February 21, 2016: A Nine Dollar Eyepiece? The 23mm Vite Aspheric Eyepiece

After reading some very positive reviews about them in this Cloudy Nights thread, I decided to buy some super-duper-cheap eyepieces, for no other reason than to satisfy my curiosity about them.  Well, and because I’m super-duper-cheap, too.  These are the Vite aspheric 62-degree EPs, which cost just NINE BUCKS each.  Incredibly, some of the reviews they are receiving there are comparing them favorably to TeleVues!  I find that difficult to choke down, but for nine bucks, sure, I’d give it a shot.

The reason they’re supposed to be so good, and not just “for nine bucks” good, but actually good, is because of the “aspheric” part of their name.  Aspherization reduces visual defects in the EP, specifically one called spherical aberration.  As a prime example in the telescope end of things, Maks are supposed to have all spherical surfaces for its optics – both sides of the meniscus, the primary, and the secondary, which is just an aluminized spot on the inside of the meniscus.  This is because it is easier to make a spherical surface, and it’s easier to make a spherical surface very accurately, due to the fact that when grinding glass, it naturally takes the shape of a sphere.  This also holds down costs as well, to a certain extent, anyway, as it costs more to take a spherical mirror and aspherize it to the paraboloidal shape that is used in virtually all Newtonian telescopes.

However, as I learned when I visited their factory showroom this summer, Questar, the Rolls Royce of telescopes, aspherizes the meniscus at the secondary spot to eliminate the spherical aberration.  This means that the curve on it is something other than part of a sphere.  It could be part of the curve of an ellipse, a parabola, or a hyperbola – I don’t know. Some folks over at Cloudy Nights seem to think that the ever-popular Synta Maks have this done to some part of their optics as well.

On the eyepiece side of things, for example, Plossls consist of four symmetrical convex lens elements.  Each side of the four elements is ground into a spherical shape of a certain, precise radius.  The Vites only use three elements, but one element is aspherized.  Whatever non-spherical curve it is, this aspheric element is actually made of clear acrylic plastic.  This means that it isn’t ground; it’s simply molded into the proper shape.  Because it’s much easier to inject hot plastic into a mold than to grind a piece of glass down, the EP is incredibly cheap at $9.

Because it’s acrylic, the coating process is also different – and, of course, cheaper – resulting in the eyepiece not being “fully multi-coated”, but instead, just “fully coated.”  In fact, over at that Cloudy Nights thread, some have mentioned rubbing the coating(s) off of the plastic lens during cleaning.  Regardless of the cheap plastic and lesser coatings, the EP is still supposed to be very sharp, especially with slow focal ratio scopes like my f/12 Mak.  That’s not too much of a surprise, given that everything looks good in a Mak.  I’m more interested in how well it’ll do in my f/5 refractor.

The Vites come in just three focal lengths, 23mm, 10mm, and 4mm.  Notably, a few months ago, Orion and Skywatcher began supplying Vites as the standard stock eyepieces that come with some of their scopes, replacing the approximately 45-degree AFOV Kellners that they used to come with.  Orion is shipping the 10mm and 23mm Vites with all the telescopes mounted on their latest goto mount, the Starseeker IV:  the 80mm refractor, the 114mm, 130mm, and 150mm newts, and the 127mm and 150mm Maks.  Interestingly, for whatever reason, Orion calls these 60 degree EPs, not the 62 that’s silkscreened onto them in the eBay listing, above; but they are easily recognized by their gold banding.  Skywatcher is also shipping these same 10s and 23s with their 80mm refractors, and their 114, 130, and 150mm Newts.  So it seems there may be something to these EPs being pretty good after all.

The Cloudy Nights thread says that the 4mm EP is pretty much worthless.  It has the 3 elements that the other two have, but it also has a Smyth lens on the bottom – which is sort of like a Barlow lens, but different.  According to them, the view is terrible, being very fuzzy everywhere except the dead center of the FOV.  My seven eight loyal blog readers already know that I have a glut of EPs at the 10mm focal length – three of them, to be precise, not including a fourth at 9.7mm and a fifth at 9mm.  So I won’t be buying either the 4mm or the 10mm.  That leaves the 23mm.

I decided to get a pair of the 23mms for binoviewing.  While I do love the nice sharp 30mm Plossls that came with my Arcturus binoviewers, they top out at 160x or so with the 3x nosepiece.  For whatever reason, the pair of 10mm Sirius Plossls I have give a slightly dimmer view, which, when I asked about this, some folks at Cloudy Nights chalked up to the 10s giving a slightly higher magnification than the triply barlowed 30s (which should work out to be exactly the same as the 10s) due to an increase in the focal length of my scope when no nosepiece is used.  While 160x is nice, I wanted to see if I could push the magnification in the binos just a bit past that, again, just for fun.  The 23mms will give me about 210x, and a slightly larger field of view at that magnification to boot.

I’m also curious to see if the 23mm works well in my f/5 refractor, because, again, any EP works great in my f/12 Mak.  You might think that I would be using a 32mm Plossl in the ST-80 as my initial widefield finder eyepiece.  After all, the 32mm Plossl would give me 12.5x and a very wide 3.92 degree TFOV – the widest possible unless I swapped out the focuser for a 2-incher.  But the 32 also gives me an exit pupil of 6.4mm.  That is larger than the entrance pupil in my middle-aged eyes, which is probably about 5mm.  The result is that if I were to use the 32 in my ‘frac, I would be losing a significant portion of the light that the 80mm objective is sending my way.  Instead of it entering my pupil, the light would just splash off of my iris, wasted.

Instead, I use a 25mm Plossl, which gives me 16x and a 3.25 degree TFOV – still pretty good – and a 5mm exit pupil, which is probably a perfect match for my aging pupils.  The 23mm Vite will give me 17x, and a 4.6mm exit pupil, both of which are still just fine.  But it will also expand my TFOV to 3.57 degrees.  Since the area of a circle is Pi times the radius squared, the Vite’s TFOV will be 20% larger than the 25mm.  Not too shabby.

I ordered the pair at the end of January, and was told to expect them after mid-March, as they must be on a slow boat from China, making their way over the Pacific to me.  But I got them within two weeks.  That boat musta been a hydrofoil.

Looking at them, they look nice, with that lovely gold band.  But feeling them, it feels like for nine bucks, I might have overpaid.  This eyepiece is very plastic, and incredibly light.  The black and gold body is plastic, the soft top, which neither folds up, retracts, or moves, is rubberized plastic, and the silvery barrel – with the obnoxious safety recess – is plastic, too.  But the inside of the barrel is deep black, the barrel is threaded for filters, the field lens and the eye lens both have a purplish tinge, indicating some kind of coating on them, and it came with two endcaps to protect both ends.  Um, so far, so good?

Amazingly, I avoided the astronomer’s curse – it was actually clear out the night I got these!  On the other hand, it was 12 degrees and sinking.  I would have braved that, but the wind was 22 mph, resulting in a wind chill of -15 or so, and that, I will not brave.  Plus, that much wind would have made the mount vibrate like crazy.  But the next night, it was the same 12 degrees with a 4mph wind.  So out I went.

I first tried the Vite in the ST-80 on M42.  As Luca Brasi said, “Not bad!”  Not great, either, but f/5 is tough on EPs.  The field of view was definitely wider, but the edge of the FOV wasn’t sharp; it sort of faded.  And the focus at the edge, maybe the last 10%, was also not tight – not as tight as the 25mm Plossl I was comparing it to.  The stars were a little spiky out there.  But it sure wasn’t awful.

One thing that is a definite drawback for me using these are that they don’t have any kind of eyeguard.  With its big eye lens, and my ambient lighting on my roof, I was getting a lot of reflections.  All it took was to lift my hand in between the light source and the EP, but an eye guard would be so handy right about now.

Then I switched over to the Mak.  Much, much better.  The EP shines (ahem) at f/12.  Everything was nice and sharp out to the edge, good contrast, almost the same view as my 32mm Plossl:  a tad narrower FOV from 1.03 down to 0.93, but at 67x vs. 48x, significantly larger.  I also tried it with the Ultrablock for fun.  It was tough to get a proper focus, because the stars are really dimmed out, but the Ultrablock did its job, and the Vite did its as well.  Dust lanes appeared where none were present before.

Now for the moon, but first with just one eye.  The seeing was good enough to tell that the Vite was razor-sharp on the moon.  The terracing in Aristotles and Eudoxus was simply gorgeous, even at just 67x.  After a break inside to warm up, I eagerly moved to the binoviewers.  Unfortunately the predicted haze rolled in on cue, as predicted, and the seeing went south fast.  Plus the AA batteries I was using instead of my “trusty” Li-ion rechargeable were quickly dying.

It was another week until I had another clear night to test them out again.  And test them I did.  But the seeing was pretty bad.  Where a week ago it was dropping down into single digits, today it hit 60.  Thank you global warming!  Because of the “heat”, the almost full moon wouldn’t come into sharp focus with anything, and I could only think that I saw an Io shadow transit on Jupiter, regardless of the magnification.  Which means I really couldn’t see it at all.  This was not a fair test to see how sharp they are.

At least the new battery was working out just fine.  No resets at all.  Swapping out the two batteries themselves shows me that it was just the cord, which must have somehow gotten frayed, that was causing all those reboots.  I can’t understand why that would be – I keep the cord plugged into the receptacle on the scope at all times; it’s not as if it’s getting trampled under foot.  But it’s always good to have a backup battery in case the one you’re using dies unexpectedly, so the money wasn’t exactly wasted.

On this second night, I was able to test them out on the Pleiades in the refractor versus the 25mm Plossl I usually use.  The Vites did have a slightly wider FOV, but not by much.   Then I switched over to binoviewing.

The first night I used them in the BV, I would have sworn that the Vites had a significantly wider FOV than the 30mm Plossls that come with the binos, and at a higher magnification, to boot.  It seemed like they were showing me the half moon both significantly larger and swimming in the night sky, as opposed to being smaller and sort of hemmed in with the 30mms.  But checking that out further tonight showed me that this was just wrong.  The higher magnification just made it seem that way.

I next tried Jupiter and had a problem.  The Arcturus binoviewers tout themselves as having “self-centering compression rings.”  Well, not really.  In fact, not at all.  In addition to the diopter adjustment for focusing each EP individually, there is a separate twist-lock feature that is supposed to lock the EPs in place.  It doesn’t work.  But it’s not a big deal, because the included 30mm Plossls fit in nice and snugly, so they pretty much self-center anyway.

I learned last night why this self-centering jazz is such a big deal, because these Vites seem to be a hundredth of an inch skinnier than they should be – they wiggled in the BV EP holders, where the 30s do not.  That meant that they weren’t necessarily centered.  And that meant that the images were not aligned – I couldn’t merge them.  I was looking at two Jupiters.  It took a simple swapping of the left and the right to fix this – which took me a while to figure out – but this was a little weird and disconcerting.

All in all, based on my limited testing under poor conditions, I would say that the Vites are not only worth every penny of their nine bucks, but that they’re worth a good 40 or 50 bucks each, more than a Plossl, and about what I paid for my 15mm AstroTech Paradigm – used.  But TeleVues, they are not – at least in the testing I could do so far.  I would like to see what they’re able to do under better seeing conditions though, before I completely make the call on these.  That will have to wait.

I also would love to see how far this technology can be taken in the form of using it in other EP designs.  Could we actually get TeleVue-like quality using some other molded plastic lens elements in, say, 40 dollar Vites?  That would be exciting!

Next time:  Science?

 

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