Thoughts on UO Orthoscopics

[chrisp9au]

OK, I've recently been stimulated by KRudd, but I can't use all of it 'cos the wife has said she wants to share the feeling!

I'm in the process of obtaining a 127mm x 1200mm (F9.45) refractor, hoping to obtain some good lunar and planetary views.
So I'm looking, within my budget, for some orthoscopic eyepieces, which I understand will be the best eyepiece design for lunar & planetary viewing.

University Abbe Orthoscopics and the newer HD versions seem to be around what I can afford, and get plenty of good reviews where ever I look.
http://www.universityoptics.com/125inch.html

UO are also offering Super Abbe Orthoscopics at much lower prices, but I can't find any reviews or mentions on the internet. Has anyone had any experience of these?

The rule of maximum usable magnification being 5x aperture in inches means my scope has a 250x usable maximum magnification.

Allowing that I have a 2x barlow, 64 year old eyes, and that I would like to buy two eyepieces, which 2 of the UO offerings would give me the best range of magnifications. Or maybe I should be considering other brands?

Cheers :thumbsup:
Chris

[richardda1st]

Hi chris.

In my search for info on these eps I came across this post of yours. Did you get any feedback. Can you pass on any info or opinion on these eps.

Thanks
Richard

[chrisp9au]

G'day Richard,

My research and the opinions I received, not on this thread obviously!, indicated these eyepieces were excellent for planetary viewing. I subsequently purchased 2 UO Orthoscopics from another IIS member, the 12mm and the 6mm. The 127mm F9.4 refractor I have been building, for planetary viewing, using a Surplus Shed objective is still to be completed, so I have only used the eyepieces in my 12" F5 dob, which isn't ideal for planetary viewing! From the limited use they have had (haven't had a good clear sky in weeks!) they appear to be good eyepieces, well worth the money I paid. Time will tell, but I am confident that they will prove their worth.

Cheers http://www.iceinspace.com.au/forum/../vbiis/images/smilies/thumbsup.gif
Chris

[dannat]

orthos are great for small objects - give very shapr views - i have bought 3 MgF orthos (from the same place as the meade orthos of the late 80/90) give nice sharp views at a cheap price. best value ep's around i reckon

[anj026]

Hi Chris and Richard

I only have 3 orthoscopics, they are UO HD 12, 9 and 7mm. They are really great eyepieces and I recommend them for all types of observing. They are sharp and good value. They are light weight and compact which are virtues in my opinion.

I use the 12mm and 9 mm the most in my 90/1500 refractor. The 7mm gets occasional use in the 102/816 refractor. The 12mm is one of my favorite eyepieces for my 152/2330 refractor. That is about 186x and I rarely use more magnification than that as the conditions are not good enough.

With your 1200mm focal length I would suggest trying the 9 and 7mm orthos. The 6mm would most likely only get used on nights of exceptional seeing or when trying to split difficult double stars.

Regards

[richardda1st]

Hi Chris.

Why do you say your 12" newt isn't ideal for planetary viewing, I hope to be using these eps on my 10" newt. Is it because a refractor does a better job on planets?

My choice of a short fl ep so far is between something like an Orion Stratus 5mm and these UO orthos. May also consider a Telvue plossl, a lens that I have tested and pleased with, thanks to another IIS member.

Thanks Chris for your comments. Any updates would also be appreciated.

Thanks Danial and Andy, you both seem pleased with the Orthos. Great price. Sacrificing a wide FOV is not an issue for planetary views, is that right.

Thanks
Richard

[gregbradley]

You bought well. I have a few UO orthos and they are great.

I had a TMB super planetary at much greater expense but I preferred the UOs as they had a wider FOV and the difference visually was so hard to pick that it wasn't worth the narrow FOV of the TMB.

Televue 15mm plossl is nice too.

Greg.

[MarkN]

Richard:

It can be an issue if the narrow AFOV with fast transit of the object from view bothers you. These EPs are only about 45 deg. at best, after all.

Having said that, the 6 mm HD in my kit has given me some of the very best high X views I've ever had.

Mark.

[chrisp9au]

G'day Richard,

12" dobsonian is F5, 127mm refractor will be F9.4, = better resolution.

12" dob has a large central obstruction, the refractor has none, = better contrast.

At least I think that is what I've been reading!

Can't stop for long, not a cloud in the sky, the scope is out cooling down to a current ambient temperature of 5 degrees.
I might get to see some stars before the moon comes up!

Cheers :thumbsup:
Chris.

[ausastronomer]

Hi Chris,

Why do you say your 12" newt isn't ideal for planetary viewing. To be honest I can't think of a much better scope for lunar/planetary work than a tracking newtonian in the 10" to 15" aperture class. A hand tracked newt is almost as good. Any 1/2 decent newtonian of 8" aperture or larger will outperform any 5" APO. A 5" Achro isn't in the hunt against an 8" newt. A 10" or 12" newt will leave a 5" achro floundering on everything.

Cheers,
John B

[ausastronomer]

Hi Chris,

You are somewhat confused with a lot of these technical terms, which can easily happen with a lot of the misinformation passed around on the internet. I suggest you buy a book called "Starware edition 4" by Phil Harrington. It is fairly cheap. This is a book based solely on astronomy equipment as opposed to observing. I was one of the contributors and proof readers for this book. Another good book is the Backyard Astronomers Guide by Dickinson and Dyer, which is somewhat more expensive.

Resolution of a Telescope is related solely to its aperture. The F-Ratio has absolutely nothing to do with resolution. The F-Ratio is merely a function of the telescopes aperture and focal length.

There are two traditional methods of calculating the resolving power of a given telescope aperture. The older less commonly used is The Raleigh Criterion and the more common these days is the Dawes Limit. The Dawes Limit is calculated by dividing 4.56 arc secs by the telescope aperture in inches.

For a 5" (127mm) telescope this is .91".

For a 12" (305mm) telescope this is .38".

From the above it is easy to see that a 12" telescope has 2.4 times the resolving power of a 5" telescope. The resolving power of the telescope is not affected at all by the central obstruction. This only affects the contrast and light gathering power. The smaller the central obstruction the less effect it has. Scientific research has shown that if the central obstruction is <20% by diameter, then the Modulation Transfer Function Curves (MTF curves) are essentially unaffected and the images are almost indistinguishable from an unobstructed telescope. In this case the greater resolving power of a 20% obstructed 12" reflector easily outweighs any minor gains in contrast. Some will argue that the smaller scope will cut through poor seeing better than the larger scope but I have never found this to be the case. In those moments when the air settles, the larger scope will easily outperform the smaller scope and you still end up extracting more detail with the larger scope, irrespective of seeing. Further if one wanted to rely on the seeing issue you could always turn the 12" reflector into a 4.5"/F13 APO by using an off axis mask on it.

Cheers,
John B

[chrisp9au]

I am frequently confused, and if I've managed to confuse anyone else I apologise! Grey cells are turning white.
I've had very little opportunity of late to look at anything due to the weather, and I'm looking forward to the chance of finding that my dobsonian is going to provide excellent views through my orthoscopics!

Cheers :thumbsup:
Chris

[wavelandscott]

I've found this to be an excellent reference too!

Cheers

[richardda1st]

Hi all, I must have been stuck in Chris's defunct other thread. But glad to join in again. :shrug:

I'm aware of the narrow fov, and that's a shame. If the Orthos give a sharp clear image as all the reviews claim, then I will be satisfied.
The UO HD Abbe Orthos at the moment will each cost $80.00 USD plus shipping.

I'm still thinking of the Televue Plossls (8mm & 15mm). Can anyone comment on how the orthos compare with these Televue Plossls? $115.00 Aus from Bintel.

Any comments regarding how the Orion Stratus 8mm performs. I'v read
one review which claimed the Stratus to almost equal one of the Televue eps, saying it's a clone of the Televue (must find the review). If the Stratus is that good I would buy one now and another later on.

Richard

[dannat]

Rcihard, both TV plossl & orthos can be tight to look thru at high mag (10mm & below) but i think the ortho i've had have been a tad sharper

[richardda1st]

I've asked UO for a total price delivered on the HD Abbe 12.5mm & 18mm plus a 2.8x Klee barlow, Will compare then decide.

Love to hear from someone who has an Orion Stratus.

Richard

[richardda1st]

I decided on the Tele Vue plossls, 11mm & 32mm plus a TV x2 barlow. :D

Not much difference in cost when compared to the UO HD Orthos & barlow combination. This gives me (with the barlow) 5.5mm, 11mm, 16mm and the 32mm. I have been enjoying the views of Jupiter and the moons. Great stuff.

Still have a nagging curiosity to try out some Orthos. As I have joined in with the SVAA (thanx 4 the intro Ken & Eric) there may be a chance that someone has some Orthos for me to try. They just better not be any better than my TV plossls.:mad2:

Thanks all
Richard

I just realized, is this wots termed, hijacking someones Thread?
woops!:whistle:

[KaStern]

Hi Richard,

the U.O. HD Orthos plus 2.8x Klee Barlow might be an interesting combination for your 10" Newt.
The Klee Barlow compensates the off-axis coma of the Newt.
I use it with m 8"f/6 Newt with some U.O. clasical and HD Orthos and I am very pleased by the views.
On axis it is contrasty and sharp. When I focus a star in the center of the field of view and let him
drift towards the edge the star stays off-axis pinpointlike until it hits the field stop.
Only downside of the 2.8x Klee is that it does not work well with long focal length eyepieces.
With a 25mm Ortho it moves the exit pupil too far out.
With the 18mm Ortho it works nicely, but the eye needs to be precisely on-axis.
With a 12,5mm Ortho it is nothing but stunning.

If you get the opportunity to use the Klee with a good jepenese ortho do not hesitate to try it.

Cheers, Karsten

[richardda1st]

Hi there Karsten:hi:

As I said, I still want to try some out. I was ready to by the standard orthos, but then read about the HD orthos which pushed the price up close to the Televue Plossls.

Regards
Richard

[bobson]

The best way to decide would be if you could personally compare them side by side.

There is a trend now that orthos are better than plossls for planetary viewing. Well, I cannot say until I compare them side by side. I have some TV plossls but don't have any orthos yet.

I attached pdf file from Cloudy Nights review for planetary eyepieces from 2004. If you read this you can see that plossls were better choice then ???

Its all personal I think.

cheers

bob

[KaStern]

Hello Richard,

since both are made in Japan the HD Orthos should be more expensive than the TV Plössl.
The TV Plössl with it`s 2 cemented achromatic doublets is a simplier design than the U.O. Ortho
(both HD and conical top) with the cemented triplett and one single lens.
So the Plössl should be cheaper to manufacture than the Ortho, all other things
(coatings, polishing quality, glass quality) being the same.

Enjoy your new eyepieces, Karsten