Why are orthoscopics so hard to come by?

[gooseholla]

Why are orthoscopics so hard to come by? Everyone raves on about them, yet very few companies make them. Now, everyone makes a plossl, a ED, majority a kellner. so why don't GSO make orthos? Why don't meade, celestron, etc. brand a generic orthoscopic? What is so special about orthos that means only a relatively small amount make them, and (from what it appears!) in such limited numbers?

[JamesF]

I love my BGOs, but they're really not for everyone because of the minimal eye relief. The market also seems to be going in the direction of "as wide a field as possible", which perhaps doesn't work in the orthoscopic's favour either. So perhaps manufacturers don't see a major benefit in that area of the market. Or perhaps they'd rather invent a design they can potentially patent or otherwise have control of as a brand. New is always better. I know this because all the advertising tells me so.

James

[michael.h.f.wilkinson]

It is not just the narrow field of orthoscopics that works against them, it is the terrible eye relief. I really really hated my 4mm Circle-T ortho. Loved the 25mm, however. With the appearance of very sharp, high transmission EPs like my Pentax XW and XFs, which do what an ortho can (or 99.99%) but over a 60 to 72 deg FOV, and with 22mm eye relief, they are squeezed out of th ehigh end, and most beginners use plossls, or switch to TMB Plantetary EPs or their clones. The same holds for the (super)monocentrics. With the advent of way better coatings, the number of air/glass interfaces is no longer nearly as important as it used to be.

Having said that, new orthoscopics are coming out, so there is a market, albeit a small one

[alan potts]

I must try one, I never have, if I don't like it I can put it with the other ep's that collect dust. Seems like a waste of time trying to sell eyepieces at the moment unless it's a Televue.

Alan.

[JamesF]

I must try one, I never have, if I don't like it I can put it with the other ep's that collect dust. Seems like a waste of time trying to sell eyepieces at the moment unless it's a Televue.

I've been eyeing at least one of the ones you have for sale, dithering over whether I should have that at a lower price or pay more for an 82 degree FOV, to be honest.

James

[gooseholla]

Orthoscopics sell, trust me! I've tried bidding on a couple.

[JamesF]

Orthoscopics sell, trust me! I've tried bidding on a couple.

Wait until you see a 12.5mm BGO come up for sale. Then there'll really be a bunfight.

James

[JohnC]

Any comments on the Baader ortho for planetary use?

[JamesF]

That's mostly what I use them for, although for small DSOs (given the relatively small field of view) they're quite nice too. I regularly use my 18mm and 9mm BGOs for compact globular clusters and small nebulae.

James

[Astro_Baby]

Well they arent that hard to find - Lyra Optics seel them, UO sell them, there are even BGOs on the shelf at FLO right now. Fact is its a small market. Most newbs are sold on the super wide angle stuff. Trust me no TMB Type II has the sharpness of an ortho but a TMB does have decent eyerelief.

They arent for everyone, and indeed these dayts fewer and fewer people use them - I snapped up a set of UO ones when they were still selling them and added some of the BGOs as well.

The Lyrao Circle T ones (same as UO) are £55 last time I looked so they arent expensive. If you have a longish F/L scope you dont need small f/l EPs so that gets rid of the ER problem. Get yerself a mak and you wont need an EP under 7mm

[JohnC]

Thanks for the info.

[michael.h.f.wilkinson]

Well they arent that hard to find - Lyra Optics seel them, UO sell them, there are even BGOs on the shelf at FLO right now. Fact is its a small market. Most newbs are sold on the super wide angle stuff. Trust me no TMB Type II has the sharpness of an ortho but a TMB does have decent eyerelief.

They arent for everyone, and indeed these dayts fewer and fewer people use them - I snapped up a set of UO ones when they were still selling them and added some of the BGOs as well.

The Lyrao Circle T ones (same as UO) are £55 last time I looked so they arent expensive. If you have a longish F/L scope you dont need small f/l EPs so that gets rid of the ER problem. Get yerself a mak and you wont need an EP under 7mm

Even on my C8, I rarely use anything below 7, but I find the 5.6m eye relief of a 7mm ortho unworkable. Even the 8mm eye relief of a 10mm is much too little. For people who wear glasses any ortho below about 16-18mm is going to be a struggle. Otherwise they are very fine EPs indeed, and very reasobly priced (unless you want a Zeiss Abbe Ortho ). I was tempted by a 25 ortho which came up for sale here, but decided against it. I would only use it in my solar scope, and there the Pentax XF8.5 provides just the right magnification for me (and gives me the full disk), so why bother with a 25mm ortho?

[E621Keith]

Orthoscopic is actually a set of eyepiece performance criteria. From memory, I think an orthoscopic must be free of spherical aberration, rectilinear distortion and must be corrected down to a f5 light cone. Any eyepiece that meet those criteria can be called an orthoscopic.

Abbe is the most common orthoscopic. Before modern anti reflection coating became common, the Abbe design was very popular for high end eyepiece because that design is more resistance to internal reflection. Reduced internal reflection improve contrast and transmission which makes them ideal astronomical eyepiece. Plossl wasn't a popular design until widespread use of coating. The eye relief of an ortho is longer than other traditional eyepiece designs such as plossl and Kellner which made them more comfortable to use. Abbe are very difficult to make, which is why they are more expensive than other traditional designs.

There are a number of other ortho designs such as the Pentax XO (a barlowed plossl) and Zeiss aspheric ortho.

Nowadays orthos are mainly used for planetary because they have relatively short eye relief and relatively narrow field compared to modern wide field long eye relief design. However, an orthoscopic is still the weapon of choice for people who want to squeeze the last bit of resolution and contrast from a planet. A top end ortho can often cost as much as top end wide field eyepiece, and the average ortho can perform as well as top end wide field designs.

[John]

You would not get on with a TMB Supermonocentric Michael !

I had the 5mm for a while. Fantastic contrast and razor sharp but a 30 degree FoV, an eye lens about 3mm in diameter and 2.8mm of eye relief

I wonder what these single glass ball eyepieces that the folks on Cloudynights go on about are like to use ?

[gooseholla]

Wait until you see a 12.5mm BGO come up for sale. Then there'll really be a bunfight.

James

Good job I have a 12.5 mm Circle T then!

[gooseholla]

Well they arent that hard to find - Lyra Optics seel them, UO sell them, there are even BGOs on the shelf at FLO right now.

Yes, I understand that there are avenues to buy them. My point was, compared to a plossl - which everyone makes - or a ED, or wide field, the market, as you say, is small indeed. But it is interesting that compared to their performance, their market is such a small one.

I guess the FOV and ER are against them, but when viewing a planet I never saw it as a problem, if your mount is set up right or had a tracking mount. I never saw a 5mm on my 1000mm fl telescope as a problem on Jupiter or Mars. I guess a young un, ER isn't actually a problem to me, yet...

I guess we'll never see a quality GSO ortho set for low cost, or other similar make. But you are right, £55 per ortho isn't dear. I do try and get them when they come up 2nd hand. But bidding sometimes goes through the roof.

[Moonshane]

I have a 13mm Ethos but prefer my 12.5mm BGO on the moon. it's cleaner, brighter and sharper in my experience. the 9mm and 7mm BGOs I have are also excellent and I use them often.

[E621Keith]

Yes, I understand that there are avenues to buy them. My point was, compared to a plossl - which everyone makes - or a ED, or wide field, the market, as you say, is small indeed. But it is interesting that compared to their performance, their market is such a small one.

I guess the FOV and ER are against them, but when viewing a planet I never saw it as a problem, if your mount is set up right or had a tracking mount. I never saw a 5mm on my 1000mm fl telescope as a problem on Jupiter or Mars. I guess a young un, ER isn't actually a problem to me, yet...

I guess we'll never see a quality GSO ortho set for low cost, or other similar make. But you are right, £55 per ortho isn't dear. I do try and get them when they come up 2nd hand. But bidding sometimes goes through the roof.

Compare to plossl, an Abbe ortho has longer ER but smaller FOV. However, the main reason is cost, an Abbe is more difficult and expensive to produce than plossl, hence low cost manufacturers avoid them. Each glass surface needs to be figure to very high accuracy and that cost money, especially for the tiny lenses an ortho uses. The ED and widefield eyepieces uses bigger lens elements, which should be easier to handle and cheaper to make. Just think how hard it is to sign you name on a grain of rice compare to a tennis ball.

Plossl gives better performance than Kellner and Kellner gives better performance than Ramsden ... Abbe is the next level of performance beyond plossl, but at that point the economy may have changed in favour of multi-element wide field eyepieces that uses exotic glass, instead of trying to make the precision optics needed in an Abbe.

There is one more factor to consider - seeing. In most evening when the sky is seeing limited, you won't be able to get the full benefit of an ortho compare to a high end wide field eyepiece, so you may well go for the more comfortable option.

[Astro_Baby]

Its worth saying that the 'limited field' of an orthi isnt actually as limited as you might think. Last year soome of the best views I have ever had of M42 were with orthos used in a Mak and with an F5 newt. Ok you cant see the whole panorama of M42 with an ortho but getting inside the cloud with them showed fantastic cntrast and sharpness.

The only EPs I have which show a similar level of contrast and sharpness are Pentax XWs but tats a whole different discussion, and a whole different price point as well.

I dont use any orthos below 7mm because the ER is too tight for me. I do have some BGOs in smaller sizes but almost never use them because of the ER. i also had some BGOs in larger sizes but I sold them off because I really couldnt see a difference between them and the UL VTs and the VTs were for me more clmfortable to use.

[michael.h.f.wilkinson]

Good point about the design criteria, Keith. My orthoscopic TMB Paragon had a 68 deg FOV at 20mm eye relief. Not your regular ortho

[michael.h.f.wilkinson]

You would not get on with a TMB Supermonocentric Michael !

Absolutely not!

I had the 5mm for a while. Fantastic contrast and razor sharp but a 30 degree FoV, an eye lens about 3mm in diameter and 2.8mm of eye relief

I wonder what these single glass ball eyepieces that the folks on Cloudynights go on about are like to use ?

Single glass balls have tons of spherical aberration, loads of chromatic aberration, minute FOV, and according to the Siebert page eye relief on a par with 10mm Plossls (which they call good ). I have looked through such lenses (replica of Antonie van Leeuwenhoek's microscope), and the view is far from perfect. Siebert's claim that removing glass-glass interfaces can reduce scatter is all very well, but chromatic aberration is not corrected for, and neither is spherical. Modern ultra-low-dispersion glass might help a great deal in overcoming the chromatic issues, but not the spherical aberration. This design in my opinion is throwing out the baby with the bath water. I take reports claiming that they are sharper than e.g. monocentrics with a very large pinch of salt. The emperor's new cloths comes to mind.

[gooseholla]

I do have some BGOs in smaller sizes but almost never use them because of the ER. i also had some BGOs in larger sizes but I sold them off because I really couldnt see a difference between them and the UL VTs and the VTs were for me more clmfortable to use.

Ever thought of selling them off as well?

[Astro_Baby]

Oh they will be sold...as soon as theres none left on a shelf and they acheive classic status

[gooseholla]

Ah, money making venture. Getcha.

[beamish]

Wait until you see a 12.5mm BGO come up for sale. Then there'll really be a bunfight.

James

Ooooh like this one you mean

http://www.loisirsplaisirs.fr/oculaires-baader/page16.html

I've a 12.5mm Circle T Japanese Ortho ..and I have to say I love it !