Author Topic: Eyepiece center image quality  (Read 964 times)

juskemenbo

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Re: Eyepiece center image quality
« Reply #15 on: January 22, 2018, 09:11:42 PM »
The thing with those is that they also have edge-correction
 that makes the center field 'patchy and glary somehow.
I prefer a straight 25mm 1,2-Konig plus a Tri-Mag now to the Expanse 9mm.

I could see ....a longer ortho and an inboard Barlow. Makes sense..
Most precision ortho users are trying to cut out all the glass they can....
but a think a Tri-Mag would do wonders. Distance seams to clean up
many-lens problems.

I just tested some on a more-than-eye-resolution target:
 a milkweed seed stuck on an oak 100 ft away.
To see the shine right the system needs to exceed your eye.
For this circumstance...

A cleaned and blacken-edge SMA 10mm was out in front, weirdly enough.
A 17mm plain-faced / 48 degree Plossl beat a SuperPlossl (Barlowed).
A 'stretched-spacing' barlowed 22mm Plossl was the best.
The 20mm Expanse (BArlowed) faired better than the 9mm center-field,
 but they both bugged me...contrast not great (daytime, though)..

Wish I had a good ortho for comparison.
I just have a generic Celestron 10mm...it wasn't great..

Colin Ramadan

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Re: Eyepiece center image quality
« Reply #16 on: January 23, 2018, 05:44:45 PM »
Some of us have resorted to microscope eyepieces for this. Try to stick to German made ones.

These inexpensive Leicas are great. Nice eye relief, large top lens and even Barlowed are much better than the Asian under $100 eyepieces I've tried.

http://www.ebay.com/...s-/112304091841

This is a 25mm FL, there are also ~16mm and ~12mm in this line.

brascharnide

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Re: Eyepiece center image quality
« Reply #17 on: January 26, 2018, 12:00:24 AM »
Buying used, the Vixen LV/NLV/SLV (same basic eyepiece, different clothing) might be useable, especially for lunar and planets. Ortho/plossl like fov, but 20mm eye relief. They're not ZAOs, but are decent and east to use. They also come in a boatload of fls.

inmactoopho

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Re: Eyepiece center image quality
« Reply #18 on: January 26, 2018, 12:02:48 AM »
Lots of great answers, thanks. Keep them coming!

olnceratge

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Re: Eyepiece center image quality
« Reply #19 on: January 30, 2018, 02:47:30 AM »
Quote
..........................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.
Please don’t say that Eddgie.
A short time ago I managed to finally buy a scope I’ve always wanted (Celestron C8) and have spent many hours cleaning, aligning, tweaking and collimating it to perfection. I'm not going to think about a different scope for some time
To be honest I still haven’t looked at a planet with it yet, but views of the moon, clusters and DSO look fantastic up to about 150X. Haven’t had seeing good enough to push beyond that.
Experience tells me that Jupiter and Saturn at 250X or 300X are going to be another challenge altogether…
I’m prepared for the worst, but I’d like to give the C8 the best possible chance by having the best eyepiece I can get.

ndesevtenzio

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Re: Eyepiece center image quality
« Reply #20 on: January 30, 2018, 10:59:35 AM »
Quote
Quote
..........................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.
Please don’t say that Eddgie.
A short time ago I managed to finally buy a scope I’ve always wanted (Celestron C8) and have spent many hours cleaning, aligning, tweaking and collimating it to perfection. I'm not going to think about a different scope for some time
To be honest I still haven’t looked at a planet with it yet, but views of the moon, clusters and DSO look fantastic up to about 150X. Haven’t had seeing good enough to push beyond that.
Experience tells me that Jupiter and Saturn at 250X or 300X are going to be another challenge altogether…
I’m prepared for the worst, but I’d like to give the C8 the best possible chance by having the best eyepiece I can get.
A C8 is a quality scope, and can deliver wonderful planetary images. Given that you use decent eyepieces, your seeing, collimation and temp acclimation will play a much bigger role in the planetary image that you see in comparison with your eyepiece.

Brandon Garrido

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Re: Eyepiece center image quality
« Reply #21 on: January 30, 2018, 01:51:16 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?

I haven't found anything better than my Pentax XO and TMB SMC orthos for on axis. However, neither has great eye relief, and certainly aren't cheap.

Eye relief is easier if you have a great barlow, too. For instance, the TMB 1.8 barlow on a 12mm will give you basically a 6mm with better eye relief.

What most people don't think about when you're dealing with ~30 deg AFOV eps is that they're a pain in the butt to use. A tracking mount is pretty much required, and then focusing can be an issue where you need to go look at something bright to focus properly, then slew back to the dim thing you were looking at before... and hope your gotos are good enough to keep the little dim thing in that tiny AFOV at high magnifications.

helppomgido

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Re: Eyepiece center image quality
« Reply #22 on: February 09, 2018, 10:39:44 AM »
Quote
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.
"Is $250 too high?"

Yep."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."

I like this idea, but then with a 2x barlow for a 7.5 mm. Just have to make sure the costs of great plossl and barlow don't add up too much.
By the way, isn't the Hyperion using an internal Barlow too?

"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"

Do you have any specific eyepieces in mind?

"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."

I've dealt as many of these as I could, the only other thing I can influence is the eyepiece choice.
Well, at least if you don't count adaptive optics

olaralal

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Re: Eyepiece center image quality
« Reply #23 on: February 09, 2018, 10:43:47 AM »
Quote
I haven't found anything better than my Pentax XO and TMB SMC orthos for on axis. However, neither has great eye relief, and certainly aren't cheap.
Eye relief is easier if you have a great barlow, too. For instance, the TMB 1.8 barlow on a 12mm will give you basically a 6mm with better eye relief.

What most people don't think about when you're dealing with ~30 deg AFOV eps is that they're a pain in the butt to use. A tracking mount is pretty much required, and then focusing can be an issue where you need to go look at something bright to focus properly, then slew back to the dim thing you were looking at before... and hope your gotos are good enough to keep the little dim thing in that tiny AFOV at high magnifications.
I have some experience with that too.
I've used a 5mm kasai ortho in the past with a manual mount and I couldn't wait to get a motor driven mount!
I don't have Goto but I have a dual axis drive. I enjoy observing way more than before, but I wouldn't want to go back to 42 degrees if I can avoid it.