Louis D

I'm sure that's what's going on. During the dead of summer here while we have a stationary high pressure dome parked over us for months (can you say drought?), the seeing is rock steady and temperatures drop slowly at night. As such, it's quite easy to bump up the power on large Dobs to have the same exit pupil as that of a smaller frac. Under these conditions, it is so much easier to make out fine planetary details at the larger image scale and higher theoretical resolution of the big Dobs than in nearby fracs. UK seeing conditions are probably the dominant reason for the lack of popularity of big Dobs there. They would probably just show a boiling mess of turbulent atmosphere.

There are several newer computerized EEVA telescopes that are supposed to make the process foolproof: eVscope eQuinox Vaonis Stellina 😉

I look at it this way. If you've got $10,000 to spend toward getting the best planetary views, a decent sized Dob with a Zambuto mirror will blow the doors off a similarly priced APO and quality mount on most nights here in Texas. Perhaps things are different in the UK, but I've always been underwhelmed by the planetary views through high end APOs when compared to the views through high end Dobs of similar money at star parties here. We are generally pretty far south of the jet stream, though.

21mm Ethos - $853.00 20mm ES-100 - $799.99 20mm APM XWA- $329 There's no reason to not spend the extra $53 and buy the Ethos over the ES-100. However, the APM is less than half the cost of either of the other two. The APM is lighter than either of the other two (678g vs 968g for the ES-100 and 1021g for the Ethos). Most reviews on CN comparing the three put the Ethos well out front in correction and contrast in fast scopes with the APM not far behind, suffering only in the outer 10% to 15% of the field and having some slight stray light control issues. The ES rates similarly to slightly behind the APM. The 20mm APM is generally regarded as the weakest of the XWA line of eyepieces, and yet gives up nothing to the ES. There is literally nothing to recommend the ES over the APM unless it were to be availability for immediate purchase.

On closer inspection of this photo, I realized that you'd need an M48 spacer ring (empty filter ring) to keep the field lens of some 2" eyepieces from crashing into that raised metal ring inside the M48 thread if you tried to screw the eyepiece directly to it. Legitimately, I could see attaching an 12mm ES-92 to it with minimal vignetting, although I'd probably go the route of the 2" to T2 thread visual back for quicker eyepiece swaps. Of course, the eyepiece would weigh more than the entire scope (1011g for the 12mm ES-92 vs. 792 for the Mak).

Found this available in the US: Blue Fireball Eyepiece Holder (1.25") with T / T2 Female Thread (T2 Visual Back) # E-10 And if you want a 2" to T2 visual back: Blue Fireball Eyepiece Holder (2") with T / T2 Female Thread (T2 Visual Back) # E-09

That means a 2" eyepiece with filter threads could be screwed onto the back as well. You should try a max field eyepiece with a ~46mm field stop diameter on it for giggles to see how much it vignettes. 😁

Even better as a root beer float with a couple of scoops of vanilla ice cream. Yummy!

There is the older PICO-6 60mm Maksutov, of which I have a used copy, that can accept 1.25" accessories natively. However, the optics have severe spherical aberrations visible at anything above the lowest power possible, so it's more of a conversation piece for me.

Now that you mention it, a few years ago I had bought a loveseat for my son's room in a fraternity house built in the 50s. It turns out, the doorway was too narrow to fit it through no matter how much the delivery folks tried, so it had to go back to the warehouse for a refund. My son was pretty bummed out.

And I'm sure the UK has a LOT more older houses and multifamily dwellings (apartment buildings in US English) than the US to be grandfathered. 😉 However, if you do a major remodel (gutting interior walls, moving entrance doors, etc.), you may have to meet ADA guidelines during the permitting process of the redesign. In the US under ADA guidelines, businesses have to make accommodations unless they can get protected historical status (like old basement pubs). There was a lot of grumbling when the ADA was signed into law 31 years ago, but now it's just accepted as the current normal. Things like office building ramps have turned out to be a boon for delivery folks with heavy pallets, so it's had unforeseen benefits. Ample handicap accessible parking has been welcomed by the aging Boomer generation as well.

Since the eye lens is about the same diameter for both (~30mm), I wouldn't doubt you would be able to see at least as much of the field in the XWA as in the NT4 (~82°) while wearing eyeglasses. However, can you actually see the entire 100° of the XWA with eyeglasses? I can just take in the 92° field of my ES92s by resting my glasses against the folded eye guard of each, and they each have a 43mm diameter eye lens! I tried an Ethos at a star party while wearing eyeglasses and could only see the inner 70° or so with ease, and it also had a ~30mm diameter eye lens.

I'm investigating a theory of mine that thread depth is also a factor. I've noticed on closer inspection of some troublesome male filter threads that they are deeper and sharper compared to less troublesome threads which are shallower and blunter. I think it's because a lot of female filter threads are not very deep on inspection. Thus, the male threads have to "chase" the female threads to make them deep enough to thread into.

I'm guessing there's no ADA (Americans with Disabilities Act) equivalent in the UK dictating such things nationwide. Getting a wheelchair through a 28 inch doorway would be a serious challenge. Getting a washer/dryer set through that door would also be tight.

It's basically the same thing as the generic Moon & Sky Glow filters that go for under $20. Just do your homework and look for the pale blue filter color and the spectral chart.

If you watch the classifieds, you should be able to pick up a used 2" GSO (Revelation, TPO, etc.) dielectric diagonal for under $100. A 2" SCT visual back generally goes for under $30. You won't be able to use your R/C with them due to vignetting. Is it worth the upgrade, that's a question only you can answer. The true field of view with a 32mm Plossl and R/C is about the maximum possible with an SCT already. I'm puzzled why you have both 30mm and 35mm ED eyepieces. At the low end of the power scale, there isn't a whole lot of difference between them. I am also puzzled why you don't have more eyepieces at the shorter focal length end. You could do with a 4.5mm to 5mm eyepiece as well as a 9mm to 12mm eyepiece to fill in some of the gaps. I suppose you've been using your 2.5x Barlow to fill these roles? How often do you find yourself using it for higher powers? If it is a lot, I highly recommend getting a dedicated eyepiece in that range (or ranges). The BH would do okay with the SCT but not with the Dob. I'd stick with Morpheus, Delos, or XW eyepieces for the Dob's sake.

How narrow is your front door? Most construction codes dictate a minimum 32 inch wide front door; however, most are 36" wide.

I would think vintage American made SCTs from Celestron and Meade would both be higher priced in all of Europe than in the US during the first sale in the same way Tele Vue eyepieces are consistently more expensive in Europe than the US. This initially higher price then continues over to the used market. I'm also going to guess that SCTs didn't sell in as high a numbers over there as they did here, so the used market isn't so flooded as here, driving up used prices in Europe as a whole.

I would think well annealed "float" glass. At their original price point, you weren't going to be getting Pyrex, Quartz, or Sitall glass. Some deluxe SCTs intended for imaging may have come with Crown glass correctors.

Pistol cases are pretty cheap in the US, but probably harder to come by in the UK. I have several for binoviewers and smaller eyepieces. They're not waterproof, but they're good enough for my less expensive eyepieces. I use Pelican style waterproof cases for my more expensive eyepieces. There are some decent Chinese made knock-offs available, just with lower density foam.

What a gorgeous conversation piece. Those lines were classic.

Preaching to the choir you are. You're comparing classic American manufacturing to modern Chinese manufacturing.

Or any undercut if the collet is high as with the Arcturus. It tends to push the eyepiece up and out of the holder because it's trying to tighten on the upper taper. I have to jam it down while tightening to prevent this from happening. Even with thumbscrews I've had this issue (on a diagonal) when it is too high and also pushes the eyepiece up and out while tightening because it's pushing against the upper taper. I don't know how high the Norin BV thumbscrews are mounted, though.

Same with the Arcturus BV. It's actually funny in a sad sort of way to watch one image circle around the other while spinning the diopter adjuster.

I'm picturing the coatings were made from agar (think Petri dish lining).