Louis D

Is this for imaging or visual use?

Any idea of how long it took to transit the sun? What direction was it moving relative to the sun/horizon? How about size relative to the sun? Remember, satellites move at all sorts of different speeds depending on their orbital altitude. A geosynchronous satellite would stay in the same location on the sky while the sun passes behind it, for instance.

Hmmm. I used the stop Celestron visual back on my 127 Synta Mak for a while before moving to a 2" visual back and don't recall diagonal "flopping" being an issue, whatever you might have meant. It seemed nice and secure. Yes, you should be able to make the 2" visual back to 1.25" diagonal approach work if you take @Zermelo's advice above. You could also just mount a better 1.25" SCT visual back with the Mak to SCT thread adapter such as this or this if you're never going to use a 2" diagonal and eyepieces.

I was able to use my 3.5mm Pentax XW on Mars during the last opposition to good effect. However, as I've said before, the view was much better with two eyes through my binoviewer at similar powers. That's why I've felt zero need to pick up a used 3.2mm BST/Paradigm just to see how it performs. It's a one or two trick pony as you say.

Starting out with limited funds (by my current standards) a quarter century ago, I bought a 38mm Rini MPL 2" eyepiece, a 14mm Pentax XL, a 9mm Vixen LV, and a 5.2mm Pentax XL. What's that, 2.7x, 1.6x, and 1.7x jumps? I never felt the jumps were too large. Even today, I don't use my 20mm to 30mm eyepieces very much because my most used telescopes are operating at somewhat shorter focal lengths. If I was regularly using my 15" Dob, I would probably use them much more. Thus, I don't think think there's much of a need for eyepieces between a widest field 2" finder eyepiece in the 35mm to 42mm range and mid-power 1.25" eyepieces in the 12mm to 17mm range for most folks using sub-1500mm focal length scopes. Today, I'm more of an astro tourist staring out the window at the overall beauty of the scene rather than being a detailed observer looking to make microfine observations and logging them. As such, I prize the overall presentation and quality of the view over having the absolute sharpest on axis view possible given the moment by moment seeing conditions. I sometimes enjoy observing with multiple eyepieces of nearly the same focal length just to experience the different viewing esthetics of each. Given my ever brightening backyard skies, there are fewer and fewer objects I can observe, so different eyepieces with different presentations can spice things up. I am looking to buy a second home out and away from most light pollution. At that point, I may reassess my eyepiece collection and usage.

Wow, the rare 7mm Vixen LV! They rarely come up for sale on this side of the pond. Vixen dropped that focal length for the NLV and SLV lines for some reason. You're missing the Vixen 30mm LV or LVW and the 50mm LV to fill in a couple of 2" gaps. 😉😁

I actually only clean my eyepieces about once a decade or so because I always observe with eyeglasses, so my eyepiece eye lenses tend to remain pristine. Even when I do clean them, I prefer Windex because it has a bit of detergent and leaves no streaking. Pure alcohol solutions like BWF don't seem to cut through tree sap spots which are my main grunge. If I put a fingerprint on an eyepiece eye lens, I immediately wipe it off with a dry microfiber cloth after blowing off dust and then huffing on the lens to give it a bit of moisture to lubricate the cloth. It's the same technique I've been using for 40 years with my photography lenses to good effect. If you don't immediately clean off a fingerprint, it seems to harden over time and becomes a much bigger problem to remove.

I'm using GSO diagonals (which are sold under a variety of brands) with either an SCT to M48 thread converter on the front with a 15mm M48 extension ring or an SCT male thread to 2" nosepiece adapter as a single piece solution. Simply screwing the TSFLAT2 onto the front of the diagonal nosepiece provides too much separation (about an extra 15mm, IIRC) and overcorrects the field curvature. I've read that the Long Perng diagonals (the ones with the convex eyepiece receiver barrel sold as WO, Orion, StellaMira, etc.) natively have M48 threads on the nose barrel thread instead of SCT threads, so that might be an easier approach to mounting a TSFLAT2. Perhaps someone on here who has one can confirm their nosepiece thread size. I've got a bunch more M48 spacer rings of various lengths now, so I'll see if I can fine tune the spacing for both the 72ED and 90mm APO in the future. Technically, the 90mm should require 12mm less separation having a 50% longer focal length, but I've found 15mm of extension to still provide better field flattening over no extension, subject to the aforementioned fine tuning.

You really need to verify which issue you're seeing. If you're truly seeing field curvature, you can focus it out by refocusing for the edge. If you're simply seeing field distortion as others above describe, it is not called field curvature. Calling it that simply misguides us in trying to help you out. If you are truly seeing field curvature, a TSFLAT2 used ahead the diagonal can generally flatten the field. I use them on both my 72ED and 90mm APO refractors to good effect with my wide field eyepieces.

I don't know about European models, but the ones sold in the US have 1/4"-20 threaded holes, the same as the tripod thread on cameras.

Yes. It is just about perfectly flat of field and astigmatism free edge to edge. It's also easy to take in and hold the view with eyeglasses. However, it is massively heavier and larger than the other contenders listed as well as being 2"-only.

I have the 9mm and 14mm, and the overall design is fine. I just find the font and color ridiculous. Compare my 14mm Morpheus in the middle to a couple of actual cartoon font samples: OR Admittedly, the Morpheus font is nice and even with no slanting, but it just doesn't look understated or matter of fact like most eyepiece lettering. It sort of screams "Look at me!!!".

Got mine a few days ago. It was literally shipped from China to the seller who then slapped a USPS label over the Chinese one. Regardless, all of the M48 rings appear to be of excellent quality. Now I can fine tune my CC and field flattener spacings.

Exactly! I figured that out long ago when shopping for a 14mm to replace my Pentax XL once presbyopia set in. I'm already annoyed by having to crank my focuser a 0.25" outward to bring the 10mm Delos to focus. I suppose I should just add 0.25" of O-rings to it and be done with it. Such a simple solution is not possible with the 14mm Delos, thus I went with the 14mm Morpheus which does focus more or less at the shoulder. It makes swapping eyepieces a royal pain when searching for the best magnification. That, and coma correction is not ideal with the fixed distance of the GSO CC when not focusing at the shoulder where I set it.

It's so hard to get past the rainbow stars in the last 30% of the field in the 13mm AF70 that I've never noticed EOFB out there. That level of chromatic aberration would surely smear any faint fuzzies out there into even more unrecognizable blobs.

You're right about EOFB. It's way too subtle to show up in my images. The worst for EOFB I've found is the 12mm NT4. It has a lightening that starts out bright at the edge and gradually gets dimmer toward the center, but never goes away completely. I swapped between it and the 12mm ES-92, 14mm Morpheus and 10mm Delos, and none of them were showing any field brightening like that. I'll have to check the 12.5mm APM for that next time I'm out since I didn't have it at the time I noticed EOFB in the Nagler. I can't recall it being objectionable so far in it, but I also haven't been faint fuzzy hunting with it. My images also don't reveal field curvature since the taking lens has quite a bit of depth of focus mimicking human focus accommodation.

I was kind of put off by the 14mm Delos needing a negative profile 2" to 1.25" adapter to make it parfocal with the majority of my eyepieces that focus at their shoulder. I'm not even sure it would fit down inside the necessary distance thanks to its rather thick lower barrel. Tele Vue sells their In-Travel Adapter ($53!!!) for it, but I'm not sure it actually recesses the eyepiece a full 0.25" when you figure in the adapter's lip thickness. Here you've already paid a premium for the eyepiece, and it's not even parfocal with most other eyepieces, nor does it come with an adapter to help it be more parfocal. My 25mm Paradigm (BST Starguider) already won't come to focus in my Dob's low profile focuser with the GSO CC in place, so I know I'm close to my in-focus limits. I've already shifted my primary mirror forward as much as I'm comfortable doing. My focuser's 2" to 1.25" adapter is already a zero profile adapter, so that leaves a negative profile adapter as my only option.

I'm most off-put by the cartoonish font and color used for text on the Morpheus. I think the color was dictated by the glow in the dark requirement. I can't think of another eyepiece using a fat outline font. Compare it to the 14mm Pentax's refined looking metal plate and lettering that just exudes Japanese quality. That eyepiece is 24 years old and still looks terrific! I used it during every observing session for 18 of those years, so it wasn't mollycoddled, either.

The 12.5mm APM Hi-FW yields a wider true field of view than the 14mm Morpheus (19.8mm field stop vs 18.4mm FS). It's nicely sharp across the field as well and quite usable with eyeglasses (both have 18mm of measured, usable eye relief). It has a very different distortion (barrel) from the others on your list (pincushion) in that it doesn't stretch the edges but compresses them instead. In fact, it is slightly wider than my 12mm ES-92 (19.8mm FS vs. 19.7mm FS) because of this. I'm still comparing it to the ES and Morpheus, but so far, it's a winner. I think Don may have used the 12.5mm APM as well. My 14mm Pentax XL has noticeable field curvature. Reportedly, the 14mm XW did not fix this shortcoming. However, if you're young and your eyes still focus, you won't notice it. It is astigmatism free at the edge once refocused. To my eye, the 14mm Morpheus has a slight bit of field curvature and astigmatism at the edge that can't be focused out. I disagree with Don on this point. He doesn't see either, so YMMV. It's extremely minor, but it's there in a field flattened f/6 refractor. By comparison, the 9mm Morpheus has neither to my eye and is just about as perfect as my 10mm Delos, only with a wider AFOV. That, and it has just a slightly smaller FS (12.5mm vs 12.8mm). Here's some images of and through eyepieces I own in the 12mm to 15mm range:

You and me both.

I wish I'd had the disposable income I have now back when my back was strong and my eyesight super sharp (and focusable). Ahh, to be young and poor again.

My 3.5mm Pentax XW is fantastic, but gets very little productive use, so I've toyed with the idea of selling it. When I want powers that high, I generally find my binoviewer working at 3x with 8-24mm zooms yields a more detailed image. However, it nicely completes my 3.5mm XW, 5.2mm XL, 7mm XW, 9mm Morpheus, and 10mm Delos power progression. I sometimes wonder if I should get the 6mm and 8mm Delos for filling in the holes.

My favorite is the vintage, Japanese made Meade Series 400 #140 APO 2x Barlow. They come up used on this side of the pond all the time for $40 to $65. I have several in different usage configurations. One is as a Barlow for 2.4x, one is as a binoviewer GPC/OCS/OCA to reach focus and boost magnification by 3x, and one is combined with a 0.5x reducer and 45mm of spacer tubes to achieve 1.0x with the binoviewer when used in a Newtonian. They're highly versatile. I've even put the nosepiece on the front of a 1.25" diagonal and the 0.5x on the binoviewer to get to a vignetted 0.7x power. Screwed onto an eyepiece yields 1.6x. All the measurements were taken with a 14mm Pentax XL that focuses at its shoulder. I have the GSO 2" ED 2x that's also sold as Stellalyra and many other brands. Look for the Taiwan label to distinguish it from the Chinese variants. It is very good and compatible with the TV Panoptic Barlow Interface to make a poor man's Powermate. It yields 2.1x natively. I haven't measured the other usages' magnifications. @John usually recommends the Baader Q-Turret 2.25x Barlow, especially as used with a 7.2mm - 21.5mm zoom. However, because of the way it screws into filter threads, your eyepiece can't have its field lens down near to bottom of the insertion barrel.

I enjoy using my 72ED refractor for low power sweeping of the skies. In particular, I can pick out large star clusters and associations that are not obvious at higher powers. Rich star fields in Orion and Perseus come to mind.

I have the 3.5mm Pentax XW and find myself using it only a few times a year, such as during Mars oppositions. It's super sharp and with no obvious flaws. However, I've found that at high powers, I see much more on planets with binoviewers. My floaters become much more manageable, and two eyes process the image much better than one.