Orthoscopics versus Plossl's?

[Guest]

I know that both Orthoscopic and Plossl eyepieces have two sets of twin lenses in their construction.Although in different configurations. That in it's self would make the two perform differently. But how different. It is said that the Orthoscopics would have a conservative field of view. How is that compared to a Plossl's?

They are both said to perform well on planetary observation.

One commented recently recommending a 7mm Orthoscopic eyepiece to observe Sirius in an attempt to see The Pup star. This was because of the narrower field of view reducing glare and increasing the contrast. Is this right? Would a 7 mm Plossl or Orthoscopic eyepiece do the same job compared to wider field multi element modern eyepieces? Is there still a need for one or two Orthoscopics or Plossl's eyepieces in any worthy observers armoury?

[John]

I've found that good orthoscopics such as the Baader Genuine Orthos, Astro Hutech's and Fujiyama's have a bit less light scatter than a comparable plossl. The orthos tend to have apparent fields of view of around 42 degrees wheras plossls provide 50 or 52 degrees.

For me, it was the low scatter combined with sharpness that gave the orthos the edge on spotting Sirius B. The glare from Sirius A is the main obstacle to seeing the B star so as much control of this as possible is needed.

That said, I don't have any orthos or plossls at the moment. The Pentax XW's have been the best wide field, multi-element eyepiece for spotting Sirius B and they seem to get very close to orthos in this respect.

[Louis D]

Here's an eyepiece types diagram to help you visualize the different classic types.  The original orthoscopic uses a singlet and triplet while the original plossl uses two doublets.  Unlike a symmetric (dialsight in the diagram?), the two doublets are not the same.  Scatter is as much about the quality of the lens polish as it is about the particular design.  It's one of the reasons Pentax XO and Zeiss Abbe orthos are so good.  Improved polish requires more and longer polishing steps increasing cost.

[Timebandit]

 

  

Hello, I have and use both plossl and Ortho. But only in the refractor and mainly for planetary and lunar. I did like the good old plossl, until I tried some Baader Genuine Ortho. These Orthos really did get me hooked onto using a good quality Ortho in the refractor. They seem to concatenate the eye on the target better IMO due to their narrow field of view. And  a good Ortho when it comes to sharpness and contrast really does take some beating and optically they can take on eyepieces costing many many times their cost. If you have a refractor and love planetary and lunar viewing that are tack sharp with great contrast then IMO the Ortho of quality should be in your eyepiece case, and best of all they are very sensible money☺

[jabeoo1]

6 minutes ago, Louis D said:

Scatter is as much about the quality of the lens polish as it is about the particular design.  It's one of the reasons Pentax XO and Zeiss Abbe orthos are so good.  Improved polish requires more and longer polishing steps increasing cost.

If its scatter you are wanting to minimise then Brandon eyepieces have a very good reputation for controlling low angle light scatter.  The 6mm is an option or a longer focal length with a barlow.  Not cheap though but obtainable with patience on the secondhand market.   

[nightfisher]

I have use a lot of Plossl ep`s and a good few orthoscopic, its a single horse race for me i would choose an ortho every time, if you could find a BGO 7mm snap it up

[chiltonstar]

With my very long focal length Mak, I've certainly found orthos very good for controlling scatter on Sirius A/B and Antares, but the eye relief is very small though which can be a problem with a scope with the EP at the back end.

Chris

[jetstream]

9 hours ago, Grumpy Martian said:

This was because of the narrower field of view reducing glare and increasing the contrast. Is this right? Would a 7 mm Plossl or Orthoscopic eyepiece do the same job compared to wider field multi element modern eyepieces? Is there still a need for one or two Orthoscopics or Plossl's eyepieces in any worthy observers armoury?

Keeping Sirius at bay really helps with seeing its companion through a narrow TFOV. Things depend on focal length a bit, ie the 21E hyperwide does a great job in the 1828 fl 15", but in my 10" I narrow up the field with my tight zoom.

Any eyepiece that has scatter issues just won't help... TV plossls and good orthos have very good scatter control as do many quality widefields such as Xw's, Delos and Ethos.

Another good test for scatter is trying to view the Flame neb near Alnitak.

So yes, I personally believe that orthos and plossls are a great asset to have- I own 5 orthos and 4 TV plossls.

[Don Pensack]

On 1/31/2017 at 08:39, Grumpy Martian said:

I know that both Orthoscopic and Plossl eyepieces have two sets of twin lenses in their construction.Although in different configurations. That in it's self would make the two perform differently. But how different. It is said that the Orthoscopics would have a conservative field of view. How is that compared to a Plossl's?

They are both said to perform well on planetary observation.

One commented recently recommending a 7mm Orthoscopic eyepiece to observe Sirius in an attempt to see The Pup star. This was because of the narrower field of view reducing glare and increasing the contrast. Is this right? Would a 7 mm Plossl or Orthoscopic eyepiece do the same job compared to wider field multi element modern eyepieces? Is there still a need for one or two Orthoscopics or Plossl's eyepieces in any worthy observers armoury?

Both can produce excellent images if well-made, but generally the Abbe orthoscopic will have a narrower field of view, say 42° instead of 50°.

Narrower fields don't yield better sharpness or contrast--it's the design.  The sharpest eyepieces I've ever used have 62° fields.

[Guest]

What eyepieces were the 62° field Don?

[John]

3 hours ago, Grumpy Martian said:

What eyepieces were the 62° field Don?

My guess would be the Tele Vue Delite

 

[Louis D]

Don's a vendor (EyepiecesEtc.com).  Though he is well regarded in the astro community, he has to be cagey about endorsing products online.

[Moonshane]

Having a 7 & 11 mm Delite I am certainly impressed and intend doubling these up for BVs if I can find used ones and adding a 9 & 13mm even if I have to buy new. At 7mm that would be my recommendation.  that said am bgo is a lot cheaper.

[Rick_It]

I have compared a lot a TAL Plossl 6.3mm with a 7mm Volcano Top Ortho. This is a fair comparison, being the two design of a comparable quality (I'm not comparing a Takahashi Abbe MC with a super cheap chinese plossl).

Here what I found:

- The Volcano Top is way more comfortable to use, because of the combinations of greater eye reliefs and the Volcano housing.

- The Ortho is slightly sharper, but the difference is not too high. It was quite noticeable on Jupiter, for example, in looking at the fine details on the NEB and SEB which were easier to see on the Ortho. Difficult to say how much this difference depends from the pure optical quality of the eyepiece and how much from the comfort to use (I do not have to squeeze my eye super-close to the eyepiece with the Ortho).

- No ghost images, reflections or other annoying things in both eyepieces (big difference with some cheap plossl).

The bottom line is that ortho is more comfortable but if you look at what you could see, more or less they are on par, with a slight advantage for the Ortho. The point is that the only good quality plossl around are from televue. I suspect that any ortho compared with a low cost chinese plossl will result to be much better, not because of the superiority of its design, but because of a better quality / lens blackened etc.