Starbase 'Orthoscopic Plossls'

[Zeta Reticulan]

The Starbase four element ‘orthoscopic’ series of eyepieces are distributed by Takahashi Seisakusho Ltd. There are supposedly five in the range consisting of: 20mm, 18mm, 14mm, 9mm and 6mm focal lengths. The 6mm and 14mm versions are bundled with the Starbase 80 telescope package. 

The Starbase achromat and the eyepiece series are apparently both made by the Kubota Optical Corporation in Hanamaki, Japan. The eyepieces are not a traditional Abbe orthoscopic design and are purportedly an asymmetrical doublet defined and designated as an Orthoscopic Plossl (Orthoscopic/PL). They are recommended for use with focal ratios up to f/6. 

“In the early days, it was made by Cook in England and Steinheil in Germany. This is an achromat type eyepiece that combines two Ramsden lenses. A well-made Japanese-made eyepiece is an almighty eyepiece that can be used from low to high magnification because ghosts are not noticeable and spherical aberration and distortion are small. By the way, NIKON's orthoscopic eyepieces, which are still very popular today, were PL type” 

~ op cit (diagram and definition from the Scopetech webpage).

Etymologically the compound adjective ‘orthoscopic’ literally means corrected vision. Unlike most contemporary modern eyepieces the Starbase series probably aren’t edge-blacked. They feature a ‘retro’ volcano top without rubber eyeguards. The eyepieces each have a single high quality coating as opposed to being multi-coated (I'll return to this later). The proclaimed rationale behind using only a single coating of superior quality is that it gives much better transmission than relatively inexpensive mass produced multi-coatings. Except for the barrel undercut they have the vintage appearance of an erstwhile era. The AFOV varies between 43° and 53° throughout the range.

The 20mm has a 45° AFOV and 14mm of eye relief. I make the eye lens a decent 17mm with a 15mm field stop. I find this a quite pleasant eyepiece to use. Around 13-14mm is my preferred eye relief distance. The field stop is sharp and defined, as the stops are throughout the range. The chromed brass barrel is high quality with good baffling and has a filter thread. Although, to my chagrin, I discovered my broadband Explore Scientific OIII and Astronomik UCE-E filters would only thread in a small amount. This problem was the same with the other focal lengths. 

It should be enough when placed in a 1.25” diagonal. I would have concerns about it coming loose in a 2” diagonal or a Newtonian focuser. My Baader filters had no problems in any of the four eyepieces. Interestingly the ES OIII has no issues at all threading smoothly and completely into my 1.25” Tele Vue Everbrite and Baader BBHS diagonal nosepieces. So, no surprise there then with the known compatibility issues of Japanese filter threads! The end caps fit well and the undercut gave me no problems. In my f/5.8 Sky-Watcher Evostar 72ED DS Pro, at 21x for a 3.4mm exit pupil, it gave nearly a hundred and twenty nine arc minutes of true field of view. This is nigh on four and a third Full Moons and only around twelve arc minutes less than my 25mm Ohi-made Abbe orthoscopic. I could just about get the entire Coat Hanger (Brocchi’s Cluster) in the FOV. The 20mm eyepiece showed an abundantly bright, well contrasted image, displaying excellent transmission and on-axis acuity. However there is some lateral astigmatism approaching the field stop. I did expect this with the f/5.8 Evostar as it is a bit unforgiving with some eyepiece designs. I tend to observe mainly on-axis anyway so it didn’t really bother me. Apart from the thread issue the ES OIII worked well with the 20mm giving me a vivid view of M27 and nicely revealing the Eastern and Western Veil Nebulae. 

At 53° the 14mm has the widest AFOV,  and in my opinion it definitely shows. My first impression was of a very agreeable field of view for such a physically small eyepiece. I make the eye lens 15mm and the field stop at least 13mm. I find the 12mm eye relief to be quite comfortable. Eye placement is undemanding and the eyepiece has a good ergonomic feel about it. Although it also showed some astigmatism towards the field stop. The transmission was bright, well above average, and I even got a glimpse of M57 at 30x. When deployed in a 2x Vixen Deluxe Barlow for 60x it was equally sharp, the astigmatism had disappeared, and it displayed no vignetting. I found both Hercules clusters at 60x with ease and split several doubles including the beautiful γ Andromedae.

The 9mm has a 45° field and the 7mm eye relief is about average for its focal length. By comparison my 9mm Circle- T Abbe has a 7.6mm eye relief. When used in conjunction with the Vixen Barlow in my 72ED DS Pro the 9mm Orthoscopic/PL really came into its own as a planetary eyepiece. The Barlow slightly improved the close eye relief. Both Saturn and Jupiter were very sharp at 93.3x. Colour separation and contrast were excellent. The Cassini Division and some surface detail on Saturn were easily observed as was Titan. I was impressed with the amount of detail I could actually see as Jupiter approached transit. Although occasionally I thought I detected a tiny bit of scatter. The planet is quite bright and only a few weeks from opposition though. I was also using a Baader Neodymium filter in the diagonal nosepiece which may have contributed to this effect in some way. It was a damp and dew laden early morning session. With excessive humidity filters can often have a tendency to fog slightly in the nosepiece. I believe I also occasionally saw a hint of the reflection of my own cornea, which may be a consequence of the single coating. After some use this disappeared. In later sessions I didn’t notice either phenomena. The barrel undercut plays well in the Vixen Barlow as it has no compression ring. 

With only 4mm of eye relief and a 43° apparent field the 6mm Orthoscopic/PL is the least ergonomic of the quartet. Again, compared to an Abbe of the same focal length, it has almost a millimetre less eye relief. Images of Saturn and Jupiter used without a Barlow in the 72ED at 70x were very sharp and bright. The intensity of the rich colours and excellent contrast impressed me.  I was immediately quite taken with the 6mm O/PL, especially when used in the Vixen Barlow. The volcano top almost certainly contributed to the comparative ease of viewing and eye positioning. I’d expected it to be more demanding to use, so this was a pleasant surprise.  At 140x (with the Barlow) the 6mm O/PL gave an approximate 0.5mm exit pupil. I split ε Boötis and I thought it was one of the best views of the binary I’ve had so far this year. As Cassiopeia got higher in the sky I discovered ι Cassiopeiae also split beautifully. I’m convinced these views were enhanced by the above average transmission of the single coating. 

Saturn still looked excellent even when it was past transit. During the first session it wasn’t quite as sharp on Jupiter at 140x. This wasn’t surprising however as the seeing was only average and the transparency was relatively poor. What was surprising was just how well the 6mm performed on Jupiter at 140x in a 72mm ED doublet. In a later session of better conditions I could see what appeared like Ganymede’s shadow on the surface near the limb. I actually first witnessed this at 93x with the Barlowed 9mm. I knew Ganymede would eventually become visible as it transited the surface. I impatiently switched back to the 6mm as I wanted to view this emergence before I lost the transparency. Eventually I was rewarded with the bright point of light of Ganymede seemingly separating itself from the planetary limb.

The Starbase O/PL’s were originally acquired for my 102mm Sky-Watcher SkyMax Maksutov Cassegrain. Its focal ratio of f/12.7 should ameliorate any aberration problems that were noticed in the faster scope. The initial rationale behind buying these eyepieces was that they were relatively light in weight, ergonomic (I like volcano tops), and had good build quality. The whole SkyMax grab and go kit needed to be light and portable and fit into a small holdall-type bag.

The 20mm Starbase gave me a nice view of Saturn and Jupiter at 65x. It was when I started using the 14mm it started getting interesting. Although I did notice the undercut snagging occasionally when swapping eyepieces. The three screws of the Baader helical compression ring can often be a little finicky with barrel undercuts. The 14mm O/PL gave a fairly sharp 92.8x. The seeing was above average, but not as good as the previous night. Jupiter’s GRS was just noticeable near the western limb and would be about central at transit (03:20). Ganymede, Callisto, and Io were close together on the western side of the planet with Europa on the opposite side. I could perceive colour in the moons and discern some Jovian surface detail. As the planet rotated the GRS became more easily visible. I decided it was time for the 9mm ‘Orthoscopic Plossl’. At 144x I lost a lot of acuity and furthermore there appeared to be quite noticeable ghosting. Jupiter was very bright with a visual magnitude of -2.8.

Overall I like these 'retro' eyepieces. Although purists may find they perform better at f/8 or slower. However, they do have certain faults in my opinion. The single coating is probably the biggest contributing factor. The advantage is above average transmission, ideal for many deep sky objects. Unfortunately the single coating appears to be responsible for a fair amount of ghosting and light scatter. On the other hand, the colour separation, contrast and acuity are very good. Swings and roundabouts. 

[Don Pensack]

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.

 

Edited August 15, 2022 by Don Pensack

[Knighty2112]

I have the 6mm EP. Works well on lunar and planetary observations. The narrow fov does make it a little hard to work with, but for the price it is a good EP with its limitations none the less.

[Zeta Reticulan]

18 minutes ago, 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.

 

Thanks for the info Don. I suspected the single coating was an economic decision. Either that or the Starbase are just an old design.  I'm not sure that they're even edge-blacked, which may explain some of the scatter and ghosting I saw.

Edited August 15, 2022 by Zeta Reticulan

[Zeta Reticulan]

5 minutes ago, Knighty2112 said:

I have the 6mm EP. Works well on lunar and planetary observations. The narrow fov does make it a little hard to work with, but for the price it is a good EP with its limitations none the less.

I think the general consensus is that the 6mm is the best of the range. 

[Louis D]

1 hour ago, Don Pensack said:

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.

Well, Brandon eyepieces didn't seem to pass on the cost savings of single coating.  These 4 element eyepieces are $280!

[Zeta Reticulan]

39 minutes ago, Louis D said:

Well, Brandon eyepieces didn't seem to pass on the cost savings of single coating.  These 4 element eyepieces are $280!

They're probably really good single coatings lol.

[Don Pensack]

17 hours ago, Louis D said:

Well, Brandon eyepieces didn't seem to pass on the cost savings of single coating.  These 4 element eyepieces are $280!

Where they are made is a big part of the price, as well as the polish on the lenses.

Double the lens polishing time for a 3% improvement, and production costs increase 100%.

Coating the lenses is just a small part of production costs.

 

When I was referring to high-end, I was referring to Zeiss ZAO, Pentax XO, Astrophysics SPL, TMB Supermonos, etc., not the innumerable labels

for the Ohi Optics orthoscopics and the like at the lower price points.

Edited August 16, 2022 by Don Pensack

[IB20]

I had a shootout between the BCO & Starbase 6mms on Saturn with the 76DC recently; the Starbase showed a touch preferable contrast and seemed to control light scatter a bit better. It wasn’t by much and the seeing was quite poor so it’s something I’ll do again and on other targets in the future.

[Zeta Reticulan]

2 minutes ago, IB20 said:

I had a shootout between the BCO & Starbase 6mms on Saturn with the 76DC recently; the Starbase showed a touch preferable contrast and seemed to control light scatter a bit better. It wasn’t by much and the seeing was quite poor so it’s something I’ll do again and on other targets in the future.

Interesting. Both my 6mm BCO's are now toast. I've always thought the 6mm Starbase was the best of the bunch. I have an 18mm BCO, I'm tempted to get the 18mm Starbase now just to compare them. lol

[Ags]

These eyepieces look great. Ten out of ten for style.

[IB20]

16 minutes ago, Zeta Reticulan said:

Interesting. Both my 6mm BCO's are now toast. I've always thought the 6mm Starbase was the best of the bunch. I have an 18mm BCO, I'm tempted to get the 18mm Starbase now just to compare them. lol

I have the 14mm as it came with the Starbase 80 scope.  On axis it’s good but I remember seeing some edge curvature. 

I have a 9mm BGO so would like to compare a 9mm Starbase.

[Zeta Reticulan]

1 hour ago, Ags said:

These eyepieces look great. Ten out of ten for style.

They're nicely retro, and look and feel good. However, I think they work best in slower scopes. The 6mm and 14mm are probably the best of the range.

[Zeta Reticulan]

1 hour ago, IB20 said:

I have the 14mm as it came with the Starbase 80 scope.  On axis it’s good but I remember seeing some edge curvature. 

I have a 9mm BGO so would like to compare a 9mm Starbase.

I like the ergonomics of the 14mm, but it can suffer some edge distortion. 

Does your BGO look a bit like this? I think the BGO's were all Ohi. Totally different animal IMO. The BGO/Ohi would be far superior.

[IB20]

It’s this model. I found in comparison to the 10mm BCO it steals it in contrast and scatter control. Harder to look through though!

 

[Zeta Reticulan]

8 hours ago, IB20 said:

It’s this model. I found in comparison to the 10mm BCO it steals it in contrast and scatter control. Harder to look through though!

 

I think the Circle T and BGO's had Ohi glass.

[Roy Challen]

Good review and interesting thread overall. I do have a gap between my 7mm Meade RGO and 10mm BCO, which an 8 or 9 needs to occupy. Having had many different orthos over the years, I think the main difference between them is control of light scatter, the less of which helps with improved contrast. The BCOs are quite good in this respect, the 7mm Meade RGO I have is noticeably better than the 6mm BCO, I don't have any BGOs at the moment but I'd like a couple. The Zeiss CZJs I had some years ago I recall were even better still - should never have sold them. I am very comfortable with the short eye relief of orthos so they are my preferred EPs whether for solar or planetary observing. It's good to see that they're still being made.

Edited August 20, 2022 by Roy Challen

[Roy Challen]

22 hours ago, Zeta Reticulan said:

Interesting. Both my 6mm BCO's are now toast. I've always thought the 6mm Starbase was the best of the bunch. I have an 18mm BCO, I'm tempted to get the 18mm Starbase now just to compare them. lol

What do you mean by toast? My 6mm is good but gives a higher mag in my achro than is usually useable most nights. It's great for close double splitting though.

[Zeta Reticulan]

3 minutes ago, Roy Challen said:

Good review and interesting thread overall. I do have a gap between my 6 and 10mm BCOs, which an 8 or 9 needs to occupy. Having had many different orthos over the years, I think the main difference between them is control of light scatter, the less of which helps with improved contrast. The BCOs are quite good in this respect, the 7mm Meade RGO I have is noticeably better than the 6mm BCO, I don't have any BGOs at the moment but I'd like a couple. The Zeiss CZJs Inhad some years ago I recall were even better still - should never have sold them. I am very comfortable with the short eye relief of orthos so they are my preferred EPs whether for solar or planetary observing. It's good to see that they're still being made.

Thanks. I'm a big ortho' fan myself. FLO sell the Ohi now. 

I have a few under different brands.

[Zeta Reticulan]

2 minutes ago, Roy Challen said:

What do you mean by toast? My 6mm is good but gives a higher mag in my achro than is usually useable most nights. It's great for close double splitting though.

They both mysteriously developed debris in the field of view. I couldn't clean it. I think it migrated from the rubber around the field stop. 

[Roy Challen]

2 minutes ago, Zeta Reticulan said:

Thanks. I'm a big ortho' fan myself. FLO sell the Ohi now. 

I have a few under different brands.

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.

[Roy Challen]

2 minutes ago, Zeta Reticulan said:

They both mysteriously developed debris in the field of view. I couldn't clean it. I think it migrated from the rubber around the field stop. 

Ah, I see. Have you not tried to dismantle to clean? A true Abbe is a cemented triplet and singlet so pretty easy to clean and hard to get wrong when reassembling. Give it a go, or send them to me, I certainly don't mind trying!

[Zeta Reticulan]

1 minute 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.

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

[Zeta Reticulan]

Just now, Roy Challen said:

Ah, I see. Have you not tried to dismantle to clean? A true Abbe is a cemented triplet and singlet so pretty easy to clean and hard to get wrong when reassembling. Give it a go, or send them to me, I certainly don't mind trying!

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

[Roy Challen]

1 minute ago, Zeta Reticulan said:

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

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?