Louis D

More than likely, no, it won't noticeably impact viewing for the time being.

Because Pentax eyepieces are weatherproofed, the threads are threadlocked and are nearly impossible to loosen without strap wrenches.

Pentax eyepieces are supposed to be weatherproof to protect against this very problem. You might want to check with Pentax Europe first. Here's their warranty in the US: PENTAX THE PENTAX "WORRY FREE" WARRANTY The PENTAX "Worry-Free" Warranty is available on all PENTAX Sport Optics products purchased in the United States, on or after March 1, 2006, from an authorized PENTAX Sport Optics dealer. PENTAX Sport Optics products are of the highest optical and mechanical quality. If your PENTAX Binocular, Spotting Scope or Riflescope purchased in the USA from an authorized PENTAX Sport Optics dealer requires repair, PENTAX will repair or replace it to the original purchaser (even if damaged by fault) for a charge of $19.95, to cover handling and return shipping.* This warranty does not cover cosmetic damage, theft or loss. (Replacement may be with comparable model at PENTAX's discretion if the original model is no longer available.) *Applies only to unmodified equipment or product with modifications performed by authorized PENTAX repair personnel.

If you have a Tele Vue eyepiece, their online specs are quite accurate in my experience. You can start with that eyepiece as the baseline for your measurements. First, setup a ruler or yard/meter stick a good distance (20 to 40 feet minimum) from your telescope. Next, put the TV eyepiece in the focuser, focus on the ruler, and note the left to right distance from field stop edge to field stop edge. Next, substitute your unknown field stop eyepieces and measure the displayed distances. Since it's a direct linear relationship between distance on the ruler and field stop diameter, all you have to do is divide the TV field stop number by the distance it showed on the ruler. This becomes your conversion coefficient from ruler distance to field stop diameter. Now, just multiply each ruler distance by that coefficient to calculate each eyepiece's field stop diameter. Due to measurement errors, you shouldn't expect FS diameter accuracy better than about 0.3mm in my experience. This method is completely independent of eyepiece magnification distortion across the field of view or location of the FS within the eyepiece. If you don't have any TV eyepieces to boot strap the process, you might try a 32mm Plossl which generally has a ~27mm field stop diameter and is completely measurable with calipers to get better accuracy. In fact, any simple positive-only eyepiece like a Plossl, Kellner, Ortho, Huygens, RK, RKE, etc. will work as long as you have calipers accurate to sub-millimeter distances to generate your baseline coefficient. In fact, if you have multiple coefficient measurements from multiple eyepieces, you can average them for better accuracy.

That's why I only cap eyepieces in my airtight cases while outside. The air sealed inside is very dry and only slowly humidifies long after the eyepieces have warmed. Eyepieces, diagonals, finders, and OTAs not sealed in airtight cases are left uncapped in open cases to warm up to prevent fungal grown. 20+ years of practical experience later, and I've not had any evidence of fungal grown on anything.

Those low cost 0.5x FRs impart loads of field curvature to the image, so not very useful in my opinion. If you go with a 2" visual back, 2" diagonal, and 2" widest field eyepiece, you'll see an improvement in true field of view similar to below with gradual vignetting: It does help when centering bright objects in particular given how narrow the true field of view is.

I put my Paradigm (Starguider) eyepiece collection in a B&W Type 1000 case. Of course, I picked it up for only $10 on sale at Fry's before they closed up for good a few years ago. They're quite a bit more expensive nowadays.

I thought the SVBONY CLS looked pretty decent under Bortle 9 skies in that filter review. In a 1.25" size, they're only $30+tax shipped here in the States. At that price, you don't feel too bad if it doesn't get a lot of use.

Check to see if the eye cup is 2" in diameter. The one on my Celestron Regal zoom is, and a soft plastic 2" cap fits over it perfectly: You could then store away the original thread-on cap in the original eyepiece box if you want to resell it later.

First off, what f-ratio is the scope you're going to be using it in? Second, will you be using a Barlow to boost the power and/or reach focus? It makes a difference in the required quality of the eyepiece for wide fields of view. The NPL being a Plossl should be fine at f/6 and above. I don't know if they're worth about twice the money of the Astro Essentials or Revelation 20mm Plossls. Has anyone compared them to see if the lens polish, coatings, and stray light control of the NPLs are that much better than budget Plossls? I use a 2x Barlow nosepiece operating at 3x in my binoviewers, so I have an effective f/18 focal ratio or longer in my scopes. As such, a pair of SVBONY 68° Ultra Wide Angle 20mm eyepieces work great for me. They just about max out the unvignetted field in my BVs. I wouldn't recommend them for scopes below f/10 natively, though. I wrote up my thoughts on the SVBONY below:

The twist-up eye cup on my Celestron Regal 8-24mm zoom unscrews if you keep twisting down the eye cup. It's counterintuitive on purpose, I believe. The resulting exposed thread is perfect for winged eye guards for binoviewer use both because of its diameter and because it doesn't rotate during zooming like the BHZ's top. Did I see that right in the video at the 2:25 mark? The eye lens cap screws on over the entire eye cup assembly? That is so cool! I can't think of another eyepiece with such a cover.

But you've felt no need to raise the twist-up eye cup due to excessive eye relief?

Does it have 20mm of usable eye relief for eyeglass wearers as claimed by both Orion and FLO?

I wonder how well carbon fiber tripods stand up to being banged in the side during loading/unloading in a car. My well used Manfrotto 058B has a good ding in one of its aluminum legs that doesn't affect it ability to extend at all. I do wonder if it creates a weak point where buckling may someday occur. Given that I never extend the legs, and there are two more leg sections inside, I don't think it would lead to a catastrophic failure. The 26 pound load rating is for when it is fully extended to 7 feet tall. I have no idea what its load capacity is when not extended with the geared column all the way down and locked. I put 25 pounds on it all the time with the DSV-2B mount and two small to mid sized scopes without any issues. If I crank up the center column, it has to be exactly level or there is some binding that goes on during the motion. I'd rather have the heftier geared center column of the Manfrotto 161 (Bogen 3058), but they're hard to find for under $200 used. If I even move up to a DSV-3, I'll probably have to get one, though.

Worked for this guy:

Since it proclaims Schott glass on the side label, it's pretty safe to assume it's an ED scope of some sort.

How low can you set a Berlebach tripod for seated use? I use the adjustable leg angles on my Manfrotto 058B to allow the legs to splay out enough to bring the eyepiece down to a seated level. If I'm observing near zenith, I just crank up the elevator a bit. How do you adjust the height of the Berlebach to account for differences between low altitude and high altitude objects? On soil, vibrations naturally damp out very quickly. If I'm setup on concrete, I put Sorbothane pads under each foot to reduce damping time from 3 seconds to 1/2 second, which is quite acceptable during focusing.

I did a quick Google search and found the following imaging comparisons: https://star-hunter.ru/en/optolong-l-pro-clip-eos-review/ I would say it's more applicable to general imaging than visual from light polluted skies where maintaining color balance and shorter exposures is important. Visually, it would have a subtle effect, but would probably be a decent choice for galaxies. For nebula, there are better choices. It just depends on what you want from a filter.

You'll also get less vignetting with the 2" camera adapter.

Yes, focuser travel is generally setup assuming use of a diagonal. You shouldn't have any issues with the DSLR if using a T-mount because it will add 55mm of extension which is very similar to the optical path length of a 1.25" diagonal (65mm to 95mm, depending on prism vs. mirror and brand).

You'll have to hunt down an original Vixen LV 7mm. It was dropped for the NLV and SLV lines. The 7mm Pentax XW is decent enough, though.

Looks like the designer chose a path similar to Hubble Optics for the upper cage.

Speaking of close focusing, when taking test photos inside my house through the 127 Mak with an eyepiece, I can't rack the mirror enough to bring an object at 35 feet into focus. It's not a problem at all with either the 72ED or 90MM APO to reach focus, though. So, I add about 50mm of extension to the rear port and leave the mirror roughly at its infinity focus position. As a bonus, it is still operating close to its design focal length. Apparently, close focusing is not a strong suit of Maks.

You have to find out the design back focus relative to the rear port; and then focus something like the moon, which is effectively at infinite distance, on something like Scotch tape at the back focus distance. Now your mirror is at the design distance from the secondary and you can start to take measurements. The problem is, has Synta ever published the design back focus for their 127 Maks? Celestron and Meade generally published this information with their SCTs which have the same issue.

You'd want to look at the lens using a stereo microscope to try to figure out what's causing the residual fogging before doing anything more. Is it on the surface, inside, or perhaps the cement between lenses in a group that's foggy? Perhaps it was etched by fungus. Perhaps it was coating failure. Polishing is likely to just make matters worse and/or change the lens's figure. I've got old military eyepieces with lens fogging that I can't clean off or even lessen. I can't even figure out what caused it. I've just accepted the status quo with them.