Louis D

At least you're consistent. 😉

It probably would work, but I've read nothing about it's use visually. The problem becomes getting the spacing correct for the majority of your eyepiece collection as with the GSO. I also don't know if it has any field flattening effects as does the GSO and Paracorr, or what its in-focus requirement is. I also don't know how much spherical aberration it introduces at higher powers. I remove my GSO CC at high powers to get sharper images because of SA not visible at lower powers. Users of the Paracorr T2 claim it does not have SA and can be left in the focuser at all powers.

I used the projection method of shining a bright flashlight into my AT72ED with an eyepiece in the diagonal and measuring the distance from the top of the folded down rubber eye guard to the point where the exit pupil was smallest in diameter when projected onto parallel card stock. Sometimes with SAEP and CAEP, this covered an entire range of distances (as with the 30mm ES-82), so I use the middle of this range. For eyepieces with stiff rubber eye cups that are easily removable like AF70s and Aspheric 62, I measure the distance with them removed since that is how I tend to use them with eyeglasses. I haven't scratched an eyeglass on any of them yet. If you don't push in hard, you won't scratch your eyeglasses. I did scratch an eyeglass on the top retaining ring of the TV Panoptic 27mm despite leaving the flipped down rubber eye cup in place by pressing in hard, so leaving the eye cup in place is no guarantee of scratch-proofness if you wear front surface convex lensed eyeglasses. Yes, some of the numbers don't match up with "feels like" eye relief, and I can't explain it. I have remeasured multiple of these eyepieces, sometimes just shining a distant flashlight straight into the bottom of them with the same result. Obviously, there's more to eye relief distance than the point at which the exit pupil is smallest in diameter. Not being a trained optical designer (I'm a computer chip designer by education and trade), I can't offer any further insights into it. I agree, the 22mm NT4 has more usable eye relief than the hard numbers would show. Go ahead and repeat my testing with your setup on such eyepieces and see what numbers you get. I guarantee a few will surprise you. Feels like and measured ER sometimes disagree. I agree that narrow AFOV eyepieces are sometimes fairly easy to use with eyeglasses. I have little trouble with my short ER Kellners and such with just a bit of head bobbing from side to side. An alternate method to measure effective eye relief depends on measuring the distance to a phone camera lens once the camera is at the exact position the field stop pops into view while viewing an actual, distant test target. This seems more accurate because the incoming light actually forms an image. The distances will need an offset added to them to account for the location of the camera's entrance pupil location with its lens, but it will be a constant. It can be derived by comparing the two measured ER distances and arriving at mean value that most eyepieces agree on. This measurement might provide more insight into "feels like" ER distance because the camera is acting like an eye and may need a different distance than the point at which the exit pupil is narrowest in diameter. This is how I arrived at the 10mm value for the 26mm Meade MWA due to its massive SAEP. It refers to the ER to see the field stop. I may work on adding a cardboard wrap around the eyepiece and push it down with the phone body and then measure the distance to the top of the cardboard from the top of the eyepiece once the camera is removed. All I need is more free time to repeat this dozens of times. I'd start with the ones that have an obvious disconnect between feels like and measured ER, though.

The ES-62's are basically 5 element super Plossls (the older Meade 5000 Plossl line reintroduced). As such, they are fine in the inner 50% of the field, and gradually fall off with astigmatism to the edge. The polish and coatings are quite good. You'll want a coma corrector for that Dob. The GSO (Revelation, TPO, etc) CC is quite good once you add a 25mm M48 spacer ring between the eyepiece holder and the optical section. Of course the Paracorr T2 is better, but vastly more expensive. If you don't need to wear eyeglasses, you can get away with using eyepieces with 12mm of usable eye relief or more. Below that, it starts to get a bit uncomfortable for extended viewing sessions. Ask on here about usable eye relief before buying. ES in particular likes to recess their eye lenses and quote design eye relief. This disappoints many buyers because the usable eye relief is generally much less. The BST Starguiders are a good step up eyepiece range. They have 12mm of usable eye relief from 18mm on down, no noticeable kidney beaning, and are quite sharp for the money spent. The Baader Morpheus would be a good choice to step up to premium level performance at a reasonable price. The 9mm in particular compares very favorably to the 10mm Delos. I would get the 30mm APM UFF for a near widest field eyepiece. It is very well corrected and should work well in your Dob. You could also look into Abbe Orthos for high power, planetary eyepieces since you don't need to wear eyeglasses. However, the narrow field of view can be a pain when manually tracking at high powers because you don't get much dwell time with each nudge.

It's also dependent on your nose bridge to eye socket depth and eyeglass style. Technically, you could get away with wearing a monocle wedged into your eye socket to use low eye relief eyepieces. To answer your question, I need 18mm of measured eye relief to avoid touching the top of the eyepiece, 17mm when touching, 16mm when pushing in slightly, 15mm when really pushing in, and 14mm when cramming my eye in to the point of hurting my eye socket with my eyeglass frame. I say measured eye relief above because manufacturers claimed eye relief is rarely the usable eye relief. Here are my measured usable eye relief figures for my eyepiece collection: Eyepiece Focal length Measured Usable Eye Relief Pentax XW 3.5 18 Meade Series 5000 HD-60 4.5 14 AstroTech Paradigm 5.0 12 SW 5-8 Zoom 5.0 7 Pentax XL 5.2 21 Generic Huygens 6.0 3 SW 5-8 Zoom 6.0 7 Meade Series 5000 HD-60 6.5 15 Pentax XW 7.0 18 SW 5-8 Zoom 7.0 9 Surplus Shed 7.2-21.5 Zoom @ 7.2mm 7.2 10 AstroTech Paradigm 8.0 12 Celestron 8-24 Zoom @ 48x 8.0 16 SW 5-8 Zoom 8.0 11 Generic Kellner 9.0 4 Meade Silvertop Plossl 9.0 5 Vixen LV 9.0 18 Meade Series 5000 HD-60 9.0 17 Baader Morpheus 9.0 20 Celestron 8-24 Zoom @ 40x 9.6 15 Televue Delos 10.0 21 Surplus Shed 7.2-21.5 Zoom @ 14mm 12.0 9 Meade MA Astrometric 12.0 5 Celestron 8-24 Zoom @ 32x 12.0 13 Pentax XF 12.0 16 AstroTech Paradigm 12.0 12 Meade Series 5000 HD-60 12.0 17 Televue Nagler Type IV 12.0 16 ES-92 12.0 17 Generic Kellner 12.5 5 Celestron Microguide Ortho 12.5 10 AstroTech AF70 13.0 18 Pentax XL 14.0 18 Baader Morpheus 14.0 18 Meade 4000 UWA 14.0 18 AstroTech Paradigm 15.0 12 Celestron 8-24 Zoom @24x 16.0 13 B&L WF 16.7 19 AstroTech AF70 17.0 17 Televue Nagler Type IV 17.0 15 ES-92 17.0 16 AstroTech Paradigm 18.0 12 Meade Series 5000 HD-60 18.0 19 Gary Russell Konig 19.0 15 Celestron 8-24 Zoom @20x 19.2 13 Generic Huygens 20.0 13 Generic Reversed Kellner 20.0 10 SVBONY 68° Ultra Wide Angle 20.0 14 Orion Centering SWA 20.0 11 UW80 20.0 28 Surplus Shed 7.2-21.5 Zoom @ 21.5mm 21.5 11 AstroTech AF70 22.0 16 Televue Nagler Type IV 22.0 14 Aspheric 62 degree 23.0 18 Olivon 8-24 Zoom @ 16x 24.0 14 APM Ultra Flat Field 24.0 17 Edscorp Abbe Ortho 25.0 16 AstroTech Paradigm 25.0 17 Meade Series 5000 HD-60 25.0 18 Meade Silvertop Plossl 26.0 16 Orion Sirius Plossl 26.0 11 Meade MWA 26.0 10 Televue Panoptic 27.0 14 Edmunds RKE 28.0 26 Rini Modified Plossl 29.0 10 APM Ultra Flat Field 30.0 16 UW80 30.0 18 Explore Scientific 82 30.0 16 Kasai Super WideView 90° 30.0 12 Orion Sirius Plossl 32.0 15 GSO Super Plossl 32.0 15 Rini Modified Plossl 35.0 17 US Military WF 35.0 28 Baader Scopos Extreme 35.0 16 Aero ED 35.0 14 Rini Modified Plossl 38.0 22 Meade Series 5000 Plossl 40.0 27 Meade Series 5000 SWA 40.0 24 Pentax XW-R 40.0 17 Rini Erfle 42.0 23

If you sell it on to someone in the US, can you reclaim that VAT tax at that time from the guv'mint?

FLO's 10mm Astro Essentials Super Plossl Eyepiece is only £20 and in stock. It should work fine as a direct replacement. If budget isn't an issue, I highly recommend the 10mm TV Delos at £336 from FLO. Mine is essentially flawless even in fast scopes.

I would guess you'd have to try them back to back to see which works better under your skies. I could see the narrower band pass photographic filter pulling ahead in heavily light polluted skies where a 10% loss in transmission of one line and complete loss of the other line is more than offset by increased contrast against background skyglow.

Seems to be little more than a large soft sided cooler. That's a good idea if it will be packed in with hard, shifting objects. Again, wrap it in bubble wrap or a camping ground pad and place it in the case. You don't want it bouncing around inside the hard sided case.

If you've got the spare cash lying around, and you've done due diligence with the seller, why not? You just want to avoid any as-is sales on such high dollar items in case they're trying to pass off a damaged item with undisclosed defects. ebay is pretty good about protecting buyers in non-as-is sales, so no worries there.

Generally, if you wrap the OTA in several inches of bubble wrap and put it in a duffel bag, you should be okay for personal transport. Just make sure the corrector end is sturdily capped. The mount should be fine when taken down to pieces and transported similarly. In fact, the tripod legs will be fine with a camping ground pad wrapped around them to prevent dings and scratches. Transport by airline or common carrier is a whole 'nother matter.

There is a hidden 20% VAT now that I think about it in UK pricing absent from US pricing. Since sale tax varies state by state, county by county, and city by city, it would be impossible to quote it in prices online here. It comes down to £552.63 without VAT, which is still $772. I suppose the rest of the difference (~$100) is import tariffs and importer markup.

I was thinking the same thing. Coincidence? I think not!

They're only $666 new here in the US, so $621 (converted) isn't much of a discount for us.

I thought they already sold out some time ago, at least in the US. Are they still available elsewhere?

You can always use an off axis aperture mask on a larger reflecting scope to see if the image improves.

In that price range, I would probably go down the Morpheus route. I have the 9mm and 14mm, and both compare favorably to Pentax XW/XL and TV Delos offerings. The 14mm is regarded as the weakest of the line, and yet it is quite nice in my experience. I would probably skip the 14mm if starting fresh and get a 12.5mm and/or 17.5mm instead. The 14mm and below are actually 78 degree AFOV eyepieces while the 17.5mm is actually 74 degrees, IIRC.

That version is a clone of the Vixen zoom, and is pretty well thought of. It would be difficult to do better at $46. If it doesn't work out, you should be able to easily recoup your money selling it on.

Which Celestron zoom? If you provide a link to it, that would help.

Thanks for clarifying that. I had been thinking Long Perng was Chinese like KUO, JOC, and JROIC. I've been touting GSO products for years, so I'll add LP to that list as well.

Do you wear eyeglasses while observing due to astigmatism? I've found most zoom eyepieces lack sufficient eye relief for eyeglass wearers. As far as zooms, I pick up the older Celestron Regal 8-24mm zooms (also sold as Olivon) that came with ED spotting scopes. I find them on ebay and CN classifieds for about $60. Once the eye cup is completely screwed off, I can use them with eyeglasses. Since I tend to use them with a Barlowed binoviewer, they perform pretty well across the field.

🤔The Vixen looks nothing like the Stellalyra: Not only that, they were introduced about 20 years apart into the market. The Vixen was Japanese made as I recall, while the StellaLyra is Taiwanese made.

Not every eyepiece is suited for every focal ratio. That's why we end up with a wide range of eyepiece focal lengths. I tend to use my AT72ED at 100x and below. Above that, purple fringing becomes very apparent. Thus, the 4.5mm would be fine for your ZS73 which will show even less fringing with its FPL-53 glass. With my f/12 127mm Mak, I tend to stay below 200x due to exit pupil issues. Thus, the 6.5mm would be about the max for your C5. Clearly, get both. 😁

Try repeating the lateral color test with a highly elevated, bright star to gauge just how much there is. My 13mm AstroTech AF70 has the most LC of any mainstream eyepiece I own. It throws up a very pretty rainbow starting at 70% out from center.

Sounds like it's time to start another eyepiece case. 😉