Starbase 'Orthoscopic Plossls'

[Roy Challen]

3 minutes ago, Zeta Reticulan said:

I threw them away and used the barrels on other EP's. I'm tempted to get another one day. 

Blimey! If you have any other 'dirty' eyepieces, do please PM me before thinking about binning them!

[markse68]

10 minutes ago, Zeta Reticulan said:

I threw them away and used the barrels on other EP's. I'm tempted to get another one day. 

Hi Zeta, the BCO 6mm has had at least 2 versions- the latest has the lenses in a stalk housing that is easily removed for cleaning. The earlier had flush mounted lenses I think. 

Mark

[Zeta Reticulan]

4 minutes ago, markse68 said:

Hi Zeta, the BCO 6mm has had at least 2 versions- the latest has the lenses in a stalk housing that is easily removed for cleaning. The earlier had flush mounted lenses I think. 

Mark

OK, thanks.

[Roy Challen]

17 minutes ago, markse68 said:

Hi Zeta, the BCO 6mm has had at least 2 versions- the latest has the lenses in a stalk housing that is easily removed for cleaning. The earlier had flush mounted lenses I think. 

Mark

Thanks for the link, I probably read it back then but good to reflect every now and then. I definitely concur with John's view on the 10mm BCO, it's my most used planetary EP even though it 'only' gives a max mag of 125x in my frac or mak. Enough for Jupiter at least, but maybe that's why I need a 9mm...and an 8!

[IB20]

35 minutes ago, Zeta Reticulan said:

They're not cheap, that's for sure. Cheaper than Tak's though.

How do you find the Tak 6mm? I’m looking for a high end 6 and I’m a sucker for Tak gear.

[Zeta Reticulan]

16 minutes ago, IB20 said:

How do you find the Tak 6mm? I’m looking for a high end 6 and I’m a sucker for Tak gear.

Ergonomics are very good, it feels like a slightly larger 6mm ortho'. There are a couple of extra degrees of field, probably to aid location. Contrast is excellent, but slightly less transmission than a 6mm Ohi.

[Don Pensack]

18 hours ago, Roy Challen said:

Yes, I have seen them but they're not cheap are they? I'd rather wait for a nice example to pop in the for sale section.

Not, I suppose, a giveaway bargain, but £83 is a pretty inexpensive eyepiece.

It's a nice Japanese eyepiece for the price of a Chinese eyepiece.

FLO has a lower price than many of the EU dealers.

[Roy Challen]

24 minutes ago, Don Pensack said:

Not, I suppose, a giveaway bargain, but £83 is a pretty inexpensive eyepiece.

It's a nice Japanese eyepiece for the price of a Chinese eyepiece.

FLO has a lower price than many of the EU dealers.

Agreed in general, but everything is relative. Most of my eyepieces were bought second hand, some for as little as £10. Even those I've bought new were less than £60. Most expensive ep I have right now is my Meade RGO which was £70 Actually most of my astro equipment was bought second hand.

Unfortunately, I am 'transitioning'  between employers, so everything is expensive!

[Zeta Reticulan]

19 hours ago, Roy Challen said:

Nice collection ☺️, I had a couple of the 0.965 MCs but didn't find them as good as the alternatives. I notice there is no 7mm in your set. They don't do one anymore? 

Tak' have recently ceased production of their current ortho's and the LE's. There were 7mm ortho's in the past but the most recent series was: 32, 25, 18, 12.5, 9, 6 & 4mm. Maybe they will re-introduce a 7mm in a new series.  Ohi have a 7mm, mine is a KK.

Some are old 'Astro Hutech'. 

Edited August 21, 2022 by Zeta Reticulan

[Zeta Reticulan]

38 minutes ago, Don Pensack said:

Not, I suppose, a giveaway bargain, but £83 is a pretty inexpensive eyepiece.

It's a nice Japanese eyepiece for the price of a Chinese eyepiece.

FLO has a lower price than many of the EU dealers.

I agree it's a pretty reasonable price for an Ohi ortho'. Although I don't see any real difference with TS Optics. FLO is much more convenient for UK customers of course. I'm hoping one day the Chinese will learn how to make orthoscopics properly.

I'm pretty convinced this was made in China. Could do better lol. They'll probably get there eventually.

[Andrew_B]

On 15/08/2022 at 19:31, Don Pensack said:

The argument for single layer coatings has to do with axial light scatter, not transmission.

Transmission with single layer coatings is likely to be ~93-94% at best.

With multicoatings on all surfaces, it could be ~97-98%.

The biggest difference is in the UV-deep violet, where the difference is larger.

That difference is completely unimportant unless the greater internal reflection causes ghost images.

Otherwise, a 4% difference is in the low hundredths of a magnitude, especially unimportant for lunar/planetary usage.

Note, however, all the ultra high-end planetary eyepieces have been multi-coated, so a single layer coating is more likely to be a cost-cutting decision.

 

Do you know if anyone has examined the issue in detail to measure differences in scatter or other properties between single and multi-coated eyepieces?

My understanding is that a good broadband AR coating requires quite a few layers, the thickness of which can vary enormously and must be precisely controlled not only to perform as designed but also to prevent irregularities in the surface from multiplying. If that's the case then I can see how a single coating might be preferable to a cheap and poorly done broadband coating but I can't remember seeing an in-depth comparison to back this up.

[Roy Challen]

3 hours ago, Zeta Reticulan said:

Tak' have recently ceased production of their current ortho's and the LE's. There were 7mm ortho's in the past but the most recent series was: 32, 25, 18, 12.5, 9, 6 & 4mm. Maybe they will re-introduce a 7mm in a new series.  Ohi have a 7mm, mine is a KK.

Some are old 'Astro Hutech'. 

Yes, I had heard this. Great shame. As an ortho fan, and plossl too, I've no interest in the trend for wide field eyepieces. The SAEP often leaves me exasperated with anything above 60degree AFoV. The subject of multicoatings vs single coatings, mentioned above, is interesting though, and I do agree with @Andrew_B in his post above 

[Zeta Reticulan]

54 minutes ago, Roy Challen said:

Yes, I had heard this. Great shame. As an ortho fan, and plossl too, I've no interest in the trend for wide field eyepieces. The SAEP often leaves me exasperated with anything above 60degree AFoV. The subject of multicoatings vs single coatings, mentioned above, is interesting though, and I do agree with @Andrew_B in his post above 

Not many of my eyepieces suffer kidney beaning, at least not for me. I just think for planetary observing it's difficult to beat something small like a Plossl or ortho'. Notwithstanding you can fit a fair few in a pocket. 

[Louis D]

I picked up a used 25mm Edscorp volcano top Abbe ortho, and haven't been all that impressed so far at f/6.  I took it apart and cleaned it, tried all four possible orientations of the two lens groups, and the way I received was the best, so it's just the execution or design.  Perhaps this design works better only at shorter focal lengths.  Since I can see the astigmatism in my observing eye at 1mm exit pupil, I still need to wear eyeglasses even with short focal length eyepieces, so the field narrows even more.  This becomes a royal pain on my manual alt-az mounts.

Notice how the Edscorp isn't all that great across the field sharpness-wise.  I'll have to check sometime at night to see if contrast, stray light control, and on-axis scatter are better than in my other eyepieces in this range.

[Zeta Reticulan]

I'm guessing the 'Edscorp' is Ohi made? I used a 25mm Astro Hutech pair in a bino but in a slow scope. I might give one of them a spin at f/6 and see what they're like. 

[Stu]

@Roy Challen somewhere I have a 7mm BGO which shows a strange effect in the centre of the view, a slight distortion or newton rings if I recall correctly. I believe the problem is the separation between elements is not enough so they are touching. If I can find it I’ll happily send to you to see if you can dismantle it and get it sorted? Any use?

[Andrew_B]

18 hours ago, Zeta Reticulan said:

I agree it's a pretty reasonable price for an Ohi ortho'. Although I don't see any real difference with TS Optics. FLO is much more convenient for UK customers of course. I'm hoping one day the Chinese will learn how to make orthoscopics properly.

I'm pretty convinced this was made in China. Could do better lol. They'll probably get there eventually.

Is that one of the Kson orthos?

I've got a pair of the 16.8mm ones for my binoviewer and I was pleasantly surprised by the image quality. The main negative point is that they could probably do with better control of stray light as there can be a halo outside the field stop when viewing bright objects. If I was feeling brave I'd consider taking them apart and applying a bit of matt black paint to see if that helped but it's not a showstopper and I don't want to end up making things worse. They're not going to trouble a good Japanese ortho but the pair only cost me £52 so I'm not complaining!

[Zeta Reticulan]

2 hours ago, Andrew_B said:

Is that one of the Kson orthos?

I've got a pair of the 16.8mm ones for my binoviewer and I was pleasantly surprised by the image quality. The main negative point is that they could probably do with better control of stray light as there can be a halo outside the field stop when viewing bright objects. If I was feeling brave I'd consider taking them apart and applying a bit of matt black paint to see if that helped but it's not a showstopper and I don't want to end up making things worse. They're not going to trouble a good Japanese ortho but the pair only cost me £52 so I'm not complaining!

They're sold under a variety of names.

I don't know who actually makes them. I think it's a good attempt at an ortho'. I'm not holding my breath for relatively good quality mass produced Chinese orthoscopics yet though. I think Abbe orthoscopics are too specialist for any Chinese manufacturing investment in a world of 'Plossls' and wide angle eyepieces.

[Don Pensack]

21 hours ago, Andrew_B said:

Do you know if anyone has examined the issue in detail to measure differences in scatter or other properties between single and multi-coated eyepieces?

My understanding is that a good broadband AR coating requires quite a few layers, the thickness of which can vary enormously and must be precisely controlled not only to perform as designed but also to prevent irregularities in the surface from multiplying. If that's the case then I can see how a single coating might be preferable to a cheap and poorly done broadband coating but I can't remember seeing an in-depth comparison to back this up.

The 'evidence' I've seen is almost completely anecdotal, as an endlessly-repeated comment from Vernonscope about Brandon eyepieces and why they have single layer anti-reflection coatings.

The coatings explained:

https://www.edmundoptics.com/knowledge-center/application-notes/lasers/anti-reflection-coatings/

https://www.edmundoptics.eu/knowledge-center/application-notes/lasers/an-introduction-to-optical-coatings/

I've read over a hundred studies about this, and the conclusions investigators come to are that the scatter is almost totally dependent on the smoothness of the surface the coatings are put on, not the coatings themselves.

When you stop and think about it, if the surface reflects LESS light, how could scatter be MORE unless the surface becomes rougher with each layer?

I guess I could see that a rough lens surface will scatter more light, but it's hard to see how a multi-layer coating will scatter more light unless the multicoating adds to the roughness of the coated surface.

That is possible, but comparing a cheap eyepiece with multi-coatings to an expensive eyepiece is likely comparing surface smoothness more than it is the coatings.

Brandon eyepieces have low scatter because of a higher end lens surface roughness figure. 

And Zeiss uses multi-coatings but has superior lens surface polish.

This explains the main rating used for surface smoothness:

https://www.advancedoptics.com/scratch-dig-specifications.pdf