with the C8 are similar to those with the refractor PS 72/432. With the 56 mm eyepiece, I saw the shadow of the secondary mirror on the C8; I did not notice it with the other eyepieces.

Even after this test, the 56 mm eyepiece did not impose itself on me, and the 35 ED seemed to me to be superior to the two TSWA eyepieces (32/38) once again. I did not like the 18 from ES during the day on the C8 as well, and it had a very short eye relief, even if the advertising states otherwise.

 

Comparisons at Night

Quick Comparison Using M 15

On 29.11.2019 I compared the borrowed and some of my eyepieces informally in Erkerode with the C8 at the globular cluster star M 15. This is a less bright object, so color fringes did not play a role. M 15 was very nice with all eyepieces:

Conclusion: With fainter DSO, the color fringes disappear that can be seen during the day on bright planets or on the bright moon (see below), and all eyepieces are usable, so that in the end, focal length and AP should be the deciding factors when choosing an eyepiece.

Note: I was able to replicate these results on December 4, 2019, when I observed the globular star clusters M 2 and once more also M 15 with the C8 and various eyepieces (56, 35, 28, 24, 18, 16, 10 mm).

Comparisons Using the Crescent of the Moon (November 30, 2019 and December 2, 2019)

On November 30, 2019 and December 2, 2019, I compared most of the eyepieces in Erkerode at night using the C8 and the crescent of the moon:

Since both days revealed approximately the same results, I summarize these for both days:

Brief Conclusion

Again, I do not like the 18 mm eyepiece from Explore Scientific on the C8, this time at night and brighter objects. I was surprised by the conspicuous yellow color fringes of the TSED35 at the edges of the moon. Otherwise, I did not see any differences to the TSWA32 and TSWA38 eyepieces, except for the size of the sky section in the field of view and for small differences in magnification.

Comparisons Using the Half Moon (December 4, 2019)

This time, the moon remained bright in Erkerode during the comparison using the C8. The telescope had more or less cooled down, although the image was still "flickering", particularly fine structures on the moon...

Brief Conclusions

In the meantime, I had bought the 56 mm eyepiece and will not discuss it further, because it plays in a slightly different league than the three 30 mm eyepieces.

32/35/38: The half moon showed a larger bright area compared to the crescent moon, so that only here certain things, above all color fringes, come to light. In my opinion, it is therefore better suited for the eyepiece comparison than the crescent moon. Even if a decision is difficult and sometimes results seem to be reversed, I have arrived at the following order for the three eyepieces:

  1. TSED35: showed in my opinion and that of my wife the image with the most contrast richest details of all three eyepieces; at the terminator (red/yellow?) color fringes were practically not perceptible, at the moon edges quite pronounced (yellow)
  2. TSWA38: showed in my opinion the second best image; at the terminator faint red color fringes were perceptible, at the edges of the moon (bluish and) less pronounced than the TSED35.
  3. TSWA32: showed in my opinion the poorest image of the three eyepieces (but not a poor image!); at the terminator, red color fringes were clearly perceptible and disturbed the perception of details; at the edges of the moon, the (bluish) color fringes were similar to those in the TSWA38 and less pronounced than in the TSED35.

18: Again, I had problems with the look, causing some wide colored fringes at the edges of the field of view. The (yellow/purple) color fringes at the terminator were recognizable, but not disturbing. Altogether, I would prefer my 16 mm UWA eyepiece (1.25") to the 18 mm ES eyepiece.

18 mm Explore Scientific Eyepiece on the Globular Star Clusters M 2 and M 15 (December 4, 2019)

While the half moon is a very bright object, globular star clusters, such as M 2 and M 15, are rather "faint" objects, so that color fringes hardly appear - or not at all. Accordingly, the 18 mm ES eyepiece was very useful on M 2/M 15! I assume that this will also be the case with other DSOs. However, the problem remains that I often only get a "tunnel view" with this eyepiece and have to approach the eyepiece very closely with the eye in order to obtain a larger field of view.

Light Pollution, O III and UHC Filters at the Orion Nebula M 42/43 (December 4, 2019)

At the end of the observation night, I tested the three filters (Light Pollution, O III and UHC filters), which I had borrowed together with the eyepieces, on the Orion Nebula M 42/43 using my TSED35 eyepiece. That means, I wanted to see if they had an effect at all and if so, which one. This was the first and only time I ever got to test the filters on a suitable sky object. In short: Only the UHC filter showed an effect and made the Orion Nebula even more beautiful, especially according to my wife. After this test, I consider buying such a filter as well...

By the way: When screwing the Light Pollution and the O III filter into the 2" TSED35 eyepiece, I quickly encountered resistance and did not turn any further. Only the UHC filter could be screwed in correctly. Later, I searched the Internet for the Sky-Watcher Aero 40 mm eyepiece, which is apparently out of stock and maybe no longer manufactured. At the Website of an English dealer, I found a customer comment saying that the AERO eyepiece has a problem with 2" filters - you cannot screw in filters more than half a turn. This means for me: (1) my TSED eyepiece is actually identical to the AERO eyepieces, and (2) the whole AERO series seems to have a problem with the filter thread, which is incomprehensible to me.

The next day, I tried again to screw in the filters (carefully and only as far as possible!) and got the same results. The UHC filter could be screwed in completely without any resistance, but I "felt" that the thread was slackening quite a bit... I find all this very annoying!

 

Conclusions

The eyepiece comparison was on the one hand very interesting for me, on the other hand it was not under a lucky star, because there were only few opportunities for a comparison. Fortunately, I also made comparisons during the day. These results are only partially transferable to night observations, but, at least, with brighter objects such as the moon, some of the day results can be transferred. Besides, I am indeed not an experienced tester, and write just down what I notice. Since I always could only use one eyepiece at a time at the telescope, a "parallel test" was unfortunately not possible, which might have eliminated one or the other ambiguity.

Basically this test was about the following questions:

I answered the first question above with respect to the half moon:

Following my comparisons, the differences are more pronounced in daylight, whereby my order is the same. The starfriend, from whom I borrowed the TSWA eyepieces, uses the TSWA32 only on the StarTravel 120/600 and the TSWA38 only on the C8. Thus, he also needs just one of the TSWAs on a telescope...

The 56 mm eyepiece (Omegon) did not really convince me, but I bought it from my starfriend to have an option for a maximum field of view.

The 18mm eyepiece from Explore Scientific did not convince me during the day and on the moon. On DSO, however, which are much fainter, it should work satisfactory. I found it OK for globular star clusters, but I did not have the time anymore to test it more thoroughly.

I do not know yet, whether I will prefer the 24 mm TeleVue or the 28 mm LET; the TeleVue should be a bit better anyway... But if I have two telescopes in use, I can use one of those eyepieces on each...

My current gradation of eyepieces that can be used on the C8 is (without the focal lengths in red; italic = 1.25"):

I believe to recognize gaps at 40 mm and around 20 mm... In the meantime, a closed one of the gaps and bought a used Lacerta ED 40 mm eyepiece (same manufacturer as for my TSED35).

 

Links

 

Appendix: Brief Comparison of TSWA32 and TSED35 Eyepieces

I did the following quick comparison between the TSWA32 and TSED35 wide-angle eyepieces in September/October 2019, when a starfriend lent me his StarTravel 120/600 refractor and the TSWA32 eyepiece. It can be found on the original on the ST120 page and was slightly modified here.

Figure: My 2" eyepieces and the TSWA32 (at the center)

Together with the Explorer 150PDS came a 28 mm LET eyepiece from Sky-Watcher, which I used very little in the past. For rich-field observations with the PS 72/432, I purchased a TSED35 eyepiece (2", 35 mm focal length, 69° angle of view). Before I bought this one, I was a little bit torn between the TSED35 and the cheaper TSWA32 and therefore asked Telescope Service, which one is better suited to my needs. They hesitated somewhat, but eventually, like me, they preferred the TSED35. The hobby astronomer, from whom I borrowed the ST120, had bought a TSWA32 eyepiece (2", 32 mm focal length, 70° angle of view) and gave it to me together with the ST120 for testing, because he uses it exclusively on the ST120.

Generally, both eyepieces are very similar, and I found it difficult to find a difference between the two both during the day and at night, especially as I was not able to observe with both at the same time.

Comparison at Daylight

During the day, I found violet color fringes on TSWA32, whereas on the TSED35 weaker wider yellow color fringes and maybe a very thin violet fringe on the edges as well. Which type of color fringing one prefers is surely a matter of personal preferences... The sample photos with the PS 72/432 may not be representative and do not show the yellow color fringes of the TSED35, but show some blue-green fringes.

Figure: Sample photos with TSED35 (top row) and TSWA32 (bottom row) at the PS 72/432

Figure: Sample photos with TSED35 (top row) and TSWA32 (bottom row) at the ST120

Overall, the TSED35 may provide a somewhat sharper image, but I find this hard to judge. At first glance, I see it in the (narrow) lead... With regard to the exit pupil, however, the TSWA32 at the ST120 and also at the Explorer 150PDS with a value of 6.4 is better off than the TSED35 with a value of 7.

Comparison at Night

On our vacation in France in September 2019, I compared both eyepieces once again using the StarTravel 120 at night and was not able to see any differences, especially since I could only look through the eyepieces alternately. The TSWA32 was superior in this combination with respect to focusing, because it had room in both directions, whereas the TSED35 was "at the limit " and just came into focus. A closer inspection at home, however, revealed afterwards that there is a tiny bit of room for focusing with the TSED35.

 

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12.12.2019