Page 1 of 1

Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Wed Nov 03, 2021 10:12 am
by 25585
About a year ago, Noblex, formerly Docter, eyepieces stopped being produced. However, APM are selling them again, the real deal Docter. I have bought one, or rather paid & am awaiting shipping, which may take a few months.

Last year I bought a Noblex & decided it is so good I wanted a binoview pair. This new chance may be the last.

Superb eyepieces, enough effective eye relief for glasses, no kidney-beaning, ortho like optical quality, eye spa viewing comfort.

Comparing a Doclex with my 12mm ES92 & 12.5mm Baader Morpheus 76°, its in-between for weight, AFOV, and has the easiest eye alignment of all 3, Morpheus being 2nd.

I have not tried APM's own 12.5mm 84°, but others have.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Wed Nov 03, 2021 2:54 pm
by Don Pensack
25585 wrote: Wed Nov 03, 2021 10:12 am About a year ago, Noblex, formerly Docter, eyepieces stopped being produced. However, APM are selling them again, the real deal Docter. I have bought one, or rather paid & am awaiting shipping, which may take a few months.

Last year I bought a Noblex & decided it is so good I wanted a binoview pair. This new chance may be the last.

Superb eyepieces, enough effective eye relief for glasses, no kidney-beaning, ortho like optical quality, eye spa viewing comfort.

Comparing a Doclex with my 12mm ES92 & 12.5mm Baader Morpheus 76°, its in-between for weight, AFOV, and has the easiest eye alignment of all 3, Morpheus being 2nd.

I have not tried APM's own 12.5mm 84°, but others have.
Notes:
--the price is radically higher than the earlier production. You could buy 3 or 4 Morpheus eyepieces for the price of 1 Noblex.
--Great optical performance in a tracking scope. In a non-tracking scope the angular magnification distortion makes the sky appear like it's moving over the surface of a ball or globe as the sky moves--the center of the field appears closer to you than the edge.
This may or may not bother you at all, but it made the eyepiece unusable for me. At the now higher price, if you have a non-tracking scope I would advise trying one first. Perhaps a friend can lend you his at a star party.
--The APM 12.5mm is sharp enough, but lacks the contrast of the Noblex. It is equally comfortable with glasses on, however.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Wed Nov 03, 2021 8:10 pm
by j.gardavsky
The Docter eyepiece became iconic.

And of course, we can say that for the price of Docter you can get 3 or 4 other eyepieces.
But t is like saying, that for the price of Audi, you can get 3 or 4 other cars, and they will be also doing the job, their own jobs.

Best,
JG

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Wed Nov 03, 2021 8:58 pm
by Bigzmey
j.gardavsky wrote: Wed Nov 03, 2021 8:10 pm The Docter eyepiece became iconic.

And of course, we can say that for the price of Docter you can get 3 or 4 other eyepieces.
But t is like saying, that for the price of Audi, you can get 3 or 4 other cars, and they will be also doing the job, their own jobs.

Best,
JG
Hi JG
Just out of curiosity, how image quality of Docter compares to the closest FL of Pentax XW?

Thanks.
Andrey

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Wed Nov 03, 2021 10:03 pm
by John Donne
@Don Pensack
"Great optical performance in a tracking scope. In a non-tracking scope the angular magnification distortion makes the sky appear like it's moving over the surface of a ball or globe as the sky moves--the center of the field appears closer to you than the edge."

I have not experienced this on any of my refractors.

I am curious with which telescope have you experienced this strange distortion. ?

It would seem that it should be the same with a tracking or non tracking scope.
Very interesting.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Wed Nov 03, 2021 10:34 pm
by j.gardavsky
Bigzmey wrote: Wed Nov 03, 2021 8:58 pm
j.gardavsky wrote: Wed Nov 03, 2021 8:10 pm The Docter eyepiece became iconic.

And of course, we can say that for the price of Docter you can get 3 or 4 other eyepieces.
But t is like saying, that for the price of Audi, you can get 3 or 4 other cars, and they will be also doing the job, their own jobs.

Best,
JG
Hi JG
Just out of curiosity, how image quality of Docter compares to the closest FL of Pentax XW?

Thanks.
Andrey
Hello Andrey,

my closest Pentax SMC XW would be the 10mm.
On my part, I have the Pentax SMC XW 3.5mm, 5mm, 7mm, and 10mm for the galaxies, and when looking up some planetary nebulae..

The DOCTER is my only UWA eyepiece at the moment.
When I put it on the Leica APO 82mm Televid, and compare it with the Leica Asph Zoom at the corresponding setting, then the DOCTER performs like in the Leica class.

Otherwise,
the 12.5mm DOCTER has 2 close neighbours in my arsenal:
Zeiss D 30x/40x B WW 12.6mm 68° AFOV
Leica B 32x WW 13.75mm 73.6° AFOV
but these Zeiss and Leica are discontinued spotting eyepieces, and as good as unobtainables.

The closest astronomy eyepiece would be my Takahashi Abbe MC 12.5mm 40° AFOV, but DOCTER delivers definitely more contrast and crisp views.

Regarding the optics design of the DOCTER, it behaves on my 6" F/5 achro neutrally,
so it basically preserves the CA characteristic secondary deviations polynomial of the achro. The spotting eyepieces make some small correction. Some Zeiss microscopy eyepieces (S-Pl, W-Pl) correct even more.

Otherwise,
our friend 25585, who has started this thread, can comment on how the DOCTER compares with the Pentax SMC XW eyepieces.

Best,
JG

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Thu Nov 04, 2021 5:12 pm
by Don Pensack
John Donne wrote: Wed Nov 03, 2021 10:03 pm @Don Pensack
"Great optical performance in a tracking scope. In a non-tracking scope the angular magnification distortion makes the sky appear like it's moving over the surface of a ball or globe as the sky moves--the center of the field appears closer to you than the edge."

I have not experienced this on any of my refractors.

I am curious with which telescope have you experienced this strange distortion. ?

It would seem that it should be the same with a tracking or non tracking scope.
Very interesting.
It's well known the Noblex/Docter has significant Angular magnification distortion (AMD) that results in things at the edge of the field being lower in magnification than the center. This type of distortion is not unique to that eyepiece, being found in the Nikon NAV-SW eyepieces and the APM 12.5mm 84°. It results in the field appearing closer to you in the center than the edge, but you only notice is scanning across a field.
Generally, astronomical eyepieces will reduce that distortion to a minimum, which leaves in a lot of rectilinear distortion (RD), which causes straight lines to curve as they cross the field, like ) | (.
Rectilinear distortion is usually not noticeable in a widefield astronomical eyepiece, but is not desirable in a daytime spotting scope eyepiece, so RD is usually reduced in daylight use eyepieces, leaving in lots of AMD.
Note that both forms of distortion are larger the wider the apparent field of the eyepiece, so not usually seen in narrow field eyepieces.

If the focal length of the scope is short, a 12.5mm eyepiece isn't a very high power, so the field drifts across the eyepiece slowly, which is why you probably don't see the "rolling ball" or "globe" distortion in the Docter/Noblex eyepiece.
In my scope, which doesn't track, my focal length is close to 2 meters, so the field drifts across fast enough to notice the movement of the stars in the field and the nature of the distortion.

That all such optical solutions are compromises can be seen here in this discussion of distortion in binoculars:
http://www.holgermerlitz.de/globe/distortion.html
The Docter is similar to the k=1 condition, where most astronomical eyepieces are closer to k=0

Here is a relevant discussion:
https://www.cloudynights.com/topic/1098 ... try1446673
Note: back then, I hadn't seen a Docter, or APM 12.5 or Nikon NAV-SW eyepieces. But I hadn't used spotting scope eyepieces adapted for astronomy then.

In a friends scope, which tracked, the Docter was a very nice eyepiece. I immediately saw the Barrel distortion in my dob, however (barrel distortion accompanies positive AMD).

The TeleVue Apollo 11 eyepiece (similar AF of 85° and similar focal length) is completely different, and scanning across fields didn't display any noticeable distortion, proving to me that reduced AMD, with RD, is a preferable solution to reduced RD, with AMD.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Thu Nov 04, 2021 5:24 pm
by notFritzArgelander
Since I like to slow pan around a target even with a tracking mount (use motion to find threshold details) I'd have trouble with it even on a tracking mount.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Thu Nov 04, 2021 6:50 pm
by John Donne
@Don Pensack
Thank you Don.
I understand.
Very interesting.
I am most often using a refractor telescope of f5.8 - f9 and less than 1000mm focal length.
This must be why I find the docter so satisfying.
Thank you.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Thu Nov 04, 2021 9:09 pm
by j.gardavsky
Globe effect on DOCTER

As being a user of this eyepiece, I can't confirm the globe distortion of the DOCTER on my 6" F/5, and in my eyes.
The DOCTER eyepiece has the classical pin cussion distortion offset, as the concept of this eyepiece has been originally derived from the Zeiss Aspectem.

A distortion may become visible when you pan with the telescope, and center your eyesight far away from the middle of the AFOV on your eyepiece.
But who is consciously doing it to hurt his/her/its visual perception?

On a side line,
Leica Noctivid, Svarovski EL Swarovision, and ZEISS SF, have reduced the pincussion offset, and they got some criticisms for doing it.

Best,
JG

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Fri Nov 05, 2021 3:11 pm
by Don Pensack
Look at a straight edge in the daytime and move the straight edge from center to edge.
If it curves like this as it crosses the field: ) | (, that is positive rectlinear distortion and is described as "pincushion".
If it curves like this as it crosses the field: ( | ), that is negative rectilinear distortion and is described as "barrel".
The sample of the Docter I tried had barrel distortion.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Fri Nov 05, 2021 4:12 pm
by WilliamPaolini
It is important to realize that each observer has different levels of tolerance for particular distortions or aberrations from an eyepiece or the main objective. So it is largely subjective of what level of distortion or aberration will be a bother. In my case, like JG mentions, I am a center of the FOV observer. If there is something at the periphery that I want to observe I will move it to the center of the FOV rather than observe it with direct vision at the periphery of the FOV. I personally dislike strong RD for star fields and dislike even moderate RD for lunar observing as I know what structures on the Moon should be linear and find it distracting seeing them bowed in the off-axis with my peripheral vision. AMD also does not bother me all that much. Using the 12.5mm APM version of this eyepiece I did not find its level of AMD of any consequence for me. What did bother me ergonomically was the heavy weight of this eyepiece compared to other similar focal length wide fields (XWs, Morpheus). So it felt like a white elephant in the room when I mated it with other wide fields. If I recall it also showed some EOFB at my dark site (SQM 21) which I was not particularly fond of.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Fri Nov 05, 2021 7:26 pm
by j.gardavsky
Don Pensack wrote: Fri Nov 05, 2021 3:11 pm Look at a straight edge in the daytime and move the straight edge from center to edge.
If it curves like this as it crosses the field: ) | (, that is positive rectlinear distortion and is described as "pincushion".
If it curves like this as it crosses the field: ( | ), that is negative rectilinear distortion and is described as "barrel".
The sample of the Docter I tried had barrel distortion.
Hello Don,

the DOCTER UWA has according to the designer H. Köhler, when mounted on the 80mm aperture Aspectem, the 17.3% edge of field pincussion, which would be twice as much as on a Zeiss Abbe ortho when its 40° AFOV would be extrapolated to the UWA edge of field.

Otherwise, the visually perceived distortion, if barrel or pin cushion, finally depends on how the eyepiece distortion is working together with the telescope field distortion.

Best,
JG

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Sun Nov 07, 2021 12:14 pm
by 25585
I have a single Docter already, so know its advantages and foibles, #2 is for binoviewing. Also using Nikon SWs, ditto. Objects appearing larger at centre don't bother me, but smaller would. Fall-off scale is an important factor looking at star clusters. I star hop slowly, like stepping stones across a stream, fast scanning usually overshoots my targets.

Compared to my 10mm XW, the Noblex is easier, 9mm Morpheus is closer & actually beats its 12.5mm casemate.

I originally passed on APM's 12.5mm 84°, due to reports of edge if field brightening, though not noticed that in other eyepieces where its been seen. I think my brain has been trained to ignore lens edge performance due to wearing glasses my whole life. Great edge performance is always a pleasant surprise for me, not an expectation.

I would like to try an Apollo, but TV eyepieces optical designs don't work for me apart from the 62° Delites & a few long focal lengths in other ranges.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Mon Jan 31, 2022 2:33 pm
by 25585
APM has moved its availability date back to 31/3/2022. So the wait continues.

Re: Docter/Noblex 12.5mm 84° ..... are back soon.

Posted: Sat Jun 11, 2022 11:31 pm
by Piero
I have used the docter for several years and it is one of the very best eyepieces I have tried.
I found that the level of contrast it delivers is on par with the Zeiss zoom D-vario 20-75x and Vixen HRs, and superior to the Delos 12mm.

Regarding AMD vs RD, to me it is completely down to one's preference. Personally, I actually favour some AMD in an eyepiece rather than a minimisation of it. A 24 Panoptic represents the moon in a highly unnatural way for instance.

The good thing is that there are many eyepieces for all our tastes.