Don Pensack

That could have been the eyepieces in question. Assuming your scope is f/5, I would guess a 1mm exit pupil (5mm eyepiece) would be about the minimum for the Airy Disc to present a noticeable size. At 6mm, you should not have detected any decrease in brightness of Vega. The overall field brightness would be dimmer, but Vega? I would suspect your 6mm eyepiece may have a significantly lower transmission than the 32mm.

Nope. The star image's brightness represents the entire primary. When you use a higher power, you stop down the field size of the eyepiece, but every point on the telescope's focal plane is STILL illuminated by the entire primary. You aren't reducing the brightness of the star point. That's why the faintest stars are always visible at high power, not low. Yes, there is an increase in contrast, but that increase in contrast would not occur if the star images dimmed with magnification.

That is making the detail large enough for the eye to see. It's a fine line: dimmer with magnification, but larger and easier to see. There is a "eutectic" point somewhere in there that yields the best visibility. That usually requires experimentation.

Say you use and eyepiece that yields a 7mm exit pupil and your pupil size is 7mm. That will be the maximum brightness you can see in the scope. Use an eyepiece yielding a 3.5mm exit pupil and the image will be 1/4 as bright due to the smaller exit pupil. You can also look at it another way--the doubling of the magnification results in the brightness being 1/4 as great. Now, use an eyepiece that yields a 14mm exit pupil (refractor in this illustration). You have effective stopped down the scope by only admitting 1/4 of the light in the telescope's exit pupil. Why is the image the same brightness as the eyepiece that yields a 7mm exit pupil? Because the magnification is only 1/2 as much, which results in a 4X increase in brightness. 1/4 x 4 = 1. That's why using a larger exit pupil than your eye doesn't result in a dimming of the image, and why using a smaller exit pupil than your pupil does.

The exit pupil is an image of the primary mirror. It is not the image of the sky. It is the distance we hold our eye from the eyepiece to see the entire field of the eyepiece. To show an eyepiece is not focusing the light, back away from the eyepiece. The image stays in focus, but you are progressively seeing less and less field. Exit pupil and field go hand in hand, but focus is in the eye.

I think you meant if the field size increased, not the diameter of the eyepiece (which has little relevance). The exit pupil (brightness) and magnification go hand in hand. A larger apparent field spreads the light farther into your peripheral vision, but does not brighten the image. If it did, we'd all want to use 150° eyepieces. The purpose for larger eyepieces is to get wider true fields, because a 32mm 50° eyepiece will have the same brightness as a 32mm 100° eyepiece, but the latter has 4x the field area. Remember, every point on the focal plane of both eyepieces is illuminated by the entire primary (* see below) * In practice, we do not choose secondary sizes that illuminate the edges of the field to 100%, we choose secondaries to have about a 30% light drop off at the edge (we don't see it, though a camera can, so photographic secondary sizes are larger). So if a 32mm 50° eyepiece has a 30% light loss at the edge, a 32mm 100° eyepiece would have significantly more light loss at the edge. That's why we choose the size of our secondary mirrors to illuminate the field stop of our lowest power, largest field, eyepieces to 70° at the edge. At some point, as the magnification goes up and the field stop of the higher power eyepieces get smaller, the illumination at the edge reaches 100% because the effects of secondary edge of field light loss gradually fall to zero.

Yes, KUO does make these eyepieces.

You misunderstand the relationship between exit pupil and apparent field. The exit pupil is the image of the primary mirror. Essentially, every single point in the exit pupil is illuminated by the entire primary mirror. When your iris blocks part of that exit pupil, you are blocking part of the primary mirror (an astute observer would note that so does the secondary mirror in both center and edge), but it doesn't reduce the apparent field of the eyepiece. It reduces the field illumination in the eyepiece. But you can simply move your eye laterally to see one edge of the field or the other since the field is being illuminated exactly as before, merely that your eye is not taking it all in. Your supposition that a larger exit pupil is not wasted is correct. The reduction in magnification brightens the image and the light loss exactly equals it, so for the field you see, it will be exactly as bright as the image when the exit pupil matches your pupil diameter. That is only safe with a refractor, though. With a reflector, as the exit pupil grows larger, so does the shadow of the secondary. At some point, the shadow becomes a large portion of your pupil diameter and you start noticing its presence.

and it's a rare eyepiece that doesn't have some chromatic aberration in the outer field.

If you have to stick to 1.25", the APM 24mm Ultra Flat Field would be a good candidate. It's also sold by Altair as their Ultra Flat in a fairly unique green anodizing.

As has been reported elsewhere, Meade dealers don't have the 26mm, only Meade, and I'd be afraid they would run out permanently. On the other hand, it could be they've just arrived. The thread on the eyepiece: https://www.cloudynights.com/topic/701095-meade-26mm-100afov/ Looks like it is not the 100° claimed, also that the eye relief is perhaps less than 20mm. It looks like there is no Omegon version of it, unlike the other focal lengths.

It sounds like perhaps the issue has been addressed with current batches. If so, when buying used, caveat emptor.

Plössls have very little eye relief when shorter than about 14mm focal length. These go down to 3mm with about 14mm Plössl eye relief. It's reasonable to think of them as longer eye relief Plössls.

Yeah, I have tried them on the Ethos, but noticed 3 things: 1) the eye relief shrinks a lot--to about my eyelashes length 2) the images at the edge seemed more distorted when looking at the edge directly because of the oblique angle through the DioptRx lens 3) it was harder to look at the edge of the field with the DioptRx in place. In contrast, I have no similar issues with the DioptRx on eyepieces with longer eye relief or narrower fields. Fortunately, I can still use Ethos eyepieces below 11mm without glasses.

I didn't want to pre-prejudice your review with my comments. No posted comparison from me. I'll wait for your comments.

Looks like Meade did it for you: the 26mm MWA is around 90° and very inexpensive.

That will vary, John, with the nature of the eye's astigmatism. For me, stars became small stick men instead of points. Others see the stars turn into comets, even in the center of the field. Others see a few spikes that don't correspond to the spider vanes. But, it is visible in the very center of the field unlike coma. With my current prescription, I can look at the sky with my glasses on and all the stars as points. If I take my glasses off, all the stars look WORSE than Venus when Venus is on the horizon. And faint stars disappear.

Would you want a 25mm Delos if it was 2" and weighed close to twice what a 17.3mm weighed and cost 50% more?

Assuming you don't wear glasses. I just went back to a 22mm Nagler after 10 years with a 21mm Ethos because my astigmatism has gotten bad enough I needed the eye relief.

I'll be interested in reading your comparison. I did just that with a 31mm Nagler, 30mm UFF and 30mm XW just 2 months ago.

The Nagler Type 4s were long eye relief. Type 5s were to create longer focal lengths. Type 6s were to create shorter focal lengths and binoviewer compatibility. No real difference in performance. The ES eyepiece has more scattered light and unresolved outer field astigmatism, but is pretty good above f/6. I personally use a 22mm T4 Nagler and I'd recommend it. It's perhaps THE eyepiece that defines "immersive". Seriously, it's a special eyepiece.

within your requirements, what Louis recommended is a great one. I have an f/7 triplet as well and found the TeleVue Delites gave superb performance. I hesitated about a longer focal length, but if you do not wear glasses, the obvious eyepiece is the TeleVue 24mm Panoptic. If you do wear glasses, the 24mm APM Ultra Flat Field.

Though probably not the case with the ES TeleXtender, a normal 2X 2" Barlow would not yield 2" with the Morpheus used as a 2" eyepiece. The focal plane of the Morpheus is closer to the top of the 1.25" barrel, so using them as 2" eyepieces places the focal plane closer to the barlow lens, reducing the magnification.

Most people use a 2" eyepiece at low power to get a wide field. And people usually have 1.25" medium power eyepieces, so why double a 2" eyepiece to yield a duplicate medium power? Ergo, most barlows, and rightly so, are 1.25". So if choosing, choose a 1.25" barlow to yield high powers from a medium power eyepiece.