Are orthos sharper than the tmb planetAry eyepieces

[ddufresne50]

Would any orthoscopic no matter What kind of telescope be sharper on the images of the planets thAn the TMB planetary Eyepieces? I mean Better contrast less scatter light and No ghosting? Dale

[michael.h.f.wilkinson]

Most people would say yes, although the difference might be small on slow scopes. However, eye relief of orthoscopic EPs is so poor at short focal lengths that I for one would never consider buying them.

[ddufresne50]

That is why I got tmb planetary for high power with the better er and wider 58 fov but I do have some orthos in the mid range like 9mm and a 12.5mm eye relief is not to tight there dale

[KaStern_Former_Member]

Hi folks,

good orthoscopics are not sharper, but contrastier than the TMB planetaries.

I fould less scatter, no ghosting and no of the annoying flares I could see

in some TMB Planetaries or their clones with other "brandnames".

Eye relief of an Ortho is about 4/5 of the focal length.

I routinely use Orthos with a barlow for high magnifications.

Cheers, Karsten

[michael.h.f.wilkinson]

BTW, very often good planetary EPs with long eye relief are effectively ortho-like constructs with a Barlow-like lens or group (Smyth lens). Incidentally, the idea of using a Smyth lens for long-eye-relief is credited to none other than Ernst Abbé, best known in the astronomical EP field for his famous orthos an interesting link is here:

http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/forum/Smyth-Barlow%20lenses.html

[ddufresne50]

That is a great report mike I kind of used the mid range orthos so the eye relief is not as bad as say with a 4mm dale

[ronin]

Oddly if you read the assorted reviews of the TMB's over time they are good but not outstanding eyepieces. Even the originals had to undergo several improvements owing to an assortment of minor problems. They then were reissued as type II's, and even with the improvements they never took off.

Recently I think someone on CN summed it up nicely: TMB's perform as expected for the $60 eyepiece they are, A-T Paradigms perform well above the $60 eyepiece they are.

I suppose if you think about it TMB was known for designing refractor lens not for eyepieces, Al Nagler is known for eyepieces and not for refractor lens. Perhaps a gift for one field does not transfer over to the other.

[cs1cjc]

Hi folks,

good orthoscopics are not sharper, but contrastier than the TMB planetaries.

I fould less scatter, no ghosting and no of the annoying flares I could see

in some TMB Planetaries or their clones with other "brandnames"...

I think that this is exactly right.

I did some detailed tests on Mars and Jupiter with a couple of different 9mm TMB type Planetaries and an Antares 9mm Ortho. When I could determine a difference, it was always the Ortho that showed most.

[michael.h.f.wilkinson]

Oddly if you read the assorted reviews of the TMB's over time they are good but not outstanding eyepieces. Even the originals had to undergo several improvements owing to an assortment of minor problems. They then were reissued as type II's, and even with the improvements they never took off.

Recently I think someone on CN summed it up nicely: TMB's perform as expected for the $60 eyepiece they are, A-T Paradigms perform well above the $60 eyepiece they are.

I suppose if you think about it TMB was known for designing refractor lens not for eyepieces, Al Nagler is known for eyepieces and not for refractor lens. Perhaps a gift for one field does not transfer over to the other.

However, the TMB Paragons are wonderful EPs, real stunners. Only the (far more expensive) 31T5 Panzerfaust managed to nidge my TMB Paragon 40mm from my EP case

[great_bear]

Al Nagler is known for eyepieces and not for refractor lens. Perhaps a gift for one field does not transfer over to the other.

Not sure that's fair at all: TeleVue refractors enjoy an excellent reputation, and London's own Richard Day no doubt did his homework before selecting TeleVue as the lens supplier for the AR101/15 telescope.

[John]

Not sure that's fair at all: TeleVue refractors enjoy an excellent reputation, and London's own Richard Day no doubt did his homework before selecting TeleVue as the lens supplier for the AR101/15 telescope.

I agree. I've read nothing but praise for Tele Vue refractors and, as you say, Richard knows what he is doing.

I also reckon Thomas Back was quite capable of designing an excellent eyepiece.

[great_bear]

I also reckon Thomas Back was quite capable of designing an excellent eyepiece.

Indeed - the majority of issues around the TMBs relate to manufacturers [*ahem*] "build refinements" rather than the optics as originally specified by TMB.

[ddufresne50]

Yep I love the tmb s They have no distortions in my scope and a flat field edge tomesgenin my scope I got The 4 5 6 7 and 9mm Dale

[KaStern_Former_Member]

Hello John,

" I also reckon Thomas Back was quite capable of designing an excellent eyepiece. "

me too.

But what if the eyepiece manufacturer choose to build the eyepieces not according to the specs of Mr Back?

Here is a link to where M. Back writes upon the TMB/Burgess Eyepieces:

http://www.brayebrookobservatory.org/BrayObsWebSite/HOMEPAGE/BO-TMB-review.html

" The design has a 2-element air-spaced field group followed by a 2-1 positive assembly. It is thus a 1-1-2-1 design (I have disassembled it to determine this). "

I have "tested" some of the TMB/Burgess, first and later ones,

and some with other brandnames on them.

They all weren`t flawless. Some exhibited strong flaring, some minor light scatter issues.

I ended by using further my orthos + a barlow.

If this barlow is a 2.8x Klee Barlow this barlow is a 3-element in 3 groups barlow.

Together with the 4 lenses of the ortho it sums up to 7 lenses in 5 groups,

wich translates to 10 air-to-glass-surfaces.

Despite this light scatter is very low and contrast is high.

Good manufacture quality seems to be more important than counting the number of lenses.

I have seen the lowest light scatter ever using a 5mm Pentax XO.

It was even slightly better than a 5mm TMB monocentric.

The XO is a 1-2-2 design, the monocentric has 3 lenses in 1 group.

Cheers, Karsten

[John]

I agree Karsten and thats interesting information. I have owned a TMB Supermono 5mm and agree with your assessment - an outstanding eyepiece if you can live with the small field of view. I've not had the pleasure of using a Pentax XO 5.1mm as yet.

We can only wonder what might have been had all aspects of the TMB Planetary project been controlled by Thomas back.

[KaStern_Former_Member]

Hello John,

the 5mm Pentax XO has a very tight eye relief too. It is only about 3.6 mm:

http://www.tele-optic-tecnica.de/pentax-xo.html

Ragards, Karsten

[michael.h.f.wilkinson]

What people often forget about observing is that comfort is as important as optical quality. The two are not entirely separate: ghosting, flare, low contrast, and kidney-beaning can seriously reduce the comfort of an EP. However, an EP that allows me to relax more, gives me a better chance of seeing fine detail, or faint, elusive objects than one which is difficult. This is one aspect that makes EP-choice a very personal thing. What is OK to one observer is unacceptable to another. 3.6mm eye relief (I had that on a Circle-T Ortho 5mm way back) is just not acceptable for me. My XWs give near-ortho performance over a massive FOV at 20mm eye relief. I can relax, take in the whole FOV, and track down all sorts of detail which I never could in my Circle-T, because I kept banging into that EP with my glasses causing all sorts of vibrations.

I loved the 25mm Ortho I had (0.965" fitting, sold with my old 6" F/8), but guess what? That had 20mm eye relief.

[great_bear]

That's a good point Michael, and one I should remember when going on holiday.

Don't pack the orthos.

Oh hang on... They're the lightest, most transportable eyepieces!

Oh dear... Another conundrum to have sleepless nights over before leaving...

At home I've got a nice comfy seat and all the other creature comforts. On holiday there's a lot more compromises:

- Wobbly tripod

- Uncertain environmental conditions

- Lack of infinitely adjustable adjustable seating

- Unskilled strangers wanting a quick view etc.

- Children wanting a peek

Certainly a good excuse for a set of "Holiday TMBs" or similar I'd say...

[michael.h.f.wilkinson]

That's a good point Michael, and one I should remember when going on holiday.

Don't pack the orthos.

Oh hang on... They're the lightest, most transportable eyepieces!

Oh dear... Another conundrum to have sleepless nights over before leaving...

At home I've got a nice comfy seat and all the other creature comforts. On holiday there's a lot more compromises:

- Wobbly tripod

- Uncertain environmental conditions

- Lack of infinitely adjustable adjustable seating

- Unskilled strangers wanting a quick view etc.

- Children wanting a peek

Certainly a good excuse for a set of "Holiday TMBs" or similar I'd say...

Go on, you know you want them. Cheaper than buying a van and dragging all the kit along. Guess how long I objected to my wife wanting to replace our ageing Daewoo Nubira Wagon with a second-hand Renault Espace

[KaStern_Former_Member]

Hello Michael,

" What people often forget about observing is that comfort is as important as optical quality "

good point. That is why I own a mixed set of Pentax XL / XW eyepieces too.

I bought them used one after another.

They combine good optical quality with long eye relief and good comfort.

Cheers, Karsten