cheaper than an Ethos... ;-)

[Ags]

If you're mad for 100 degree fields of view, you might be interested in this 9mm EP (I haven't seen it mentioned on the forum before):

TMB "The TMB 100" 9mm 100° field 1.25"/2" eyepiece

TMB is highly respected but I have no idea if the original Mr TMB designed this one.

Even at $270 it is way out of my league though.

[John]

They are discussed quite a lot on the "Cloudynights" forum - they are sold under the Zhumell brand name in the USA as well as TMB. Here is a report comparing the 16mm to the 17mm Ethos:

Telescope Reviews: Z16 100º vs 17 Ethos - a quick comparison

Edit: I've just found an SGL thread on these started by me last year !:

http://stargazerslounge.com/equipment-discussion/93065-16mm-100-deg-fov-eyepiece.html

[Ags]

Telescope Reviews: Z16 100º vs 17 Ethos - a quick comparison

Edit: I've just found an SGL thread on these started by me last year !:

http://stargazerslounge.com/equipment-discussion/93065-16mm-100-deg-fov-eyepiece.html

:-) I've just skimmed that thread, pretty confusing!

[sixela]

Not that confusing.

Bottom line: perfectly OK if you have a slow scope and want 100° AFOV on a budget, but it won't replace your Ethos or Explore Scientific 100° if you have a fast scope (sadly, it's just on fast scopes that you want large 100° AFOV eyepieces, to combine a large true field of view with moderate exit pupil).

[Ags]

The thread was a bit confusing because the posters were confused as to who manufactured what, which brands were equivalent and so on.

I'm sure any kind of scope could benefit from a 100 degree EP thaough, not just the fast ones...!

[Astro_Baby]

I'm not so sure Ags that they can, Maks tend to have a very narrow field of view and even if they didn't not everyone finds a 100' FOV very comfortable. I dont for instance and I own one. I'm not sure the cost/value is all it should be when you look at the price of 100' FOV EPs.

I know its about sharpness as well and both the Ethos and the Explore Scientific are super sharp and contrasty but so are a lot of other EPs which are a lot less expensive.

I found the 100' thing cool initially but on balance I am pretty certaion I wouldnt buy another one. To get the 100' view you have to sivel your eyeball about inside vthe eyepiece and its not very comfortable - its like being too close to a large screen.

[sixela]

I'm not so sure Ags that they can, Maks tend to have a very narrow field of view

True field of view, but large apparent field eyepieces work quite well (though they're a lot less essential). But yes, large 100° AFOV eyepieces are sometimes a bit difficult and smaller ones usually less useful for general purpose usage.

On most 127mm Maks form Synta, a 35mm 70° AFOV eyepiece is usable but the outside of the field is already quite visibly vignetted, whereas a 30mm 70° AFOV eyepiece shows a bit less vignetting.

Usually, something like a 23-26mm 82° AFOV is already pleasant enough, and the 16mm 100° eyepiece is still usable, though already too much magnification for many targets.

But it's actually not that bad to have a set of eyepieces that all have the same true field of view that approaches the maximal available in the scope and just different magnifications.

and even if they didn't not everyone finds a 100' FOV very comfortable. I dont for instance and I own one. I'm not sure the cost/value is all it should be when you look at the price of 100' FOV EPs.

Well, that's just the good point about that TMB eyepiece. It's fairly cheap for a 100° AFOV eyepiece.

To get the 100' view you have to sivel your eyeball about inside the eyepiece and its not very comfortable

until you learn to instinctively compensate that with head movement, it does tend to cause blackouts because that moves the exit pupil out of the eye pupil. But eventually, you do get the hang of it.

Large SCTs are different still. f/10 delivers an exit pupil of 1.6mm for a 16mm TMB and that's not too shabby for general purpose work, and things like a 20mm ES 100° can be the only eyepiece you use for an entire evening, combining a pleasant 2mm exit pupil for most DSO work and the maximum field of view that these scopes can show.

[lunator]

I was speaking with Chris Lord about these super-wide eyepieces and explained that you cannot see all around the eyepieces unless you move your eye around. Much as Astro baby found.

He explained that anything over 60 degrees is affected by this.

Cheers

Ian

[Ags]

I'm not so sure Ags that they can, Maks tend to have a very narrow field of view and even if they didn't not everyone finds a 100' FOV very comfortable. I dont for instance and I own one. I'm not sure the cost/value is all it should be when you look at the price of 100' FOV EPs.

A 9mm 100 degree EP would have the same true field as an 18mm plossl, well within the capabilities of any normal scope.

But I struggle with the 68 degrees of my hyperion, so I think I need to take baby steps here, and not spend tons on an EP I would not be able to use properly.

I posted because it seems like an affordable 100 degree option that I'm not sure many on the forum are aware of.

Sixela: my 102mm Mak shows the full field of a 24mm 68 degree EP, just to support your point.

[Astro_Baby]

Its not the blakouts sixela - the Explore Scientific in 14mm is very tolerant of that it just seems to me a bit pointless to have an eyepiece where you can only see the edge by moving your head/eye about - its rather like looking down a toilet roll tube and trying to see whats on the very edge nearest your eye. You can do it but its just simpler to nudge the scope. For instabce the double cluster will just about fit into the FOV of my EXplore Scientific 14mm but its nowehere near as nice a view in terms of comfort as say a 32mm.

These things are always a personal thing of course - and one persons delight is anothers poison.

For widefield you may as well backj off the power a bit to get more of the view in rather than increase the FOV which gets more in but only at the edge where you have to move your head around. Just seems simpler (and cheaper) to have say 70-80' FOV and less power.

[John]

The whole point of a truly immersive eyepiece is NOT to be able to see the edges of the FoV IMHO

When I want to see the edges of the FoV then I use Baader Genuine Orthos - no doubt where it is with those !.

It's interesting that these 100 degree eyepieces are becoming available at prices lower than the Ethos but, personally, I think I'd rather spend less than £200 on something like a used 9mm T6 Nagler which would be sharp to the edge of its 82 degrees in virtually any scope and would retain it's resale value as well

[robbieince]

In my view, the 100 deg field has the prime benefit of increasing contrast by darkening the background ie spreading the background light over a greater apparent angle.

This allows you to see fainter things more clearly.

Also, I find that the view. Is simply more natural when all my own eyes actual field of view is filled by the eyepiece image.

I have a 12 inch dob and use it with an ethos 13mm and am getting a 6mm for chrimbo, if I am good.

[sixela]

This allows you to see fainter things more clearly.

Depends on the object, the amount of light pollution, and how small the details that you're trying to observe are (the less there is inherent contrast between object and background, the larger it is and the better your skies are, the better slightly lower magification might enable you to detect really hard to detect contrast features).

But yes, if an object is clearly visible at lower powers and you have very clear contrast detection more magnification will reveal a lot more detail.

[joner]

I think you'd be better off buying a Nagler for the same cost.

[Ags]

jahmanson & joner, that is probably the killer argument. Why buy a TMB 100 EP that is pretty good in some scopes when for the same money you can buy an Nagler EP that is virtually perfect in any scope?

[shaunster]

I love people who say they get eye strain using an ethos, your not using it right

[sixela]

- its rather like looking down a toilet roll tube and trying to see whats on the very edge nearest your eye.

I find it's much more like looking out a window, in which you also look around. The alternative for seeing these objects that would be hidden in a smaller AFOV eyepiece is panning by moving the scope, and I find that a lot less natural.