Louis D

I love the big fields of view in my various 2" eyepieces for sweeping star fields. I love 1.25" eyepieces for close-up views of smaller objects. Each has their place, and I wouldn't be without either.

I did try to use the Bahtinov mask that came with one of my scopes for focusing, and I couldn't make out the lines well enough visually to be of any help.

@LaurenceT Here's the "trippy" view of Jupiter through my apodizing mask: And here's the mask itself:

When buying diagonals, watch out for the ones with a curvy eyepiece holder. They tend to have largish lips inside them restricting the use of widest field eyepieces in either 2" size for 2" diagonals or 1.25" size for 1.25" diagonals. See the following thread:

Remember, FCD-100 is basically the same as FPL-53, only from Hoya instead of Ohara, so consider scopes using it as well. Consider an FPL-51/FCD-1 102mm. These are generally referred to simply as ED scopes. It will save you some money if your budget is fixed, and will show increased color fringing only at higher powers. It still won't have anywhere near the level of unfocused colors as in an achromat. Even an FPL-53/FCD-100 doublet will show some false color at higher powers. No refractor will ever be 100% color free like a pure reflector as with a Newtonian. The Canon Digisuper broadcast zoom lenses come mighty close, but at a $200,000 cost. Consider getting a sturdier alt-az mount that doesn't require a counter weight. Why lug dead weight up that 200m hill? Put that same weight into a better mount. A GSO dielectric diagonal will probably be just as good visually as that prism diagonal starting out, but at much less cost. A range of magnifications from 46x to 93x with the APM SZ would be fine for most observing, but you'd still want something wider to maximize your true field of view for objects like the Pleiades and for centering objects. For higher powers, you might want to invest in a good Barlow as well. I'd save a few bucks and get either a basic RDF or a Rigel QuikFinder instead of the Baader SF RDF.

I do tend to skip from a 40mm (Meade 5000 SWA, Pentax XW, or Lacerta ED) directly to either the 22mm NT4 or 17mm ES-92 (which have similar TFOV, 31.1mm FS vs. 27.4mm FS, respectively). So yes, the XW23 might be a better fit with the XW40. I'm guessing the XW23 will have a slightly larger field stop (FS) than the 22mm NT4, so maybe 32mm to 33mm.

Closer to the equator for a better launch boost, and the entire Atlantic Ocean to abort into.

Figure on increasing divergence from the distortionless calculated value the wider the apparent field of view (AFOV). The divergence often increases even more if the eyepiece is very well edge corrected.

Is that the same as self-adhesive weather stripping? I've never heard the term draught excluder before. Must be a UK-US English thing. 🤷‍♂️

Boeing is the Artemis prime contractor. They are a legacy defense contractor (think B-29s and F-15s). They build to a spec from the government on a cost-plus basis. They were required to do things a certain way as a result. Everything has to work perfectly on the first launch. SpaceX was self-funded, so they had a clean slate with which to start. They used aggressive prototype development techniques. Thus, all of the spectacular launch failures they've had. Here's an anecdote of saving weight to increase payload. Some SpaceX engineer did the numbers and questioned why they were using 4mm thick fuel tank walls when 3mm would suffice. Tanks had always been that thick going back to the 50s. Elon said, go ahead and make a tank 3mm thick, fuel it up and put it through the flight qualification tests. It worked perfectly, and they saved 25,000 pounds that could be added to the payload instead. By comparison, no Boeing engineer would have dared speak up because the culture is to always design to the government requirements. Asking to change them would have taken years of back and forth between subcontractors, Boeing, and the government, and the engineer would have risked his/her career to even bring it up because it shows they're not a team player willing to go along with the herd. Thinking outside the box is simply not in defense contractors' culture. The lone exception are skunk works projects like the SR-71 and the Manhattan Project where defense contractors are given very high level requirements and are allowed to run wild with them with very little public oversight.

You are correct. There are several non-US versions that include a straight through finder instead of the RACI. However, I have yet to see this version sold in the US. The Zhumell, Apertura, and Orion Skyline versions are/were all identical to the StellaLyra. My 6" f/5 GSO Newtonian came with a straight through finder, so it is possible the US may yet see a version of this Dob without the RACI, so buyers should definitely pay attention to the details.

How does it differ from SkEye? Is it possible to tilt the phone for easier reading and still align on objects? Any plans to add plate solving with the selfie camera to improve accuracy?

If weight is critical, harmonic drives are hard to beat because you can often get away without using counterweights.

No joke. I'll try to remember to snap a pic through it of Jupiter sometime.

Missed that. I'm out unless screwing off the upper ring restores most of that eye relief. Despite my 40mm XW's eye lens being recessed 7.5mm, I still measure 17mm of usable eye relief rather than the 15mm quoted in the chart up above. There is a threaded ~6mm tall metal lip above the glass. I suppose you could machine it off if you didn't want to be able to thread on the eyecup any longer and get to about 22mm of eye relief. Perhaps something like this could be done with the new XW85s.

That seems odd. They make a 25mm ES-100 (with a touch of vignetting). It seems like 23mm to 26mm at 92 degree should be doable.

So does my 7mm XW at the edge. My old 5.2mm XL does not. I've never detected any aberrations edge to edge in it.

If you need long eye relief, I would steer you toward the 30mm APM UFF or one of its other brandings. As you say, the 32mm is little better than an Erfle from what what I've read over the years, which is to say pretty bad at f/5. It boggles the mind retailers ask more than $120 for them based on performance when there are $200 28mm UWAs that trounce it AFOV and correction-wise. At 22mm, I can highly recommend the Omegon Redline since I've had the Astro-Tech AF70 version for years. It is nearly perfect to the edge at f/6. Only the last 5% shows mild astigmatism. Eye relief is very comfortable, no vignetting, and no SAEP/CAEP.

Wow, that is a loaded, open-ended question. How much money do you have? I can point you to many excellent eyepieces ranging from $300 to well over $1000 each.

New branding perhaps, but these GSO scopes have been available under multiple other brands for years. I recall the Zhumell ones coming out well over a decade ago. Here's a 2009 review. Otherwise, very nice write-up. I agree about the collimation knobs protruding being a concern. I have a GSO 6" f/5 OTA with the same issue. I guess since I've never had a Dob with a navigation knob, I've never missed having one. I just curl my fingertip around the end of the tube. Handles, especially two on the base, make moving an assembled solid tube much easier. I just hug mine to my body, straighten my knees, and off I go with it.

Hopefully edge correction is better than in the 30mm and 40mm XWs. The 30mm suffers from edge chromatic aberrations and the 40mm from edge astigmatism and field curvature, and they're only 70 degrees. The 23mm appears to be almost identical in size to the 30mm while the 16.5mm will be a bit taller. With MSRPs of $479.95 for the 16.5mm and $499.95 for the 23mm, I'd have to think long and hard about buying them since I already have the 17mm ES-92 and 17mm and 22mm Nagler T4s. What I really want is for ES to release a 23mm to 26mm ES-92. I'll take a wait and see attitude toward these new XWs for now. Press release image: Here's a couple of press releases I found about them.

If that is a 127mm Mak, you could adapt it to use 2" eyepieces to get to a wider field of view. I did it with mine. However, why would you want to use a 2x Barlow with a 127 Mak? It is slow (f/12) and has a long focal length (1500mm). 8mm is about the shortest eyepiece I use with mine.

Probably should just return to seller as "Item misrepresented" or work directly with them on an exchange with possible credit, making them swallow the additional shipping costs. Was it this ad? If so, it was definitely misleading. It can accept a 1.25" eyepiece with the included adapter, but it is always listed as a 2" Barlow by every dealer I've ever seen. Here's the same GSO-made Barlow under the Altair brand on the ENS website properly labelled as a 2" Barlow.

You could use it to achieve critical focus visually, I suppose. You would then remove it to observe and resist the temptation to tweak the focus. There is an apodizing mask you can make from window screen material and crafting foam board to supposedly improve planetary views. I made one back in the late 90s and get it out sometimes to see if it helps. My impression of it is that it makes very little difference in contrast or sharpness. However, it makes for a really trippy view with lots of diffraction effects going on everywhere outside of the center.

The sheer weight of these EQ mounts puts me off immediately. My wonky back makes dealing with the heavy head, legs, and counterweights a literal pain in the back.