Ok, as promised, I did get the opportunity last night to compare my new ExploreScientific 30 mm (52 degree field) eyepiece to other similar focal length eyepieces and to see if it truly has a place in my ExploreScientific 1.25" eyepiece case.
The short answers are: 1) It does very well, and 2) Yes, it has it's place in my ES 1.25" eyepiece case, but as some of you probably want more information than this...…...here it is:
Last night in New Orleans was good, not great, but for what I was doing good was good enough. The temperature was in the mid-70's and the humidity was low enough that the eyepieces and the telescope objective did not fog. Being that I am just about 5 miles from the activity on Bourbon Street , on the best of nights my limiting magnitude is about 4.7. I did not take a reading last night but I estimate it was about 4.4 to 4.5. The Moon was not a factor because I was done hours before Moon rise.
I only looked at one object/area for my comparative testing, the Double Cluster in Perseus which was about 30 degrees up when I started and about 45 degrees up when I finished. The telescope used was my Astro-Tech AT 102ED f/7 with the FeatherTouch upgrade, so I was operating at just about 700 mm of focal length. The mount used was my Astro-Tech Voyager which has a single fork arm. Perfect for grab and go and a good match for this telescope. The diagonal used is an older TeleVue 2" mirror diagonal, which has been in my arsenal for probably about 20 years. It is relatively rare as it has "TeleVue" in green lettering (go figure) printed tastefully on the upper prism housing at the base of the eyepiece receptacle.
Eyepieces in 1.25" format used include - ES 30/52, ES 26/62, ES 24/68, ES 20/68, TV 30 mm plossl, and my Vixen LVW 22 mm (this one is actually a hybrid as the upper barrel allows for direct use with a 2" diagonal). The other 1.25" eyepieces required the use of a 2" to 1.25" adapter in the diagonal.
Eyepieces in 2" format used included - TeleVue 22 mm Type 4 Nagler, ES 24/82 and my Astro-Tech 22 mm AF 70 (reportedly the Olivon 22 mm has the same optics).
Let me first say that while I created a crude chart on paper and periodically took notes, made checks and compared one eyepiece to another before moving on (#1 compared to #2, then #1 compared to #3 and #2 compared to #3, and so forth, and periodically coming back to eyepieces as I worked down the line, ultimate favorites/keepers are as much about how it all works together than it is about adding points and determining a winner. What I believe is good or best may be completely different from what others may think because of what telescope I used, my viewing conditions, my eyes, etc. I try to be as unbiased as I can be and as all the eyepieces used are mine, there is no bias in respect to comparing my eyepiece(s) to someone else's eyepiece. Every eyepiece has a place use except for one. It and one other were purchased at the same time by me, both are new and very carefully handled - one to keep and one to be a door prize at our upcoming Deep South Star Gaze. Had they been further apart in focal length I would be keeping both or if I could find some way to rationalize keeping both in spite of being close in focal length I would be keeping both. Ultimately I could not do that so someone will be winning a very nice eyepiece.
On my evaluation page I had columns for: the eyepiece name/focal length/apparent field, a second column for overall impression, a 3rd column for eye relief utility without glasses (I wear glasses but observe without them), 4th column for eye relief utility with glasses on, a 5th column for perception of astigmatism, a 6th column for perception of flatness of field, a 7th column for sharpness, and a final column for contrast coupled with notes that could relate to anything.
30 mm/52 ES eyepiece - the first eyepiece put in the diagonal. I was curious. It was very, very nice. I noted no astigmatism and the field was nice and flat. Brighter stars within the Double Cluster brought to the field edge remained undistorted and in focus. I repeated this process several times to verify. I like it!!!!! No problem at all with eye relief in spite of the fact that the eye lens is recessed about 14 mm below the top edge of the folded down eye cup. The field stop edge is very sharp, easily seen and frames the field nicely. I tried again with my glasses on. (My correction is 2.25+ and my lenses are relatively thin.) I could not see the full field, but I could see most of it, and this eyepiece did better in this respect than most of the other eyepieces. In fact, with glasses on I could not see the full field in any of the eyepieces used. Maybe it is me as I don't ever observe thru an eyepiece with glasses on, I don't need too. I have no astigmatism, or if I do, it is minimal. I can focus stars to sharp points and if the telescope/eyepiece combinations are good, stars remain tight stars across the field if properly focused.
32 mm TeleVue plossl - I have always liked this eyepiece and have used it in the past for afocal projection of the Sun using one of my point and shoot digital cameras. However the ES 30 mm/52, to me, is a better eyepiece. The overall view in the ES is better, sort of an impression hard to describe, but just better. Objectively the field is not quite as flat with the TV30. Allowing stars to drift to the field edge in the TV 30, I would have to tweak focus a little bit. I did not need to refocus with the ES 30/52. If I was in a situation where I would only be keeping one, it would be the ES 30/52. The TV plossl had good eye relief, and was the best one, eye relief wise if I had to observe with my glasses on. Non issue for me however.
26 mm/62 ES eyepiece - this is one of those eyepieces that just feels good to the eye. However as others have said in other posts, it does suffer from astigmatism in stars closer to the field edge. Really a shame as the eyepiece yields an overall good view. With the Double Cluster I would notice that brighter stars began to become "spiky" about 60% of the way out from the center, mild at first but objectionable at about 80% of the way out. Focus would not help as it would had this been a flatness of field issue (but then if focus would help near the edge, stars at the center would be out and my eyes are too old to accommodate well). I had done a lot of comparison with this eyepiece and the next eyepiece reviewed, and testing last night helps confirm my initial impressions. In respect to eye relief the ES 26/62 is much like the ES 30/52, both are very nice eye relief wise without glasses - great sharp field stops with the whole field easily seen. With glasses on the ES 26/62 has a field edge which "almost" can be completely seen, not quite, but almost.
24 mm/68 ES eyepiece - among the best low magnification wide field 1.25" format eyepieces. In an earlier post my impression was that I did (and do) like it better than my TeleVue 24 mm Panoptic, and that is saying a lot. Compared to the ES 26/62 it has a marginally wider field, but at a higher magnification and with better contrast, making it more immersive. No astigmatism noted, or if there it is very mild. The field exhibits mild "unflatness" with mild refocus needed for stars at the edge. A compromise focus may be possible for most, particularly those that can accommodate well. I view this as a non issue. I was very happy with the overall view. Eye relief was good without glasses but I was more aware of my upper cheek and eyebrow resting on the eyecup (but not pressed into it). The 26/62 was better in this respect. I would unfortunately say that this is an eyepiece that would not work well for those who have to observe with glasses on, I tried and it did not work for me. Yes, I could see the central field, but too much of the wide field is taken away. Great eyepiece for me as I do not wear glasses to observe. Those with glasses on will be disappointed due to the restrictions.
Vixen LVW 22 mm with a 65 degree field - sort of a hybrid barrel, although it was not advertised that way. 1.25" lower chrome barrel with the body of the eyepiece being very close to 2" diameter with a widening above that. Any in the series of discontinued eyepieces from the 3.5 mm up to the 22 mm will work in a 2" diagonal and the lower 1.25" barrel will not hit the mirror on a 2" diagonal. I typically use mine in a 2" diagonal without any adapter. (I only use in diagonals that I have replaced the metal thumbscrew with a nylon one to avoid scratching or denting the eyepiece. The 22 LVW performed last night as expected - No astigmatism, with a nice flat field with stars remaining tight points to the field edge. As reported by many others, there is an impression that the light thru-put is not quite up there with other eyepieces. I get this impression too but when I then chase the faintest stars in the field and compare to other eyepieces where I get the impression that they have a brighter thru-put, I see very little difference. Maybe on the order of 1/10th of a magnitude, and a determination that requires careful study. One other aspect of using any of the LVW eyepieces is that eye placement is very good. Novices "can find the view". Additionally, due to the long eye relief this is a good outreach eyepiece as there is little chance of eyelash or makeup contact with the eye lens.
Having said this, the eyecup is pretty thick and stiff. I do not need to fold it down. I have "kinda tried" but have not pursued this as my impression is that if it could be folded down it would have a short longevity and would likely crack/split after moderate use. With my glasses on, I cannot see the full field, but not an issue for me. If folded down, I think many with glasses might be able to see the full field. I have not experimented with taking the rubber eyecup completely off. While a 65 degree field is reasonalbly large, it did seem "smallish" when compared to the next eyepiece.
20 mm/68 ES - little brother (or is it sister) to the 24 mm/68 ES - another real nice eyepiece and a great complement to the 24 mm/68. Same features and benefits compared to the ES 24/68. Real differences are increased magnification and a darker background sky as your exit pupil is now smaller. Eye relief friendly if you do not wear glasses, but will not work well for those keeping their glasses on, you will lose a lot of field. Mine, for me, is a keeper.
TeleVue 22 mm Type 4 Nagler - this 2" eyepiece has an 82 degree apparent field and it along with my 17 mm Type 4 Nagler are among my most frequently used eyepieces. Eye relief is great without glasses and fairly good with glasses on, not perfect, but good. No astigmatism noted by me, and the field is fairly flat, with very mild re-focus necessary for stars at the field edge. Pick of the litter for all eyepieces tested last night. Wow! Wow! Wow!
Astro-Tech 22 mm AF 70 - not a bad 2" eyepiece at all for the price. Now discontinued, but many feel that the Olivon eyepieces which are available thru Eyepieces Etc. have the same optics in different bodies (I have the Olivon 13 mm and it is well made and performs well). The AT 22 performs in all parameters except field size about the same as the 22 TV Nagler. Eye relief is good without glasses. It does have a stiff and thick eyecup which resists folding down and I did not want to challenge it for this comparative review. With the eye cup up it does not work with glasses on. With the eyecup removed it may work for some, but I will not speculate beyond this. The 22 mm Olivon has a twist up eye cup and it may be a good and only option as the Astro-Tech AF 70 series is discontinued.
24 mm/82 ES - this is a 2" eyepiece. It is a big and heavy eyepiece. Adequate eye relief without glasses and with the eye cup down. But my impression is that it will not work for those wearing glasses, too much field loss, at least for me. No astigmatism noted, and an almost completely flat field with only mild re-focus needed when stars drift to the field edge. A less expensive option to the 22 Type 4 TV Nagler…….but, that hard to describe greatness goes to the 22 Nagler. To me, the 22 Nagler has the more magnificent view.
So that is it and I find the 30mm/52 to be a great complement to my ES 24mm/68. Star images are perfect thru the 30 mm/52, and while the apparent field is smaller - 52 degrees vs 68 degrees, the true field is smaller by only about 1/10th of a degree, an inconsequential loss. The appearance of the 30 mm makes it easier to not lament not keeping the 26 mm/62.
Hopefully my review will help those in a position to make some buying and selling decisions.
Edited by BarrySimon615, 31 October 2018 - 10:46 AM.