47 replies to this topic

[Tom T]

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[Deep13]

Wow, tiny little thing, isn't it! Are you sure that isn't just a black bowling pin? At what point does it stop being an eyepiece and start being a face-piece?

[Tom T]

I'm waiting for an eyepiece I can put my head inside and look around... Talk about a sense of immersion...

[Meiling]

Let's all go to NEAF and yell: 25, 25, 25, 25, 25, !!!!
Maybe that would help us get what many yearn for

[sixela]

BTW, the Greek plural is Ethe.

[Shawn H]

Nice article again Tom! Absolutely agree with "whats next, and how much" I'm hooked Shawn

[Mike Rapchak]

Tom,

Another great writeup, as usual.

BUT! - note what sixela says! The dilemma is at last resolved!

Mike Rapchak Jr.

[Matt Lindsey]

Tom,
Very well done report. I especially like the mention of Roger Clark's book. I've never seen any book more invaluable for deep sky observing. I got my copy when it was first published and am sure glad I never parted with it, although, somewhat ironically, one could sell it now and almost completely fund an Ethos!

[Cosmosphil]

Excellent quick review. I think some folks here are critical of this line of EPs as a gimmick. But, as you say, it isn't just the emotional hit of the massive AFOV its the excellence of the optical quality and correction of all abberations. When John Rhodes showed up at one of our club's star parties with the full line up of field prototypes I just had to pop the 17mm into my 15". After about 45 minutes that's all she wrote and I was placing my name on the wait list the very next day.
It now has replaced my much beloved 20mm T5 which I had considered the best widefield I had ever used in that scope but not any more!! As with the 20mm before the 17 lives in the focuser for most of the night!!

[coutleef]

The 17mm Ethos is the perfect eye piece in a 8" SCT equipped with a powerswitch. It provides magnifications that are perfect for deepsky observation (80x and 120x) and when barlowed gives 240x that is perfect for looking at globular clusters.

But on axis, i still find that the TV plossls are sharper than the nagler or ethos, for small targets. Havent done the comparison on planets yet.

[helpwanted]

In my opinion, the correct way to select the proper eyepiece is to go for the highest power that seeing will support which properly frames the target while taking the sky background to black. Beyond that, contrast is simply lost between the target and the sky and increased magnification becomes counterproductive.

great article Tom... but in your above comment... where do you find that sweet spot? is it by any chance, at 2mm exit pupil?
with so many f5 and f4.5 dobs out there, i can't believe there isn't a 10mm Ethos yet!!!!

thank again for another great review.

david

[astroghlo]

Very nice. Hooray for TeleVue.

[RAKing]

Great writeup, Tom.

My experiences with the 13, 8, and now 17 have been simply amazing. These eyepieces deliver where it counts for me - right at the optic nerve.

Thanks,

Ron

[Starman1]

Tom said that there was little or no rectilinear distortion in the Ethos.

In fact, there is quite a bit, and it is easily seen as a bending of telephone poles near the edge of the field when used in a spotting scope during the day.

TeleVue says the angular magnification distortion is nowhere in excess of 1% in the field of view, and my tests confirm that.

Which means, of optical necessity, that rectilinear distortion is significant. At 50 degrees off axis, the 2 curves of RD and AMD deviate by a fair amount. If AMD is controlled (and TV does an exceptional job at that), then RD must be significant.

That, however, is no put-down for an astronomical eyepiece. RD is unnoticeable on a field of stars unless quickly scanning across fields of view, whereas AMD is noticeable quite easily on any extended DSO [on pure stars, AMD would be hard to detect].

What that does mean is that, though the Ethos eyepieces are stunning in the field at night, they are not the absolute best in the field during the day. Eyepieces with less RD would be better for typical daylight, spotting scope, use.

Other than this nitpick, Tom's comments are apropos.
I would also add that I have found that light transmission does not seem to be noticeably less than with eyepieces having half the element count, pointing out that TV has used some fairly exotic coatings here, probably partially explaining the cost.

Hey, TV people, how about a 22?

[ALCHEMIST1]

Good review. I have thus far had no success convincing the CFO that I NEED these. Oh well, I guess that my 22mm and 15mm Pan will remain in my diagonal for a lot longer than I had hoped.

[Tom T]

Tom said that there was little or no rectilinear distortion in the Ethos.

Don, I intended my statement to mean as compared to say - a panoptic - where the rectilinear distortion is noticeable even at night when scanning starfields.

I'll clarify. Thanks for pointing that out.

The statement now reads:

and while scanning starfields
there's little to no noticable rectilinear distortion to my eye (especially as compared to something like the 22 panoptic)

T

[Tom T]

In my opinion, the correct way to select the proper eyepiece is to go for the highest power that seeing will support which properly frames the target while taking the sky background to black. Beyond that, contrast is simply lost between the target and the sky and increased magnification becomes counterproductive.

great article Tom... but in your above comment... where do you find that sweet spot? is it by any chance, at 2mm exit pupil?
with so many f5 and f4.5 dobs out there, i can't believe there isn't a 10mm Ethos yet!!!!

thank again for another great review.

david

Hi David, IMO, it depends on the scope, target and sky conditions. 2mm is a good rule of thumb, but not a natural law.

[Bart]

Very informative report.

But, until Bill Gates and I have more in common, the Ethe will always be beyond my price range.

Too bad, it's a nice EP.

[Vic Menard]

I purchased the 13mm Ethos shortly after it became available (and sold my 13 t5 Nagler, which had replaced my upgraded 13 t1 Nagler with knurled grips and rubber eyecup with relieved top corners, which had replaced my "original" 13 t1 Nagler...)

I got my first good look through the 8mm Ethos at the PSSG last year and was very impressed with it's clean resolution, particularly with globular clusters.

I attended this year's WSP with the intention of adding a new Ethos to keep my 13mm company. I was fortunate to be able to testdrive the 17mm in both my 22 F/4 StarStructure Telescope and a friend's 5-inch AstroPhysics refractor. While the views were, as Tom says, "Ethos quality", I was finally swayed by the rampant rumor mill trumpeting a forthcoming 21 or 22mm Ethos. So I bought the 8mm (and sold my 9mm t6). I was truly stunned by the 8mm combined with the WSP's legendary seeing. The Pup was easy, Saturn's rings and moons were tack sharp, and M82 was simply loaded with dozens of "sparkling" stellar points, particularly in the star forming region--something I had never seen before in any aperture!

FWIW--I also sold my 20 t5 anticipating my next Ethos acquisition. I'm still on the fence whether or not my 26 t5 (arguably one of my favorite low power widefield eyepieces) will still keep its space in my eyepiece box next to the 31mm t5 if a new 22 Ethos is indeed in the works. If not, the 17 Ethos may eventually win me over, but the 13mm Ethos already delivers 200X and a half degree true fov in my 22SST, and it's a killer view!

[Starman1]

So, Vic, do you think you were actually seeing supergiants in M82?
I've seen stars in M31 with 12.5", at just past mag.17.
Your 22 under the same skies might reach 18.2 or so. Are there any stars in M82 of that magnitude, or do you think you just saw star clusters?
Don

[Mr. Bill]

Good job, T.

Well, I think I'll wait for the $1K 20mm Ethos, since I have the 13mm E. and a 17mm N. I'd like a little more spread for the money laid out.

One problem between the 13mm E and the 17mm E is the difference in focus of 0.66 inches...not exactly handy for swapping back and forth. If the difference in focus is scaled (with the 17mm E needing to be racked in 2/3 inch from the 13mm E) the (putative) 20mm E may be a challange to many low profile focusers to have enough in rack focusing.

On the positive side, if the fieldstop is scaled like the difference between the 13E and 17E, the 20E would be around 35mm, easily doable in a 2 inch format.

[Vic Menard]

So, Vic, do you think you were actually seeing supergiants in M82?
I've seen stars in M31 with 12.5", at just past mag.17.
Your 22 under the same skies might reach 18.2 or so. Are there any stars in M82 of that magnitude, or do you think you just saw star clusters?

You know Don, I'm not sure. But I am sure I was seeing lots of tiny stars embedded in M82 because several other observers also saw them. I haven't been able to find a high resolution image of M82 that shows the number of stars we were seeing, but I won't soon forget the view! And I don't think these were foreground stars because they were definitely visible on the galaxy structure--not around the galaxy.

Some of the stellar points seemed to sparkle a bit (these were tiny points reminiscent of the central star in the Ring Nebula when it can be seen with direct vision) and several were visible the next evening long before M82 culminated.

[Starman1]

Vic, I just researched this and the giant stars in M82 (seen by Hubble) are mag.23.7-23.9, definitely NOT visible in a 22" inch scope.
So they could have been forground stars or simply chunks of star regions (likely).
Here's a deep photo to compare:
http://www.astrophoto.com/M82.htm

[Vic Menard]

...could have been forground stars or simply chunks of star regions (likely).

They seemed to be associated with the brighter star regions but they definitely appeared stellar (sans diffraction rings). I'm equally puzzled. Like I said, it was the first time I've ever seen anything quite like it. There were too many involved within the galaxy structure (and nothing similar in number away from the galaxy) to all be foreground stars.

If you look at this image (zoomed in), the stars in the left/center of the galaxy are where we were seeing the most sparkles.
http://www.sflorg.co...42406_02_02.jpg

For reference, the star to the left of the brightest star in this image (just on the edge of M82--looks like a foreground star) was easily visible by comparison.

[Starman1]

In the larger image, the "stars" left of the nucleus appear to be, perhaps, globulars. It's just conceivable you could have seen some of those.