21 replies to this topic

[Procyon]

I have a few questions, is it just the widefield eyepieces that most people can't see the field stop with? Or are there exceptions everywhere, in any AFOV class?

 

For example some say they can't see the field stop with a 27mm TV Panoptic? To the users who own one, do you feel the same or?

 

Besides 100º eyepieces, what eyepieces can't you see the field stop with? Does this always cause the "porthole into space" feeling?

 

What causes this effect in some eyepieces?

 

 

[Tony Cifani]

I recently acquired an old Meade 4000 UWA 14mm, currently my widest AFOV eyepiece at 78º (from what I've read here on CN from user tests). I can see the field stop but I have to place my eye at an exact spot, probably the distance of the measured eye relief, and really look for it. When my eye is higher, the field stop is not visible. It seems like eyepieces with generous eye relief and large eye lenses (maybe this is the "porthole effect") have less obvious field stops? Honestly, at dark sites when I'm observing faint objects, I usually don't notice the field stop in many eyepieces anyway.

[25585]

I would worry less about seeing a field stop, and be more concerned with how much view you can easily see overall.

[TOMDEY]

Provided you can get the pupil of your eye at the exit pupil of the telescope + eyepiece combination... at least in theory, if you have your eye right there and staring straight along the axis --- you should, in principle --- see the entire field (and therefore the field stop comfortably around the outer part of your visual field). On the other hand --- if you want to shift your central gaze at and around the edge of the field --- thats takes some practice to keep and maintain your rolling eyeball + head with your eye's pupil still maintained on the system exit pupil. And that takes a heck of a lot of practice --- until it becomes ~natural~, and you just do it automatically. This substantially explains why so many observers (even many otherwise experienced ones) gripe incessantly about blackouts etc. etc. and blame it on the eyepiece.

 

Quite frankly, it's actually rather surprising that we do as well as we manage.

 

PS: The healthy eye's native field of view is actually quite generous, a lot wider than even the extra wide field eyepieces'. But in practice at the telescope or (even worse) ultra wide-field binocular --- the brow, nose, and cheek can get in the way.

 

Like learning a musical instrument... visual practice beyond one's current comfort level is the only way to get better. Otherwise, we make the same mistakes over and over again, without improving. It takes hundreds of more hours at the eyepiece to gradually ease into it. I know there are many folks here with thousands of hours under their belts --- and still honing their skills. Me, I've been there... but am very rusty now, having drifted away from those manic all-nighters or yore.    Tom

 

PS: Some eyepieces that push the limit of the barrel size don't even have a dedicated field stop in there. Instead, the tube end or other restrictions default to a fuzzy field edge, where it's just glorified vignetting that ultimately defines the available field.    Tom

Edited by TOMDEY, 21 April 2025 - 10:03 PM.

[CrazyPanda]

I have a few questions, is it just the widefield eyepieces that most people can't see the field stop with? Or are there exceptions everywhere, in any AFOV class?

 

For example some say they can't see the field stop with a 27mm TV Panoptic? To the users who own one, do you feel the same or?

 

Besides 100º eyepieces, what eyepieces can't you see the field stop with? Does this always cause the "porthole into space" feeling?

 

What causes this effect in some eyepieces?

I had a very, very hard time seeing the field stop of the 8mm TV Plossl. The effective eye relief of that eyepiece was like 0. Literally have an easier time seeing the field stop in a 5mm Meade Series 3000 Plossl.

 

Regarding the porthole into space effect, I'm not sure not seeing the field stop is related to that.

 

If the eye relief of an eyepiece is so tight I can't see the field stop with any measure of comfort, I simply don't use the eyepiece. Not seeing the field stop of an eyepiece, to me, is a non-starter of a viewing experience. A clean, well-defined field edge is important to me.

 

The porthole into space is not caused by not seeing the field stop, but rather when the perspective of the virtual image formed by the eyepiece's field appears to hide the physical bezel of the eyepiece behind it. That is, the eyepiece almost physically disappears and you see a weird combination of a thin black field stop that transitions into your surroundings.

 

The 28RKE has this effect, as do de-cloaked DeLites (especially when binoviewing with them).

[Procyon]

The porthole into space is not caused by not seeing the field stop, but rather when the perspective of the virtual image formed by the eyepiece's field appears to hide the physical bezel of the eyepiece behind it. That is, the eyepiece almost physically disappears and you see a weird combination of a thin black field stop that transitions into your surroundings.

Exactly the 2" types I'm looking for and what I meant to say, thanks.

 

Basically, an edge that feels endless. I don't really care much about looking at the edge, I just like the feeling and presence of endless space at the corners of my eye. 

Edited by Procyon, 21 April 2025 - 10:02 PM.

[TayM57]

Regarding the porthole into space effect, I'm not sure not seeing the field stop is related to that.

The porthole into space is not caused by not seeing the field stop, but rather when the perspective of the virtual image formed by the eyepiece's field appears to hide the physical bezel of the eyepiece behind it. That is, the eyepiece almost physically disappears and you see a weird combination of a thin black field stop that transitions into your surroundings.

The 28RKE has this effect, as do de-cloaked DeLites (especially when binoviewing with them).

For the porthole into space effect, either the image formed by the eyepiece or the field stop has to appear close to the eye lens. In the case of the ES92s, the image formed appears close to the eye lens instead of some distance "down the barrel".

The Morphii are another excellent example of the porthole effect into space, despite their narrower AFOV compared to 82° class EPs. In the case of the Morphii, the field stop appears close to the eye lens AND it blurs/merges with the outer casing of the barrel, particularly with the eye guard completely unscrewed which is how I use all of the Morphii.

The Morphii are some of the best EPs around when it comes to the porthole to space effect, but the ES92s reign supreme.

The Delites, as you pointed out, do have a similar effect when decloaked.

Edited by TayM57, 21 April 2025 - 11:37 PM.

[Ernest_SPB]

I do not understand this: "can't see the field stop..."

What does is mean?

Feeling limitation FOV when your eye directed at FOV center... 

Or ability to see FOV edge when you scan it... 

And to say honnestly in both cases with right eye position you will see edge of the filed stop. 

 

Note that average human with normal eyes have FOV 115 deg. in vertical and 150 deg. in horizontal direction.

[eblanken]

Hello (aka Procyon) & All,

 

I have a few questions, is it just the widefield eyepieces that most people can't see the field stop with? {For me, YES}

 

Or are there exceptions everywhere, in any AFOV class? {Also, Yes}

 

For example some say they can't see the field stop with a 27mm TV Panoptic? To the users who own one, do you feel the same or?

 

Besides 100º eyepieces, what eyepieces can't you see the field stop with?

 

Does this always cause the "porthole into space" feeling?

 

What causes this effect in some eyepieces?

 

Short answer: Design Tradeoffs . . . 

 

For the porthole into space effect, either the image formed by the eyepiece or the field stop has to appear close to the eye lens. In the case of the ES92s, the image formed appears close to the eye lens instead of some distance "down the barrel".

The Morphii are another excellent example of the porthole effect into space, despite their narrower AFOV compared to 82° class EPs. In the case of the Morphii, the field stop appears close to the eye lens AND it blurs/merges with the outer casing of the barrel, particularly with the eye guard completely unscrewed which is how I use all of the Morphii.

The Morphii are some of the best EPs around when it comes to the porthole to space effect, but the ES92s reign supreme.

The Delites, as you pointed out, do have a similar effect when decloaked.

 

 

I do not understand this: "can't see the field stop..."

What does is mean?

Feeling limitation FOV when your eye directed at FOV center... 

Or ability to see FOV edge when you scan it... 

And to say honnestly in both cases with right eye position you will see edge of the filed stop. 

 

Note that average human with normal eyes have FOV 115 deg. in vertical and 150 deg. in horizontal direction.

 

Starting with Ernest's comment: Even though I know that my eyes are capable of 100 to 150 Degrees, my brain is now used to ignoring what is in the periphery of my vision because I wear eyeglasses and the frames aren't allowing corrected vision beyond the outline of the lenses of my tri-focal lenses. I wear large "Aviator" Frames with big lenses, but even these cut off my full vision AFoV. My choices in eyepieces are Pentax XW 68 Degree AFoV and TeleVue DeLite 62 Degree AFoV. I can easily see the field stop in these Full Sets. I even like Plossls which are narrower AFoV at 50-ish Degrees or narrower (Example is 40mm Plossl is just fine for me where others preach 32mm Plossl as widest in 1.25 inch format and still others say 24mm/68 Deg Panoptic). My brain gets "dis-oriented" in wide AFoV eyepieces like TeleVue Ethos because my brain likes to see the boundary of the field stop. Others like the field stop to be out much wider than I like.

 

My preference is dominated by the interaction of the eyepiece's Exit Pupil Placement with my eyeglasses and the Vertex Distance (inside of eyeglass lens to Cornea of my eye) requires about 20mm of Eye Relief (ER) for eyepieces for me to use well and comfortable. Tay sold me the Pentax XW Set. He prefers wider AFoV eyepieces than I, so his eyeglasses are different than mine and he gets to enjoy the wider AFoV choices, but I limit my choices to Narrower as a Trade-Off to get more ER. I live with the "tunnel-effect" knowing that I much prefer the field stop to more present to me and not out wide.

 

Another part of my preference is associated with the reality of tracking mounts. I'm appreciative of Large Dob Guys, but I'm not an owner of any mounts that don't track. Drift time is really important to others, but not to me, so wide AFoV isn't a priority to me.

 

Eyepiece choices are very subject to individual preferences.

 

Best,

 

Ed

 

P.S. Good Thread because of good questions and good comments & shared experiences.

Edited by eblanken, 22 April 2025 - 03:35 AM.

[Ernest_SPB]

Somebody likes narrow FOV, somebody likes wide (super-/ultra-/extra-wide). But in any case limits of human vision larger and eyepiece AFOV cuts it more or less, making field stop effective (visible). That is my point.

 

BTW I do not understand how narrow FOV can be liked by anybody. In the case such people should use sort of blinders in normal life. But we can put up with narrow FOV gaining better contrast, less light scattering. We like better image quality even in less FOV, but not just a less FOV.

[Highburymark]

I have a few questions, is it just the widefield eyepieces that most people can't see the field stop with? Or are there exceptions everywhere, in any AFOV class?

For example some say they can't see the field stop with a 27mm TV Panoptic? To the users who own one, do you feel the same or?

Besides 100º eyepieces, what eyepieces can't you see the field stop with? Does this always cause the "porthole into space" feeling?

What causes this effect in some eyepieces?

27mm Panoptic is as easy to see the field stop as other Panoptics.

[Procyon]

Does Jon's famous 32mm TV Widefield "big easy view", 40mm TV Widefield and the 48mm Brandon have this effect? 

 

Same for the 2" 32mm and 40mm Brandon Konigs and Erfles.

Edited by Procyon, 22 April 2025 - 08:07 AM.

[SeattleScott]

As pointed out, unless there is something wrong with your eyes, you will be able to see the field stop, at least in your peripheral vision, if you get your eye close enough. Granted, with shorter ER, some might prefer to stay a little further back and sacrifice a little AFOV for improved ER. Especially with hyperwides, as the ER isn’t long, and the view being cutoff is just peripheral vision anyway.

I visited a house once with an incredible 180 degree view, where I could see all the way from Mt Baker on the left to Mt Rainier on the right. Interestingly, I almost felt like the view was too wide. The view was so wide, with so much to see, it felt busy. There wasn’t a natural place to look. I felt like I didn’t know where to look because there was so much to see. In that way, I might prefer 70-80 AFOV and just move my scope around to see more, rather than hyperwides where the view is too wide to really take it all in at once. On the rare occasion I use a hyperwide, I normally back off and use it like a long ER ultrawide. If a target is so big that I have to squeeze in close to see all of it, I end up feeling a bit overwhelmed with not knowing where to look, because no matter where I look, part of the target is going to be off in my peripheral vision. There is something to be said for using a little less magnification and being able to fully take something in rather than squeezing it into 100-110 AFOV and part of the target being out in your blurry peripheral vision.

[25585]

What makes a field (of view), stop, when looking through an eyepiece? It is a boundary, whatever causes it. The edge of a field of view can be the fieldstop, or just where a view through is cut off because your vision can see no more, whatever the cause. 
 

I think Procyon wants a wider field from eyepieces than his vision normally sees, so that the effect appears he is looking into unbounded space, say if he tilts his head. 

[eblanken]

Hi Again All,

 

The question is, does Procyon wear corrective eyeglasses like many of us now do ? The interactions of both frames and lenses with the eyepiece exit pupil (EP) is a major determination of if the eye can be positioned at EP or not. Also, can the eye-lens of the eyepiece "hide" the field stop to get the "space-walk" presentation or is the eye cup big in angular terms and is the image presented "deep-in-the-tunnel" or "shallow" ? An example of this "big" eye cup is the Pentax XW family: they have the adjustable eye cup and unless the cup is removed entirely, the view has a substantial surround which spoils the "shallow" angular surround with something that is seen in the outer peripheral vision . . . I keep the cup all the way down . . . I have a friend who just took the eye cup completely off and gets what he wants . . . 

 

People rave about the TeleVue Ethoi and the Panoptics, but I can't use them with my eyeglasses, unless I stay further out and then can't see field stop or take off glasses and forego correction for Astigmatism . . . 

 

Best,

 

Ed

Edited by eblanken, 22 April 2025 - 05:45 PM.

[John Huntley]

I don't wear glasses when observing.

 

The only eyepieces that I have used where the field stop edges have been challenging to see were the Ethos SX 3.7 and 4.7 and the Myriad 5mm and 3.5mm. These eyepieces claim an apparent field of view of 110 degrees. 

 

In the same ranges, the 100 degree eyepieces I have no trouble in seeing the field edge with. 

 

Personally I rather like the "limitless field of view" effect when I can get it and when it is sharp across that ultra wide view.

[luxo II]

This is subjective, ie depends on the observers eyesight. There is no one-answer-fits-all.

 

I've had the "porthole into space" experience with a 70 degree SWA.

Edited by luxo II, 22 April 2025 - 10:10 PM.

[Starman1]

I have a few questions, is it just the widefield eyepieces that most people can't see the field stop with? Or are there exceptions everywhere, in any AFOV class?

 

For example some say they can't see the field stop with a 27mm TV Panoptic? To the users who own one, do you feel the same or?

 

Besides 100º eyepieces, what eyepieces can't you see the field stop with? Does this always cause the "porthole into space" feeling?

 

What causes this effect in some eyepieces?

Out of around 400 eyepieces, I have seen zero in which you could not see the field stop, even the 120° eyepiece, though many were vague and not in focus.

There are reasons people don't see the field stops, but they all indicate misunderstanding how to use the eyepiece:

--being farther away from the eyepiece than the exit pupil

--using glasses with eyepieces not designed to be glasses compatible

--not understanding that looking directly at the field stop requires rolling the head over to do so on anything wider than 50°, whereas seeing the field stop with peripheral vision merely requires being at the exit pupil.

--not seeing a sharp field stop doesn't indicate you aren't seeing the field stop, merely that it isn't in focus for your eye (and some are not in focus for any human eye).

[Jon Isaacs]

Lots of good stuff in this thread... 

 

There are some eyepieces that do not have field stops... The 30 mm and 42 mm GSO Superviews have no field stops so you really see them. What happens is the edge of the transitions from full illumination to zero illumination over a band of vignetting maybe 3° wide.

 

Jon

[Starman1]

Lots of good stuff in this thread...

There are some eyepieces that do not have field stops... The 30 mm and 42 mm GSO Superviews have no field stops so you really see them. What happens is the edge of the transitions from full illumination to zero illumination over a band of vignetting maybe 3° wide.

Jon

And a star dims in that band, but it dies eventually wink out as it crosses the I.D. of the barrel. I once had a 12.5mm UO Plossl without a field stop, and seeing the edge required getting only a couple mm from the glass. That eyepiece was a mistake at the factory, but how could I resist?

[Procyon]

If anyone can see the field stop of an Antares 31.5mm 90º awesome little bizarro eyepiece I'll...be amazed?

 

I may have mistaken with what I meant to say, I was really looking for eyepieces with views that feel like a 2" RKE 28mm...but when you look through the eyepiece, you feel as if the view stretches right under your seat even. Was it the Antares massive AFOV or can an eyepiece like 25585's Vernonscope 40mm have that type of view? (Or Jon's "big easy viewer" TV Widefield).

 

PS> I don't usually wear glasses, but when I do I just flip them upwards. Still rolling with the contact lenses.

 

31.5mm Antares 90º 

 

Edited by Procyon, 23 April 2025 - 02:10 PM.

[25585]

This topic crosses over to the immersive eyepieces thread. 
 

Those eyepieces with high field stops, might have them looked past, so unseen as in not noticed.