tmb super monocentric ep

[enigmacell]

I was looking at the http://www.12dstring.me.uk/fov.htm website and I noticed a huge improvement in magnification using the tmb monocentric eyepieces. Is the viewing really that much better ?

[michael.h.f.wilkinson]

Monocentric eyepieces are regarded as ultra sharp eyepieces, and some regard them as the ultimate planetary eyepieces. However, they have two key shortcomings: very small eye relief, and only 30 deg field of view. Another problem is that they are difficult to get (no longer made(?)).

You could opt for orthoscopic eyepieces as the next-best option

[haitch]

I think you could be confused by the fov.

On that website look at that and a Nagler of the same/similar focal length. It will appear the same size in both but will have more background fitting in the wider fov.

Hth

[enigmacell]

Thats a shame they are no longer made. They seem to be in a league of their own. Were they very expensive then?

[enigmacell]

I think you could be confused by the fov.

On that website look at that and a Nagler of the same/similar focal length. It will appear the same size in both but will have more background fitting in the wider fov.

Hth

Ok so does that mean the lense is tiny on the tmb and quite big on the nagler?

[michael.h.f.wilkinson]

I think the market for them was very small. Not everyone appreciates the small eye relief and FOV of these. Thomas Back considered his planetary design the better trade-off, as can be read here:

Burgess Optical Message on Planetary Eyepieces from TMB

[johninderby]

I had the 4mm and 5mm TMB super monocentrics. The virtually zero eye relief and tiny FOV made them very unpleasant to use, and while they were sharp and contrasty the Ethos eyepieces are just as sharp and contrasty and slightly brighter.

Got rid of them after a couple of months as I so strongly disliked them.

John

[michael.h.f.wilkinson]

I had the 4mm and 5mm TMB super monocentrics. The virtually zero eye relief and tiny FOV made them very unpleasant to use, and while they were sharp and contrasty the Ethos eyepieces are just as sharp and contrasty and slightly brighter.

Got rid of them after a couple of months as I so strongly disliked them.

John

I have the same problem already with orthoscopics. I much prefer newer designs with more eye relief. The Delos range (of two as yet) seem very interesting.

Monocentrics also tend to have quite some field curvature, which is a problem in both Dobs (frequent nudges needed), and on lunar work.

[haitch]

Ok so does that mean the lense is tiny on the tmb and quite big on the nagler?

Not necessarily the lens size - you can have a relatively small lens with a wide fov but you'll have to get your eye very close to see it.