TeleVue Ethos 13mm v.s 14mm 100° Explore Scientific Review

By: Vlad Fedosov
07/31/2019

Intro:

The 13mm Ethos is the eyepiece that started the entire 100° Field Of View(FOV) revolution. Though I started with a collection of Nagler eyepieces in my early days of amateur astronomy, by the time the 100° eyepieces were coming to market I was a convert to Explore Scientific(ES) glass. Recently I had the opportunity to extensively compare the 13mm Ethos to one of my permanent eyepiece case citizens; the 14mm ES 100°. Let’s dive right in and see how these titans stack up!


Testing:

I evaluated the eyepieces in question on a variety of nights and from a variety of locations. This ranged from my light-polluted back yard to a dark sky star party in Goldendale, WA. The scopes used also ranged greatly from a 16” f/4 premium dob to a 7” f/9 APO. I’m no stranger to premium eyepieces as I have used about every design under the sky. I will make a disclaimer that I’m no ES fanboy and I do like TeleVue eyepiece(my only gripe with them is that for the ULTRA premium price they should be made in the USA!). This is just my personal opinion of how the eyepieces compare.


The first thing that I noticed when I started a night of observing with these eyepieces at a dark sky star party in Goldendale, WA was how easy the entire FOV was to take in in the 13mm Ethos compared to the 14mm ES that I was used to using. The 14mm requires you to be much closer to the glass and to really get your head “into” the eyepiece to see the entire FOV all at once. With the 13mm Ethos you also had to be relatively close to glass but it did not feel like your eye had to be glued right onto the glass. Overall it was much more comfortable. That was a very nice first impression! Another very nice benefit of the Ethos is that it is physically smaller and a lighter(20.15oz v.s 30.4oz) than the ES. If you have a smaller scope I would think that the Ethos would certainly be a bit easier to manage with it.


The second thing that I noticed is that I could have sworn that the FOV in the Ethos looked quite a bit smaller than in the 14mm ES. At first, I thought that I was imagining this. But switching from one eyepiece to the other it was certain that the FOV appeared much larger in the 14mm. Now, this is not just a difference in the slightly higher magnification of the 13mm. I swapped back from one eyepiece to the other several times to confirm this and it appeared that indeed the ES 100° had a wider FOV compared to the 13mm. After more analysis of the FOV I did confirm that this was just an illusion. The FOV of the Ethos was the claimed 100° but just “appeared” smaller. I’m not sure why this is, but I think that it has to do with the fact that the ES requires you to be much closer to the glass and kind of look around to see the entire FOV whereas with the Ethos you can take it in much easier as mentioned above. It might also be the glass size itself. I have noticed a similar effect with the Nagler T6 eyepieces. The FOV always looks smaller in them compared to the older Nagler designs that used larger glass.


Comparing the sharpness and contrast of the two glass I can confirm that it is very hard to pick out the difference between the two as far as sharpness and contrast. Some objects that I looked at I could have sworn that the Ethos would have better contrast just to than think that the ES was better on the next object. There is a difference in the correction of the eyepieces in about the last 10% of the FOV. The Ethos is better here. Not a huge difference but it is there. Overall I can comfortably say that I would be happy to use ether eyepiece from a performance standpoint. They are both very nice!

Conclusion:

So what eyepiece would I chose for me? Well, I do own a nice trio of the ES 25mm, 14mm, and 5.5mm 100° FOV. After testing out the Ethos extensively I can confidently say that it is a very nice eyepiece but there is not much incentive that I see in paying the extra money to upgrade to the TeleVue's for me. I also do like the perception that the FOV in the ES is larger. In the end, I would be very happy using either of these eyepieces!