Louis D

To really justify the asking price, the seller needs proper provenance papers showing it was actually used to film the original NASA missions of the '60s and '70s and the Challenger explosion as alluded to in the description. At that point, it has serious collector value as a witness to history. Otherwise, it may just be a surplussed spare that was never used.

What about designing a large format focal reducer for it to bring the focal ratio and focal length down along with shrinking the image circle to a more manageable size?

I've never used Sky Safari. I was thinking in terms of SkEye that keeps the pointing direction centered while slewing the map as needed to achieve this. What's the advantage of not slewing the map to the current pointing direction in real time, map rendering time? Is there an option in Sky Safari to turn this on, so you don't have to go hunting for the current position indicator every time you move the scope?

Maybe we need to petition Baader to include several thin M43 sized O-rings for fine tuning the eye cup height as you did on the 4.5mm Morpheus. They already include the useless clip for the eyepiece holster that's supposed to be used for tactile nighttime identification of eyepieces, so why not include something actually useful that costs pennies/pence in volume?

During Freedom Find mode, does the star chart in the app move in sync with the manually slewed scope, so if you see an object through the eyepiece that you want to identify, all you have to do is look at the app to see what's in or near the center of the current field of view?

If I did use it first on here, it was only reusing a term from 50+ years ago. Tupperware invented the airtight plastic storage container market years ago (at least in the US); and in commercials, they would refer to "burping" the lid to push out excess air (at about 35 seconds in):

Do you mean way in, as in closer to the objective? Racking the focuser outward mean extending it away from the objective in my experience. The 2" lower barrel section on the SZ acts like a built in extension tube in 1.25" mode. I get the same effect with Morpheus and similar eyepieces.

Well, the TV PBI was discontinued over a decade ago, so I wouldn't expect you to have heard of it. I think I bought the last one in stock at Adorama in 2010 for $60. Since the intended Barlow for it, the TV Big Barlow, has basically the same focal length as the GSO ED 2" 2x Barlow, the latter works well with the PBI. On the other hand, I tried it with my 1990s Japanese made Orion 2" 2x Barlow which has about a 50% longer focal length, and the combo is horrific. I have no words for the very odd distortions going on with those two. It hurts the brain trying to focus on objects when viewing through that combo. Thus, serendipity for the GSO/PBI combo. That, or GSO simply copied the TV BB optical design.

The Astro-Tech AF70 (Omegon Redline SW, etc.) have M43 eye cups as well, just extremely stiff. They basically can't be folded down at all, so I have to unscrew and remove them altogether. Here's an image of mine showing the eye cup attached to the 17mm version: M43 is a fairly common size for eyepieces, video cameras, and digital camera adapter tube filter threads. I believe the 24mm APM UFF has that thread size as well. However, the 30mm APM UFF has an M45 thread, so not universal even with the UFF line.

Let us know how it interacts with your 2" eyepiece collection. I have a poor-man's 2x 2" Powermate, a 2" 2x GSO ED Barlow + TV PBI. It works well with most eyepieces, but not all. Here's my findings back on July 9th: Next, I tried them all in a GSO ED 2x 2" Barlow with a Tele Vue Panoptic Barlow Interface without the GSO CC since I don't have enough in-focus for both at the same time. Surprisingly, the 40mm Lacerta didn't improve very much at the edge. The 35mm ED improved a bit more, but was not perfect. The 40mm Pentax didn't play well at all with it. The outer field wasn't sharp anymore. The 40mm Meade SWA worked exceptionally well with the Barlow, showing a sharp edge and flat field. The 35mm Scopos and 26mm MWA both worked well Barlowed, but there was a bit of exit pupil instability with the former and no change in SAEP with the latter. The 40mm Lacerta was a bit tight in the TV PBI, but not as bad as in the GSO CC.

I was genuinely surprised after having used doublets for years at just how slowly a triplet cools. Basically as slowly as the 127 Mak, if not slower. I just wanted to put that out there to avoid someone else like me upgrading to a triplet and being shocked by how slowly it acclimates. If quick acclimation is the goal, definitely stick with doublets.

I assume you've read @John's comparison of the Hyperions with the Vixen LVWs from which they were cloned? If not, it's a good starting point.

I guess you've never used a triplet refractor. Mine takes at least 30 minute to acclimate. All sorts of pinched optics looking artifacts until then.

Since I buy most astro gear used, I'd go for the 127 Mak because they show up so often in the classifieds, at least here in the US. I don't think I've ever seen a SW Heritage 150 on the classifieds. I know used prices have gone up recently, but in the last 4 years I've picked up two Synta 127 Maks for $200 each. One was for me and one was for my grown daughter. Keep in mind you'll need to budget for a mount and tripod for the 127 Mak while you can technically use the SWH 150 right out of the box on a table top.

If it's anything like the 12.5mm APM Hi-FW, you can roll the eyecup down over the exposed threads more easily than with the knurled ring in place to maximize eye relief. It's a little tricky until it's snugly ringing the threads, then it stays nicely in place. It's the second one from the right below. I couldn't get the eye cup to roll down and stay down over the knurled ring. I now know that @badhex needs less eye relief; but I thought I'd share my learnings with KUO eyepieces having that knurled ring in case others need more, rather than less, eye relief.

I use a GSO CC in my f/6 scope with a 25mm spacer ring. It nicely cleans up the coma in my widest true field eyepieces and in my UWA eyepieces like my ES-92s.

Binoviewers help in six main ways I've found: With two eyes, the brain selectively filters out floater blockages from one eye with information from the other eye creating a much better image. It has its limits when floaters in each eye obscure the same part of the view. Try closing one eye for a while and look at a clear blue sky. You'll see obvious floaters. Now open both eyes and look again. Fairly quickly, the obviousness of the floaters dissipates quite a bit. Overly bright objects like the full moon, the solar disk, and planets at opposition are much improved with two eyes. I chalk it up to the brain not being able to combine a super bright image with a pitch black (or nearly so) image. On both the full moon and Mars, I have gone from seeing a washed out disk to high contrast, detailed views just by switching to my binoviewers. Two eyes working together is much more natural for the brain to process, and low contrast details just seem to pop in binoviewers that were all but indiscernible with one eye, even with dimmer objects that aren't washed out in monovision. Eye strain disappears and viewing become very relaxing with binoviewers once you get everything dialed in perfectly (which admittedly can take some trial and error). I stared at Mars for 20 to 30 minutes at a time without fatigue. It was an amazing feeling. The apparent field of view appears about 5 degrees wider than when monoviewing with the same eyepieces. My 60 degree AFOV microscope eyepieces appear to show about a 65 degree AFOV. I think your brain normally stiches together two images of slightly different viewpoints into a wider TFOV image (try closing one eye to see how much TFOV you lose); so instinctively, you perceive a two eyed view as being wider even if it is showing the exact same view as monovision. As such, I don't feel compelled to search out ever wider AFOV eyepiece pairs. Besides, you can't see the edges except in peripheral vision because the moment you look off axis, you lose one, and sometimes both, eyepiece views. You don't need ZAOs, TMB Monocentrics, Vixen HRs, or Tak TOEs to see low contrast, fine detail with binoviewers. Fairly basic eyepieces that are well executed give excellent views in BVs in my experience.

The vignetting would be fairly moderate and would only be visible in the outer field for truly maximum TFOV eyepieces. You'd probably have to look at a clear blue sky to detect the vignetting.

Mine is certainly sharp enough, but I rarely use it. The exit pupil gets super tiny with scopes slower than about f/5 and my eye floaters become intrusive. I have to keep flicking my eye to get them out of the way for a fraction of a second to get a sharper view. Bright planets and the full moon tend to get washed out looking at those high powers for some reason. You'd think the high power would take the brightness, but it doesn't. I got much better views of Mars at the last opposition using an entry level binoviewer and a pair of vintage 15x microscope eyepieces with a nose piece from a vintage Meade 140 Barlow to reach focus and to boost power by 3x. Depending on how much you pick up the various pieces for, it might be a wash cost-wise.

I bought my used GSO CC over 6 years ago, so it is likely close to a decade old. It had the pot metal screws that jammed and then sheared off in one of the holes. I would surmise that the use of these screws greatly predates the pandemic.

I would get a 32mm Plossl to max out your true field of view. I find low power views very rewarding, bright, and sharp. They also help when centering an object for higher power viewing.

At what power were you observing it? If you push the power up to at least 200x, you might start to see some outer straggler stars and brighter core stars resolving as twinkling pinpoints of light. Globular clusters take power and aperture really well because they start to resolve at high power in large scopes, which cuts through light pollution. M10 from Hubble: Do you see how some stars are intrinsically brighter? Those are the ones that start to stand out from the fuzzy background collection of dimmer stars at higher powers.

The only SCT I've looked through that inch for inch rivaled a Newtonian with a hand figured mirror and undersized secondary for planetary views was a Celestron Edge HD (8" in particular). With a 10mm Delos, Jupiter was sharp, false color free, and showing lots of fine belt details. It was stunningly better than the multitude of standard SCTs around the observing field that night. I think it's down to the optics putting all the light bundles where they're supposed to be:

That's the way varifocal eyepieces like the Speers-Waler 5-8mm and 8-12mm eyepieces work. They have constant AFOV and are nowhere close to parfocal. Zoom eyepieces have a Barlow-like group at the bottom that moves downward while a middle group moves upward to maintain some semblance of parfocality. The downside of this approach is a non-constant AFOV.

A pair of compact porro prism binoculars would work fine for daytime use for up to 10x. I've used a pair of Nikon Venturer 2 10x25s for years to good effect. They're compact enough to fit in any case or pack. They're not quite pocketable, though. The exit pupil of 2.5mm matches or exceeds most folks daytime pupil dilation. For nighttime use, you'll want to target an exit pupil of around 5mm to 7mm. For 8x, this would be 40mm to 56mm. For 10x, this would be 50mm to 70mm. You have to be dark adapted for a long time, and young, to reach 7mm pupil dilation to properly take in all the light of a 7mm exit pupil. Thus, I recommend 5mm as plenty of exit pupil. Thus, the popularity of 7x35, 8x40, and 10x50 binoculars. Roof prism binoculars are generally weather sealed, internally focusing, and difficult to knock out of alignment, but they really need phase coatings to get sharp, contrasty views comparable to porro prism binos. Unfortunately, I've yet to see phase coated binoculars migrate down to the $100 end of the market, which is about all I want to spend on something I use so infrequently. They also can't have large objectives due to their straight through light path, limiting the side-by-side size of the tubes. This is why I recommend porro prisms despite their weight and size at a 5mm exit pupil.