(Very!) quick ES100 20mm first light

[GazOC]

After catching the "100 degree bug" due to buying a 13mm Ethos a month or so ago I decided to buy a similar longer focal eyepiece. Mainly due to the price of the 21mm Ethos I went with the ES100 20mm.

Tonight was the first time I've had it out under the stars and here are my first thoughts on the eyepiece after just an hour or so of not-so-serious observing:

I used the eyepiece in a 80mm f6.25 Equinox, an f7.5 ED120 and a 14" f4.5 Newt. In both of the refractors the view was sharp out to around 90% of the FOV with a slight deterioration after that that I had to tilt my head into the eyepiece to see.

In the f4.5 Newt the ES100 wouldn't some to focus without me using a Baader coma corrector to get the extra in-focus. This is due to my scope having a non-standard mounting plate that pushes the eyepiece further away from the scope than is usual rather than any fault of the eyepiece. With the Baader in place the view was sharp to roughly 80% of the way the edge with a clear drop off in performance after that. Its worth noting that I didn't have the correct spacing between the eyepiece and corrector, how much difference getting this right will make to the performance will be interesting.

The edge performance isn't as good as the 13mm Ethos but thats to be expected given how much more sky the ES100 is showing. Both eyepieces barlow very well, I'm very happy with the the ES but I think at <f5 maybe "try before you buy" might be good advice as different people have different thoughts/ tolerances to edge of field imperfections.

This is just a quick "first look", I'll try and put together more comprehensive reviews on both the ES100 and 13mm Ethos in the future. One thing that did cross my mind seeing the Ethos and ES side by side is they surely must come from the same factory, barrel design and size excepted they are like peas in a pod!!

[John]

Very interesting stuff Gaz - I'm looking forward to more

Someone on "Cloudynights" posted X-ray photos of an Ethos 13 and an ES 14 100 - the internal lens layout was remarkably similar !.

Thanks for the posting.

[michael.h.f.wilkinson]

Similar lens layout does unfortunately not always mean a lot. The type of glass used is easily as important, as is just simply quality control.

Still clearly an interesting EP to try, although I doubt I will beable to use the whole FOV given my glasses (works OK with my Nagler 22mm T4, a bit troublesome on my Meade UWA)

[weega]

[cut]

Someone on "Cloudynights" posted X-ray photos of an Ethos 13 and an ES 14 100 - the internal lens layout was remarkably similar !.

[cut]

link please

[cut]I'm very happy with the the ES but I think at <f5 maybe "try before you buy" might be good advice as different people have different thoughts/ tolerances to edge of field imperfections.

[cut]

very very good to know, thanks!

ciao

dan

[joner]

link please

very very good to know, thanks!

ciao

dan

Heres the link,

Explore Scientific 14mm Ethos 13mm English

[weega]

o__0 it's astonishing!

I've reported the link in an italian astroforum.

They seem twins.

I believe in the reviews that say the two eyepieces work in different way.

So I can only suppose that the choise of the right glass is a very important parameter, like the secret ingredient of CokeCola :-)

ciao

dan

[barkis]

With regard to the very high prices of certain eyepieces these days, it goes without saying, how very useful these reviews are, and how appreciative prospective purchasers must feel.

Although I will be primarily Imaging in future, In no way will I give up Observing, and I will need at least a couple of very good Eyepieces to get the best out of the telescopes I have.

I shall be paying a lot of attention to the review section.

Thanks for the Information you have supplied in this thread Gaz.

Ron.