BillP

At f/5 the 31T5 will be far superior. In the review I did that others linked to, in my f/8 the Masuyama was well controlled only in the center 75% of the FOV, so at f/5 I would expect it to be worse. Given how good the contrast was in the eyepiece I was able to tolerate only the central 75% being tight, so liked it in my f/8. But have to tell you, that the 31T5 is one heavy and large brick. So ergonomically I have never liked that eyepiece as just too big and bulky, and it overwhelms smaller scopes. The Masuyama was compact and light so a joy to use in that respect. What kind of scope are you using? If an f/5 Dob then FWIW realize that even the 31T5 will show a poor off-axis as it will not correct the coma from the mirror. So if you do not have a coma corrector for the scope then that would be my first order of business, especially when wanting to use long focal length wide fields. With eyepieces of 15mm and shorter you don't notice the coma so much since they show less TFOV so can easily get by without a coma corrector. But longer than 15mm focal length and wide fields, then a a coma corrector makes a world of difference to the view when using f/5 and faster Dobs/Newts.

Over the past 4-5 weeks I've put the Carl Zeiss Apochromatic Sharpest Binoviewer thru its paces (offered by Denis Levatić of Croatia). This was a very interesting binoviewer as it incorporates mirrors instead of having long glasspath through prisms. Performed excellently. Enjoy! Tue 1/19/2021 11:13 AM Zeiss CZAS Binoviewer.pdf

FWIW, at the last two locations I have lived at, the behavior was/is quite the same and that between 2-4am the seeing seems to really settle down. That was the time I used for most of my Mars observations for the article as the planet was rock steady with details abounding.

Only problem there is that have a 2.5mm exit pupil at 250x magnification requires a 750mm aperture telescope (about 30"diameter)!!!!

John, Hi. Yes I saw that Orion guide as well as oodles of others. Also the ALPO guide. But vast majority of what they showed did not pan out for me. Indeed when working at <1mm exit pupil to get to descent planetary magnifications, many of the filters recommended in guides are just too dark and excessively dimming. I think that for descent image scale of a planet one needs at least 150x. The aperture needed to be at 150x and say a 2mm exit pupil so the planet and features are bright enough to work with many of the darker filters would be 300mm. Larger than what most folks have. So IMO the common guides one finds on the internet for what filters help what I feel are basically unrealistic. But I put the caution in my write up that things may change with larger apertures when one can get to planetary magnifications with larger and brighter exit pupils. So I think what I saw is probably extensible to apertures as large as 200mm. Larger than 200mm and one is getting enough extra light that more color filters might start to become a little more useful, and by the time you get to 300mm aperture probably a whole different ballgame as long as observing at 2mm exit pupil and larger. If the seeing is good enough that one can get to a .75mm exit pupil with a 200-300mm scope, then I the filter field will be limited to the useful ones I discovered.

After half a century of reading internet sites touting how seemingly every color filter made enhances just about everything for planets, I decided to buy a set and compare them on the planets, and also compare them to a few specialty filters like the Baader Contrast Booster, Moon & Skyglow, and Semi-APO filters. Spent almost 4 months observing and comparing and here is what I saw. Enjoy! Using Filters for Lunar-Planetary Observing v20200917 (lowres).pdf

I hear you. Me too usually. I have had a few permanently collimated items though, including a scope. They never went out, of course I usually do not drop things or knock over my scopes so no unreasonably hard bangs. 🤪 My WO Binos never lost collimation and had them for well over a decade. None of binoculars have either. I don't believe any of my diagonals are collimatable. The main optic is the only thing I guess I like to be collimatable, rest of the stuff is small should not have issues if reasonably built, and that has been my experience to date. Large glass or mirror objectives though have so much mass that it is a challenge for the cells that hold them. FWIW the warranty is 2 years I understand on the MKIIs.

Thanks all! After many years with the WO Binoviewer I was thrilled at how well these kept the eyepieces centered no matter what, so merging was always spot on. And adjusting the diopter without rotating the eyepiece was a godsend for me. Finally, being able to use my 24 ES 68s without vignetting made them everything I was hoping for. Finally a binoviewer that was not a hassle to use while giving great views without breaking my diminishing bank!!

Over the past 4+ weeks I have put the new MaxBright-II Binoviewer though many observations using my TSA-102 and APM/Lunt-152 Apos. Wonderful ergonomics in the field! Excellent overall! See attached write up. Baader MaxBright II Review (2 May 2020 PD).doc

But that compare would be off from what I was suggesting. My expectation is that a 12.5mm Abbe with the TV 2.5x vs. a 5mm Abbe will be quite close if not exactly the same view. However, a 12.5mm Plossl with the TV 2.5x will probably show a softer view than a 5mm Abbe. Just something that I noticed in my experimentation than Plossls do not Barlow as well as other designs.

If you do a test I'd be interested to hear, especially if you Barlow them. A few years back I did a personal experiment and took some common Abbes and a few Plossls of similar focal lengths and Barlowed them for high magnification lunar and planetary observing. None of the Plossls when Barlowed were able to produce as crisp of an image as the Abbes Barlowed to the same magnification. Was a real eye opener. Convinced me that Plossls are not a good choice to Barlow for planetary observing.

It really wouldn't make sense IMO to do an evaluation of a ZAO between say my TSA-102 and a SW120ED because they have so many different attributes that one would not be able to tell what improvement was being driven by the eyepiece, vs the main optic. Now if you want to evaluate a ZAO in a TSA-102 vs. a SW100ED then more likely we could make some inferences relative to what the eyepiece was bringing to the table in each. But in my experience with testing so much stuff, it has stuck out to me that the more refined the optical chain, the more benefit I see in a ZAO vs. a lesser eyepiece. I generally see less of a distinction with my Newts because a little dust on a mirror has more impact than a little dust on a refractive optic, so the additional scatter can start to mask some of the improvements the eyepiece could have generated. But after a fresh cleaning of my mirrors, then the distinctions are more pronounced. Getting rid of all the stray light potentials in an OTA and keeping the optics as dust free as possible really does work wonders (and don't stop at the OTA as I found some diagonals or 2" to 1.25" adapters have some pretty shiny and reflective surfaces reflecting back towards the main optic). IMO anything that lessens contrast is the biggest contributor to poor views.

Ole Bugs is my favorite you know

I quite agree with you. For this price point on the used market, it is hard to justify. In fact, many times I have decided to sell my 6mm ZAO and 5mm XO because they are so expensive and used so little. But then, even after using all the premium eyepieces you mentioned, an evening comes where I am on a target appropriate for these little gems, and the sky conditions are also supporting the venture, and when I put them in and look at the view I just gasp. They really are the pinnacle of the eyepiece art IMO and show it well when all else is in place in the optical chain. So then, when I do this, then I think how foolish I was considering selling them because there is just nothing out there that shows as refined and transparent of a view. So for me at least they are very much of a paradox...too expensive and impractical and the small AFOV really only good for a narrow band of targets...and also worth every penny and difficult to imagine not being able to have such a view when I want to. In the end, very happy the day rolled along where I could afford them, and hope I am never foolish enough in the future to ever let them go.

For the common focal lengths of 16mm and shorter I've never seen one for less than $500-600 USD. For the rarer 25mm and 35mm ZAO-1's at least $1500 USD.