Louis D

Why not just buy an Astronomik OWB Type 3 Clip-Filter EOS APS-C? It seems like the most reasonable solution for you. Here's the tech info:

@HollyHound Do you observe with eyeglasses at those focal lengths? I have such strong astigmatism in my eyes that I need a minimum of 17mm of usable eye relief to comfortably see the entire field of view of an eyepiece. My 12mm and 17mm ES-92s exactly tick that box, so I have no incentive to get the 16.5mm XW. My XL, XW, Hi-FW, Delos, and Morpheus eyepieces all provide at least 18mm of usable eye relief, so are also quite comfortable to observe with. I've held off purchasing the 23mm XW to replace my 22mm NT4 because I've read that the eye relief is marginal for eyeglass wearers.

I use a GSO 6" f/5 on a DSV-2B alt-az mount without any major issues. However, anything bigger, and I would prefer a Dob mount. One issue I have with my alt-az mount is that if I move my rig to a different spot in the yard to dodge sky obstructions, any bit of being out of perfectly level and the azimuth axis swings around to the low side. This pretty much does not happen with Dobsonian mounts unless you've got a really heavy load in the focuser. Having to relevel a mount in the dark is a pain, so there's a win for the Dob.

In head to head comparisons with the 30mm APM UFF, 27mm Panoptic, and 35mm Baader Scopos Extreme at f/6 and faster, I found the ES-82 30mm to have slightly bloated stars across the entire field of view at best focus. Enough so that I found it annoying. If the bloat were confined to the field outside the TFOV of these other eyepieces, I'd be totally good with that, but it's there even in the central region. I suppose if I had no frame of reference from never having tried those other eyepieces, I might not have ever noticed the central bloat. I was in this situation for years before getting a coma corrector. Once I knew what the field could look like with a CC, I could never go back to not having a CC in my Newts. Why pay big bucks for an APO to have pinpoint stars only for those same stars to be bloated by your eyepiece? That's why I have other eyepieces in this range, because no one eyepiece does it all (ultrawide field and pinpoint stars center to edge) in my experience at f/6 and faster. Due to its prohibitive price, I haven't yet tried a Nagler T5 31mm to see if it manages to have pinpoint stars center to edge like the UFF, Panoptic, and BSE.

Are these OO Newts intended for imaging? Otherwise, why suffer the consequences of a large enough secondary to illuminate a focus point well outside the tube?

Your best budget bet for visual is a GSO coma corrector that is sold under numerous brands around the world. I have two, each with a 25mm spacer ring added between the optical section and the eyepiece holder for best correction with my eyepieces that focus near their shoulders. They're really good except at high powers when the spherical aberration they introduce degrades the view. I remove it at high powers as a result. I've found they require 11mm of additional in-focus as I have them configured.

I have the original ES-82 30mm decloaked, and the APM UFF 30mm is sharper across the field, especially toward the edges. The ES-82 splits red from blue, giving two images of planets in the last 15% as they drift across the field of view. Point is, give the APM UFF 30mm a try if you were looking to improve the image quality over the Axiom 31mm at the expense of a bit of field of view. It's much lighter and more compact as well.

Or at least be pronounceable.

I haven't tried it for astrophotography, but I have one that I used for years for stage photography under available light. Stopped down to f/2 to f/2.2, it is sharp edge to edge with little to no light falloff with a crop sensor EOS DSLR. Autofocus is also quiet, fast, and instantly manual overridable. Not that any of that matters for astrophotography. However, it could do double duty for school stage performances by your kids. I probably shot over 125,000 exposures with it over a decade of dance studio performances by my daughter and the rest of the dancers, so it's also quite durable.

If you're referring to item at the lower right, give it a few years/decades to take on that vintage brass patina, then we'll see if it resembles a plumbing fitting. 😏 Right now, it's too shiny to be mistaken for plumbing parts.

I had to go back to my Svbony zoom write up to remind me of what I saw in the 3.5mm Pentax XW versus the Svbony zoom at 3mm: So, I'd recommend looking for color fringing on bright stars as you move them center to edge. The XW shows none anywhere while the Svbony zoom shows increasing amounts toward the edge.

From your Stellarview filter review: I employed a special approach and sent this curve to Vic Can you post what that curve was that you suggested? I'm wondering how similar it looks to the Baader Semi APO curve in dark blue below: I have that one, and it does a good job of avoiding adding a yellow cast to the image. However, it doesn't suppress all the unfocused violet and none of the unfocused red. I've found a Hirsch #12A Light Yellow and a Hirsch #82B Light Blue (Cyan) combine for a yellow-green view that suppresses pretty much all of the unfocused violet and red and really sharpens up planetary views without darkening the image too much like a #11 Green or especially a #56 Green does. I recently picked up an X0 Yellow-Green filter, and it looks promising as well.

Given all the tarnished brass, I'd first have guessed it was some sort of old plumbing fitting were it not for the optics. 😁

Do the same test holding one up to each eye, but with zoom and the SLV. It could be that if you are concentrating on the central region against a dark sky, you aren't noticing the wider FOV. It could also be the tighter eye relief coming into play. You really need to mash your eye into the zoom's eye cup to take in the entire FOV, especially from 3mm to 6mm.

You need not have bothered with the in between setting. I measured the 3mm setting to actually be 3.5mm in the central region. It grows to 2.5mm at the edges due to distortion. And I also noticed considerable softening at the "3mm" setting. I consider it a bonus focal length to be used when you don't have anything better.

I noticed the 4mm setting getting slightly softer, but still quite usable. From 5mm to 8mm, I'd rate the Svbony zoom as excellent.

There shouldn't be much apparent field of view difference between the SLVs and the HR. The LVs, NLVs, and SLVs below 9mm all have 45 degree apparent fields despite what the later versions claimed. Check it for yourself. Hold up a ~50 degree plossl to one eye and either the 4mm or 6mm SLV to the other eye while looking at a bright background. The SLVs will have a smaller image circle. The Svbony zoom has an AFOV between 58 and 61 degrees, so it should look considerably wider than either the SLVs or HR.

To build on what has been said above, I would recommend not going with a wider passband than that found in a UHC type filter. Think of them as a more selective light pollution filter for use on nebula. The only way you're going to see galaxies is to seek out a truly dark sky site to observe from.

The focus wheel is not to be confused with a zoom wheel. The image is getting larger out of focus, but it is not a useful image to observe. You might want to buy a zoom eyepiece to get started with observing if you like the idea of zooming to enlarge the image on the fly. Once inserted in the focuser, you bring the image to focus such that it is at its smallest. Then, you can twist the collar around the eyepiece to zoom in or out to enlarge or reduce the image size in a continuous manner. You might need to refocus at each zoom setting because zooms tend to not be parfocal (remain in focus at all settings).

As long as the primary mirror movement lubricant is still in good shape to allow smooth focusing, it should work right out of gate. I've had two of these Synta made Maks, one Orion and one Celestron, and both are spot on in collimation and have no focus shift or backlash. You'll just need a decent alt-az mount/tripod and red dot finder to get started. It looks like it was used on a photo tripod based on the still attached quick release plate. The tripod and head are probably kicking around somewhere in that same attic. If you can't find the tripod, you'll need to unscrew and remove that quick release plate before using it in a dovetail clamp based mount.

Interesting, I've found just the opposite. My old, long focus Barlows won't come to focus in refractors when used in the diagonal because they require so much in focus (up to 4 inches). Of course, you can use them ahead of the diagonal at a higher than marked power without focus issues. This in-focus issue doesn't arise in all but the smallest Newts because the secondary mirror is so far away from the focuser. You simply insert the Barlow 4 inches into focuser. Try doing that with a diagonal! Of course, you may introduce a diffraction effect if the Barlow protrudes into Newt's light path. In practice, I've not noticed it with even my longest Barlows. Shorty Barlows come to focus in everything in my experience, so are generally the better choice unless going for the highest quality views possible. I've found that the older, Japanese made long Barlows of the 90s produce the tightest images at high powers. The difference is subtle, but it is there over shorty and mid-length Barlows of similar cost (sub $150). I've not tried any of the super premium Barlows or Powermates because I can't justify the cost involved for how little I use Barlows.

Here's some APOD moon halo images: https://apod.nasa.gov/apod/ap220102.html https://apod.nasa.gov/apod/ap210201.html https://apod.nasa.gov/apod/ap180502.html There are many more that have been featured over the years.

Here's evidence at least the 25mm Meade 3000 went to Taiwan:

If you're using an iPhone, pick up a used phone with the necessary sensors, but older or with a bad SIM card tray. You don't need service to use SkEye.