Orthos. Nostalgia or useful?

[Richard N]

I was hankering after an ortho eyepiece for lunar observation. Am I right in thinking that they aren’t really worth buying these days or is my desire just a manifestation of rampant nostalgia? I just use budget plossls at the moment. Happy to be convinced either way. Probably 7mm-12mm. My eyes are far from perfect. 

Edited July 16, 2023 by Richard N

[rl]

Minimum glass aficionados swear by them. Good orthos are relatively cheap with respect to the usual suspects in the eyepiece quality league and punch well above their weight in terms of contrast and sharpness. Modern multi-element eyepieces can be as sharp with more field, but at vastly inflated cost. Most visual observers keep a couple in the back of their eyepiece case. Anonymous circle T or circle V are fine, Baader maybe a slight step up. Scratch that itch...try one secondhand and just sell it on if the 45 degree field or short eye relief is an issue. 

MK1 eyeball can be the limiting factor for more experienced observers like myself (read "old")...exit pupils much below 1mm are fairly useless for me because of floaters. 

Edited July 16, 2023 by rl

[John]

They can still be some of the very best eyepiece "buys" around.

The Baader Classic 10mm and 18mm orthos are optically superb performers against any competition, for example.

As said above though, check that you are OK with the shorter eye relief (around 80% of the eyepiece focal length) and relatively limited apparent field of view. 

[Zermelo]

My BCO 10mm is probably sharper than any other I own, and has excellent contrast and good control of stray light. It has a narrow FOV by modem standards, but I do all observing with a tracking mount.

I also have the 6mm, but find the eye relief quite tight on that one. People who have the discontinued BGOs also rate them highly.

My 10mm is a keeper, and I always have it in the bag. It is still very good value for the price.

Edited July 17, 2023 by Zermelo
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[Ratlet]

I've not tried an ortho, but I'd give it a shot.  I've had loads of fun testing out different eyepieces and it's great to find out what you like when viewing.  I quite like a narrow field of view myself so I should probably looking at a set myself!

[bosun21]

I found that the BCO 18 & 10mm are very sharp eyepieces indeed and great value for money. I recently just sold the 6mm and 10mm though as I don’t really get on with short eye relief eyepieces. I have kept the 18mm and will buy another for a binoviewing pair.

[Mr Spock]

I like orthos for planetary. I do prefer using longer focal lengths with a x2.5 Powermete though. They have a clarity which suits planetary well, especially Jupiter. 

[MalcolmM]

Eyepieces are a very personal choice as I have found out from the many posts in this forum!

I have a few premium eyepieces from different manufacturers but I always prefer my Tak Abbes (I think they are orthos?).

For me, they are sharper, brighter and more contrasty than anything else I have, and that is more important to me than a wider field of view. They are also very light. If I want a wider FOV I first try a longer focal length of Abbe before going for a wide FOV eyepiece. 

No nostalgia on my part, I'm very recently into this game!

Malcolm 

[F15Rules]

I've really liked decent quality orthos for years, for specific observing applications..

I would summarise the main pros and cons like this:

Pros:

- excellent for planets, lunar and double star observing

- simple design, with few inherent design aberrations

- good contrast and sharpness

- good (accurate) colour rendition

- premium brands (Tak, Baader, TMB) have good light transmission. In particular Baaders' Phantom coatings on their Baader Genuine orthos and Classic orthos are excellent.

- can deliver wonderful high power views in good conditions 

Cons:

- Narrow field of view, typically 40-46 degrees, so not ideal for Dobs or Altaz mounts at high power

- short eye relief on anything of c7mm or less. This becomes more problematic with age.

- not ideal for extended objects eg M42, M31 or star clusters and wide double/multiple star systems

- prone to showing floaters at high powers with increasing age

- probably best for F8 or slower scopes for Cyclops use, if you want the higher powers that orthos do best

Additional thoughts:

- I use an equatorial mount driven in R.A. only, with manual adjustment for the Declination axis. With just a line of sight alignment with Polaris ( I have a Polar axis finder but don't often use it) I can keep an object at high powers, say 150-200x in view for a good 30-40 minutes. 

I do appreciate that this is more difficult with an undriven Altaz or DOB mount.

- To help with short eye relief, I now use a pair of Tak Abbe 12.5mm for binoviewing. These have all the positive attributes mentioned above, and better eye relief than shorter focal lengths...by using them with a 2x or 2.25x Barlow, I can convert them to a 6.25mm or 5.5mm focal length to give higher powers, while maintaining acceptable eye relief..oh, and I use winged eyeguards which really help to control stray light and add comfort, for me at least.

- Floaters definitely seem less troublesome when orthos are used in pairs in a binoviewer..not exactly sure why, but perhaps two eyes help the brain to better relax and combine the best of both our eyes?

I really enjoy Double Star splitting with orthos, probably above all other uses👍😊

Dave

Edited July 17, 2023 by F15Rules
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[Richard N]

Some great replies. Thanks all. I'm very, very tempted now!

[Zermelo]

20 minutes ago, Richard N said:

Some great replies. Thanks all. I'm very, very tempted now!

https://www.firstlightoptics.com/baader-planetarium/baader-classic-ortho-bco-eyepiece.html

They don't seem to have gone up as much as some others have, in the last couple of years.

[Zermelo]

3 hours ago, F15Rules said:

Floaters definitely seem less troublesome when orthos are used in pairs in a binoviewer..not exactly sure why, but perhaps two eyes help the brain to better relax and combine the best of both our eyes?

I've not seen anything definitive, but I always assumed this was because the artefacts were specific to the left or right eyeball, and the chances of having an obstruction in both, at the same place at the same time, was low.

[Stu]

18 minutes ago, Zermelo said:

I've not seen anything definitive, but I always assumed this was because the artefacts were specific to the left or right eyeball, and the chances of having an obstruction in both, at the same place at the same time, was low.

I’m sure that’s correct; whilst binoviewing doesn’t get rid of floaters completely it does reduce their visibility because your brain has both images to work with, and as you say, floaters will be in different places in each eye.

[Richard N]

You’re a rotten lot. Baader 10mm Classic Ortho and Starbase 6mm Ortho on their way from FLO. I felt sure that I could rely on you to dissuade me but you have failed. 

[rl]

Look on the bright side; TeleVue don't make orthoscopics.....

[IB20]

25 minutes ago, Richard N said:

You’re a rotten lot. Baader 10mm Classic Ortho and Starbase 6mm Ortho on their way from FLO. I felt sure that I could rely on you to dissuade me but you have failed. 

I love the clarity and sharpness afforded by orthos, certainly not wistfully either. I have both those eyepieces and you won’t be disappointed with the views, particularly on the moon and planets. I remember my best ever views of M5 was with the 10mm BCO. 

[Franklin]

Different types of targets require different types of eyepieces. For high power planetary observation you won't beat an orthoscopic and the small field is irrelevant for such observations as long as you've got tracking. Short eye relief may be a problem if you wear glasses.

[Littleguy80]

It’s also worth noting that Orthos are amongst the best for DSOs too. On the faint objects I will go from the 10mm Delos to the 9mm BGO. I particularly remember getting my first views of Stephan’s Quintet with the 9mm BGO. My 7mm Meade RGO has given me my best views of Jupiter and Saturn. 

[bosun21]

2 hours ago, Littleguy80 said:

It’s also worth noting that Orthos are amongst the best for DSOs too. On the faint objects I will go from the 10mm Delos to the 9mm BGO. I particularly remember getting my first views of Stephan’s Quintet with the 9mm BGO. My 7mm Meade RGO has given me my best views of Jupiter and Saturn. 

What? Not even a glance through your newly acquired 10mm BCO?🙄.

[RT65CB-SWL]

I agree with what @F15Rules says.

That said, I own three Ortho’s. One is an unknown 0.965” at 6mm [used with a 1.25” adaptor]. It was the only ‘upgrade’ purchase I made when I used to own a Prinz Astral 500 refractor. The other two are Circle-T [volcano top] 1.25” at 6mm & 12.5mm.

Edited July 19, 2023 by RT65CB-SWL

[Littleguy80]

6 hours ago, bosun21 said:

What? Not even a glance through your newly acquired 10mm BCO?🙄.

Haha the weather hasn’t been kind so far. It’s had a couple of quick test runs on the sun. Very good there  

[Richard N]

My orthos are here - thanks FLO. Slightly disappointed that the Starbase just comes in a plastic bag. Hope to get time for a daylight look through them later (and yes I do know that is vastly different to using them at night).

 

Update: both work nicely in daylight. the 10mm BCO seemed exceptionally clear. Looking forward to star testing.

Edited July 19, 2023 by Richard N

[stormioV]

I think I'd like to try an Ortho in my SCT.  BCO 10mm seems a frontrunner for me?

[dweller25]

Orthos are excellent eyepieces, I have an insanely sharp 12.5mm Volcano top 🙂

[Piero]

Well, I'm probably the black sheep here but I much prefer modern designs with more eye relief and wider fov for all targets TBH.

For observing more details, I use a telescope with larger aperture.

I used to have a few Vixen HRs and they were excellent, although, as said above, 42 deg afov feels too restrictive to my eye.