Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.



Some alternatives to Ethos and Panoptic widefield eyepieces

Recommended Posts

9 hours ago, Stu said:

Just posted this on the Eyepiece Cases thread, but here so you don't miss it :) 


I really like the look of these, Stu, and you describe them as solid performers insofar. I hope to read that they are making the most of clear nights for you soon.

I have enjoyed their green-lettered counterparts for a while, now, and while they are all superb, I have regularly experienced that no two of them fit into a single session with a single scope, so to speak. Recently, I have even pondered the actual need for more than one of these in a single EP case (believe it or not) , carrying out "what if" experiments by limiting myself to only one of them on a given night.

This brings me to the question I would like to put to you. Given that you, having missed the widefield views, have acquired all three in short succession, were there any specific considerations behind the acquisition of each one, naturally given your current array of excellent scopes, etc.?

In other words, I've started to wonder why I have all three, nice as they are. I hope to gain insight from why you have all three.

Are they meant for use in different scopes, or is each one suitable for specific targets, or something else?

  • Like 1

Share this post

Link to post
Share on other sites

I'll answer your post tomorrow Mike :) 

  • Like 1

Share this post

Link to post
Share on other sites
On 23-1-2017 at 00:00, Stu said:

I'll answer your post tomorrow Mike :) 

Still interested, Stu, if you're so inclined.


Share this post

Link to post
Share on other sites

Sorry! I have a half drafted response that I will finish soon!

  • Like 1

Share this post

Link to post
Share on other sites
2 hours ago, Stu said:

Sorry! I have a half drafted response that I will finish soon!

No worries, just wanted to confirm my interest. Looking forward to reading!


Share this post

Link to post
Share on other sites

So.... to come up with an excuse for having all three eyepieces.... tricky.... ;) 

Seriously though, it is simply about having flexibility to cover different observing situations, and with different scopes. Let's say I only had the Tak FC-100D, 100mm f7.4, 740mm focal length. At home, my skies are not very good, say mag 19 at best, often more like 18.5 and that is at the zenith, significantly worst below 45 degrees altitude. That means large exit pupils just result in washed out views unless filtered heavily.

The 40mm gives x18.5, 3.68 degrees fov and an Exit Pupil of 5.4

The 30mm gives x24.7, 3.32 degrees afov and an Exit Pupil of 4.0

The 20mm gives x37, 2.70 degrees afov and an Exit Pupil of 2.7

I’m unlikely to use the 40mm at home, whereas the 20mm was really quite effective the other night observing with my club just a little way down the road where it is slightly darker. Next time I will try the 30mm and see whether the sky background is acceptable; with a UHC filter it is likely to be really quite effective.

Ultimately it is a balance of actual field of view vs exit pupil, fitting the object within the fov whilst maintaining a perceived contrast which is acceptable (or better). I remember quite a while ago, using a 41mm Panoptic to try to view a conjunction between a two planets (I think but I can’t quite remember). Basically I ended up fitting them in the field of view, but it was so washed out and they were so close to the opposite edges that it wasn’t a particularly rewarding experience. One of those, “I did it, but….” things where I could chalk it up as something seen but not that memorable. Learning here was that field of view per se is not important, nice, contrasty field of view is.

When I travel to a dark site in the UK, it is often during the late summer, when Cygnus is well positioned. My two favourite targets are the Veil and the North America Nebula. Under dark skies (best I normally see are around mag 20.5 or so, so not really pristine but much better than normal). The Veil needs over 3.5 degrees, nearer 3.7 to comfortably fit the whole object in, so here the 40mm will be really useful, with an OIII filter it will look fabulous. The Tak is a little slower than I would ideally like for this sort of thing, in the past I have had a 106mm f6.5 triplet  which gave the same field of view with a 31mm Nagler. Potentially better contrast due to the smaller exit pupil, and same fov as the Tak with the 40mm. That said, under a very dark sky, the larger exit pupil may well work nicely.  The 20mm under a dark sky should be great for DSO observing of smaller galaxies etc.

Taking different aperture and focal length/ratio scopes into consideration, the justification becomes even easierJ. For instance, I have a C925, 2350mm focal length, the 40mm gives a 4mm exit pupil, 1.16 degree fov so is perfectly useable from home and gives a nice maximum fov for this scope. Put the same eyepiece in my MN190 which is 190mm aperture, f5.3 so 1000mm focal length and you get an unuseable 7.55mm exit pupil.  Even the 30mm gives 5.66mm, great from a dark site, but  probably too much from home, so the 20mm becomes very handy at 3.77mm exit pupil and a 2 degree fov.

So, a justification of sorts :). If you have scopes of similar focal ratio, say a number of fracs around f6 to f7 or just a big fast dob then you can get away with fewer eyepieces. With a range from f5.3 to f14, it's necessary to have more bases covered. My nag zoom which is excellent in the Tak, becomes way too powerful (in magnification terms) in the OMC140; 3mm gives x667 vs x247 in the Tak.

I find these sites useful for calculating object surface brightness and visibility:




I’ve also just re-discovered observer.pro on iOS as a great way of choosing targets based upon their visibility. It lists surface brightness in the object details which is handy for understanding whether they are likely to be visible or not.

Finally, this is a pivot table of my 2" eyepieces in each scope, excluding combinations which are not useful.



  • Like 4

Share this post

Link to post
Share on other sites

What about your lovely Dob? That would be flying with the 20 & 30mm.

No point in aiming one of your refracty pea shooters at the Veil.....??


Share this post

Link to post
Share on other sites


Well, that's rather enlightening - especially the bit about exit pupil. Never was aware that a larger true field could get washed out due to this.

Well worth the wait. I appreciate you taking the time to formulate this so thoroughly.

I'll have to take all of this in before I can draw any conclusions with regard to my own EP collection.


Share this post

Link to post
Share on other sites

Thats very impressive Stu :smiley:


  • Like 1

Share this post

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Similar Content

    • By redhat
      Hello everyone,
      Bit of a backround: I've been a keen stargazer when in my teenage years, then couldn't pursuit my passion, but recently, in my forties, it hit me again, as I moved  and life is good (South facing large garden, obstructed only from the North by our house, but then I just move the scope further and viola!). Started with 90mm refractor, but was always thinking of reflector.
      Long story short, I've got my SkyWatcher Star Discovery 150P GOTO a week ago. Bought it second hand, very good condition, and good mirror. Have got two nights stargazing, cought cold and I AM LOVING IT.
      Now I would like to get me a nice wide angle ep for DSO spotting.
      The scope is 150mm / 750mm f5. I've done some reading obviously, and Explore Scientific 82 degree series have all good reviews and fit within my budget. I can afford only one, and apparently  the best for DSOs is the one that gives 2mm exit pupil. Now, for my scope that would be 10mm piece, and that is not within ES 82 degree range, so it's down to 11mm (2.2mm exit pupil) or 8.8mm (1.76mm exit pupil).
      My question is: which one would be better for my rediscovered passion? I'm gonna be using that ep for faint mostly.
      Thanks to  everyone in advance for any kind advise.

    • By Ignoro
      I've searched the internet (or CN and SGL) and found mixed info about these...
      Do any of you own ES 52, how good are they really? Are they premium simple design like TV plossl, with nice premium coating? Or they are just some nothing special eyepiece with ES stamped on it?
      I can't seem to find any on used market, so no one is selling them. There doesn't seem to be much hype about them now...
      I also found some huge review here, from someone who signed up just to make that review, it does seem a bit odd 👨‍👩‍👧‍👧... 
    • By Kronos831
      Heyyy its meee kronos and i have been wondering about getting a filter...I really want the best contrast and brightness i can on my nebulas(i want to view M42 M57 M27 M31  M81 M82 and lots more) with my future 8" dob. Is this filter really going to help me?
      If it just a matter of quality of the filter itself  can you suggest a better one in the same price range?
      Or will not the uhc filter help me in general .IF so can you reccomend another one?
      Also is this         https://www.firstlightoptics.com/uhc-oiii-visual-filters/uhc-filter.html         this       https://www.firstlightoptics.com/uhc-oiii-visual-filters/es_uhc_filter_125.html        https://www.firstlightoptics.com/uhc-oiii-visual-filters/baader-uhc-s-filter.html               this better?
    • By Neil27
      For sale is my lovely Explore Scientific APO ED 102mm triplet refractor.
      Lovely condition, great optics that are unmarked and blemish free, views are stunning and pin sharp.
      Selling due to lack of use, as a recent change of job keeps me away from home quite a bit, so its not getting any use.
      Comes with:
      Essential 102mm triplet APO refractor
      Tube rings with integrated carry handle
      Vixen dovetail
      2 inch visual back / adaptors and focuser
      Aluminium case
      It is the essentials model so didn't come with any finder or diagonal.
      Price is £450 ovno due to condition and inclusion of vixen dovetail.
      Payment accepted is cash, cheque or bank transfer (which is easiest) or PayPal if buyer pays fees.
      Pick up only or can meet half way by arrangement - don't really like sending optics through the post.
      Thanks for reading and if you have any questions then please pm me and we can discuss in more detail.

    • By jeffkane5
      I am wanting to take up astrophotography and recently sold my Celestron 5se as this was not giving me the results I want.
      I have been researching scopes over the last year or so and have made a short list based on what I can afford and what will give me the results I am after and of course build quality.
      My short list in no particular order is 
      Explore scientific 80 triplet
      William optics z61
      Skywatcher 100ed
      My dilemma is which one to go with. All the reviews are equally as good although 1 or 2 negative notes on the skywatcher but not enough to put me off. Whatever I go with will most likely be a second hand unit as I hate buying items like this new. The exception may be the Williams as not too many come up on the used market. Is this a good sign I ask?
      Can anyone give me a steer as to which scope to settle with?
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.