Author Topic: Eyepiece center image quality  (Read 48 times)

grumepinod

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Eyepiece center image quality
« on: December 27, 2017, 12:06:32 PM »
I might be asking the impossible, but here it goes.

Many discussions on modern eyepieces concentrate mostly on the large field of view and the improved off-axis image quality all the way up to edge of the field.
When using high magnification I’d be glad to renounce to off-axis performance and huge FOV in exchange for excellent sharpness and image quality on center, and preferably not having to brush my eyelashes against a tiny eye lens!

Are there any modern eyepieces that are equal (or even better) than the good old Ortho or Plossl as far as image quality on-axis is concerned, and are more comfortable to use?

Many recommend Pentax or Televue wide angle eyepieces but unfortunately these premium eyepieces are too expensive for some of us.
Can I get a better on-axis performance by updating a Hyperion or a TMB planetary with an modern wide angle by Explore Scientific, or other brand that offer eyepieces in a similar price range?



Jason Hillyer

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Re: Eyepiece center image quality
« Reply #1 on: December 29, 2017, 03:32:59 AM »
The new Vixen HR have been reported to have excellent on axis sharpness. I wish they would come out with a few more FL.

coreanoguf

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Re: Eyepiece center image quality
« Reply #2 on: December 29, 2017, 11:18:34 AM »
I found the UO HD's and BGO's went a little deeper than the others (you currently own). The difference is noticeable but not huge and the trade off is of course a smaller FOV.

Mike

blasbunmena

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Re: Eyepiece center image quality
« Reply #3 on: January 04, 2018, 03:40:25 PM »
I have no issues with the Type 6 Naglers for on-axis sharpness. I spend a fair amount of time splitting close doubles, the issues I have are not with the eyepieces.. But I am not one who looks to the eyepiece as a big player in getting the best possible on-axis views at high magnifications, that's about having enough aperture, making sure the scope is a good one, properly setup and any thermal gremlins have been addressed. And then it's the seeing, when the seeing supports 400x, the Type 6 Naglers provide sharp views. When the seeing supports 600x, the Type 6 Naglers provide sharp views.

Jon

brunenrizap

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Re: Eyepiece center image quality
« Reply #4 on: January 08, 2018, 12:00:34 AM »
TV Radians for me.

adpotabza

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Re: Eyepiece center image quality
« Reply #5 on: January 09, 2018, 06:11:29 AM »
Every eyepiece design being produced today is diffraction limited down to f/5 and many are diffraction limited down to f/4.

You may read a lot on CN that makes you think that changing to this or that eyepiece is going to make a substantial improvement in your views, but I find many of these reports being over-optimistic. In most cases, the difference in center of the field between any two good quality eyepieces made today can be difficult to see.

If you are using TMB or Hyperions today, you may find a tiny amount of improvement buy going to a good Plossl or Ortho. If you need eye relief, buy a really high quality Barlow and use a longer focal lenght Plossl or Ortho.

But don't be surprised if the difference in the view is not easily seen. Sorry for saying this, but I think some people think that if they just spend enough money on the eyepiece, their views will suddenly be so much better.And here is what I always say to this. If you want a view that has more contrast for planets, most of the money you would spend on eyepieces would be many many times better spent on a better instrument.

If you don't have the money today to upgrade to a better telescope, save the money you would spend on more eyepieces and use it later to upgrade the telescope. A better telescope is the 100% sure fire way to make a real difference in the view. Everything else that you spend your money on is a diversion.  You probably won't find nirvana in an eyepiece case.

For planets, my strongest advice is to always put the money in the instrument. Even an inexpensive Plossl in a 4" ED scope will deliver better planetary views than the most revered "Planetary Eyepiece" money can buy would make in a 4" Achromat.

It is the instrument that forms the image. The eyepiece only magnifies it. If you want a better image, save for a better telescope.

belmadeasus

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Re: Eyepiece center image quality
« Reply #6 on: January 10, 2018, 05:18:00 AM »
Alternatives :
A good barlow + 12/15/21mm RKE : because this is EO lens polishing and they have the same coating policy as the Brandons (light scatter good, sharp guaranty to +/-15° around center)
  Even standard Kellner and Huyghens can be center sharp, but now they are no more well polished : they fell down in the cheap category, -> you can try some old one coming from microscopy in good state and good brand.
You can try ball lens too (Siebert Optics) : "built by gravity" http://www.microscop...07/jd-lens.html https://www.edmundop...g-ball-lenses/
If you are a DIY and know optics, I got one or two optics formula to be checked.

Lamar Davies

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Re: Eyepiece center image quality
« Reply #7 on: January 11, 2018, 04:28:47 AM »
Using longer fl ortho's in a binoviewer coupled with a Barlow screwed to its nose, will deliver amazing lunar and planetary detail across the field, that even the finest single high end eyepiece will struggle to match!

Mike

Rick Reiter

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Re: Eyepiece center image quality
« Reply #8 on: January 11, 2018, 04:59:36 AM »
---------------------- "
Are there any modern eyepieces that are equal (or even better) than the good old Ortho or Plossl as far as image quality on-axis is concerned, and are more comfortable to use?
--------------------- "You also mentioned eye relief.
For me it's the 1-2-Konig, no doubt.
Center field it matches a good Plossl, and it has about 1-1/2 times the relative eye relief.
Great at 10mm and 12mm.
I had to harvest them from 10x25 and 12x25 binocs.

There are some available used as Celestron SMA, although the field is smaller (50+ degrees).
(they have a flat obj-facing surface, not concave)

The closest relative in formal production is the Edmund RKE.
When you stretch the lens spcaing on a 1,2-Konig and tweek the surfaces,
 you end up with an even flatter field and keep the high eye relief:
https://www.edmundop...eyepieces/2075/
8mm eye relief in an 8mm EP.
Some folks are quite fanatic about the precision of their RKE.
It does have a 45 deg. field, just so you know.

,
And Brandons, if you want to spend:
http://agenaastro.co...piece-12mm.html
43n degrees view, though... If you field-stopped a Plossl to that it would
be amazing too...

tessacubadc

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Re: Eyepiece center image quality
« Reply #9 on: January 11, 2018, 02:11:30 PM »
Quote
Every eyepiece design being produced today is diffraction limited down to f/5 and many are diffraction limited down to f/4.

You may read a lot on CN that makes you think that changing to this or that eyepiece is going to make a substantial improvement in your views, but I find many of these reports being over-optimistic. In most cases, the difference in center of the field between any two good quality eyepieces made today can be difficult to see.

If you are using TMB or Hyperions today, you may find a tiny amount of improvement buy going to a good Plossl or Ortho. If you need eye relief, buy a really high quality Barlow and use a longer focal lenght Plossl or Ortho.

But don't be surprised if the difference in the view is not easily seen. Sorry for saying this, but I think some people think that if they just spend enough money on the eyepiece, their views will suddenly be so much better.And here is what I always say to this. If you want a view that has more contrast for planets, most of the money you would spend on eyepieces would be many many times better spent on a better instrument.

If you don't have the money today to upgrade to a better telescope, save the money you would spend on more eyepieces and use it later to upgrade the telescope. A better telescope is the 100% sure fire way to make a real difference in the view. Everything else that you spend your money on is a diversion.  You probably won't find nirvana in an eyepiece case.

For planets, my strongest advice is to always put the money in the instrument. Even an inexpensive Plossl in a 4" ED scope will deliver better planetary views than the most revered "Planetary Eyepiece" money can buy would make in a 4" Achromat.

It is the instrument that forms the image. The eyepiece only magnifies it. If you want a better image, save for a better telescope.

Edgie is right of course, but it seems most would rather fixate on details that are undetectable. All modern eyepieces are quite sharp on axis, from Plossls to wide fields. The differences are swamped by the differences in the quality of one's objective or mirror. A better scope is the answer to seeing more detail, if seeing more detail is your goal.

excunisep

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Re: Eyepiece center image quality
« Reply #10 on: January 11, 2018, 11:50:03 PM »
Quote
You also mentioned eye relief.
For me it's the 1-2-Konig, no doubt.
Center field it matches a good Plossl, and it has about 1-1/2 times the relative eye relief

Well, XCell and HD-60, AFAIK, are simply a Konig with an ad-hoc barlow. That's probably the reason why they seem to perform well on axis.

A very interesting design for hi-res would be an orthoscopic + ad-hoc barlow, not sure if some eyepieces use it (may be takahashi Hi-Le? - 6 elements in 3 group).

Matt Victorin

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Re: Eyepiece center image quality
« Reply #11 on: January 12, 2018, 04:17:33 AM »
Quote
A very interesting design for hi-res would be an orthoscopic + ad-hoc barlow, not sure if some eyepieces use it (may be takahashi Hi-Le? - 6 elements in 3 group).
Yes, Takahashi Hi-Ortho 2.8 and 4mm used this design, and also their Hi-LE 2.8 and 3.6 are designed Ortho+Barlow.I have the former two and like them very much on my short f.l. Apo. Never found anything I liked better to this very day.But don't know the new Vixen HR2.4 (HR2.0 and HR1.6 would be way too short in my case).Chris

lodersconsharp

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Re: Eyepiece center image quality
« Reply #12 on: January 18, 2018, 09:37:17 AM »
The theory says all eyepieces are the same on-axis.

Experience of discriminating planetary observers and many opticians says there are differences.

Whether this is on-axis, or a combined "total performance" of the eyepiece hardly matters. The differences exist and can be seen.

Planetary performance is a game of adding up small advantages, and avoiding factors that reduce performance.

That being said, the advice of this thread to first concentrate on the telescope is sound.

When you get the telescope situation nailed down as well as your circumstances (economic/physical/environmental) permit, then start worrying about eyepieces to give you the last little edge.

The converse of this is that eyepieces alone will not be your savior.

riaherrvodo

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Re: Eyepiece center image quality
« Reply #13 on: January 20, 2018, 01:13:46 PM »
Quote
I might be asking the impossible, but here it goes.

Many discussions on modern eyepieces concentrate mostly on the large field of view and the improved off-axis image quality all the way up to edge of the field.
When using high magnification I’d be glad to renounce to off-axis performance and huge FOV in exchange for excellent sharpness and image quality on center, and preferably not having to brush my eyelashes against a tiny eye lens!

Are there any modern eyepieces that are equal (or even better) than the good old Ortho or Plossl as far as image quality on-axis is concerned, and are more comfortable to use?

Many recommend Pentax or Televue wide angle eyepieces but unfortunately these premium eyepieces are too expensive for some of us.
Can I get a better on-axis performance by updating a Hyperion or a TMB planetary with an modern wide angle by Explore Scientific, or other brand that offer eyepieces in a similar price range?

Is $250 too high? If not, the TeleVue Delites come to mind (long eye relief and extremely small spot size on axis)
If it is too high, find used TeleVue Radians.
Both have comfortable eye relief at short focal lengths (down to 3mm)
If their prices are too high, look for Plössls or Abbe orthoscopics, both of which have extremely small spot sizes on axis and can be found new at low prices.
However, that latter solution doesn't get around the small eye relief in shorter focal lengths, as you point out.
As was suggested, a longer focal length eyepiece with a superb barlow might do it for you.
A 15mm Plossl, with 10-11mm of eye relief becomes a 5mm eyepiece with >11mm eye relief when a good 3X barlow is added.
And there are some barlows out there that have superb image quality (probably not the $50 and down variety)
It might take some experimentation and re-selling of eyepieces not kept, but the modern generation of 58-62° eyepieces for $55-$100
may have some gems that work well for you, and all of them have more eye relief than Plössls and orthos.
As you know, however, other factors will make a bigger difference in image quality than the eyepieces: telescope optics, seeing, cooling of the optics, collimation of the optics.

Mortimer Concepcion

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Re: Eyepiece center image quality
« Reply #14 on: January 21, 2018, 09:41:51 AM »
Quote
<p class="citation">Quote
You also mentioned eye relief.
For me it's the 1-2-Konig, no doubt.
Center field it matches a good Plossl, and it has about 1-1/2 times the relative eye relief

Well, XCell and HD-60, AFAIK, are simply a Konig with an ad-hoc barlow. That's probably the reason why they seem to perform well on axis.

A very interesting design for hi-res would be an orthoscopic + ad-hoc barlow, not sure if some eyepieces use it (may be takahashi Hi-Le? - 6 elements in 3 group).[/quote]a DIY with a plano concave field lens raising ER to ~10mm, all standard Thorlabs, not tried yet. Adding the PLC degrades a bit the center focus, but it is kept inside Airy disk.
Hoping about precision polishing and optomecanics to maintain this.