The *real* value of eyepieces for serious deep sky observing...

[RolandosCY]

Last night I was with two friends at a moderately dark site for some casual observing. One of the main targets was comet 168P Hergenrother, now in Pegasus. I used my 18" Obsession dob with my 31mm nagler to readily locate the bright comet at its predicted position, then did observe it with my 13mm Ethos. In the same field I could readily locate the galaxy NGC 7775 (given by Megastar as mag 14.0). One of the friends who were with (owner of a 16" Lightbridge) brought with him his eyepieces in order to play both with my telescope and NicosCy 4" Stellarvue. After observing and sketching the comet, he asked me if he could use my Obsession for a comparison of my Nagler 31 and his newly purchased Scientific Explorer 30mm (82 degrees). I agreed, provided I could have a look first!

Well.... With both eyepieces stars looked pretty similar and so did the overall appearance of the comet. But the amazing difference came upn NGC 7775. With the 31mm Nagler, although very faint, it just popped into view with direct vision. Not so with the 30mm Scientific Explorer. It COULD BE DETECTED but only after a careful study of the field and even then it was held steadily only at times with direct vision. The test was performed even by my getting down the stair and not knowing which eyepiece was in the focuser (they look pretty similar in the dark). NGC 7775 was always readily seen direct vision with my 31mm Nagler, but even knowing it was there, it remained barely detectable with the SE 30mm. This was also the conclusion of my friend who owned the 30mm SE.

I have read many comments in various forums about the "revolution" that the SE 82-degree 30mm eyepiece would bring, finally giving the venerable Nagler 31 a real run for practically half the cost. But, for serious deep sky observers, and especially those who prefer the VERY DEEP like me, this ability of the Nagler 31 to bring out the faintest details in the field with such clarity, more than justifies the extra cost...

[nicoscy]

Well, being the previous owner of the specific Explore Scientific 30mm (having moved to a Nagler 31mm about a month ago), I wholeheartedly agree that the ES 30 does not give the Nagler 31 a run for its money.

The two eyepieces are in a different category. There's the best (Nagler 31mm) and the one that plays second fiddle (ES 30mm).

I need to stress here that if budget is an issue, then the ES 30mm is the best given other possible options in the $250 category for a wide eyepiece.

Some people may not have the funds to immediately push for a Nagler 31. Purchasing the ES 30 to enjoy the wide field coma free views is a good stepping stone as this eyepiece does hold up its price well when sold second hand.

You will be hard pressed to find much difference in the views between the two eyepieces except for the fact that the coatings on the Televue are clearly superior and allow those few extra photons to hit the eye.

I really don't think that Uncle Al makes as much money as some people think on Televue eyepieces. Quality comes with costs attached. The price difference is justified IMHO. If one can make the leap to the Nagler 31, you will not for one second think that you paid too much for the eyepiece.....

[Pawel_T]

I wonder how the Pentax XW30 would compare here. Pentax is known for second-to-none optics as well. I am very satisfied with my XW7, for example yesterday it showed the NGC 51 group (6 galaxies - NGC 48,49,51 and IC 1534,1535,1536) much better than 10mm Delos. All six visible directly in the same FOV.
I had a chance to buy the XW30 for reasonable money some time ago, but I went for the N31 instead, which I bought even cheaper on a second-hand market. Never regretted!

[Marko]

There will be other factors in the view between a 7mm and 10mm eyepiece so it would be interesting to see thoughts on XW7 vs say a 7mm T6 Nagler or 6mm Delos (closer match to exit pupil to the 7 but still not same). My favorite range eyepeices for dim galaxy groups peak out around 6-7mm. This in an 18" f/3.7 dob. Nice comparison on the comparable SE30 and Nag31. My largest Nagler is the 26 so I don't actually have 'The Holy Hand Grenade' (31mm Nagler Instructions: one must count to 3 before use, Not 2 nor beyond 4 and 5 is right out of the question - Monty Python similar paraphrased quote)

[Preston Pendergraft]

A little late responding here. But I have always gotten the impression the ES designs for their 82degree eyepieces were more in line with the Type 1 and 2 Naglers in performance.

I would be interested to see how the ES eyepieces would fair against those models. However the 30mm is clearly trying to be competition to the 31 Nagler which is seems to fall short against.

[nicoscy]

A little late responding here. But I have always gotten the impression the ES designs for their 82degree eyepieces were more in line with the Type 1 and 2 Naglers in performance.

I would be interested to see how the ES eyepieces would fair against those models. However the 30mm is clearly trying to be competition to the 31 Nagler which is seems to fall short against.

The ES 30mm basically has less kidney beaning than the Nagler 31 (for those that are affected by eye placement) but the "slight" loss in contrast (I believe due to inferior coatings relative to the Nagler 31) is a determining factor when you are at the limits of detecting a DSO. Therefore, for those that push it to the edge, stay away from the ES30mm. For those who follow a more casual approach, the ES may not be the best but it will serve you well.

[Astrojensen]

Well, I've just invested in a 30mm ES 82°, as well as an 18mm/82 and an 11mm/82. Together all three were LESS than one 31mm Nagler. Being on a limited budget, I couldn't justify getting the 31mm Nagler, when I could get three eyepieces with nearly identical specs for less than the same price. I know I wanted the Nagler, but it was financially out of reach. I do think the ES'es will perform well, though, and I don't expect miracles. Right now I use ultra low budget GSO Superviews and I am quite impressed with what they do for how little they cost. If there was no ES, I would be stuck with my GSOs. From the reviews, it seems to be quite clear that ES is the runner up to TeleVue. Not quite there, but impressive performance for the money. That will have to do for me for a while.


Clear skies!
Thomas, Denmark

PS: Please do invite me over and let me have a look through your Naglers at star parties, please!

[Dragan]

Thomas,

Premium EP's have their place, sure. After all, the EP is more or less 50% of your optical system and they should be of quality. No doubt. But to be honest, some of my absolute favorite views of deep sky objects (and planets for that matter) come from $60 University Optic Orthos.

They may not be Supermonos, but there's no denying the value. A quality view can be had at ALL price points!

[Gonzo56]

I read these comments with interest. I've got a 5mm, 7mm and 11mm Naglers that I've enjoyed for sometime. I wanted to fill the spot between the 7mm and 11mm Naglers so I gave the ES 8.8mm, 82 degree a shot. Unfortunately, I don't think it measures up. The comments from others seems to confirm what I see. As for the Naglers, most of the time when I'm trying to observe the really faint stuff I use my 7mm Nagler. If conditions allow, I'll use the 5mm. That being said, I really like my 11mm.

[Astrojensen]

I've yet to give my 8.8mm ES82 a real test, but so far, I am very impressed. I tested the 11mm ES82 against my 10mm Zeiss ortho on faint stars in NGC 2158 with my 6" refractor and could not determine any difference in limiting magnitude between them, which is extremely impressive, given that the 11mm operates at 10% lower magnification. There was also no difference in perceived sharpness, although it must be admitted that perhaps an open cluster is not the best target for judging this.

Unfortunately, I have no Naglers with which to compare them, only orthos and plössls from several different makers.

From what I've seen so far, I'm extremely impressed with my ES eyepieces. They have already delivered more than a few "best ever" views of several different objects in several different telescopes.


Thomas, Denmark

[Preston Pendergraft]

The best advice I have read is get two premium eyepieces in the powers you use most often. For me that is a 22mm Pan and a 14mm UWA 4000. But honestly most nights I stick to the 22mm Pan. I just love that eyepiece. The 14mm is awesome too though!

The ES 82 eyepieces I have observed through we're very nice and I would be very happy with them. What ever gets you observing is all that matters though in the end

[akarsh]

I have found the contrast in Delos to be higher than Nagler, and my Delos 10mm has replaced my 7mm Nagler as the primary observing eyepiece.

Dragan, when you refer to the University Optics orthos, are you referring to these:
http://www.universityoptics.com/125inch.html#SU

I need two high-contrast eyepieces in the 20mm and 25mm range for all those diffuse, low surface brightness objects. Any suggestions?

Regards
Akarsh

[Dragan]

I have found the contrast in Delos to be higher than Nagler, and my Delos 10mm has replaced my 7mm Nagler as the primary observing eyepiece.

I think many others are finding similar results. When the Ethos first came out, many gravitated towards them since they were outperforming the Naglers as far as contrast, transmission and color correction. And now, it seems, that many feel the Delos may be outperforming the Ethos in the same way.

Dragan, when you refer to the University Optics orthos, are you referring to these:
http://www.universityoptics.com/125inch.html#SU

Actually, no. my UO orthos are the volcano top variety. I'm actually surprised that they're not on the website. Does anyone know what happened?

Also, I believe Alvin did a comparison between the older volcano style and the super abbe some time ago. Alvin, can you elaborate?

I need two high-contrast eyepieces in the 20mm and 25mm range for all those diffuse, low surface brightness objects. Any suggestions?

I still swear by my orthos. Also, though I don't own one, the 24mm Brandon is another great EP I've had some experience with. My very best view of M81 was provided using the Brandon 24.

[omahaastro]

I always got the impression that I was one of the only one's who didn't jump on the Ethos bandwagon. I've liked my 12, 17, and 22 T4's so much, I couldn't give them up. I'm an eyeglass wearer as well, and never really appreciated the Ethos field, felt like contrast was minimally better... and T4's seemed to give a bit better relief.

That said, I've heard such good things about the Delos', I'm tempted to order a couple, possibly finally supplant some of the Naglers. I haven't had an opportunity to try them, but all the accounts sound really promising. In particular, I'm liking the idea of giving up some FOV in return for the promise of greater contrast/transmission, while retaining the eye relief I enjoyed with T4's.

I'm defiitely thinking of getting a 10 to possibly replace my venerable 9mm T1 (why don't all eyepieces have a 2" skirt?!), but for a second example to try, wondering whether I should initially go for a 14 or the 17.3 (possibly replacing one of either my 12 or 17 T4's).

[omahaastro]

My wife 'surprised' me with a 10mm Delos for my birthday... anxious to see how it compares to my old reliable, the type 1 9mm (obviously no shortage of eye relief). I guess I'm a little behind... this is my first new eyepiece in a decade.

[nicoscy]

I love my Ethoi but I would love to try a Delos. That huge lens looks so comfortable and inviting...

[ransanjaya]

Hi I'm new to this forum. My main interest is DSO obseving.
I'm ossillating between Delos and Pentax xw s. I wear eyeglasses for
astigmatism (2.5D) and my scope is 10" f/4.7. Any suggestion is highly
regarded.
Thank you...!

[Ivan Maly]

I can take in the field of my 2" Pentax XW 40 mm with my glasses on if I put its adjustable lens guard (eye guard) in the lowest position. That said, I usually take my glasses off.

[akarsh]

@omahaastro: Why do you like the TV 9mm Type I Nagler?

[omahaastro]

Akarsh, I've spent most of my time observing with an 18" f/4.5. It's an undriven scope... and I always liked the wide apparent field the 9mm provided (along with the other Naglers I have) to buy me time (I also do a lot of outreach, obviously helps there as well). Plus it has good eye relief. Not quite that of the longer type 4's I have, but better than the garden variety Orthos/etc I'd used up to the time I acquired it back in the 90's (I do still have a number of volcano top University Optic pieces which I use when the situation calls for it). Finally, I have just come to really appreciate the quality of Televue's products. This said, as I've began to go deeper over the past few years, trying to coax out more from the view, I'm beginning to embrace the idea of what the Delos can do for that, little better transmission with lower glass count/improved coatings, while retaining decent AFOV, and good eye relief which I like (I observe with my glasses most of the time).

[Don Pensack]

Look, let's be a little skeptical about the original post that started this thread.
If an object is visible with direct vision, it is quite a bit brighter than an object that is visible only with averted vision.
And an object that is visible with averted vision only a small fraction of the time is quite a bit fainter than an object visible with averted vision 100% of the time.
In fact, having evaluated objects with a spread of visibility from direct 100% to direct 50%/averted 50% all the way down to averted only 10% of the time, I can tell you the difference represented there is probably close to 2 full magnitudes.
The scenario described in the first post would indicate a difference in light transmission of around 0.3 or 0.4 magnitudes, and the difference in transmission between the 31 Nagler and the ES 30 is, maybe, 0.05 magnitudes, which is nowhere near a large enough difference to explain the difference in visibility.
I'm not saying the difference wasn't seen, merely that the difference wasn't in the transmission differences between those eyepieces.
The easiest explanation, and most likely, is that the difference in exit pupil size was primarily responsible for the difference in object visibility. That difference is about 6.7% by area, and is more likely to have a reaction by the brain in terms of visibility that a 3 or 4% difference in transmission. It could be a combination of the two, but I think it far more likely to simply be due to exit pupil differences.

[nicoscy]

Don,

The scope was the Classic 18" f4.5 Obsession.

- The TV yields 65x magnification, TFOV 1.19d and exit pupil of 6.89mm.

- The ES yields 69x magnification, TFOV 1.22d (due to slightly larger field stop by 1mm VS the TV) and exit pupil of 6.67mm.

- The ages of the observers in that test referred to are 40+ so I am not sure they were taking full advantage of the exit pupils involved.

Questions:

1. Could partial loss of illumination occur as a result of potential aperture reduction lead to this difference?

2. Would a difference of 0.22mm of exit pupil justify such a difference (we are at the realm of 6.5mm + exit pupils on both eyepieces)?

Just trying to learn a bit more here so feedback is most appreciated!

[Ivan Maly]

I note that the test object, NGC 7775, is not only faint but small (Vm 13.3, 0.9x0.8'). Could it be victim of a "blackout"? How are the exit pupil aberrations and the ease of exit pupil acquisition in the ES compared with the Nagler? Such a deficiency might be undetectable under dark sky but still black out objects and masquerade as a need for averted vision.

[Don Pensack]

Don,

The scope was the Classic 18" f4.5 Obsession.

- The TV yields 65x magnification, TFOV 1.19d and exit pupil of 6.89mm.

- The ES yields 69x magnification, TFOV 1.22d (due to slightly larger field stop by 1mm VS the TV) and exit pupil of 6.67mm.

- The ages of the observers in that test referred to are 40+ so I am not sure they were taking full advantage of the exit pupils involved.

Questions:

1. Could partial loss of illumination occur as a result of potential aperture reduction lead to this difference?

2. Would a difference of 0.22mm of exit pupil justify such a difference (we are at the realm of 6.5mm + exit pupils on both eyepieces)?

Just trying to learn a bit more here so feedback is most appreciated!

Well, I was thinking a much longer focal length instrument with smaller exit pupils, and you're right to assume that probably most observers weren't using the entire exit pupil of either eyepiece.
The difference, now that i think of it, would simply be in the two primary differences I've noticed between the two brands:
--scattered light control
--induced field astigmatism
In the case of the first, the sky background in the ES would likely be a little greyer, reducing contrast--definitely a no-no for a marginal object.
In the second case, this slight blurring of point sources would tend to drop the visibility of smaller objects near the limit.
Add to that the slight difference in magnification (lower surface brightness in the 30 than in the 31) and a small difference in light transmission (maybe 3-4%),
and you have a combination of factors that would conspire together to reduce the visibility of a faint spot.
Normally, this difference would take one object from visible 50% of the time with averted vision only to 10% of the time with averted vision only, but you may have been lucky enough to find an object where the difference was visible directly versus visible mostly averted.
I've seen N7775 in my 12.5", though, and I would not think it's a limit object at all in an 18". So I suspect Ivan's explanation has some merit. If it was simply harder to hold the exit pupil on one versus the other, this would explain a lot.

[nicoscy]

Don and Ivan,

Thanks for the feedback. Funny thing (as the previous owner of that eyepiece) - I found that the TV was more sensitive to eye placement vis a vis kidney beaning.

But the rest of the explanation does have merit. Still, the ES is an excellent eyepiece. I only moved to the TV as the funds were available and to have a full TV eyepiece set as opposed to finding a deficiency to the ES.