A couple months ago, my wife decided to buy me the TeleVue Apollo 11, in part because I’m a fanatic when it comes to the Apollo programme. The Apollo programme remains the largest civilian project in history, employing over 400,000 civilians at the height of the programme. Al Nagler of TeleVue was involved in the Apollo programme, specifically the optical components used for the LEM simulator that helped prepare the Apollo astronauts for what they would be encountering when landing on the surface of the Moon.
I thought it would be interesting to have a A/B shootout/comparison between the TeleVue Apollo 11 and the Explore Scientific 92° 12mm, a favorite of mine. The Explore Scientific 92° series of eyepieces are outstanding eyepieces that give a wide AFOV of 92°. The obvious drawback of the Explore Scientific 92° eyepieces are their weight which exceed the limit of some observers’ preferences and can lead to balance problems in some scopes. The weight of the ES92° eyepieces have not been a problem for me, but, I do get concerned about the stress put on my focuser as it has loosened the draw tube on my Moonlite focuser in the past. This is why I rarely powermate my ES92’s. In this review I will refer to the Explore Scientific 92° 12mm as the ES92 12, and the TeleVue Apollo 11mm as the A11.
The scope used for the comparison between the ES92 12 and the A11 is a 10” f/5.6 Reflecting Newtonian called the Gustav IV. This scope can be viewed in my signature. The scope is named after my son, now 13 years old. The IV denotes Gustav’s status as the 4th living generation of the Seidel lineage. The focuser is a Moonlite focuser that was made by Ron of Moonlite. The Gustav IV is equipped with a Telerad on a 4” riser. The Nexus DSC is installed on the Gustav IV and was used to find the targets for this review. The secondary diagonal is 1.83” in size and provided by Antares Optical. It is mounted on a four-vane spider made by Randy of AstroSystems. The primary mirror is a Pyrex mirror that is 1 ¾” thick. The primary is cooled by three 80mm fans placed in the back of the mirror cell. The fans are wired via a female to male USB cord that is connected to a 22,000 mAh portable battery. The fans can be switched between High, Medium, Low, and off. For the comparison between the ES92 12 and the A11, the scope was set outside at least 2 hours prior to the start of observing sessions, and the fans were left on high throughout the session as they do not produce any visible artifacts in the eyepiece image. The nighttime temperature remained above 70° on all four nights as it has been quite a warm summer in the Pacific Northwest this year.
I ground, polished, and figured the mirror under the tutelage of my friend Steven Swayze in 2010. The original coating on the primary was done by Paul at Spectrum Coating. The second coating, which was done in November of 2020, was performed by Carl Zambuto. The secondary diagonal was also re-coated along with the primary in November 2020.
For the following observations delineated below, no coma corrector was used. Coma was visible in both eyepieces. There were differences between the two eyepieces that I felt prevented a fair comparison between the ES92 12 and the A11, which I will discuss in the conclusion section following the observations section.
Observations were made over a course of four nights during new moon July. I hoped to make more critical comparisons at a Bortle 1 sky in the John Day Fossil Beds region, but wildfire smoke from the Bootleg Fire in Southern Oregon completely obscured the nighttime sky during our two night stay in Dayville, Oregon. We may still travel to the Steens Mountain region for new moon August for more critical comparisons between the ES92 12 and the A11, but plans are uncertain at this time due to the unpredictable nature of the Bootleg fire which is currently migrating in a Northeast direction at the time of this writing. The smoke from the Bootleg fire has reached as far as New York City as of July 21st, 2021.
Both eyepieces were used when sitting down in my white Starbound chair. Panning and scanning characteristics of both eyepieces were not evaluated as all targets were acquired by the onboard Nexus DSC. I used my distance glasses with a correction of 3.75 diopters on the cylinder for all observations. The lens of my eye glasses are quite thick and cut down on the effective ER for me. I also used a black t-shirt as a shroud for all observations so that differences in contrast would be more apparent to me.
7/9/21 Night I
13 miles North of Moses Lake, WA
Observing Conditions Summary:
Darkness improved significantly after 130AM. Observations were made in a Bortle 4/5 sky. The milky way was visible overhead but lacked the complex structure seen at truly dark sites. The milky way was also invisible to the south, near the horizon owing to the light dome from Moses Lake which was situated directly south. To the west, the light dome from Ephrata was visible, but not to the extent of the Moses Lake light dome. The observing session started at 1130P PST. The pollution from the light domes to the south and west decreased as the observing session moved into the small hours of the morning. All eyepieces showed EOFB, which likely indicates high water content in the atmosphere. A thin haze started to develop near the horizon of the sky dome and started to creep up towards zenith at 2:30AM, at which point I concluded the observing session.
M13 The Great Cluster in Hercules:
The core of M13 was visible in both the ES92 12 and A11, however the A11 showed slightly more contrast. The A11 also showed a pinch more depth between the foreground stars and the background stars in the cluster. The depth was still evident in the ES92 12, however, the depth or the perception of it, was slightly flatter. The difference here was very slight. An inexperienced observer would not see this depth difference.
M57 The Ring Nebula:
The central star in the Ring Nebula was visible with averted vision in the A11 although it was not especially prominent. In the ES92 12, the central star was difficult to tease out, I could not do so. The increased contrast in the A11 owing to the higher magnification factor could account for the visibility of the central star in the A11 and the absence of it in the ES92 12.
In the A11, I watched a group of three stars that are aligned in a straight line about 18 arc minutes from M57 leave the field stop. The stars remained aberration free, until the field stop was contacted, at which point the stars turned very slightly blue and then green before exiting the field of view. The green hue was observed very briefly and after multiple views of this particular star group leaving the field of view. In the ES92 12, the same group of stars showed lateral color in the last 5% of the field stop. Coma was also more evident in the ES92 12 owing to the larger AFOV of 92° compared to the 85° AFOV of the A11. There was also a hint of glare that lasted approximately 500-600 milliseconds in duration at the field stop just after the star group left the field of view, which indicates to me that the ES92 12 has some light scatter. This glare was not at all visible in the A11 as the star group left the field of view. The A11 controls for scatter better than the ES92 12.
7/10/21 Night II
13 miles North of Moses Lake, WA
Observing Conditions Summary:
Transparency was improved for this observing session over the previous night although a smoky haze extending from the horizon was evident. The nighttime sky seemed darker overall than the previous session on 7/9/21. EOFB in eyepieces is less prominent than the previous 7/9/21 observing session and the effects of EOFB decreased as the observing session progressed into the small hours of morning. By 3AM, EOFB was no longer prominent in both the ES92 12 and A11.
The ES92 12mm was used first for the Dumbbell Nebula to open the observing session. I rated contrast at 3/5 and sharpness at 4/5. I noticed the contrast suffers from EOFB. The core and wispy shell was evident in the ES92 12, but lacks depth and “pop”. In the A11, I rated contrast at 5/5 and sharpness at 5/5. The view in the A11 was engaging and contrasty. In the A11, the depth of the view was deeper, and the core of M27 stood out against the fainter outer wispy shell. EOFB was less prominent and was tightly controlled, although it was still evident at the field stop. The stars were more pinpoint in the A11 than the ES92 12. The ES92 12 presented an image that appeared to be slightly washed out when compared to the A11.
NGC 457 E.T. Cluster:
The ES92 12 opened the observing session for the E.T. Cluster, which has always been a favorite target for my three children. Children in particular, really get interested in astronomy if interesting names are attached to DSOs, like the E.T. Cluster name for NGC 457. I rated contrast at 3/5 and sharpness at 4/5 in the ES92 12. I noted haze around the stars in the torso area of the E.T. Cluster. The lack of depth was most apparent in the hues of the blue stars not contrasting against the black sky as well as in the A11. In the A11, the stars that define the torso area contrasted nicely against the velvet black sky which made the image at the eyepiece pop to my eyes. In the A11, I rated contrast at 5/5 and sharpness at 5/5. The eyes of E.T. were especially pinpoint and the view was highly engaging owing to the depth of the foreground stars against the black background. Stars appeared to be a richer blue hue in the A11 than the ES92 12. In the A11, the E.T. Cluster fills the field of view all the way out to the last 10%. This appeared to lend the E.T. Cluster a greater majestic factor than in the ES92 12, which was placed against a larger star field, owing to the 92° AFOV of the ES92 12. In particular, the stars that form the legs of E.T. appeared to pop with blue hues in the A11 and appeared to be more pinpoint in the A11 than in the ES92 12. Aberrations like coma and likely a lack of sharpness impact the ES92 12 to a greater extent than the A11, likely owing to the larger AFOV of the ES92 12 and better correction in the A11 lens. After completing my evaluation of both the ES92 12 and A11 on NGC 457, I put the A11 into the focuser and observed the E.T. Cluster for enjoyment. A fabulous eyepiece that fed candy to my eye.
M57 The Ring Nebula; Lumicon UHC Gen 3 filter:
The ES92 12 opened the show when I returned to M57. This was at 3AM, so darkness was at the best for the night, which almost completely eliminated EOFB from earlier in the observing session. In the ES92 12, the image presented appeared to be flat in terms of contrast and the stars had a blue haze around them. The Ring Nebula stood out against the background and was quite bright however the small apparent size was noticeable against the large star field provided by the wide 92° AFOV. I rated contrast at 3.5/5 and sharpness at 3/5. I switched to the A11 and installed the UHC filter. The Ring Nebula was stunningly bright. I found the brightness of the Ring Nebula to be so contrasty, that it had the feeling of being “burned” into my retina. The central star was begging to be teased out, unlike in the ES92 12. The stars surrounding M57 had a blue hue, and no haze around them. After I finished my comparisons between the A11 and ES92 12, I put the A11 into the focuser and enjoyed the eye candy being fed into my eye from the A11.
7/11/21 Night III
13 miles North of Moses Lake, WA
Observing Conditions Summary:
I planned on observing the Whirlpool galaxy (M51), the Pinwheel Galaxy (M101), Bode’s and the Cigar Galaxy (M81/82), the Surfboard Galaxy (M108), Vacuum Galaxy (M109), and the Owl Nebula (M97). However, the zodiacal light and the light dome from Ephrata to the West washed out the objects in Ursa Major considerably. I decided to instead observe several DSO’s in the Cygnus Constellation which was positioned at zenith.
NGC 6826 The Blinking Planetary:
The ES92 12 opened the observing session for this target. I rated contrast at 4/5 and sharpness at 3/5. Contrast was good as the nebulae surrounding the central star was bright and stood out against the blackness of the nighttime sky. Looking at the central star caused the surrounding nebulae to disappear, causing the blinking effect. I noted a distinct blue hue to the nebulae and in the star itself. In the ES92 12 however, the target appeared quite small against the wide view yielded by the wide 92° AFOV of the ES92 12. The stars surrounding NGC 6826 were not as sharp as in the A11, which caused the stars to appear dimmer than in the A11. In the A11, I rated contrast on NGC 6826 at 5/5 and sharpness at 5/5. In the A11, I was able to achieve a “cleaner” focus and the stars appeared brighter as a result. The sharper stars in the A11 lent the view more depth. The higher magnification of the A11 lent more contrast to the nebulae surrounding the central star of NGC 6826 and the blacker background made for a more pleasing view than in the ES92 12. The bright patches on both sides of the blinking planetary which are known as fliers, was not visible in both the ES92 12 and A11, likely due to the magnification being too low.
NGC 6960 Western Veil; Lumicon UHC Gen 3 Filter:
In the ES92 12, I rated contrast at 4/5 and sharpness at 3/5. The western limb was visible as a single tendril from Cyg 52 to the north (south in the eyepiece). Structure was observed. The structure was most prominent further north from Cyg 52. As I viewed the single tendril in its entity, I noted that definition of structure decreased as I traversed further south up to Cyg 52, where definition was almost completely lost at Cyg 52. Nebulosity south (North in the eyepiece) of Cyg 52 was faint to the point where structure was lost. In the A11, I rated contrast at 5/5 and sharpness at 5/5. The western limb was prominent and featured definition in the structure, which was nicely contrasted against the black background of the nighttime sky. The Western Veil filled the entire 85° AFOV of the Apollo 11. The view was contrasty and stars around the Veil were pinpoint, more so than the ES92 12. The view of the Western Veil was overall more pleasing in the A11 due to the higher contrast, however, the ES92 12 framed the Western Veil nicely.
NGC 6992/6995 Eastern Veil; Lumicon UHC Gen 3 Filter:
In the ES92 12, I rated contrast at 4/5 and sharpness at 3/5, the same as on the Western Veil. I expected the ES92 12 to come out ahead owing to the larger 92° AFOV, however, the object was so big that I ended up panning around the Eastern Veil quite a bit. In the A11, I rated contrast at 5/5 and sharpness at 5/5. The views in the A11 were more contrasty, however, the panning around became a bit much. I soon came to the realization that both the ES92 12 and A11 provide too high of a magnification in my scope on the Eastern Veil. The ES92 12 and A11 are both not suitable eyepieces for the Eastern Veil.
7/14/21 Night IV
13 miles North of Moses Lake, WA
Observing Conditions Summary:
For this observing session, the skies exhibited poor transparency. NGC 7354 was an averted vision object due to the poor transparency. Stars were a mushier than previous nights which indicates poorer seeing conditions than previous nights. EOFB was still an issue during this observing session, with regards to the ES92 12.
NGC 7354 Planetary Nebula in Cygnus:
The A11 showed NGC 7354 with averted vision. I used a pair of stars to the north (south in the eyepiece) to help focus the A11. The star pair were pinpoints. With averted vision, I could see the shell of NGC 7354, which was a circular shape. There was no color that I could detect, and it was faint in these Bortle 4/5 skies. NGC 7354 was nicely contrasted against the starry background. For the A11, I rated contrast at 5/5 and sharpness at 5/5. Switching to the ES92 12, I was immediately presented with a larger star field which lent an immersiveness to the view. NGC 7354 is also an averted vision target in this eyepiece. Contrast suffered due to the larger exit pupil, and EOFB was especially noticeable, unlike in the A11. The ES92 12 I thought, could be too low a power for this particular target as NGC 7354 appeared quite small in the AFOV when compared to the A11. For this target, after switching back and forth between the A11 and ES92 12 for critical A/B comparisons regarding the optical performance of these respective eyepieces, I finally settled on the A11 to observe the target for enjoyment. The views through the A11 were more pleasing.
The A11 showed the two component stars as perfect pinpoints. The orange hue of the larger star was readily apparent, and the blue hue of the smaller component star was apparent. The two component stars contrasted nicely against the background. Coma on these two component stars became quite apparent as the stars drifted closer to the edge of the field. During my initial observation of the two component stars, I watched them drift to the edge of the field. I noted lateral color increased as the two component stars neared the edge. I thought this was an interesting since I had not noticed this characteristic of the A11 during my other observations. I suspected the angle at which I was viewing the stars at with my glasses was causing this lateral color. I again centered the stars, and kept my head straight as the two component stars drifted to the edge, and noticed no lateral color. I rate contrast at 5/5 and sharpness at 5/5 in the A11. In the ES92 12, the hues of both component stars are just as apparent as in the A11. However, sharpness was not quite as tack-sharp as in the A11. I also noticed EOFB in the ES92 12, which was not as apparent in the A11, if it was indeed present. On axis, the two component stars were not as tack sharp as in the A11. However, the larger AFOV of the ES92 12 lent context to Albireo and made for quite a pleasing view. I rate contrast at 3/5 and sharpness at 3/5 for the ES92 12 on Albireo.
When my wife told me that she purchased the A11 for me, I immediately thought it would be useful to do a A/B comparison between the A11 and the ES92 12 because of their close focal length and relatively close AFOV. However, observations revealed the differences between the two eyepieces to be fairly significant in terms of magnification, as shown in the table below.
Eyepiece Focal Length Magnification AFOV
TeleVue Apollo 11 11mm 131x 85°
Explore Scientific 92° 12mm 120x 92°
The magnification difference of 11x manifested itself by showing significant differences in contrast and the framing of objects, which was further compounded by the large difference in AFOV. On the surface, a 7° difference in the AFOV between the two eyepieces seems insignificant, however, it is made significant by how objects are framed owing to the magnification factor of the two eyepieces. It is because of this that the ES92 12 was put at a disadvantage as objects often appeared to have less contrast than in the A11. The A11 had the advantage of a smaller exit pupil, if not larger AFOV, that appeared to contrast objects against a blacker background than the ES92 12. On some objects, the majesty factor was larger in the A11 because the framing was tighter and contrasty, more so than the ES92 12. After several nights of completing A/B comparisons between the ES92 12 and the A11, I felt that I could not fairly compare the two on contrast. EOFB is more prominent in the ES92 12 than the A11, likely owing to the larger exit pupil of the ES92 12. To be clear, EOFB was due to the sky conditions, not the design of the eyepieces themselves, as EOFB disappeared as the observing sessions progressed into the small hours of the night on the second and third night of observations in both eyepieces.
Coma was apparent in both the ES92 12 and A11, as I use no coma corrector at f/5.6. Observations using the ES92 12 and A11 made me realize the value of a coma corrector, and I will be purchasing the TeleVue Paracorr II in the near future. Setting coma aside, the A11 was superior to the ES92 12 on-axis in showing pinpoint stars. I was able to immediately achieve a tight and clean focus in the A11. In the ES92 12, I had to fiddle with the focus in the ES92 12 to make sure I was in focus. The stars in the A11 also appeared to be tack sharp and pinpoint on-axis in the A11, while the ES92 12 on-axis showed stars that were not quite as sharp to my eye as in the A11.
The A11 tightly controls for light scatter, while the ES92 12 does not. Stars in the A11 left the field without presenting flashes or glare. In the ES92 12, there was one instance where there was a brief flash of glare as two bright stars contacted and left the field stop. This behavior was not observed in the A11.
I thought that the TeleVue Apollo 11 was superior than the ES92 12 in terms of its optical properties. The views were more pleasing to the eye owing to the greater sharpness on-axis and greater contrast. It is important to note that this review is comparative in nature. Any defects or flaws in the ES92 12 are only apparent when compared against the A11, which has a smaller exit pupil and a smaller AFOV. This review would look quite different if I reviewed only the ES92 12mm, and would likely be more glowing in its praise. If I observed through the ES92 12mm on an execlusive basis without directly comparing it to the A11, I would have not noticed that the stars were less pinpoint and sharp on-axis than the A11.
The A11 is comfortable to use, owing to its large eye relief. The lack of SAEP in the A11 and the presence of SAEP in the ES92 12 manifested itself during the observing sessions as I had a pinch more difficultly with eye placement in the ES92 12. I had no half-FOV blackouts in the A11 than in the ES92 12. I do not recall an instance where half of the FOV blacked in the A11, but I do remember half-FOV blackouts in the ES92 12. The ES92 12 is by no means a difficult eyepiece to use. It is simply the fact that the A11 is easier to use.
I used glasses for all observations with the ES92 12 and the A11. I found the ES92 12 easier to acquire the exit pupil, but found the A11 easier to hold the exit pupil. In other words, the A11 has better exit pupil behavior. My eye glasses have a correction of 3.75 for my astigmatism. My wife who does not wear eye glasses, finds the A11 easier to use. She experiences blackouts with the ES92 12 and does not like the design of the rubber eye guard. She finds the A11 more intuitive to use, and uses the A11 with the eye guard up. I suspect the smaller size of the eye lens on the A11 leads to greater ergonomics which translates to a more practical experience for a wider variety of people on the A11, my wife being one of them.
I cannot recommend either eyepiece over the other because of the differences in focal length and AFOV. Both are excellent eyepieces that compliment one another nicely, and I find no fault with those who decide to compliment the ES92 12 with an A11, or vice versa. Both are outstanding eyepieces and have their places in any eyepiece collection. The weight of the ES92 12 does put the ES92 12 at a significant disadvantage, more so than the performance characteristics that I observed. I feel that the weight is a bigger consideration for some, than the focal length and AFOV characteristics that separate the the two eyepieces. However, for those who wish to do Lunar observations, the A11 is clearly the superior eyepiece. For general purpose observing, I would have no problem recommending the A11 over the ES92 12 simply because the A11 roundly beat out the ES92 12 during my previous lunar comparisons between the two eyepieces. You can do a search on the Cloudy Nights forum for my review that compared the two on Lunar observations. I did not compare planetary views between the two eyepieces.
Should TeleVue decide to release more focal lengths to compliment the TeleVue Apollo 11, I would not hesitate to purchase more focal lengths. I feel the same way about the Explore Scientific 92° series of eyepieces. Should they release more focal lengths in the 92° series, I will be the first in line to purchase more. Both are outstanding eyepieces, and I feel fortunate to own both in addition to the ES92 17.
Edited by TayM57, 22 July 2021 - 03:14 PM.