My First Over $100 Eyepiece
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My First Over $100 Eyepiece
https://agenaastro.com/celestron-2-ulti ... 93454.html
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Re: My First Over $100 Eyepiece
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Re: My First Over $100 Eyepiece
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Delos, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.
Solar: HA: Lunt 50mm single stack, W/L: Meade Herschel wedge.
Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2461, Comets: 34, Asteroids: 261
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Re: My First Over $100 Eyepiece
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Re: My First Over $100 Eyepiece
- notFritzArgelander
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Re: My First Over $100 Eyepiece
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Re: My First Over $100 Eyepiece
It's the negative-positive design of the eyepiece causing this. I suggest an explanation here:Refractordude wrote: ↑Sat Jun 05, 2021 12:41 am Just did a day time test on some distant tree leaves. This eyepiece really is sharp right to the edge. However, there is a very thin blue line around the edge not visible during night observations. Thought it was because I am using an achro, but the blue ring is still visible with aperture mask at f/16. Not bothersome to me, but your thoughts about the ring. Thanks.
viewtopic.php?f=34&t=10809&p=92870&hili ... ing#p92039
It's a good sign, really.
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Re: My First Over $100 Eyepiece
It’s nominal for the negative-positive eyepiece designs as you pointed out in that nice thread that you started.Ruud wrote: ↑Sat Jun 05, 2021 10:19 amIt's the negative-positive design of the eyepiece causing this. I suggest an explanation here:Refractordude wrote: ↑Sat Jun 05, 2021 12:41 am Just did a day time test on some distant tree leaves. This eyepiece really is sharp right to the edge. However, there is a very thin blue line around the edge not visible during night observations. Thought it was because I am using an achro, but the blue ring is still visible with aperture mask at f/16. Not bothersome to me, but your thoughts about the ring. Thanks.
viewtopic.php?f=34&t=10809&p=92870&hili ... ing#p92039
It's a good sign, really.
- Don Pensack
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Re: My First Over $100 Eyepiece
The thin colored line right at the field stop is NOT what is referred to as the "Ring of Fire".notFritzArgelander wrote: ↑Sat Jun 05, 2021 12:59 am The ring of fire effect is common among wide field astronomical eyepiece designs. Naglers are orange IIRC. If you can’t stand it an eyepiece for spotting scopes and daytime use may make you happy. Leica?
The term was coined when the 31mm Nagler was found to have a strong orange tint to the outer 10° of field when used in the daytime as a spotting scope eyepiece.
The 30mm
It is, essentially, a chromatic aberration of the exit pupil, or CAEP.
The thin colored line at the field stop is lateral chromatic aberration in the field and has a different cause,
Almost all eyepieces have that. It is a VERY rare eyepiece that has no colored edge to the field right at the field stop.
I have seen it in eyepieces with only positive lens sets, so it is not caused by a negative field lens.
I have seen it in eyepieces from 30° to 120°, so it is not caused by a wide field, either.
But, and I'll repeat, this is NOT the "Ring of Fire", and has a different cause.
Currently using a 12.5" dob and a 4" apo refractor
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Re: My First Over $100 Eyepiece
Thank you for your take. I heard you the first time.Don Pensack wrote: ↑Sat Jun 05, 2021 3:09 pmThe thin colored line right at the field stop is NOT what is referred to as the "Ring of Fire".notFritzArgelander wrote: ↑Sat Jun 05, 2021 12:59 am The ring of fire effect is common among wide field astronomical eyepiece designs. Naglers are orange IIRC. If you can’t stand it an eyepiece for spotting scopes and daytime use may make you happy. Leica?
The term was coined when the 31mm Nagler was found to have a strong orange tint to the outer 10° of field when used in the daytime as a spotting scope eyepiece.
The 30mmES 82° also has it, as do several other eyepieces.
It is, essentially, a chromatic aberration of the exit pupil, or CAEP.
The thin colored line at the field stop is lateral chromatic aberration in the field and has a different cause,
Almost all eyepieces have that. It is a VERY rare eyepiece that has no colored edge to the field right at the field stop.
I have seen it in eyepieces with only positive lens sets, so it is not caused by a negative field lens.
I have seen it in eyepieces from 30° to 120°, so it is not caused by a wide field, either.
But, and I'll repeat, this is NOT the "Ring of Fire", and has a different cause.
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Re: My First Over $100 Eyepiece
BTW, I have seen the thin line at the edge in every color from red to violet. Perhaps that is dependent on glass type and coating properties?
I remember some 50° eyepieces I had in the '90s that had a beautiful amber tint right at the field stop.
The Apollo 11 has a blue tint right at the field stop, but the dimension of the tint is so narrow that catching a star going blue as it exits the field is a little like catching the green flash at sunset--wink and you miss it.
Currently using a 12.5" dob and a 4" apo refractor
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Re: My First Over $100 Eyepiece
I'm not offended. I even understand your point about from the eyepiece designer's and/or maven's POV that the causes may seem different. Granted that. I do have a difficulty with the physics being different. It's all about rays at or near the field stop having different paths in different colors. But as a physicist, as long as the words satisfy the physical concepts I'm OK.Don Pensack wrote: ↑Sat Jun 05, 2021 5:29 pm I didn't mean to offend, but a lot of people who have heard the term "ring of fire" and never having seen it, mistakenly call the thin line at the field stop by the same name.
BTW, I have seen the thin line at the edge in every color from red to violet. Perhaps that is dependent on glass type and coating properties?
I remember some 50° eyepieces I had in the '90s that had a beautiful amber tint right at the field stop.
The Apollo 11 has a blue tint right at the field stop, but the dimension of the tint is so narrow that catching a star going blue as it exits the field is a little like catching the green flash at sunset--wink and you miss it.
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Re: My First Over $100 Eyepiece
Hi RD, imagine how did I freaked out when I bought my fistRefractordude wrote: ↑Sat Jun 05, 2021 12:41 am Just did a day time test on some distant tree leaves. This eyepiece really is sharp right to the edge. However, there is a very thin blue line around the edge not visible during night observations. Thought it was because I am using an achro, but the blue ring is still visible with aperture mask at f/16. Not bothersome to me, but your thoughts about the ring. Thanks.
Anyway, as other already indicated, it is quite common for wide fields, enjoy your
Mounts: SW: SkyTee2, AzGTi; iOptron: AZMP; ES: Twilight I; Bresser: EXOS2; UA: MicroStar.
Binos: APM: 100-90 APO; Canon: IS 15x50; Orion: Binoviewer, LG II 15x70, WV 10x50, Nikon: AE 16x50, 10x50, 8x40.
EPs: Pentax: XWs & XFs; TeleVue: Delites, Delos, Panoptic & Plossls; ES: 68, 62; Vixen: SLVs; Baader: BCOs, Aspherics, Mark IV.
Diagonals: Baader: BBHS mirror, Zeiss Spec T2 prism, Clicklock dielectric; TeleVue: Evebrite dielectric; AltairAstro: 2" prism.
Filters: Lumicon: DeepSky, UHC, OIII, H-beta; Baader: Moon & SkyGlow, Contrast Booster, UHC-S, 6-color set; Astronomik: UHC.
Solar: HA: Lunt 50mm single stack, W/L: Meade Herschel wedge.
Observing: DSOs: 3106 (Completed: Messier, Herschel 1, 2, 3. In progress: H2,500: 2180, S110: 77). Doubles: 2461, Comets: 34, Asteroids: 261
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Re: My First Over $100 Eyepiece
I agree. The CAEP is hardly noticeable in the A11. In the DeLites, it is non-existent from what I recall. In the ES92's, it's quite prominent, to the point where it becomes a distraction on bright objects like Luna.Don Pensack wrote: ↑Sat Jun 05, 2021 5:29 pm I didn't mean to offend, but a lot of people who have heard the term "ring of fire" and never having seen it, mistakenly call the thin line at the field stop by the same name.
BTW, I have seen the thin line at the edge in every color from red to violet. Perhaps that is dependent on glass type and coating properties?
I remember some 50° eyepieces I had in the '90s that had a beautiful amber tint right at the field stop.
The Apollo 11 has a blue tint right at the field stop, but the dimension of the tint is so narrow that catching a star going blue as it exits the field is a little like catching the green flash at sunset--wink and you miss it.
The ES120 9 has the ring of fire in addition to CAEP.
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Re: My First Over $100 Eyepiece
The thin ring at the field stop is not called the ring of fire, and it has a different cause.
Currently using a 12.5" dob and a 4" apo refractor
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Re: My First Over $100 Eyepiece
A ring of fire I define as a orange/reddish hue that extends about 10-15% from the field stop. I've only seen this in the ES120 9 when looking at bright objects like Luna. I haven't seen this in the 31T5 because I don't typically look at bright objects at the moon with that long of focal length
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Re: My First Over $100 Eyepiece
The thin ring of color right at the edge is simply uncorrected lateral chromatic aberration, the result of using lenses whose curves are great enough to act like prisms. I have seen nearly every color of the rainbow for this, though blue and blue-green are more common.
In some 50° eyepieces I had in the '80s, it was a beautiful amber color.
Eyepieces can have
It can be in the form of an exit pupil issue (where different colors have different eye reliefs), or axial (where different colors have different focus points), or lateral (prismatic smear where blue rays position the star image nearer center of field than red rays), or combinations of the various forms.
It could have been more completely corrected in the 31 Nagler, but wasn't because the eyepiece was already heavy and expensive and adding another lens (or lenses) to correct it would have doomed the eyepiece's success in the marketplace.
It's not a good eyepiece for the Moon, but as you pointed out, it's not a focal length chosen for Moon viewing.
Currently using a 12.5" dob and a 4" apo refractor
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