Carton Japan GEN 10.5mm eyepiece

[F15Rules]

I just received today an interesting vintage Carton branded 10.5mm SWA eyepiece.

There is not a huge amount of info on the internet, but what reviews there are, are good. The eyepiece was also sold under the Orion Megavista name and seems to have been offered in just 2 sizes, the 10.5mm here, and also a 16.8mm version. Both have a field of view of c68-70 degrees, and the 10.5mm has 10mm eye relief.  

Carton is not the best known brand, but everything I have ever seen made by them was of very good quality.

Perhaps best known for their long focus achromatic lenses, Carton offered, in the late 80s, a beautiful range of long focus  achromatic refractors of top quality, in my opinion better than the Unitrons so coveted in the US especially.

Richard Day of Skylight Telescopes acquired some pristine new old stock Carton 100mm objectives for installation into his well regarded Skylight F15 100mm refractors a few years ago.

The GEN 10.5mm eyepiece I have just bought was sold as "new old stock". However it is clearly not new, and has a scratch on the chromed brass barrel. The rubber eyecup has also some age related colour fading, although works perfectly. The optics do look excellent though, with a very sharp field stop. Overall I would describe it as being in excellent vintage condition.

Build quality is very nice, with a nice solid "heft' in the hands. It's not a heavy eyepiece as it's not that big, but it is larger and heavier than most plossls.

I'm very much in "selling mode" at the moment, but I've made 2 recent purchases, both for eyepieces which intrigued me (more about the other one to follow next week when I receive it?). I admit that I am a sucker for nice old Japanese made glass!?.

We are away for the weekend so it might be early next week, skies permitting, before first light, but I shall put this head to head with my beloved Pentax 10.5mm XL SWA (65deg), which is the eyepiece I've owned for longest (3 or 4 years).

I'll post up my thoughts then..☺

Dave

 

[Louis D]

I believe you'll find eye relief to be much tighter than with your Pentax XL.  Looking forward to reading about your impressions of this eyepiece.

[F15Rules]

I think you're right Louis. The XL has 20mm if ER, so I know the Carton will be a good deal less.

I do have a Fujiyama 5mm ortho which is very tight on ER, but the Carton has a nice eyecup which I can  rest my eye on, and I think I should be able to cope with the 10mm. We'll see..

Dave

[michael.h.f.wilkinson]

I am curious how this EP holds up to the XL 10.5. I have never looked through the either, but have a series of Pentax XWs, including the 10. These are outstanding. An ER of 10mm would not be sufficient for me, however.

[Saganite]

Excellent find Dave, and look forward to your thoughts on its performance.

Steve ( another old sucker for vintage Japan made glass)..

[John]

Look forward to reading what you think of it Dave - it looks in nice condition.

I had the 16.8mm quite a while back with the same branding as you know. They are nicely made

There was a rumour a while back that Tak might have either made or sold them but I've never seen that substantiated.

[Doc]

Interesting Dave, I have never looked through one of these but I have a  Carton refractor and that was very good indeed. They made quality stuff so I have no doubt the eyepie e should be good.

[F15Rules]

Well, I have now had a couple of shortish but satisfying sessions comparing the Carton 10.5mm eyepiece to my Pentax XL 10.5mm. Here are my thoughts so far:

Aesthetics, build and appearance

• The Carton ep is in very good condition, it looks, "in the flesh" a lot nicer than in my poor photos (sorry, cheap Android phone).
• The eye relief is about 10mm. The Pentax XL 10.5mm is 20mm, so a significant difference. The Pentax feels a little more comfortable in use, but that could be just as much due to my familiarity with the Pentax as to the real difference between 20mm and 10mm: however, I should point out that I don't wear glasses to observe, and I think that 10mm ER would likely be too little for observers who do wear glasses, whereas the Pentax would probably be fine.
• Build quality: both eyepieces are very well put together. The Pentax, although an older eyepiece now, is an altogether bigger, and so heavier, beast than the Carton. The rubberised wider body portion of the Pentax also makes it easier to hold in colder temperatures, versus the Carton. The Carton, though, is very solid feeling, with a nice "heft" to it, and heavy chromed brass barrel, which is smooth, with no undercut - a definite plus in my book! The Pentax does have an undercut, but it is less problematic in getting stuck in diagonals, in my experience, than other brands, for example Tele Vue.  Your experience may differ, but I much prefer either smooth nosepieces, or safety kerfs such as Morpheus. I find the Explore Scientific tapered barrels on some of their eps even worse than undercuts.
• The Pentax has a much bigger eyelens than the Carton, but I don't find that a problem: the Pentax also has an adjustable screw up/down eyecup, which I tend to use fully screwed out for best comfort for myself.
• The Carton has a fairly stiff fixed rubber eyecup - the one on this example is faded a bit, but 100% fully functional. I quite like using winged eyeguards for higher power eyepieces, and I have one which I use with my orthos which fits nicely if I remove the original one. I'll post up pictures later this evening to show how it looks.
• The Carton, with it's fairly long, smooth and quite narrow body reminds me of a "decloaked" Explore Scientific or Meade SWA or UWA eyepiece - it's a minimalist look that I actually really like.

Optical Performance

I tested both eyepieces in the same scope, my FS128 apo, and in the same diagonal, a Baader T2 32mm prism. I viewed the following objects through both eyepieces, in conditions of pretty good seeing, with little oscillation of the defocused stellar images. Objects viewed include:

Porrima (Gamma Virginis), separation 2.9" - a renowned favourite, just beautiful to look at.

Theta Virginis, triple, see here: https://bestdoubles.wordpress.com/category/4-choose-a-constellation/virgo/ - not especially an easy object as the B component is only mag 9.4 and quite close to the primary, and the more distant C component is about 70" out, and only of magnitude 10.4.

Izar (Epsilon Bootes), separation 2.9", see here: https://en.wikipedia.org/wiki/Epsilon_Boötis - another showpiece spring double system.

I also viewed several more pairs, but the above give a good representation of what I saw - and they are lovely objects to observe, whichever higher power eyepiece you use.

• Both eyepieces show almost exactly the same size fov. The Carton doesn't carry it's field of view on the eyepiece body, although I have ready elsewhere that it is between 65 and 70 degrees. The Pentax XL 10.5mm is a 65 degree unit (the later XWs being 70 degrees). Based on what I believe is an accurate rating for the Pentax, ie 65 degrees, I would say that the Carton is almost identical and would be happy to place the Carton as a 65 degree eyepiece.
• Contrast: Pentax' are known for their excellent contrast, and I was therefore delighted to see that the Carton holds it's own very well against the XL. On the two nights I compared the two eyepieces, I could not in all honesty say that either beat the other in this area. They were VERY close.
• Light Scatter: again, in this area, both eyepieces were very closely matched, both offering very good control of scattered light. Just a note here: for interest I also compared one of my Fujiyama 12.5 mm orthos with the other two, as these orthos are exceptionally good in controlling scattered light (as were the Baader Genuine Orthos on which they were based): of the range, the 12.5mm in BGO, Antares HD Ortho and Fuji have always, in my opinion, been the pick of the bunch. In fact, I sold my very good 6mm Fuji ortho as I could get comparable results with a barlowed 12.5mm Fuji whilst benefitting from improved eye relief whilst doing so. In this comparison I found that the Fuji 12.5mm was slightly, but definitely, ahead of the Pentax and Carton in terms of light scatter: the Fuji has 10.4mm eye relief according to the specs, so very similar to the Carton (10mm) - if you prefer more eye relief, though, you would prefer the Pentax over either of these others.
• On axis sharpness - all three of the above eyepieces offer razor sharp on axis images - if, like me, you use a sidereal driven mount, these will stay razor sharp in the centre of your FOV for as long as you want to look at them. If you use a Dob or Altaz mount, you might prefer to have to move your mount less by using either the Carton or the Pentax vs the Ortho.
• Edge of field: here, the Carton and Pentax are again hard to separate - if forced to pick one, I would say that by a hairs' breadth the Pentax is ever so slightly sharper right at the edge of the field (this is at F8.1) - in a shorter focal length Dob, for instance, the Pentax might well pull away a bit. But in the Tak, I was genuinely surprised at how good the Carton is across virtually the whole field of view.

Summary

I really enjoyed some prolonged viewing of the above star systems with all the 3 eyepieces mentioned. I should also say that all 3 eyepieces barlow well, too (I used a high quality Celestron Ultima Japan barlow, which although advertised as being a 2x magnification barlow, I believe actually delivers more like 2.2x). I am pleased about this actually, as with the Carton and Pentax 10.5mm it is delivering, with the Ultima barlow, about 218x in the Tak, a very nice power for many doubles, whilst maintaining decent eye relief.

Although the ortho will also barlow really well with this unit, the slight trade off for getting x183 from a 12.5mm eyepiece, is the much smaller 42 deg fov vs the 65 deg of the Pentax/Carton pair - that can make longer viewing sessions more preferable in the wider field eps, although to really squeeze the best possible low scatter, high contrast image out of the scope, the ortho is hard to beat.

I plan for now to keep both the Pentax and the Carton, even though they are both 10.5mm focal length. I want to check them both against each other on the Moon, and also Jupiter and Saturn later in the year, hopefully.

But I can heartily recommend either of these great eyepieces, if you can find one - for between c £50 -£60 for a Carton and £100 or so for the XL, they represent great value and performance.

Thanks for reading.

Dave

[Saganite]

Interesting report with a lot of good information Dave, many thanks.