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Explore Scientific 9mm 120° - thoughts ?

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#1 vkhastro1

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Posted 26 January 2019 - 01:11 PM

I am intrigued by the ES 9mm 120° eyepiece.

 

I wear progressive glasses but remove them for observing.

 

I presently thoroughly enjoy my ES 17mm and 12mm 92° eyepieces.

Great contrast and eye relief and can easily see the entire AFOV (definitely appreciate seeing the field stop without moving my head). Doesn't seem that a 9mm version is in the works.

 

In the 8 - 10mm focal length ultra wide angle I presently own the TV 10mm Ethos, 9mm APM HDC 100°, and TV 8mm Ethos. I tend to grab the APM 9mm 100° as my defacto eyepiece in the focal length range - love the views.

 

I have read CN posts concerning the ES 9mm 120° eyepiece - mainly positive - extremely emmersive views, needs an observing hood, etc.

 

I am I missing the boat by not owning this eyepiece?

 



#2 havasman

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Posted 26 January 2019 - 02:19 PM

I had several months with one that its owner loaned out to a long succession of us forum members. It's very good and particularly so if you are restricted to urban observing. Then that FOV at medium magnification is really beneficial when longer focal lengths are compromised by light pollution. In the end I was not tempted to own the ep, certainly not in favor of my 10 Ethos. From the kit you list I would never say you're exactly missing any boats but it is an interesting eyepiece.


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#3 25585

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Posted 26 January 2019 - 02:28 PM

I am intrigued by the ES 9mm 120° eyepiece.

 

I wear progressive glasses but remove them for observing.

 

I presently thoroughly enjoy my ES 17mm and 12mm 92° eyepieces.

Great contrast and eye relief and can easily see the entire AFOV (definitely appreciate seeing the field stop without moving my head). Doesn't seem that a 9mm version is in the works.

 

In the 8 - 10mm focal length ultra wide angle I presently own the TV 10mm Ethos, 9mm APM HDC 100°, and TV 8mm Ethos. I tend to grab the APM 9mm 100° as my defacto eyepiece in the focal length range - love the views.

 

I have read CN posts concerning the ES 9mm 120° eyepiece - mainly positive - extremely emmersive views, needs an observing hood, etc.

 

I am I missing the boat by not owning this eyepiece?

Thankfully its eye relief is too short. If an ES92 9mm, or thereabouts, is released, with 20mm+ usable eye relief, I would jump on it!


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#4 faackanders2

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Posted 26 January 2019 - 02:42 PM

I am intrigued by the ES 9mm 120° eyepiece.

 

I wear progressive glasses but remove them for observing.

 

I presently thoroughly enjoy my ES 17mm and 12mm 92° eyepieces.

Great contrast and eye relief and can easily see the entire AFOV (definitely appreciate seeing the field stop without moving my head). Doesn't seem that a 9mm version is in the works.

 

In the 8 - 10mm focal length ultra wide angle I presently own the TV 10mm Ethos, 9mm APM HDC 100°, and TV 8mm Ethos. I tend to grab the APM 9mm 100° as my defacto eyepiece in the focal length range - love the views.

 

I have read CN posts concerning the ES 9mm 120° eyepiece - mainly positive - extremely emmersive views, needs an observing hood, etc.

 

I am I missing the boat by not owning this eyepiece?

If you already have an APM 9mm 100AFOV you do not need an ES 9mm 120 AFOV.

 

I have both TV 10mm 100AFOV Ethos and ES 9mm 120 AFOV, and prefer/use the 10mm more because of the clarity and works best on the moon (except when at largest min perigee and slightluy exceeds the TFOV).  The 120 AFOV moon views are not pleasing due to the brown ring of fire.  On paper the TFOV should be much larger than the 10mm Ethos, but in real life it is not that much larger.  Much of the praise of the 120 AFOV may have come from the first 20 eyepieces made where cloudy nights members claimed views were as wide as 140 AFOV, and that later model (like mide) may have had a field stop added to reduce to best 120 AFOV spec.  I do not know for sure if design was really modified, since nobody with first 20 eyepieces has ever done A-B comparisons with more recent versions.  Both eyepieces work well on DSOs with no ring of fire.

 

I do not sell eyepieces (forever increasing my stock) but the 10mm 100AFOV Ethos would be my keeper, and I do like that it fits in both 1.25" and 2" focusers.

 

Good luck in your decision, and try before you buy if possible.  ES often has sales and it may be best to wait for the next one, unless you are a used buyer.


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#5 RalphMeisterTigerMan

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Posted 26 January 2019 - 02:44 PM

I recently sold my 9mm 120-degree...not because I did not like it but because I found I did not find much use for it. I use and enjoy my 21 Ethos, 13 Ethos and 6 Ethos with the Paracorr 2 but found that suitable, optimal conditions for using the 9mm did not happen very often. It's like I always said, Eyepieces are a very personal thing. It may be a great eyepiece (and it is) but it just wasn't for me. Do I regret selling it, not really. Simply because I have most of the eyepieces I will need for now.

If you have it and love it, great! Enjoy it.

 

Clear Skies.

RalphMeisterTigerMan


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#6 nicoledoula

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Posted 26 January 2019 - 03:18 PM

Evidently you'd be missing out on a brown ring of fire, ER and a big pile of change. 



#7 Starman1

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Posted 26 January 2019 - 04:42 PM

Some comments of mine from a couple years back:

1) It is well-corrected. In my 12.5" f/5 with Paracorr (result:f/5.75), it was corrected to as near the edge as I could notice. Deep-Sky observers needn't worry about this. Without a Paracorr, of course, this eyepiece would reveal coma like no other due to the hyper-wide field.
2) It is W-I-I-I-I-I-DE ! It's just a little bizarre, as someone else noted, to be looking almost in the direction the scope is pointing to see the edge of the field of view. The edge is, after all, 60 degrees off-axis!  Unless you take steps to block the light of the sky, when you look at the edge of the field toward the top of the scope, your peripheral vision will see mostly sky and the sky is brighter than the image in the eyepiece.
3) In comparison with the 8mm and 10mm Ethos eyepieces, it is a little darker. Not a lot, but the fainter stars did appear fainter in the 9mm than in either of the other two. Is it the 12 elements? Is it the coatings used? Unknown. A stupendous view, but perhaps not the ideal eyepiece for the faintest possible DSOs. If you don't do "limit observing" (and if you do, you probably prefer the Delos to the Ethos), that wouldn't be an issue.
4)The only deficit that mattered to me. The eye lens is very concave. That's good, because eyelashes won't brush even though eye relief isn't really long (the eyecup HAS to be used folded down, for instance). But it's bad because any peripheral light reflects off the opposite side of the lens directly into the eye. The only way I could use the eyepiece at this site was with my hands cupped around the eyepiece on both sides.
At a really dark site, this might not be an issue, but your peripheral vision should not be seeing anything brighter than the night sky--even a red LED will reflect into the eye.
If used with a black hood over the head, the field gets brighter and fainter stars and details become visible. Ergo, because of the field size and the large size of the eye lens, some way of blocking peripheral light should be contemplated.
5) It's a little heavier than a 21 Ethos or 31 Nagler, but if your scope balances those, this one should be no problem.

 

Here is a thread about the eyepiece with much more in-depth comments from yours truly and other observers:

https://www.cloudyni...field-eyepiece/


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#8 turtle86

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Posted 26 January 2019 - 11:27 PM

I am intrigued by the ES 9mm 120° eyepiece.

 

I wear progressive glasses but remove them for observing.

 

I presently thoroughly enjoy my ES 17mm and 12mm 92° eyepieces.

Great contrast and eye relief and can easily see the entire AFOV (definitely appreciate seeing the field stop without moving my head). Doesn't seem that a 9mm version is in the works.

 

In the 8 - 10mm focal length ultra wide angle I presently own the TV 10mm Ethos, 9mm APM HDC 100°, and TV 8mm Ethos. I tend to grab the APM 9mm 100° as my defacto eyepiece in the focal length range - love the views.

 

I have read CN posts concerning the ES 9mm 120° eyepiece - mainly positive - extremely emmersive views, needs an observing hood, etc.

 

I am I missing the boat by not owning this eyepiece?

 

 

I also got to use an ES 9mm 120 eyepiece and had a blast with it in my Dobs. There is really no other eyepiece quite like it. The experience is basically it’s the “majesty factor” on steroids.  To my eye its FOV is noticeably wider than the 10mm Ethos.  On the other hand the 10mm Ethos seems to have slightly better light transmission and slightly tighter stars.  I think those with very large Dobs might appreciate the extra FOV of the ES 9mm 120 but most people would certainly find the 100 degrees of the 10mm Ethos to be more than sufficient.

 

The ES 9mm 120 is an excellent eyepiece but the 10mm Ethos is a superb one.  For now, I can’t quite talk myself into buying one but maybe the next time ES runs a sale...



#9 MitchAlsup

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Posted 27 January 2019 - 12:57 PM

I have a 9ES120 from the first batch.

 

It is a fabulous EP, well corrected, stupidly wide FoVs. Most of the time I can see the edge of the FoV laterally but not vertically--but just barely in the lateral direction, and you have to be looking for it. It redefines what "space walk" means.

 

I wish it sold enough copies to warrant a 7ES120 clone to be developed.

 

It has a field as wide as 13E with higher mag and blacker backgrounds (excepting the ring of fire...)


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#10 opticsguy

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Posted 27 January 2019 - 08:35 PM

Well . . . .  I do own and use the ES 9mm x 120 and it is a fun EP.  Observing for me should always be fun, thus this EP is enjoyed frequently.  One of my first memories using this EP was being able to turn my head left and right to see both sides of the FOV.  I consider this fun.  

 

As always Eyepieces fit peoples eyes in different ways and what works for one person is not necessarily what another might experience. 

Did I mention this one EP is fun? 



#11 Shneor

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Posted 28 January 2019 - 01:42 AM

I have a 9ES120 from the first batch.

 

It is a fabulous EP, well corrected, stupidly wide FoVs. Most of the time I can see the edge of the FoV laterally but not vertically--but just barely in the lateral direction, and you have to be looking for it. It redefines what "space walk" means.

 

I wish it sold enough copies to warrant a 7ES120 clone to be developed.

 

It has a field as wide as 13E with higher mag and blacker backgrounds (excepting the ring of fire...)

Mine is also from the first batch. It spends more time in the focuser of my 22" than all my other eyepieces together (list in my signature). For me, it's the best eyepiece ever. Wish there were a 2.5mm 120*.


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#12 vkhastro1

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Posted 28 January 2019 - 12:05 PM

It seems the first batch (serial # 1-20) had a wider AFOV of ~140°.

The remainder (serial # > #20) have a AFOV of 120° (due to installed field stop).

 

Compared to a 9mm 100° eyepiece (APM, ES, etc) there is quite a difference in TFOV (true field of view).

The original AFOV 140° version has 1.96X the TFOV.

The current AFOV 120° version has 1.44X the TFOV.

 

The AFOV 140° version has 1.36X the TFOV of the current AFOV 120° versions.

 

Definitely obvious that the "Majesty Factor" or "Emersive Factor" of the original ES 9mm AFOV 140° version compared to 

9mm 100° eyepiece would be amazing.

If one was to buy this eyepiece, it would be obvious to purchase on of the first 20 of the ES 9mm 120° eyepieces.

However, the owners of this specific version would know this and not be willing to part with their eyepiece.

Looks like the current AFOV 120° version reviews/impressions are the only ones that can be assessed if one is considering purchasing this eyepiece.

 

I have experienced the "Majesty Factor" going from AFOV 82° to AFOV 100° eyepieces (1.49X TFOV) - very impressive.

The "Majesty Factor" going from AFOV of 100° to AFOV of 120° is basically the same (1.44X TFOV).

However, it is a lot easier to view an AFOV of 100° compared to an AFOV of 120°.

Can anyone comment on comparing the "Majesty Factor" of AFOV of 82° to 100° vs AFOV of 100° to 120°.

 

Also is the EFOB (ring of fire) very noticeable on deepsky observing (I would not use this eyepiece for planetary observing)? I am quite sensitive to EOFB - found it very noticeable on a Baader Morpheus 4.5mm.

 

Thanks, Gary



#13 rowdy388

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Posted 28 January 2019 - 04:13 PM

Makes me wonder if the field stop can be removed with a spanner wrench or if it is internal. Seems like

a good option to have a 140 degree eyepiece.


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#14 areyoukiddingme

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Posted 28 January 2019 - 05:47 PM

Makes me wonder if the field stop can be removed with a spanner wrench or if it is internal. Seems like

a good option to have a 140 degree eyepiece.

Surely there's someone who is sufficiently curious/reckless/confident to give it a try!


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#15 faackanders2

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Posted 28 January 2019 - 05:57 PM

It seems the first batch (serial # 1-20) had a wider AFOV of ~140°.

The remainder (serial # > #20) have a AFOV of 120° (due to installed field stop).

 

Compared to a 9mm 100° eyepiece (APM, ES, etc) there is quite a difference in TFOV (true field of view).

The original AFOV 140° version has 1.96X the TFOV.

The current AFOV 120° version has 1.44X the TFOV.

 

The AFOV 140° version has 1.36X the TFOV of the current AFOV 120° versions.

 

Definitely obvious that the "Majesty Factor" or "Emersive Factor" of the original ES 9mm AFOV 140° version compared to 

9mm 100° eyepiece would be amazing.

If one was to buy this eyepiece, it would be obvious to purchase on of the first 20 of the ES 9mm 120° eyepieces.

However, the owners of this specific version would know this and not be willing to part with their eyepiece.

Looks like the current AFOV 120° version reviews/impressions are the only ones that can be assessed if one is considering purchasing this eyepiece.

 

I have experienced the "Majesty Factor" going from AFOV 82° to AFOV 100° eyepieces (1.49X TFOV) - very impressive.

The "Majesty Factor" going from AFOV of 100° to AFOV of 120° is basically the same (1.44X TFOV).

However, it is a lot easier to view an AFOV of 100° compared to an AFOV of 120°.

Can anyone comment on comparing the "Majesty Factor" of AFOV of 82° to 100° vs AFOV of 100° to 120°.

 

Also is the EFOB (ring of fire) very noticeable on deepsky observing (I would not use this eyepiece for planetary observing)? I am quite sensitive to EOFB - found it very noticeable on a Baader Morpheus 4.5mm.

 

Thanks, Gary

You can read Al Nagler's comments on majesty factor on the Televue Ethos site.  He came up with the term and explains it quite well.

I prefer 100-120 AFOV vs. 82-84 AFOV.  I also prefer 82-84 AFOV to 68-70 AFOV, which people used to call "spacewalking" views.

For the same power you get a much larger AFOV and TFOV.  If you match eyepieces that have the same TFOV, the wider AFOV, would have both higher power and darker contrasting background.

 

I have not actually seen anyone write an actual  comparison between a current production 9mm 120 AFOV vs. lot/SN 1-20  9mm 120 AFOV (supposedly 140 AFOV) eyepiece, and would like someone to do an A-B side by side observing session and comparison.

 

EFOB (brown ring of fire) is only visible on the bright moon, not DSOs since they are much too dim for it to show.



#16 faackanders2

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Posted 28 January 2019 - 05:59 PM

Makes me wonder if the field stop can be removed with a spanner wrench or if it is internal. Seems like

a good option to have a 140 degree eyepiece.

I did ask ES if they would consider selling the 9mm 120 AFOV without the limiting field stop, and they never replied back, so I assume the answer is no.


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#17 MitchAlsup

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Posted 28 January 2019 - 07:44 PM

I did ask ES if they would consider selling the 9mm 120 AFOV without the limiting field stop, and they never replied back, so I assume the answer is no.

All it is really going to take is for one person with a first gen and another person with a second gen and a shop with proper measuring tools......

 

Hey, this sounds like a job for ATM...........



#18 Shneor

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Posted 29 January 2019 - 02:16 AM

The "bright ring of fire" is visible when a planet is on the edge of the field. Jupiter, for example, while not apparently changing shape, turns bright white. Same for the moon. Otherwise, it's invisible. I only realized that the field was practically 140* when I compared the view to a 13mm Ethos, and noticed that the field was identical. Then I did the math. Also, it took me a couple of years to be able to take in the full view without turning my head.

 

You can't just remove the field stop, as the eyepiece is sealed and waterproof. There are photos of the two field stops in this forum and you can easily see the difference, just search for ES120. It was posted less than a year after they were introduced.


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#19 Starman1

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Posted 29 January 2019 - 09:36 AM

Why does everyone keep talking about an eyepiece that isn't available for someone who wants it?

The current versions are 120°, not 140°, and the odds of finding one with the larger field stop is virtually nil.


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#20 MitchAlsup

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Posted 29 January 2019 - 12:51 PM

Why does everyone keep talking about an eyepiece that isn't available for someone who wants it?

The current versions are 120°, not 140°, and the odds of finding one with the larger field stop is virtually nil.

The question was not can one find an original one,

The question was can one turn the current version into the original version by disassembly; remove stop, reassembly.


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#21 25585

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Posted 30 January 2019 - 04:52 AM

The question was not can one find an original one,

The question was can one turn the current version into the original version by disassembly; remove stop, reassembly.

Being waterproof with Ar inside, disassembly would destroy the waterproofing at least.



#22 Luca Brasi

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Posted 18 April 2019 - 02:41 PM

I'm a little confused about the field stop and rumors about 140 degrees?  I just purchased an open box 120 degree from the NEAF sale.  I've only got to use it a couple nights so far, but I'm not sure how they could fit more AFOV in the thing!?!  When I turn my head to see the edge of field there is only about 5 degrees of separation between the edge of the view and the eyecup.

 

It is a pretty extraordinary eyepiece.  The eye placement is a little tricky since your head needs to float above the eyepiece and the eyecup is way to long.  But after carefully trimming a cm off the top of the cup (on a $650 eyepiece )  it works perfectly!  I don't know why they cut that corner on such an amazing piece of optics...

 

Optically it is equil to my 9mm 100 degree.  Only issues are that the brightest stars turn into rainbows near the edge and my coma corrector seems to shave a couple degrees off the AFOV.

 

All and all I'm pretty happy with it, though Imight need a stronger neutral density filter.  120 degrees of moon is downright hostle!



#23 Starman1

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Posted 18 April 2019 - 03:32 PM

Why didn't you just fold the eyecup down to lower it?

I've looked through several of these now, and all were 120°.

Supposedly, the first few into the US had a larger field stop, which gave a larger apparent field.

Your chances of seeing one are pretty slim.



#24 Luca Brasi

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Posted 18 April 2019 - 11:00 PM

Why didn't you just fold the eyecup down to lower it?

I've looked through several of these now, and all were 120°.

Supposedly, the first few into the US had a larger field stop, which gave a larger apparent field.

Your chances of seeing one are pretty slim.

I did try it for a week with the eye cup down but found it difficult to keep my head in the right position.  I find making contact with the eye cup makes it much easier to avoid kidney beans.  How do you test the AFOV?  Looking at a few diffuse star clusters I noticed that the AFOV was very close to my 14mm 100 degree.  Way closer than astronomy.tools field of view calculator seems to show.  Maybe the magnification is a little lower than it should, maybe astronomy.tools is a little off or maybe Explore Scientific put a 140 degree on display at NEAF for extra WOW factor?

 

Either way, great eyepiece!  



#25 Starman1

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Posted 18 April 2019 - 11:44 PM

Do a search on CN for the flashlight test for apparent field.
You can do a star timing to determine the true field and field stop and back into the calculated apparent field but only the flashlight test will give you the real apparent field.


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