Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10954
Loc: Los Angeles
|
|
I figured the title would make you look. 
Last night I spent several hours viewing (seven, actually) with all my eyepieces, which now include the 13 and 8mm Ethos.
But I could see each eyepiece had something to be said for it.
Some surprises for me:
--the 16mm NaglerT5 was definitely sharper than the 17mm T4. I went back and forth several times. Perhaps my 17mm sample isn't up to snuff, but it had 3 areas of inferiority: sharpness across the entire field (the 16, though a higher magnification, was sharper everywhere in the field), edge-of-field illumination (the 17, as I've mentioned elsewhere, seems to "gray out" on the edge, and it isn't blackout caused by incorrect eye distance), and field curvature (no setting of the Paracorr causes the stars at the edge in the 17 to be pinpoints--round, but not perfectly focused). Not that the 17 was bad--the 16 was just better in my scope (f/5.75 newt taking the Paracorr into account). This was the first time I spent time comparing them both on a multiple of objects.
I'd read that some other observers thought the same thing, but the 10mm eye relief is too tight for many.
--the 31 Nagler feels just like an Ethos. I know the apparent field is only 82 degrees versus 100 degrees for the Ethos. But I would have sworn the apparent field was larger. It seemed larger than the 22T4, the 17T4, the 16T5, and the 9/7/5 T6s. If I didn't know better, I'd have said the 31T5 was a 100 degree eyepiece. Compared to the 13 and 8 Ethos, all the Naglers seem cramped except for the 31. I have no immediate explanation for why--it's not the eye relief (which is longer on the 22T4, I think) and it's not the large eye lens (which is also larger on the 22, IIRC).
Anyone got any ideas?
--------------------
Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
|
MikeRatcliff
Pooh-Bah
Reged: 06/12/04
Posts: 1107
Loc: Redlands, CA
|
|
Quote:
I figured the title would make you look.
It worked! Nearly had a heart attack, or the wallet did anyway.
--------------------
16" f/4.9 dob
Tele Vue Plossls 32,25,20,15,11
13 Nagler T6
10.5 Pentax XL
Brandon 32, 16
12.5 UO ortho, 9 Circle T ortho
2x TV Barlow
|
DeepSpaceTour
Post Laureate
Reged: 10/25/05
Posts: 3023
Loc: In the dark and"WAY"out there!
|
|
I was traversing Cygnus and Cepheus last night through the 6" refractor 31T-5 and an Orion Ultra Block checking out all the bright nebula I could,this eyepiece is absolutely phenomenal, and your right this eyepiece is the farthest thing away from feeling cramped,the view looks absolutely huge,I think it's a matter of the long F/L and relatively low power and the sky it covers, makes the FOV seem larger than it is,when compared to higher powered 82 deg. T-5's and T-6's,T-4's.....yeah the 31T-5 is staying in the eyepiece collection for sure....Last night-this morning rates right up there with one of the top observing nights I have had thus far,and this, in no small part, was due to the views through the 31T-5...."STUNNING"!!!!!!!
Clear skies.
--------------------
-------------------------
Bill
-17.5"F/5 Discovery TD /Dob driver/ArgoNavis
Kendrick dew control/Obsession Alt bearings
-Antares 152-F/6.5 refractor on HEQ-5 Pro
-25x100 Binos
-15x70 Binos
-Collimating tools "LOTS"
- TV ep's *8-Ethos*13-Ethos*31T-5*
- 2" Barlows
- Pelican1600
|
jack45
Carpal Tunnel
Reged: 07/07/03
Posts: 2060
Loc: Lacey WA
|
|
The 31mm Axiom LX does the same thing!
Clear Skies!
--------------------
16"f/4.5 Discovery Split Tube/TV Paracorr
12.5"f/5 Discovery PDHQ/TV Barlow
Orion SkyQuest f/4.9 XT12"Intelliscope
Orion 120mm F/8.3 Refractor
Burgess BV 24mm aperture/Siebert 4 pc OCA
BV Pairs:26mm,20mm,17mm,14mm,12.5mm
Tele Vue Smooth Side Plossl,10.5mm,13mm,21mm,26mm,TV 11mm
UO Abbe Set,40mm 5000s Plossl,31mm Axiom LX,26mm T/5,LX,23mm Axiom LX,20mm T/2,16mm T/2,15mm Panoptic,14mm Meade UWA,10mm Axiom LX!
|
hoof
Pooh-Bah
Reged: 04/07/05
Posts: 1424
Loc: Irvine, CA
|
|
Since the title implied a discussion on yet-to-exist long-focal-length Ethos (Ethi? Ethus? What is the plural of "Ethos" anyway?), I thought I'd throw some speculation in!
I can't wait for the 20mm Ethos 
Why 20mm? Well, 3 reasons. 1) The 13mm is roughly 1.6x the focal length of the 8mm 2) 20mm is roughly 1.6x times the 13mm 3) 2" barrels are roughly 1.6x the diameter of a 1.25" barrel, meaning a perfectly scaled Ethos to 2" barrel would be about 20mm.
Of course, this would yield a very heavy eyepiece with somewhere around 24mm of eye relief. Obviously it would require careful redesign (much like the T5s allowed Naglers to be made in longer than 22mm focal lengths).
One other interesting factoid: The 8mm ethos is about 1.6x the focal length of a 5mm ethos. A 5mm ethos is 1.6x a 3mm ethos. The "1.6x" is a nice multiplier, not only the 13/8 ratio, but also the 2"/1.25" ratio. If TV decides to make Ethos in 1.6x increments, we'd end up with 20mm, 13mm, 8mm, and 5mm (and possibly 3mm). That would make a good starter set, and depending on demand, more could be made to fill in between.
Thoughts?
--------------------
Jonathan Hoof
15" F/4.14 Discovery Truss
8" F/5.9 Orion XT8i
6" F/6 Intes-Micro MN66
4.5" F/4 Orion Starblast
80mm F/7.5 Orion 80ED
18x50 IS Canon binoculars
|
Biff
Carpal Tunnel
Reged: 09/04/05
Posts: 2254
Loc: Courtice, Ontario
|
|
Quote:
Quote:
I figured the title would make you look.
It worked! Nearly had a heart attack, or the wallet did anyway.
+1! It would have to be something pretty special for me to part with my 31T5 though.
--------------------
Ryan
Antares 200mm f/6 Dob & 130mm f/5 Travel Dob.
Projects on the go...
- a couple 80mm SS refractors on the back burner.
- a few small mirrors awaiting polishing
- 260mm f/7.15 mirror... still polishing
Member of DRAA
 My house.
 DRAACO
|
helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 1757
Loc: Phoenix, AZ
|
|
i ignored the post till i saw who it was from... then i though this has to be real!!!
so Don... does all this mean there is a nagler garage sale at your house?
--------------------
|
DeepSpaceTour
Post Laureate
Reged: 10/25/05
Posts: 3023
Loc: In the dark and"WAY"out there!
|
|
Quote:
The 31mm Axiom LX does the same thing!
Clear Skies!
.....But heavier,the 31T-5 is heavy enough,thanks!!!....and won't have the same re-sale value down the road "IF" for whatever reason you want to sell....and I already have the 31T-5......and glad I do(it cost me almost nothing because I sold some stuff and that funded the 31T-5)
Clear skies.
--------------------
-------------------------
Bill
-17.5"F/5 Discovery TD /Dob driver/ArgoNavis
Kendrick dew control/Obsession Alt bearings
-Antares 152-F/6.5 refractor on HEQ-5 Pro
-25x100 Binos
-15x70 Binos
-Collimating tools "LOTS"
- TV ep's *8-Ethos*13-Ethos*31T-5*
- 2" Barlows
- Pelican1600
|
Zoomit
super member
Reged: 12/04/06
Posts: 125
Loc: Tehachapi, CA
|
|
Quote:
I can't wait for the 20mm Ethos
Thoughts?
My math says it'll be a 21mm Ethos. Nevertheless, it's fun to speculate that a 5mm Ethos will be followed by a 21mm Ethos.
--------------------
Brandon
AstroSystems TeleKit 18" f/4.6; Orion XT8 7.4" f/6.4
TeleVue 26Nt5, 13E, 3-6NZ; Antares 2" 1.6x
Astro-Physics 15x70; Nikon Action EX 12x50
|
davidpitre
Pooh-Bah
Reged: 05/10/05
Posts: 1410
Loc: Central Texas
|
|
Quote:
Quote:
The 31mm Axiom LX does the same thing!
Clear Skies!
.....But heavier
At 48 oz I guess so!!
That's around 14 oz more than the 31 Nagler.
It has got to be the heaviest eyepiece currently in commercial production.
I'd love to see it it's views compared with the Nagler.
--------------------
David
|
mosdc61
professor emeritus
Reged: 11/04/06
Posts: 510
|
|
A dobsonian mounted 31mm Ethos eyepiece!!!
Just attach scope to focuser and go.
Seriously Don, I know just what you mean. Going back and forth from my 31T5 to my 13Ethos I don't feel I lose anything and it's a wonderful pairing.
|
Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10954
Loc: Los Angeles
|
|
Quote:
i ignored the post till i saw who it was from... then i though this has to be real!!!
so Don... does all this mean there is a nagler garage sale at your house?
Possibly. I have two scopes, though. The T6's work great in the other scope.
The 17T4 will go for sure, though.
--------------------
Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
|
KWB
Postmaster
Reged: 09/30/06
Posts: 7627
Loc: Westminster,Co Elev.1646Meters
|
|
Since you have the 31T5 and I don't,why not test it with the drift time method and see what kind of AFOV your getting?  I'd be interested in hearing of your results.
--------------------
Kenny
"When dealing with a mystery,choose the most unlikely of the likely possibilities"-Sherlock Holmes
|
FirstSight
Carpal Tunnel
Reged: 12/26/05
Posts: 2515
Loc: Raleigh, NC
|
|
Quote:
--the 31 Nagler feels just like an Ethos. I know the apparent field is only 82 degrees versus 100 degrees for the Ethos. But I would have sworn the apparent field was larger.
I agree completely. I frequently go back and forth between using the 31T5 as a "finder" EP and the 13 or 8 Ethos for closer-in looks at a particular object or more local panorama *at night*, and subjectively, have a hard time perceiving the 31T5's AFOV as any less broad than the 13 or 8Es. The difference in AFOVs is much easier to perceive if you hand-hold the respective eyepieces (i.e. not in a scope) and look through their eyelenses against a bright background. Thus, in significant part, the perception at night that the AFOV of the 31T5 is just as wide as the 13E is a trick of perspective comparing a much lower widefield view containing a richer overall tapestry of stars with a generously wide field stop vs a higher magnification view containing a more constrained tapestry of stars. A similar trick of perspective makes the AFOV through a 5T6 often seem noticeably less generous than through a 13T6, even though the same daytime bright-background comparison confirms the respective AFOVs are identical.
But with respect to the 31T5, the fact that it's AFOV does seem so abundantly generous under night conditions does substantially dampen any curious anticipation (ok, make that lust) I might otherwise feel about whether a e.g. a 22mm Ethos might possibly be in the works sometime in the future.
--------------------
Chris M., aka "First Sight"
Orion XT12i Dob with Moonlite CR-2 focuser
WO Megrez 90 refractor on UniStar Light mount
Nikon 10x50 Binoculars
|
helpwanted
Carpal Tunnel
Reged: 07/04/07
Posts: 1757
Loc: Phoenix, AZ
|
|
Quote:
Possibly. I have two scopes, though. The T6's work great in the other scope.
don, have you tried either ethos in the mak?
--------------------
|
Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10954
Loc: Los Angeles
|
|
Quote:
Since you have the 31T5 and I don't,why not test it with the drift time method and see what kind of AFOV your getting? I'd be interested in hearing of your results.
About 80 minutes of field in the Paracorr.
--------------------
Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
|
Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10954
Loc: Los Angeles
|
|
Quote:
Quote:
Possibly. I have two scopes, though. The T6's work great in the other scope.
don, have you tried either ethos in the mak?
Wouldn't be prudent. My wife uses that scope a lot and I could just see us fighting over who gets to use the Ethos eyepieces at a star party.
[Actually, her favorite eyepiece is a 24 Panoptic, so not so much risk. Or is that whistling past a graveyard?  ]
--------------------
Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
|
John F
sage
Reged: 02/16/04
Posts: 308
Loc: Washington State
|
|
Jonathan
The 16mm T5 Nagler and 13mm Ethos both have 22mm field stops and Al Nagler says that they both have the largest possible fields for a 1.25-inch barrel (which can have a maximum field stop of 27mm) eyepiece. What's interesting is that with both designs Tele Vue was able to make viewable 82% of what is objective possible for a 1.25-inch eyepiece (assuming that there were no other design limitations other than the 27mm field stop itself).
In the case of the 2.00-inch eyepieces the 31mm Nagler has a 42mm field stop out of a 46mm maximum and in that case the eyepiece is able utilize 91% of the potential field stop of a 2.00-inch eyepiece. So if a new 2.00-inch Ethos eyepiece were to become available that could match that (i.e., it's 42mm field stop) then the focal length of that eyepiece would be 24mm (if it also had a 100-degree AFOV). However, I suspect that the size and weight of such an eyepiece (and if it were possible to make it) would make it impractical to use. It would also probably be very expensive.
For possible 2.00-inch Ethos eyepieces I'd like to see a 20 or 21mm and possibly a 17mm.
For the 1.25-inch size I think a 10mm would fit in very nicely between the 13mm & 8mm (I have both) and a logical model to follow the 8mm would be a 6mm version(just as it is with the Radian series). Arguably, and again following the Radian example, a 5mm, 4th & 3mm Ethos should not also not be ruled out. However, given their high cost and the fact that they'd mainly be used a planetary eyepiece, and the fact the eyepieces like the Radians and the 5mm, 3.5mm & 2.5mm T6 Naglers already exist, I'm not convinced that such high power Ethos eyepieces are needed. However, if Tele Vue came out with them (and assuming they have adequate eye relief and perform well) then I think they'd sell.
My dream Ethos EP set would include the 21-17-13-10-8-6 or 20-13-10-8-6. However, if no 2.00-inch Ethos versions ever come out, then I'd be happy with my 26mm Nagler and a set of 13-10-8-6 Ethos 1.25-inch eyepieces.
John Finnan
--------------------
Leica 7x42 Ultravid
Nikon 7x50 Prostar
Swarovski 8.5x42 EL
Nikon 10x70 Astroluxe
Leica 12x50 Ultravid
Zeiss 15x60 B/GAT
Takahashi 22x60 Astronomer
NP-127 w/Bino Vue
|
hoof
Pooh-Bah
Reged: 04/07/05
Posts: 1424
Loc: Irvine, CA
|
|
John, I beg to differ about 16mm being the maximum field stop possible for 82degrees. Both Meade and Antares make 82 degree eyepieces in the 18mm focal length with a 1.25" form factor. In fact, if you scale the Meade 18mm Ultrawide to 2" (a factor of 1.6), you get 30mm, which is one of the eyepieces they sell. The Nagler 31mm, which has exactly the same true field as the 30mm UWA (as tested by star drift testing by yours truly), could be scaled down to 1.25" and get about 19mm of focal length. If an 18mmT5 vignettes, then so should the 31T5, but as we all know, it doesn't.
Mr. Nagler could have made a 18mmT5 had he wanted to. It would have been "fatter" than the 16mm, and looked a lot like a shrunk 31mm. However, look at the lineup of Naglers before the T5 series was introduced, and you quickly see that an 18T5 doesn't make sense. Plus, an 18T5 wouldn't binoview as nicely as the 16T5, and the 20T5 would be too close, forcing the next T5 size increase to be 21 or 22, which competes with the 22T4, etc. And it would leave a big gap between the 13T6 and the 17T4. Much better to go 16/20/26/31 in sizes vs 18/22/27/31, when factoring in the T6's, T4's and how well they compliment each other.
One other factoid, a 27mm field stop in the 82 degree AFoV results in about a 20mm eyepiece, which no ultra-wide manufacturer makes.
--------------------
Jonathan Hoof
15" F/4.14 Discovery Truss
8" F/5.9 Orion XT8i
6" F/6 Intes-Micro MN66
4.5" F/4 Orion Starblast
80mm F/7.5 Orion 80ED
18x50 IS Canon binoculars
|
Rob S
sage
Reged: 03/16/07
Posts: 410
Loc: NZ
|
|
Quote:
Quote:
I can't wait for the 20mm Ethos
Thoughts?
My math says it'll be a 21mm Ethos. Nevertheless, it's fun to speculate that a 5mm Ethos will be followed by a 21mm Ethos.
Yeah, i've been predicting 21mm (and 5mm) too.
Makes sense, as they have no EP in that length. Also, they avoid any comparison with other of their EP's as the magnification will be different.
Rob.
--------------------
8" f5 Dob with Feathertouch
Brandon: 16
Pentax: 7, 10 & 20XW
TMB: 30 Paragon
TV: 8 & 13 Ethos;
5 & 13 NaglerT6;
24 Panoptic;
Leica Trinovid 8x50 BN
|
kfred
Carpal Tunnel
Reged: 11/11/03
Posts: 2001
Loc: Dayton, Ohio
|
|
You got me, I saw the title first.
Fred
--------------------
River Cam - Cambridge England
|
Fireball
sage
Reged: 03/24/06
Posts: 270
|
|
I knew you are pulling our leg a little bit
--------------------
20x90 Bino
12" Lightbridge
Meade UWAs, TV Ethoi, Pentax XW, Hyperion, AT Titan.
|
Starman1
Vendor - Scope City
Reged: 06/24/03
Posts: 10954
Loc: Los Angeles
|
|
Quote:
One other factoid, a 27mm field stop in the 82 degree AFoV results in about a 20mm eyepiece, which no ultra-wide manufacturer makes.
Now.
But they did.
There was a Japanese eyepiece called the Widescan III that had a 20mm focal length and a (claimed) 84 degree apparent field.
And if partial edge-of-field illumination is accepted, field stops can be larger than 27-27.4mm in a 1.25" eyepiece.
The 35mm 5-element "Plossl" sold by Orion, Parks, Antares, etc. has a 28.5-29mm field stop which is above the 1.25" barrel. Obviously, edge-of-field illumination isn't 100% (it rarely is), but the eyepiece works quite well.
So it is possible (assuming you can accept the large amount of infocusing necessary) to make an eyepiece with a field stop larger than the I.D. of the barrel.
--------------------
Don Pensack
12.5" Truss Dob, 5" Maksutov
Sustaining Lifetime IDA member, TeleVue junkie
|
Skywatchr
Carpal Tunnel
Reged: 06/03/06
Posts: 1573
Loc: North-Central Pa.
|
|
Too bad the Ethos can't be "scaled". That is according to Al Nagler. Each of the 2 Ethos we have now are actually uniquely designed. They are not "scaled" versions of each other.
Jeff
Quote:
Since the title implied a discussion on yet-to-exist long-focal-length Ethos (Ethi? Ethus? What is the plural of "Ethos" anyway?), I thought I'd throw some speculation in!
I can't wait for the 20mm Ethos
Why 20mm? Well, 3 reasons. 1) The 13mm is roughly 1.6x the focal length of the 8mm 2) 20mm is roughly 1.6x times the 13mm 3) 2" barrels are roughly 1.6x the diameter of a 1.25" barrel, meaning a perfectly scaled Ethos to 2" barrel would be about 20mm.
Of course, this would yield a very heavy eyepiece with somewhere around 24mm of eye relief. Obviously it would require careful redesign (much like the T5s allowed Naglers to be made in longer than 22mm focal lengths).
One other interesting factoid: The 8mm ethos is about 1.6x the focal length of a 5mm ethos. A 5mm ethos is 1.6x a 3mm ethos. The "1.6x" is a nice multiplier, not only the 13/8 ratio, but also the 2"/1.25" ratio. If TV decides to make Ethos in 1.6x increments, we'd end up with 20mm, 13mm, 8mm, and 5mm (and possibly 3mm). That would make a good starter set, and depending on demand, more could be made to fill in between.
Thoughts?
--------------------
18" F/5 Home-Built Dob. with Mike Dudley Mirror
Highly Modified Meade DS-16 in Roll Off Roof
6" F/15 Brass w/ D&G Lens on DS-16 Mount
DS-10 10" F/4.5 Newtonian
LXD650, LX200 Classic
Orange Tube C11
DayStar 0.45 with multiple ERFs
Vixen ED80sf
10" LX200 GPS SMT
11x80 Meade, 20x80 Celestron binocs (Japan Made).
Lots of Naglers and 8mm and 13mm Ethos.
Gadgets and parts everywhere.
And a Wife that loves it as much as me!
|
hoof
Pooh-Bah
Reged: 04/07/05
Posts: 1424
Loc: Irvine, CA
|
|
Quote:
Too bad the Ethos can't be "scaled". That is according to Al Nagler. Each of the 2 Ethos we have now are actually uniquely designed. They are not "scaled" versions of each other.
Jeff
Sure they can. However, scaling has other issues (e.g. a lens element could get to thin, scaling up results in rapid weight gain, changing scale affects eye relief and eye lens size). TeleVue has scaled eyepieces in the past (the T5 series is the same design scaled to 16/20/26/31mm), and the original Nagler series was also scaled (which is why the 4.8mm Nagler has such short eye relief).
However, like the T6 Nagler series, I can see why they redid the design for the 8mm. If you're interested in maintaining the eye lens size (so that you can, for example, use the astigmatism corrector, or maintain a fixed eye relief), then you have no choice but to redesign. The T6's maintain eye relief, from 13mm down to 3.5mm, by having a custom design for each one.
--------------------
Jonathan Hoof
15" F/4.14 Discovery Truss
8" F/5.9 Orion XT8i
6" F/6 Intes-Micro MN66
4.5" F/4 Orion Starblast
80mm F/7.5 Orion 80ED
18x50 IS Canon binoculars
|
Oly Olson
super member
Reged: 02/17/08
Posts: 155
|
|
I agree that the views through the 31mm Axiom are stunning but I must say that between the 31mm Nagler and the 41mm Panoptic I prefer the Panoptic on my 11" SCT. Perhaps it's the higher focal length of the scope that leads me to feel this way but I often prefer the absolute widest field I can get.
Best,
Oly
|
Previous
Index
Next
Threaded
Edit
Reply
Quote
[Re: