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Killer Beans on the Moon

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#1 Anony

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Posted 30 June 2020 - 11:38 AM

 I know the title of this thread sounds like a 1950s B horror film produced by Goya. But I have some questions about killer kidney beans.

 

Using my expanse clones (6mm/9mm) during the daytime in my refractor can produce some annoying kidney beaning, and I never tested my dob during the day (little point to it)... but last night I tried them out on the moon. And kidney beans attacked my eyeballs.

 

My question is, is this a specific issue with these eyepieces or do most wider fov eyepieces have this same issue with the moon? I assume the moon may be an issue since the edges of the view are illuminated by the size of the moon, while smaller targets are just the blackness of space... so the latter is less obvious or annoying.

 

Now if I get my eye situated just right, it's not a big deal. 6mm seemed worse than the 9mm, as it also added a little extra glare to the bean, so it became glowing kidney beans. 9mm still had issues too though. I didn't really notice any major beaning with the expanse clone at 15mm. And it is probably just a coincidence, but using a half-barlowed 15mm (so equivalent to 10mm) produced less beaning than the 9mm did ... but I didn't spend a lot of time testing that out. 10mm plossl had no beaning, but that is a narrower fov.

 

Basically curious if it's specific to my eyepieces or does this also occur with other wider fov eyepieces, specifically on the moon? I thought my f/8 scope would be immune to this, but it doesn't seem that way. Do zoom people get this?



#2 BillP

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Posted 30 June 2020 - 12:30 PM

When an optical designer designs an eyepiece, they also design the "exit pupil" of the eyepiece.  That is the surface of the image plane where the view is formed above the eye lens.  Depending on how that surface is shaped and designed, will affect whether you get blackouts, kidney beans, or other issues.  One aberration of the exit pupil, called Spherical  Aberration of the Exit Pupil (SAEP) is what causes kidney beans.  https://www.handprin...O/ae4.html#SAEP

 

When the iris of your eye is contracts and is smaller, due to bright light like daylight or observing the Moon, I find any SAEP that exists in the exit pupil design of an eyepiece is very much exacerbated.  It seems that wider AFOV eyepieces or those with longer eye relief tend to have the problem more often, but maybe that is because the designers are not paying attention to the exit pupil design so much.  Don't know.  Eye relief is also a player as the further away your head is from the eyepiece, then smaller head movements position your eye off center can affect the view.  So being seated helps a lot with longer eye relief.  In any event what you are seeing is a property of the specific eyepiece and not really a general characteristic of all wide fields.  I have come across a number of modern wide fields that have the problem, and others that do not.  The old TV Radians expressed the issue the worst I have come across for me.  But basically it is one of those things you have to pay attention to when figuring out what eyepieces you may want to buy.  Unfortunately only way to really tell is to try for yourself to see if they have it.  You can read reviews to help find out if a particular eyepiece has the issue or not, but over the years I have noticed that for a given brand and focal length that does show it, it seem that it shows if for some people a lot, and others rarely or not at all.  Tis indicates to me that the physiology of each of our eyes must also come into play as it interfaces to the exit pupil of the eyepiece, so maybe SAEP is more of a dynamic between the eyepiece and the eye that determined how prevalent the kidneybean or blackout artifacts are, rather than being solely an eyepiece issue.


Edited by BillP, 30 June 2020 - 12:33 PM.

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#3 Anony

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Posted 30 June 2020 - 12:44 PM

Figure a lot of it will be trial and error and I won't know until I see for myself.

 

I was aware that some folks had kidney bean issues with these eyepiece, mostly with faster scopes, but typically at f/8 I don't think many have had any issues. However I don't recall anyone specifically mentioning using them on the moon either.

 

Moon sort of mimics daytime viewing, so there it seems more problematic (at least for my eyes).



#4 25585

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Posted 30 June 2020 - 01:43 PM

When an optical designer designs an eyepiece, they also design the "exit pupil" of the eyepiece.  That is the surface of the image plane where the view is formed above the eye lens.  Depending on how that surface is shaped and designed, will affect whether you get blackouts, kidney beans, or other issues.  One aberration of the exit pupil, called Spherical  Aberration of the Exit Pupil (SAEP) is what causes kidney beans.  https://www.handprin...O/ae4.html#SAEP

 

When the iris of your eye is contracts and is smaller, due to bright light like daylight or observing the Moon, I find any SAEP that exists in the exit pupil design of an eyepiece is very much exacerbated.  It seems that wider AFOV eyepieces or those with longer eye relief tend to have the problem more often, but maybe that is because the designers are not paying attention to the exit pupil design so much.  Don't know.  Eye relief is also a player as the further away your head is from the eyepiece, then smaller head movements position your eye off center can affect the view.  So being seated helps a lot with longer eye relief.  In any event what you are seeing is a property of the specific eyepiece and not really a general characteristic of all wide fields.  I have come across a number of modern wide fields that have the problem, and others that do not.  The old TV Radians expressed the issue the worst I have come across for me.  But basically it is one of those things you have to pay attention to when figuring out what eyepieces you may want to buy.  Unfortunately only way to really tell is to try for yourself to see if they have it.  You can read reviews to help find out if a particular eyepiece has the issue or not, but over the years I have noticed that for a given brand and focal length that does show it, it seem that it shows if for some people a lot, and others rarely or not at all.  Tis indicates to me that the physiology of each of our eyes must also come into play as it interfaces to the exit pupil of the eyepiece, so maybe SAEP is more of a dynamic between the eyepiece and the eye that determined how prevalent the kidneybean or blackout artifacts are, rather than being solely an eyepiece issue.

There are not so many designs that get exit pupil design right, in as far as steadiness behaviour and long eye relief. Eye placement issues are apparently a difficult art, even with shorter eye relief eyepieces.

 

One problem is copying of a design, bad aspects being copied along with good ones. Another may be in-house tutoring, and "acceptable" design parameters for a company, its tutees being taught what the bosses wants, so potential could be curbed, and indivudual innovation unwanted.



#5 BillP

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Posted 30 June 2020 - 04:17 PM

Agree.  Very few really get it right...or should I say "near" right lol.gif


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#6 SeattleScott

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Posted 30 June 2020 - 04:30 PM

I don’t know if F ratio has any relevance to eye placement.

In general it seems like the high end eyepieces do well here, Delite, XW, Morpheus, LVW, etc. But then SSW are certainly expensive enough yet have some SAEP. Some say Delos are picky. A lot of it is figuring out the right distance and adjusting eyecup to guide you.

Scott
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#7 25585

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Posted 30 June 2020 - 07:23 PM

I think all should easy to use out of the box. The designers need some time in field hobby optics etc to get a grounding in user-friendliness, rather than relying on optical science alone.



#8 Ernest_SPB

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Posted 01 July 2020 - 02:09 AM

My question is, is this a specific issue with these eyepieces...

Yes... These eps are very sensitive to observer's eye position, especially in day time and for bright objects.  Kidney bean vignetting + glares.

There are a lot of WA and UWA eyepieces that are better in the respects. Inexpensive set includes HD-60/Meade, X-Cel LX/celestron, Planetary/TMB, Dual ED/Paradigm...


Edited by Ernest_SPB, 01 July 2020 - 02:11 AM.

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#9 Anony

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Posted 01 July 2020 - 12:05 PM

Yes... These eps are very sensitive to observer's eye position, especially in day time and for bright objects.  Kidney bean vignetting + glares.

There are a lot of WA and UWA eyepieces that are better in the respects. Inexpensive set includes HD-60/Meade, X-Cel LX/celestron, Planetary/TMB, Dual ED/Paradigm...

 

Thanks, that was my main question. I originally thought I escaped kidney beans, until testing with the moon. But it makes sense why the moon would have that issue and it wouldn't be a big deal for dimmer targets. As for glares, getting some with Jupiter and w/ the 6mm ... not super terrible, but there is some. I still like the eyepieces, just not so fond of them for moon stuff.

 

I'm thinking for moon viewing I might prefer an inexpensive zoom (assuming it doesn't have the same kidney bean issue).



#10 Chuck2

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Posted 01 July 2020 - 01:40 PM

Bill made one statement above that should not be overlooked... being SEATED while observing. Standing creates continuos fluctuations to the light path, and promotes kidney beaning.

 

Being seated makes a huge difference in observer's ability to consistently, place a stable light path into the observer's eye. At public outreach programs, I provide an observing chair. No more comments of "I can't see anything". Observing becomes more comfortable and relaxing if you're not continuously chasing the cone of light.

 

We place tripods under our scopes to stabilize images, should we not put an observing chair under our bodies to complete the stability? My first 20 years of observing I stood, the past 25 years I have sat. Can't imagine why it took me so long figure out the benefit.


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#11 Anony

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Posted 01 July 2020 - 01:46 PM

Bill made one statement above that should not be overlooked... being SEATED while observing. Standing creates continuos fluctuations to the light path, and promotes kidney beaning.

 

 

Yep, I always sit when observing. And it's not a huge issue for me, as whatever kidney beans I get for most targets isn't bothering me. I expect that is simply because they are darker targets.

 

The moon is like using the scope during daytime, entire field is lit up. There the beans are definitely noticeable to me, even when sitting.

 

Maybe next time I'll experiment a bit with eyeball distance from eyepiece, perhaps a bit further away (or closer) will be less beany.


Edited by Anony, 01 July 2020 - 01:47 PM.


#12 Chuck2

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Posted 01 July 2020 - 05:46 PM

Anony,

 

Yes, eyepieces with very long eye relief can be difficult to find and hold a 'sweet spot' to avoid beaning and blackouts. If available, use the twist-up or fold-up eyepiece guards. Set correctly, these can help you maintain eye distance and alignment.

 

Everyone is different (I don't wear glasses) I typically move in closer to eliminate 'beans' and get max FOV, some others would disagree.

 

Here are some great visuals of Kidney Bean and Blackouts, posted on the Stargazer Lounge...

https://stargazerslo...kidney-beaning/


Edited by Chuck2, 01 July 2020 - 06:19 PM.

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#13 luxo II

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Posted 01 July 2020 - 11:16 PM

The real issue here is that the moon is very bright so your eye pupil closes in response - probably down to 1-2mm.

If the eyepiece has spherical aberration of the exit pupil (SAEP) this means the rays from the scope won’t all pass through such a narrow eyepupil , and the result is “kidney bean”.

Conversely on dim objects in dark conditions your eye pupil opens up to 5+ mm and the same eyepiece won’t be so objectionable.

Edited by luxo II, 01 July 2020 - 11:17 PM.

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#14 Frisky

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Posted 01 July 2020 - 11:37 PM

My scope is f8.3. The Meade HD-60, at 6.5mm, doesn't kidney bean. My 9mm Expanse clones beaned terribly. I hated them until I learned to use them. I had to press my eyebrow lightly against the eyecup and I could get a good view with minimal beaning. I've been getting very good lunar viewing in with them. That said, the 6.5mm HD-60 is easier to use and gives me great views, making it my number one choice for lunar viewing. 

 

Joe


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#15 gnowellsct

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Posted 02 July 2020 - 08:08 AM

Kidney bean basically drove me away from almost all the Televue products. I find the problem minimized in Pentax XW line and for that matter the other Pentax lines as well.

It is a design parameter which TV is willing to accept an exchange for other benefits. For me that is a fatal flaw because with kidney bean you don't see anything and the fundamental purpose of the ocular is contradicted.

I don't have much to say about other lines these days because once I had the complete XW set I was no longer buying and selling oculars in search of the ones that I liked. I had found the ones that I liked. I do occasionally dabble in exotic stuff like the Leica zoom and the z a o 2 set. This is stuff that you don't really need and you only get when you are in the mood to drop a very big dime on something because you haven't bought anything in a long time.

I am too long-winded. The short answer is yes the manufacturer matters and some eyepieces have more bean than others and some manufacturers are worse than others. It is also the case that daytime viewing tends to cause a lot of problems with optics designed for astronomy. these problems are better controlled with optics designed for daytime use like binoculars and spotting scopes.

Edited by gnowellsct, 02 July 2020 - 08:09 AM.

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#16 25585

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Posted 02 July 2020 - 09:47 AM

Kidney bean basically drove me away from almost all the Televue products. I find the problem minimized in Pentax XW line and for that matter the other Pentax lines as well.

It is a design parameter which TV is willing to accept an exchange for other benefits. For me that is a fatal flaw because with kidney bean you don't see anything and the fundamental purpose of the ocular is contradicted.

I don't have much to say about other lines these days because once I had the complete XW set I was no longer buying and selling oculars in search of the ones that I liked. I had found the ones that I liked. I do occasionally dabble in exotic stuff like the Leica zoom and the z a o 2 set. This is stuff that you don't really need and you only get when you are in the mood to drop a very big dime on something because you haven't bought anything in a long time.

I am too long-winded. The short answer is yes the manufacturer matters and some eyepieces have more bean than others and some manufacturers are worse than others. It is also the case that daytime viewing tends to cause a lot of problems with optics designed for astronomy. these problems are better controlled with optics designed for daytime use like binoculars and spotting scopes.

XW Buddha speaks bow.gif  With unstrained eyes, we see the glory of our universe in comfort.


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#17 j.gardavsky

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Posted 02 July 2020 - 11:09 AM

XW Buddha speaks bow.gif  With unstrained eyes, we see the glory of our universe in comfort.


XW Buddha speaks.jpg

 

JG


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#18 gnowellsct

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Posted 02 July 2020 - 07:54 PM

bigshock.gif They are risen!  The XW 30 for $367 and the XW40 for $400 at B&H Photo!    Those are very good prices compared to days before the earthquake.



#19 Thomas_M44

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Posted 02 July 2020 - 11:56 PM

 I know the title of this thread sounds like a 1950s B horror film produced by Goya. But I have some questions about killer kidney beans.

 

Using my expanse clones (6mm/9mm) during the daytime in my refractor can produce some annoying kidney beaning, and I never tested my dob during the day (little point to it)... but last night I tried them out on the moon. And kidney beans attacked my eyeballs.

 

My question is, is this a specific issue with these eyepieces or do most wider fov eyepieces have this same issue with the moon? I assume the moon may be an issue since the edges of the view are illuminated by the size of the moon, while smaller targets are just the blackness of space... so the latter is less obvious or annoying.

 

Now if I get my eye situated just right, it's not a big deal. 6mm seemed worse than the 9mm, as it also added a little extra glare to the bean, so it became glowing kidney beans. 9mm still had issues too though. I didn't really notice any major beaning with the expanse clone at 15mm. And it is probably just a coincidence, but using a half-barlowed 15mm (so equivalent to 10mm) produced less beaning than the 9mm did ... but I didn't spend a lot of time testing that out. 10mm plossl had no beaning, but that is a narrower fov.

 

Basically curious if it's specific to my eyepieces or does this also occur with other wider fov eyepieces, specifically on the moon? I thought my f/8 scope would be immune to this, but it doesn't seem that way. Do zoom people get this?

That sounds quite frustrating.

 

Often a bargain ends up not being much of a bargain after all...

 

We've all been there.

 

Perhaps time to plan for an upgrade?

 

Good luck


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#20 Anony

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Posted 03 July 2020 - 01:27 PM

That sounds quite frustrating.

 

Often a bargain ends up not being much of a bargain after all...

 

We've all been there.

 

Perhaps time to plan for an upgrade?

 

Good luck

 

 

The expanse clones were my upgrade -- cheapskate rules apply here, not looking to spend much.

 

And I find that the clones are actually pretty decent. Again, just a moon issue, not an issue on any other targets. It's also not like I can't use them, just need to get my eyeball situated just right. And I can always just use my 10mm plossl on the moon if need be, barlowed or half-barlowed. Eventually I think an inexpensive zoom will be in my future though -- would seem a lot easier to just sort of dial-in the perfect mag than do the eyepiece swap thing.

 

My next real upgrades will be my scopes anyway. I have mount + design issues with both of mine. Just waiting to see what washes upon the craigslist shores...


Edited by Anony, 03 July 2020 - 01:28 PM.


#21 MartinPond

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Posted 05 July 2020 - 09:20 PM

Going from the X-Cel(non LX) to X-CEl-LX   or from Expanse to Dual-Ed/clones.

will knock down kidney-beaning a lot.  But..

 

If you are really being cheap and want to solve most of the issue,

Making or doing things to get that correct distance can do miracles.

A spacing tube can make the Expanse 9mm easy to place eyes on..

I have the 20mm of the infamous non-LX X-cels, and if I put the

  eyecup fully up AND wear glasses, the image is rock-steady and full.

 

Those who say distance is a key have a hint....you can space the 

eye right by various means and tame the Moon bean beast.

 

As an aside:  a Barlow almost always makes beaning worse.

A telecentric doesn't. 


Edited by MartinPond, 05 July 2020 - 09:20 PM.

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#22 Anony

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Posted 05 July 2020 - 09:32 PM

Going from the X-Cel(non LX) to X-CEl-LX   or from Expanse to Dual-Ed/clones.

will knock down kidney-beaning a lot.  But..

 

If you are really being cheap and want to solve most of the issue,

Making or doing things to get that correct distance can do miracles.

A spacing tube can make the Expanse 9mm easy to place eyes on..

I have the 20mm of the infamous non-LX X-cels, and if I put the

  eyecup fully up AND wear glasses, the image is rock-steady and full.

 

Those who say distance is a key have a hint....you can space the 

eye right by various means and tame the Moon bean beast.

 

As an aside:  a Barlow almost always makes beaning worse.

A telecentric doesn't. 

 

One interesting and odd thing I noticed during some moon/bean tests last night --

 

9mm expanse clone causes beaning on the moon. 6mm causes glowing moon beaning (meaning I need to also flock the thing). However, the 15mm expanse doesn't cause any major beaning either at 15mm (expected), 10mm (1.5x barlow) or at 7.5mm (2x barlow).

 

So... not entirely sure why I am getting beaning with the 6/9mm flavors and not the 15mm when barlowed into the equivalent (sorta) magnifications. Unless it has to do with the fact how each eyepiece is designed...

 

As both the 6mm and 9mm is sort of auto-barlowed (I think) with a little built-in lens on the bottom of each that acts like a barlow. While the 15mm is like the top half of the 6/9mm design, minus the built-in barlow. But maybe using my own barlow is better than whatever barlow lens the 6/9mm come with?

 

*shrugs*

 

Not sure what the reason is, just that for the moon, the 15mm barlowed seems to work a lot better than the 6/9mm do.


Edited by Anony, 05 July 2020 - 09:37 PM.


#23 payner

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Posted 06 July 2020 - 02:31 AM

The kidney bean and black out are different, but both manifest in a partially obscured FoV. The black out occurs due to the light cone of the eyepiece being too wide relative to the exit pupil, then when one's eye is placed too close, the pupil cannot see it all. The kidney bean (so called because of the shape of the black out area) is caused from the exit pupil aberration (i.e. the exit pupil is not presented in a flat plane) known as SAEP (see detailed information here, https://www.telescop...berration_2.htm). Tele Vue eyepieces have not had that aberration since the Type 1 Nagler.

The common black out typically manifest simply from one's eye getting too close to the eyepiece (i.e. it is a matter of proper placement of the eye to the exit pupil). Improperly adjusted Pentax XW will present the black out effect, too.


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#24 GeneT

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Posted 06 July 2020 - 02:43 PM

This indicates to me that the physiology of each of our eyes must also come into play as it interfaces to the exit pupil of the eyepiece, so maybe SAEP is more of a dynamic between the eyepiece and the eye that determined how prevalent the kidneybean or blackout artifacts are, rather than being solely an eyepiece issue.

I agree that we need to remember that each of our eyeballs is its own lens, and will display characteristics differently with eyepieces of different makes or provide different experiences from what others might see in the same eyepieces.



#25 MartinPond

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Posted 06 July 2020 - 11:51 PM

One interesting and odd thing I noticed during some moon/bean tests last night --

 

9mm expanse clone causes beaning on the moon. 6mm causes glowing moon beaning (meaning I need to also flock the thing). However, the 15mm expanse doesn't cause any major beaning either at 15mm (expected), 10mm (1.5x barlow) or at 7.5mm (2x barlow).

 

So... not entirely sure why I am getting beaning with the 6/9mm flavors and not the 15mm when barlowed into the equivalent (sorta) magnifications. Unless it has to do with the fact how each eyepiece is designed...

 

As both the 6mm and 9mm is sort of auto-barlowed (I think) with a little built-in lens on the bottom of each that acts like a barlow. While the 15mm is like the top half of the 6/9mm design, minus the built-in barlow. But maybe using my own barlow is better than whatever barlow lens the 6/9mm come with?

 

*shrugs*

 

Not sure what the reason is, just that for the moon, the 15mm barlowed seems to work a lot better than the 6/9mm do.

 

Having a smaller exit pupil can make eye placement more sensitive...

...maybe that's a key to the 9mm having more trouble.

Of course, with the Moon, looking without a strong neutral density filter

   can contract your entrance pupil...that can make problems.

I always use a 12.5% Neutral, or a dark green (#46). My eyes are

too sensitive to see the Moon without attenuation.

 

The Expanse EPs use the negative lens as a real "Smyth":

   that is, it multiplies but also compensates for aberrations at the 

  edge of the very-overpushed field of view.  They can be very

  quirky...bad for some people or combinations, good for others. 

  Compensating the field of a cell pretty far away is a very

   sensitive setup.


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