RickEm

On 27/11/2020 at 19:03, Don Pensack said:

You're missing the 10mm and 17mm.  The 10mm edges the 13mm in contrast, and the 17mm edges the 21mm in correction.

If I had a set of just 3, it would be the 17>>10>>6 troika.

If I added a 4th, it would be the 3.7mm

I had all eight for years, but recently astigmatism grew large enough to rule out the 13, 17, and 21mm in favor of longer eye relief eyepieces.

When I think about which one of those I miss most, it's the 17mm.

I have a 10mm Delos from a previous scope.  I doubt the Ethos is better,  apart from the AFOV, Don.  I’ve never looked through the 17 Ethos.

The 13mm Ethos was my first one.  I liked it enough to later purchase the 21, 8, 6, 4.7 and 3.7.  I still have all of them.

16 hours ago, Don Pensack said:

Yes, look for a long eye relief eyepiece so your camera lens can pick up the field.

Does it matter if eyecups are up or down?

6 hours ago, John said:

I came across this photo of the eyepiece set that I had back in October 2009. There is a theme there

 

John, that Ethos has proven to be a cuckoo in the nest.  It has driven out everyone except the grenade.

Welcome to the club.  The 21mm Ethos is a gem.

2 hours ago, Dantooine said:

You are correct Don. I’ve topped out my magnification with this. Antares 1.6x or whatever it’s actually giving me is now redundant. 

That is one of my 3 favourites in the line (the other two being the 6 and the 21mm).

I hope you enjoy it.  Post a report when you use it! 

52 minutes ago, Dantooine said:

Now that’s on its way, the apm 3.5mm looks a good option for rare nights without a massive outlay... does this ever end 😱

Haha.  I think you already know the answer to your question.

Of the Ethos I own, my favourites are the 6 and the 21.  The 6  ‘only’ gives me 90x, but coupled with the 2” 2x Powermate, I get 180x and the view loses none of its crispness.  How is that for addressing both aspects of the original topic of the thread!

4 hours ago, Dantooine said:

I would say it depends on the amount of use it gets. For some observers it may make a lot of sense having the APM and spend the money on their most used focal lengths. Myself, I love the wandering through with my pan 27. In my scope it gives me only 26x which is fantastic. I am more happy putting my hard earned money into my mid range which happens to be some people’s low range.. funny ol’ thing astronomy!

Interestingly, the Ethos 21 gives me 26x and a 3.8* AFOV in my np-101.  The Ethos 21 is a bit of a bully, however, refusing to leave the focuser for other eyepieces.

1 hour ago, Don Pensack said:

Another example of personal preference.  The 30mm APM has just a bit more eye relief than the 31mm Nagler, so was easier to use with glasses on.

I also found the contrast in the 30mm APM to be a bit better (more than a 1mm focal length difference could account for).

But the difference I preferred was the "map-flat" field in the APM, compared to the "concave" field presentation in the Nagler.  That may be purely a psychological interaction with the eyepiece,

where the wider field just seems to be a bit closer to the eye at the edge than in the center.  I'm not sure what it is, but I preferred the flat field presentation.

[Note: neither eyepiece has field curvature per se, and stars are tiny points to the edge in both.  I'm talking about how the field appears to the eye.]

In fairness, the 30mm APM has 9 elements for a (measured) 72° field, where the Nagler has 7 elements for an 82° field, and an eyepiece designer has more options when more lenses are used.

And it wouldn't surprise me if, in a lab, the APM did not have quite as high a transmission as the Nagler.  But at 59-61x in my 12.5" scope, light transmission isn't the

primary factor influencing one's impression of an eyepiece.

The Nagler's field is 10.5% wider than the APM, so those trying to maximize true field might prefer the Nagler.

The APM yields 1.19° in my scope, however, which I find wide enough for pretty much everything except a handful of giant targets, on which I can scan back and forth as necessary.

I have a 102mm refractor for when I want truly enormous fields of view.

 

As for the 30mm XW, though it is very comfortable to use (again, a personal comment, not an optical one), I found in my scope that the edge wasn't as well corrected as either the 

Nagler or the APM.  Contrast is excellent, though, and it makes an excellent daylight eyepiece in my refractor at 24X, with a nice bright image, so transmission is also quite high.

Field of view was similar to the APM.  At this level, small nuances make the difference.  No one is losing out to have any of them.

Thanks, Don, for the analysis.

4 hours ago, John said:

I'm pleased that you like the Antares barlow and that it obviously reaches focus find with your scopes and eyepieces

The last one that I tried had a slightly different design from the one that you have bought and I think that was the reason for my focus woes. It's good that Antares have re-packaged what is a fine barlow optic so that it can be used in a wider range of scopes.

I might have to think about getting one of the new designs

This is the design that I last used:

The above seemed to use far too much inwards focuser movement. Obviously the new body design that you have has addressed that

 

That’s the version I have, John.  It works fine with my refractor.

It’s quite good; I think you’ll like it.

On 02/09/2020 at 15:19, Dantooine said:

Well I ended up getting an Antares 1.6x for my ethos. Deciding factors were it’s smaller in size and weight and gives me a really good spread of magnifications. It’s almost like having 2 sets of eyepieces the way it pans the mags out. It’s rated quite well on here so I thought I would give it a try. 

Amusingly, I own both the Antares 1.6x and the Powermate 2x.  Each has its place.

5 hours ago, Don Pensack said:

I never took to the 21mm because it had a slightly poorer outer field correction in the 12.5" than the other Ethos focal lengths.

Axial sharpness was excellent, as was contrast but it was obvious to me why TeleVue didn't stretch the focal length past 21mm.

Even using my glasses to completely correct astigmatism (I see none at 31mm with the glasses on), the edge of the field displayed some visible astigmatism when running through

focus from one side to the other.

Granted, it is WAY out in the field, but the 17mm was simply sharp to the edge, as was the 13mm.

Compared to the 22mm Nagler, the Nagler seems to have a flatter field (not field curvature per se, but the presentation of the field to the eye), and a slightly easier exit pupil to acquire and hold.

I just find the 22mm more comfortable to use.

 

I find it ironic that in comparisons I've done of all the focal lengths in the ES 100° series and the APM XWA series, that the poorest edge correction in each of those lines is with the 20mm as well.

[well, except the 25mm ES 100°, which is a "bridge too far" in my opinion]

I don't really expect perfection in an eyepiece, but I came to the 21mm Ethos after 12 years with the 22mm Nagler, and just never got comfortable with the 21mm Ethos.

In contrast, the 17mm was an example of everything an eyepiece should be.  It ended up being my most-used low power eyepiece. Because of the nature of the targets I observe,

which are usually small, my most-used eyepieces are in the 6-11mm (166-304x) range, so I use any eyepiece in the 15-30mm range primarily for the very largest targets at low power.

 

I certainly recommend the 21mm Ethos over those other two, and I used it for 10 years.  It was only when I found I needed glasses to observe that I went back to the 22mm Nagler.

Otherwise, I'd still be using it.  A 95% score is still an A grade.

 

 

 

As usual, Don, a very thorough explanation.  It’s much appreciated!  I notice that in the discussion you recommended the APM 30mm UFF over the 31 Nagler.  Was that simply for reasons of cost and weight?

On 21/08/2020 at 18:52, Don Pensack said:

My favorites in the Ethos eyepieces were the 17mm, 10mm, 8mm, 6mm, 3.7mm, though they were all a bit different.

I never really took to the 21mm, and ended up preferring my old favorite 22mm Nagler.

The 13 was very very sharp, but I never felt it had the contrast of the 17mm or 10mm.

The 4.7mm isn't as sharp as the 6mm or 3.7mm in my 12.5", though I couldn't tell you why.  Perfect focus at 400x is often tough,

but why, on the same night, the 3.7mm was sharper at 500x indicates the internal configuration might be a little different.

Some day I'll do a comparo of 4.5-5mm ultrawides as I've done at several other focal lengths, though I think the 5mm Nagler will win--that eyepiece even tests better than the others. 

Anyway, Ethos:

17mm--excellent contrast, sharp stars, great step down from 30-31mm.  Could be a low power eyepiece for me most of the time.

10mm--excellent contrast, a very sharp view, very low aberrations of any kind.  perfect magnification for most DSOs in my scope.  Perhaps my most used eyepiece.

8mm--easiest exit pupil of the series to acquire and hold--like the 11mm Apollo, just an easy eyepiece to use.  I use this one a LOT.

6mm--Is this an ortho?  Fantastic contrast and sharpness.  Close to having no flaws at all.  Stunning.  Beats all the other focal lengths in superb seeing.

3.7mm--not used that often, but rendered moons of Uranus and Neptune as tiny pinpoints and even allowed me to see a white stripe on Uranus.

Used a month ago on Mars with a Baader Contrast Booster--OMG.  Mars at 500x--incredible.  My go-to planetary nebula, smallish planets, eyepiece.

Don, what didn’t you like about the 21mm Ethos?  It’s one of my favorites.

I use a 2x 2” Powermate with my Ethos 6mm to get 180x in my NP-101.  The result is terrific.

On 24/08/2020 at 12:50, John said:

Eye cups up for me. I like to nestle my eye socket into a soft eye cup. No problem seeing the whole field of view I've found, unlike some other 100's that I've used. I observe standing 95% of the time.

I used the eye guard extender on the TV 32mm plossl when I used to have one because the rubber eye cup on that is not quite long enough. Don't need one with the Ethos's

This is a personal preference thing I think.

That pretty much describes my preference.  Touching the soft eye cup in the up position stops me bobbing and weaving when I observe standing.

49 minutes ago, Don Pensack said:

Yes, they were. Sorry.  They could be used as 1.25" eyepieces.  I use a Paracorr, and they cannot be used as 1.25" eyepieces in the Paracorr, but they certainly could without it.

I don't know where they would focus though.  It's outside the range of +0.3" to -0.4" from the focal plane, for sure.

Thanks for clarifying, Don.  I use my 13 Ethos as a 2” eyepiece.

Rick

23 hours ago, Don Pensack said:

Helpful information about focus positions:

21mm and 17mm Ethos:  0.4" IN from the focal plane of the scope (i.e. how much in travel is necessary when the focal plane of the scope is right at the top of the focuser)

13mm and 10mm Ethos: 0.3" OUT from the focal plane

3.7mm and 4.7mm Ethos (used as 2" eyepieces with included adapters): 0.3" OUT from the focal plane.

6mm and 8mm Ethos (used as 2" eyepieces with barrel extenders added): 0.7" OUT from the focal plane.

Used as 2" eyepieces, the Ethos eyepieces focus up to 1.2" apart!

 

Any of the above used as 1.25" eyepieces: focal position will vary according to the adapter used.

For example: 6mm and 8mm Ethos used as 1.25" in the Paracorr adapter: 0.3" IN from the focal plane.  If you used an adapter 10.5mm thick, then they would focus 0.6" IN from the focal plane.

Lift the eyepiece up, and more IN focus is needed.  Drop the eyepiece down and the eyepiece needs more OUT focus.

That's logical, right.  And it means that with a selection of 1.25" adapters, you can come close to parfocalizing all your eyepieces.  Adapters come with heights from -0.5" to +0.6".

 

One more thing: the T6 9mm Nagler focuses 0.25" OUT from the focal plane.

Don, in the above explanation, were the 10 and 13 Ethos being used as 2” eyepieces?