Don Pensack

Of course you notice the drop in brightness. If you didn't, they wouldn't be magnifying. The drop in brightness isn't due to transmission loss, it's due to magnification. Generally, Barlows yield sharper edge definition due to the effective doubling of the f/ratio of the scope. If they don't improve the edge of the field, there could be something optically mediocre about the Barlow. As for PowerMates, the 4mm functions about the same as the 2X version, though the extra magnification might be too much. The 5x unit has its magnification change with distance from the lens, similar to a Barlow. I think its primary market is for imagers of planets, where it increases the size of the image significantly when used between scope and camera.

I used to use those, too, until I left one in my car on a hot day and the plastic melted against my filters and ruined a dozen filters. The lesson to be learned is to not leave them in a hot car, I guess. Here is what I use now--no foam, each filter in its own box.

Filters fog easily. It's best to keep them in a case until used. Eyepieces can just be kept capped until use.

Buy the 4mm, 6mm, and 9mm and attach 2" adapters to them in a quasi-permanent fashion. Voilà! 2" eyepieces. That is no different than having 2" barrels on what are, essentially, 1.25" eyepieces.

Bear in mind, this filter will enhance the gas tails in comets, NOT the dust tails. You still want to compare the view sans filter.

All Barlows will move the focal plane of the telescope outward. IF it moves the focal plane outward by exactly the length of the Barlow's barrel above the lens, it will be parfocal with the eyepiece when the eyepiece is used without the Barlow. IF it moves the focal plane outward less than that distance, it will require in-travel of the focuser. IF it moves the focal plane outward more than that distance, it will require out-travel of the focuser. I have run into Barlows that do all 3. More have required in-focus than out-focus. How much in-travel or out-travel is required will depend on the spacing between the Barlow and the eyepiece, too. So it will vary from Barlow to Barlow as to whether you need additional in-focus or out-focus.

One really short focal length eyepiece that IS adaptable to projection photography is the Baader Morpheus 4.5mm, which has a 43mm thread under the eyecup and for which camera adapters are available.

I've used the blinking technique on planetary nebulae that are so small they are little different than star images at low powers. The nebula stays visible when almost all the stars disappear or get seriously darkened. But for fainter objects, the difficult with this technique is that the filter is essentially a mirror and reflects back so much ambient light the objects become invisible.

Pure H-ß objects: 1. IC 434 w/B33(HORSEHEAD NEBULA)2. NGC 1499 (CALIFORNIA NEBULA, naked eye and RFT)3. M43 (part of the Great Orion Nebula)4. IC 5146 (COCOON NEBULA in Cygnus)5. M20 (TRIFID NEBULA, main section)6. NGC 2327 (diffuse nebula in Monoceros)7. IC 405 (the FLAMING STAR NEBULA in Auriga)8. IC 417 (diffuse Nebula in Auriga)9. IC 1283 (diffuse Nebula in Sagittarius)10. IC 1318 GAMMA CYGNI NEBULA (diffuse nebula in Cygnus)11. IC 2177: SEAGULL NEBULA (Diffuse Nebula, Monoceros)12. IC 5076 (diffuse nebula, Cygnus)13. PK64+5.1 "CAMPBELL'S HYDROGEN STAR" Cygnus (PNG 64.7+5.0)14. Sh2-157a (small round nebula inside larger Sh2-157, Cassiopeia)15. Sh2-235 (diffuse nebula in Auriga).16. Sh2-276 "BARNARD'S LOOP" (diffuse nebula in Orion, naked eye)17. IC 2162 (diffuse nebula in northern Orion)18 Sh2-254 (diffuse nebula in northern Orion near IC 2162)19. Sh2-256-7 (diffuse nebula in northern Orion near IC 2162)20. vdB93 (Gum-1) (diffuse nebula in Monoceros near IC 2177)21. Lambda Orionis nebular complex (very large, naked-eye)22. Sh2-273 "Cone" Nebula portion south of cluster NGC 2264

It looks to be a hair under 33mm. I got 32.9mm at the top of the threads on the 4mm. The thread looks to be a fine thread, too, maybe 0.5mm Why it is threaded, I don't know, since the eyepiece has too little eye relief for camera attachment, or for use with a DioptRx. If you attach a camera, the lens will be outside the exit pupil and yield a smaller apparent field than the eyepiece. This is NOT an eyepiece designed for projection imaging.

There aren't that many manufacturers of eyepieces that we all buy in the aftermarket. I don't think any of them is a small company making a small number of eyepieces. Many are very large manufacturing plants that make a host of products, including many that are outside the astronomy business. Jing Hua Optical (Explore Scientific) makes mostly cell phone glass, and eyepieces are a side business for them, as just one example. Since Svbony seems to be a unique brand name on the 3-8mm zoom, it is likely they commissioned it to be made. Whether they, or the factory that made it, designed it, I don't know. The factory size and the number of customers they can sell an eyepiece to as a private label product determines how many can be made in a batch. It could be 100 or 500 depending.

Well, we are also lacking choice in glasses-compatible eyepieces. There are many, but only a few *lines* of eyepieces, and usually a dearth of: --short focal lengths below 5mm --with ultra to hyperwide fields of view --or choices of apparent field from 45° to 100° Example: take the 4.7mm and 3.7mm Ethos. Shrink the apparent field from 110° to 85°. Increase eye relief to 19mm. I bet the eyepieces would be the same size, albeit with a larger eye lens diameter.

Comet filters like the Lumicon, and now the Baader, help you see the gas tail more easily. But they don't help on the dust tail, which reflects sunlight. So it will depend on the comet and which details you want to see.

Living in a dreamworld, Louis. Eyepiece size night vision devices (e.g. Collins) were $4000 15 years ago, and there has been a lot of inflation since them. Camera capture takes longer (not real time), but it's a LOT cheaper.

What I'm looking for is a TeleVue 85° line with enough eye relief for glasses at all focal lengths. Nagler Type 7? Probably Ethos prices, but that's OK with me.

8mm, huh? All of these are available in 8mm: Svbony 3-8mm Zoom and 365 Astronomy Andromeda Extra Flat 365 Astronomy Magellan Wide Angle Agena Starguider Dual ED Agena Wide Angle Angeleyes (eBay/Ali Express) Wide Angle Aquila SW Arcturus Ebony Artesky Planetary SW Artesky Super ED Astro Tech Paradigm Dual ED Astromania Planetary Astromania Plossl Astromania Premium Flatfield Astromania SWA ATC (Czech) N ATC (Czech) UWS Auriga WA Baader Planetarium Hyperion Brandon Brandon Orthoscopic BST (Barsta) 58 degree Series BST (Barsta) Flat Field Datyson Plossl Edmund Optics RKE (Rank-Kaspereit-Erfle) Harry Siebert Optics Starsplitter SS4 Series Harry Siebert Optics Starsplitter SS4 Series Hercules Plano KSON Ultra Flat Field Lacerta WA Lunt "Solar Eyepieces", Flat field Omegon Cronus Omegon Flatfield Omegon Redline Orion EF Ostara UK Flat Field Saxon Australia SWA Sky Rover WA Stellarvue UWA SVBONY Plossl Tecnosky Flat Field Tecnosky Planetary ED Tecnosky Superwide HD Tecnosky Wide Angle Tele Vue Optics Delos Tele Vue Optics Ethos Tele Vue Optics Plossl Telescope Service ED Telescope Service Expanse ED Telescope Service Planetary HR Telescope Service Wide Angle TMB (Sky's the Limit, UK) Planetary II Vixen NPL

No fear. SLVs and NPLs are not discontinued. SSWs are discontinued, but that happened a while ago.

Louis, I see it quite well in your image of the 14mm Morpheus, the 14mm Pentax XL, the ES 17mm 92°. It's not as strong as some others, but it's there in your images. However, I just tried my 14mm in my 102mm f/7 triplet and saw no CAEP. So I suspect it might be due to how the eyepiece handles the CA of the doublet image. How or why, I cannot say without further research.

OK guys, the issue with the 14 Morpheus could be the same issue with the 31mm Nagler, 30mm ES 82°, so Pentax, etc. The eyepiece was not designed for daylight observing if that is the case. Nor were those others. At night the coloration is invisible. It is called "Chromatic Aberration of the Exit Pupil"(CAEP), or "Ring of Fire". Louis D here on SGL has many pictures of it. It simply means that not all colors are fully corrected at the exit pupil. It's not due to being too close or too far away from the eyepiece. If you bought the eyepiece for daylight use, you simply bought the wrong eyepiece. If you bought it for nighttime use, you will like the eyepiece. The one possible time you might see it at night is with the Moon entering that zone at the edge of the eyepiece. However, as mentioned below, I tried the 14mm in my 102mm f/7 triplet apo on some land targets just now, and though there is a thin blue ring right at the field stop, I did not see any Ring of Fire issue--no CAEP. So I wonder if there is an interaction between the doublet lens and the eyepiece, or that the eyepiece is wide enough to display lateral CA from the objective lens. I don't know, but the results posted by Elp are completely different that what I just saw. Is it possible the field lens is installed backwards? Is it possible the eyepiece is defective in some way or has been assembled incorrectly? I couldn't say without comparing it with another sample of the same eyepiece.

This one has edge vignetting and chromatic aberration of the exit pupil (aka "Ring of Fire")

And noticeable edge vignetting, too.

Weaker, in an eyepiece, could refer to: --more lateral chromatic aberration --a softer focus at the edge, or everywhere in the field --more lateral astigmatism in the field --more field curvature (where, when the center is in focus, the edge is not) The 15mm UFF has more lateral astigmatism than the 14mm Morpheus in my scope (12.5", f/5.75, coma-corrected). The big differences you would see with the 14mm Morpheus compared to the 15mm UFF are: --a 15° wider apparent field (a measured 63° vs. 78°) --Much more eye relief on the Morpheus. --an improvement in light transmission--fainter features in objects visible in the Morpheus. --in a coma corrected scope with that long a focal length, field curvature won't be an issue --the Morpheus is a much larger eyepiece, but isn't very heavy and won't be a balance problem in that scope. --the Morpheus will require a different setting of the coma corrector--setting A in the Paracorr when used as a 1.25" eyepiece. If used as a 2", it will require so much out-focus that you needn't worry about the 1.25" barrel contacting the CC lens. Its Paracorr position, when used as a 2" eyepiece, is setting H with the eyepiece pulled out of the Paracorr an additional 3.2mm (which is why using it as a 1.25" eyepiece is easier). If you use a GSO coma corrector, you might require a different spacer between the lens and the eyepiece barrel, or a very low height adapter, like the Baader Push-Fix adapter unless you have other eyepieces that focus as far in. Overall, the Morpheus 14mm is on a different level than the 15mm UFF, so is the difference noticeable? I think the answer is yes.

However, I passed my APM 12.5mm Hi-FW around at a star party, and everyone saw the same thing I saw--Edge of Field Brightening (EOFB) in the last 20° of the field all the way around. Alas, because it's a better eyepiece except for the EOFB, but I couldn't tolerate the EOFB and sold the eyepiece. My dob is a 12.5" used with Paracorr II (effective f/ratio 5.75, FL 1826mm), and I got a chance to compare the 14mm and 12.5mm Morpheus extensively over a night (not for the first time). In that scope, both the 14mm and 12.5mm Morpheus display zero field curvature--when the center is in focus, so is the edge. I could focus at the edge and see focused star images in the center. Bear in mind, the longer focal length of the dob and the field flattening characteristic of the Paracorr modifies what is seen in the eyepiece, so a short focal length refractor could be different in that regard. I have a short focal length refractor, but my observing in that scope starts at 9mm and becomes smaller in focal length, with a lot of use of the 4.5mm Morpheus. The 14mm has a bit of lateral astigmatism in the last 5° of field, and stars are stretched slightly at the field stop. It is really far from center, however, and usually unnoticeable, as I don't typically watch objects drift out of the field as I did the other night. I only noticed it in comparison to the 12.5mm, which is fast becoming my favorite eyepiece. The 12.5mm maintained tiny pin-point stars to the very edge and had a slightly improved sharpness to the 14mm everywhere in the field. Despite Ernest's measurements, the only way I could fault the 12.5mm was very slight chromatic issues in the star images at or near the edge. But I could eliminate that by merely looking through the eyepiece at a slightly different angle. I compared the image quality on many objects with a TeleVue 11mm Apollo, and if I saw any difference at all (other than magnification), it was that the 12.5mm Morpheus was slightly sharper. Since seeing was mediocre, the increased magnification was likely to blame, as the 9mm Morpheus also displayed star images that were a bit softer.

They get longer as the focal length gets shorter because the negative field lens is move farther from the upper lens assembly to increase magnification (i.e. shorten the focal length). The 12.5mm possibly uses a slightly higher power field lens than the 17.5 and 14mm, so can be a trace shorter than the 14mm.

Are you standing to observe? Long eye relief eyepieces, no glasses used, and standing are 3 things that don't go together if ease of use is contemplated. Either raising the eyecup or sitting, or both will make the use of the eyepiece easier.