Don Pensack

I have compared all of them. The 15mm is not compatible with glasses, though the 30, 24, and 18mm are. The 30mm is sharp to the edge and has a noticeably flat field, and superb contrast for its 70° apparent field (the other 3 are 65°). It is among the top 3 30-32mm eyepieces I've ever used. I preferred the APM versions because of a smooth lower barrel. The Celestrons have a tapered undercut on the lower barrels. That makes them a little problematic in binoviewers. They are the same, optically. The actual field stops are not what you find in the literature. They are: 30mm--36.3 24mm--27.6 18mm--21.7 15mm--18.2 The 24mm has, as a result of the large field stop, a bit of vignetting at the edge, but it is not obtrusive. It does make the edge a little less sharp than in the others. I consider the 30mm an "honorary" Morpheus, and the 30mm to 17.5mm is an excellent jump in scopes of less than 2000mm focal lengths. In my 12.5" (1826mm focal length), the jump is from 61x to 104x, and I never feel a need for anything in between. I look forward to your comparison with the Morpheus series.

Especially the 6mm Ethos, which is one astounding eyepiece. The specs: Tele Vue, Ethos 6 100.7 <2 3.5 5(7) diffr. diffr. diffr? The first three figures after the 100.7° measured apparent field are the spot size at f/4 in center, mid field, and edge of field. The last 3 figures are the spot size at f/10 The parenthesis on the f/4 edge of field is the actual length, radially, of the star image. What we see is the smaller figure. Anything less that 10 is seen by the eye as perfect. Diffr. means limited only by the diffraction in the scope. In seeing that allowed me to go to 3.7mm, the 6mm was as sharp as any planetary eyepiece I've ever seen. If 6mm yields a high enough power, the 6mm Ethos is excellent. For any use.

Almost every line of specialized planetary eyepieces comes and goes. There are very few who want to have 2 sets of eyepieces and/or only view planets. And because there is no 'economy of scale', they are typically expensive. So, my advice is, when a line that gets high praise is available, buy them.

Perhaps it's wiser just to think of the Baader VIP as a 1.25" Barlow for 1.25" eyepieces that happens to be usable at multiple magnifications.

Yes.

Yes, you could buy at sale costs and simply not participate in the sale. You sell almost zero during the sale period, though. JOC seems to have lost control of their distribution anyway, as there are lots of Chinese dealers selling them direct to the US for very low prices. This sale might be a way of competing with that.

Jing Hua Optical calls the shots. They wholly own Explore Scientific. They tell the retailers about the sale a little in advance, to seek advance orders. In other industries, the retailer will get a rebate for the cost differences of his stock. In this industry, they expect you to make up the loss by resupplying all your stock during the sale period and selling the lower cost stock at the full retails after the sale is over. That might work, but it defers the profits, often to another quarter, which is not good. And the wholesale sale prices end well in advance of the end of the retail sales period, so if you guess wrong, you end up resupplying at full cost and the sale just represents a loss. And, many times, ES just runs out of stock during the sale periods and you simply cannot resupply at the sale costs. Then, almost the entirety of your sales during the sales periods are at cost or below cost. And, almost the entirety of annual sales are during the sale periods. On paper, ES was a profitable line. An analysis of annual sales showed it to be a very very low profit brand. I refused to participate in the sales during the last year I carried the brand. I sold a lot less, but made more profit. The discounts this time are severe, and quite a bit below regular dealer costs. I hope it doesn't mean they are pulling out of the US market.

The likelihood is high that a refractor objective is fully coated, or fully multi coated. I've dismantle cheap plastic telescopes and found fully coated lenses. One thing is for sure--a Barlow in front of the star diagonal would magnify so much that any scope cheap enough to have an uncoated lens would be being pushed WAY beyond its maximum usable magnification. Star diagonals all vignette the image plane, but on refractors, the focuser drawtube does too, before the image even makes it to the diagonal. It only matters if the vignetting is severe enough to be visible and if the eyepiece's field stop is large enough that it matters. If done right, though, a VISUAL scope is fine with a 70% illumination at the edge of the largest field stop used. A PHOTOGRAPHIC scope will need 100% illumination over the field of the chip if designed for that chip. In practice, flat fields can eliminate a small amount of vignetting. Most refractors these days (except the cheapest ones) are being built for photography.

I know that is tongue-in-cheek, I'd be surprised if they even made a thousand.

As light passes through an eyepiece, some of the light is reflected back toward the source. If that reflected light encounters another optical surface, it can reflect forward again, albeit at a significantly reduced intensity. Still, it will be out of focus and mostly adding to the sky brightness background in the eyepiece. If there is a little dust on the optical surface, the reflection/scatter is increased. It has the same effect as a rough optical surface. This was noticed on some production runs of some Takahashi eyepieces. The eyepieces could, of course, be dismantled and internally cleaned, but most people buying a new eyepiece won't want to do that.

At 1500mm focal length, having a 20mm (75x) and a 16mm (94x) results in two magnifications only 19x apart, likely too close to be useful. You would likely use one or the other, but not both. In the shorter focal length scopes, the magnifications will be even closer together. 11mm to 16mm is a reasonable square root of 2 increase. Extend that from 16mm and your next magnification should be a 22-23mm, not 20mm. There are some wonderful and inexpensive 22mm eyepieces (like the Omegon Redline) out there, but they are 2". If your scope takes only 1.25", you might look at the ES 24mm 68° or the APM Ultra Flat field in 24mm. Both would yield much larger true fields than the 25mm SLV.

It looks like an SSW, to me--8 elements. Nope. The SSW is 7 elements. TOE is 6 elements. The LV didn't have 8 elements. Some (but not all) of the focal lengths of LVWs did. It's a mystery. By the way, HR stands for High Resolution. That pretty much says it all. The baffle at the bottom makes a difference. Try removing it when looking at something bright. A bottom baffle like that is the reason I always use the Apollo 11 as a 2" eyepiece. Remove the 2" adapter and the bottom baffle disappears, and it makes a visible difference in the image. I wish the bottom baffles were an accessory you could buy. Unfortunately, what is under the Vixen HR's bottom baffle is not a filter thread, so if you use a planetary filter of some kind, it has to be attached elsewhere.

What is a reversed Kellner, and who makes one? It is not the RKE (Rank/Kaspereit/Erfle) and it is not a König. It is merely someone looking at a 3-element design and calling it that, despite it not being that. Edmund, I think, coined the name in their literature to describe a generic eyepiece with a doublet field lens and singlet eye lens. There is no evidence, however, that Kellner designed an eyepiece like that. Edmund might have made one and called it that, but did they use the same glass types or curves? I think such a design may never have existed, but just had that name assigned, just like "Kellner Type II".

Note that Al observes with scopes with wide fields and short focal lengths. I do use lower powers (80-150x) to view the IFN next to M13, but I see a lot more stars in the cluster at higher powers, where fainter stars become visible. The area is nice no matter what the power. M14 is an example of my point. At 60x, a few stars are scattered here and there on a nebulous background. At 150x, there are now stars across the face and the background behind them is somewhat grainy. At 300x, the cluster becomes a massive ball of stars and the haziness has disappeared. However, as we all know, you have to have the seeing quality to be able to see sharp stars at 300x.

The RKE is not a reversed Kellner. It is, according to Edmund and the Patent Office, a "Rank-Kaspereit-Erfle", and it uses different curves, spacing, and glass than the Kellner design, even reversed. There have been many different eyepieces from several companies made with a doublet field lens and singlet eye lens (one of the most common is the König design).

For those not familiar, he is referring to an AstroPhysics BARADV Barlow, one of those high-end Barlows highly touted.

102x is a very low power to view M13. My best view is at 304x. It's also the best magnification for IC4617 and NGC6207 nearby.

The APM Zoom requires only a bit of in focus when used as a 2" eyepiece. When used as a 1.25", it requires massive amounts of in focus. I regard it as a 2" zoom. Unless the scope has a lot of in travel available, that means a zoom on its bottom end may likely strike the diagonal mirror in a star diagonal.

The 30mm XW and 30mm UFF have almost identical field sizes (36.2mm and 36.3mm respectively), but the UFF is sharper in the outer 10°. [in a 12.5" f/5 scope operating at f/5.75 with a Paracorr II.] The UFF is also lighter than the XW and has a couple mm more effective eye relief. I see the UFF is now available at FLO under the Stellalyra name: https://www.firstlightoptics.com/stellalyra-eyepieces/stellalyra-30mm-ultra-flat-field-2-eyepiece.html It's not like the XW is a bad eyepiece at all. In this case, it's more in the nature of small nuances.

It's only a thread-on Barlow lens, though, which might be an issue in a star diagonal for all the 2"/1.25" eyepieces out there when used as 2" eyepieces.

True field is determined by the internal field stop diameter. The eyepieces mentioned have field widths of: 30mm 70° UltraFlat Field--36.3mm 28mm 82° (Nirvana/Long Perng/etc.)--40.8mm 30mm ES 82°--42.4mm TeleVue 31mm Nagler--42.0mm Celestron Luminos 31mm--42mm? 24mm ES 82°--33.5mm 24mm 65° UltraFaltField--27.6mm Advantage to the 28-31mm range for true field of view. Advantage to the 24mm for darker background sky, with a larger true field at 2" than in 1.25" To calculate the true field for each, use this formula: True field = (field stop diameter / telescope focal length) x 57.296 I'll throw in one eyepiece to the mix to think about: 20mm 100° XWA eyepiece--34.8mm That is more true field than the 24mm 82°

You are a lucky fellow if floaters don't interfere at those magnifications in a 4"! But the logical addition to the 3-6 Nagler Zoom would be a 2.5mm Vixen SLV. That would give you 0.5mm jumps from 2.5mm to 6mm and the in-betweens as well. Those magnifications would be easy in your 12"...I'm just sayin'.😉

Some from the first batch had a blem in the glass right in the center of the field of view. They were recalled, but not every one I sold came back, and I presume that is true of other dealers, too, so there might be some bad ones still floating around the used circuit.

Forget the Pentax 23mm, Louis. It has only 12mm of eye relief from the eyecup up. You MIGHT be able to use that, but I had to press my glasses into my eye socket until my eyelashes brushed the glasses in order to see the field edge. That was not comfortable. The suitability for glasses would mean you have shallow eyes and small glasses that sit well within the eye socket. There is no eyecup out there that will help, because there is a section of eyepiece several mm above the eye lens protruding from the body of the eyepiece that you cannot remove. I tried a Morpheus eyecup and a simple stretch-on rubber eyecup, and all of them yielded about the same depth to the eye lens, which is strongly concave, as the original eyecup. It is not, alas, a substitute for the 22mm T4. The Long Perng 20mm 80° could be if the eyecup is removed and a simple stretch-on eyecup is used and folded down as a replacement. Good luck finding a 50mm rubber eyecup to fit it, though.

https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/?p=12369694 https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/?p=12369699 https://www.cloudynights.com/topic/849945-new-85°-pentax-eyepieces/?p=12369736 By the way, that thread has 602 posts, and it is only 1 of over 200 threads containing posts about the eyepieces.