Louis D

At first, I didn't realize Sharpless was a person's name. I thought it was a description of the type of objects, as in "These are less sharp objects".

At that point, it would be time to stitch them together into an all-sky panorama. 😉

You never specified where you would be observing from and if transporting the telescope would be an issue. For example, I put together a 127 Mak on an alt-az mount for my daughter and her fiancé to take along on camping trips in her CUV. There wouldn't be room in the back for an 8" Dob with all of their camping gear. I also thinking of sending along my AT72ED if the 127 Mak's narrow field of view becomes an issue for them.

And first 10 units of the 9mm ES-120 didn't have their field stop inserted, so they actually have a 140 degree AFOV. The observers who got them aren't letting them go from what I can tell.

That's why I have to dampen its swing when moving quickly in azimuth to a new target (by dampen, I mean grab it and stop it from swinging). It is indeed a swinging pendulum. Fortunately, moving slowly in azimuth to track doesn't induce the swinging motion to it. Moving in altitude has no effect on its side to side motions no matter how abrupt.

Let's run the numbers for TFOV: 35mm Orion DeepView: 37mm Field stop (Orion's claim) = 1.77° 30mm APM UFF: 36.4mm FS (my measurement) = 1.74° 30mm ES-82: 42.4mm FS (my measurement) = 2.03° 30mm 80° Wide Field III clone: 44.2mm FS (my measurement) = 2.11° 31mm Nagler T5: 42.0mm FS (Tele Vue specs) = 2.01° 35mm Panoptic: 38.7mm FS (Tele Vue specs) = 1.85° 35mm Aero ED: 44.4mm FS (my measurement) = 2.12° 40mm Meade 5000 SWA (Maxvision SWA): 46mm FS (my measurement) = 2.20° I have my doubts about Orion's field stop diameter claim because that would imply either a 61° AFOV with little distortion, or large amounts of edge distortion to squeeze in that additional 5° of AFOV at the edges in the claimed 56° AFOV. The OP has lots of options of varying degrees of edge correction, eye relief, weight, and price to choose from. My preference would be the 30mm APM UFF to start with. It may not be much wider, but it will be so much better corrected and will feel much wider with its measured 72° AFOV. That, and it has very comfortable eye relief.

Have you tried to put a 1.25" insertion barrel cap on top? I know that some of these style eyepieces are close to symmetrical top to bottom as far as diameter. The rubbery yellow/red vinyl caps might stretch enough to fit if the upper barrel is a bit oversized.

I have a 6" bolt that I screw into a threaded hole on my alt-az mount at 90 degrees to the OTA (on the bottom, rotating up to the front at high elevations). I then hang a plastic grocery bag filled with a pound to two pounds of metal washers and bolts I had laying around to counteract the backward tilt of heavy eyepieces near zenith. At lower elevations, it has little to no effect other than to bang into the tripod legs as I rotate in azimuth. Being a plastic bag, it just moves out of the way. I do have to dampen the swinging manually when that happens, though. It works like a charm to prevent my rig from turning turtle near zenith, though. It just looks literally trashy.

I have so many bulbous, long eye relief eyepieces and a long enough nose that I get to know the right eye position by the feeling of my nose touching the upper body of the eyepiece while hovering.

Not sure what you mean by "light reflection". Based on the price, I would think it has a budget first surface mirror. I have no idea how well collimated it would be nor how optically flat it is. I would think it performs best at 90 degrees, getting slightly worse toward the 45 degree end of things. I would be concerned about vignetting at 45 degrees if the mirror wasn't made large enough.

I think it's based on an oversized mirror, so it's not going to flip the image left for right like the Amici prism diagonal. As such, it won't introduce a spike on bright stars. Also, it wouldn't be a replacement for an Amici prism for terrestrial use since it doesn't flip left for right.

Depends on the condition of the finish at that price point. Are there blemishes or other wear marks aside from the dovetail? Don't forget to account for your costs to pick it up compared to shipping costs.

I generally back off on power with Jupiter to around a 1.5mm to 2mm exit pupil due to its low contrast features. At smaller exit pupils, they just sort of mush together most nights. Saturn's rings and moons, on the other hand, can take much more power due to their higher contrast. The moon is another good target for using tiny exit pupils. It's up to you and your wallet. The BSTs aren't that expensive, and you're not eating out as much as you used to, so treat yourself to a 3.2mm for fun's sake.

I have a 90s vintage Lumicon OIII that thankfully hasn't rusted (knock on wood) that does a fantastic job. I've read that the problem with Lumicon is that they have had at least 5 different sources for their filters over the decades (and changed ownership recently), so it can be hit or miss on the used market as to what you will get. It's a case of try before you buy used if possible. I use my Lumicon UHC filter (also 90s vintage) as more of a light pollution filter in my Bortle 5/6 skies. It helps increase contrast a bit, but no where near what the OIII does. I also have a Zhummel OIII that is pretty pathetic. It's not even as good as the UHC. However, I only paid $14 for it on clearance. Don't skimp on OIII filters. The cheap ones don't really work at all.

Meh, I've seen plenty of astrophotos on APOD that are much more aesthetically pleasing. I think having an eye for an appropriate foreground here on Earth really helps to connect the cosmos to our home world better than creating a faux-macro image. I do appreciate the novel technical approach taken to capture the image; though I'm not sure it's usable more than once or twice before people would tire of the effect.

I've found that if I always wear eyeglasses, my eyepieces never fog unless I have a face covering redirecting my breath up my face. The eyeglass lenses act as a moisture barrier.

2" is only relevant at low powers and for heavy eyepieces. There are plenty of 1.25" 8-10mm eyepieces out there with large eye lenses and loads of eye relief. The 8mm BST is quite good as mentioned above, but a bit tight on usable eye relief compared to some more premium offerings. The 9mm Morpheus is excellent as is the 10mm Delos. It all depends on your budget which you didn't specify.

You probably wouldn't notice it if you didn't go looking for it or didn't do an eyepiece swap with another eyepiece that didn't have it. It just looks like a fog covering the outer field decreasing contrast. It appears to be very similar to the discontinued Meade Series 5000 TeleXtender 2x Barlow Lens (1.25"). 10 years ago, there was this thread here on SGL about it. I would google the Meade for other reviews and discussions of it. Altair: Meade:

True, but the mechanical perfection of mid-century, US made Questar Maks puts today's Chinese made Maks to shame. Of course, the price differential is enormous.

It doesn't really matter because the glass in them is generally small enough that temperature differentials don't cause stresses in the glass that would distort the image. The reason people put dew heater strips on them is to prevent them from dewing up when they cool below the dew point.

I do have the 13mm AF70 (should be same optically as Olivon 70°), so I'll have to dust it off and go looking for EOFB sometime. It also has pronounced edge of field chromatic aberration starting at 70% out from center. If you like rainbows, this is the eyepiece for you.

Definitely would like to hear your impressions of the APM 12.5mm. I've got the 12mm Nagler T4 and ES-92 and have thought about picking up the APM sometime to replace the NT4 for 1.25" usage. Eye relief is a bit tight on the NT4 and the exit pupil is a bit on the finicky side once the field stop pops into view. I also noticed EOFB (Edge of Field Brightening) extending all the way to center once in the 12mm NT4. I swapped it for the 17mm NT4 which had about 50% of the amount of EFOB and practically none for the two ES-92s under the same conditions. It looked like someone had placed a graduated vignette filter over the image, only in reverse such that the image got gradually brighter center to edge. I haven't seen it since, but it was startling and completely repeatable during eyepiece swaps that night.

Of course, but there's no risk of a child going blind at night from stray light as there is during solar viewing. That's all I was emphasizing. Truss Newts have their own special safety issues for solar viewing absent in solid tube Newts.

That's a tough one because I prefer affordable mid-length Barlows like the TV 2x and Meade 140 (both 90s vintage) that won't come to focus in many refractors. I recently picked up a 3 element Japanese made shorty Barlow (Celestron Ultima, Parks Gold, etc), but I haven't had any time to try it out yet. You could get a used Meade 140 for $50 or less and screw the optics section onto the front of a 1.25" diagonal for about 3x. I use it at a similar power on my binoviewers to reach focus, and the images are incredibly sharp. There are plenty of quality shorty barlows, but they aren't cheap. Start with this list to see what I mean: 1.6x 1.25" Nikon EIC Barlow 3.0x 1.25" Televue Barlow 2.4x 2.0" Vernonscope Dakin Barlow 2.0x 2.0" AP BARCON (BARADV) Barlow 2.5x 2.0" Siebert Telecentric 2.0x 1.25" Carl Zeiss Abbe Barlow 2.0x 1.25" & 2" Baader VIP Barlow 2.25x Baader Hyperion Zoom Barlow

According to Baader Wonder Fluid's MSDS, it's 25% Ethanol and 35% Propan-1-ol. The latter is an isomer of propan-2-ol (isopropyl alcohol), so not quite the same thing as pure isopropyl alcohol.