Eyepiece FOV images

[Louis D]

I took a bunch of images through my longer focal length 2" and widest field 1.25" eyepieces with my ancient cell phone camera.  I then cropped and composited the images into the below two images.  I thought y'all might enjoy seeing the differences between the various eyepieces center to edge in sharpness and distortion as well as their apparent fields of view.  There is no resizing and I did my best to get a field stop to field stop image.  Some of the 82+ degree eyepiece images were wider than my camera could capture, but they're there for reference.  All images were taken indoors through my field flattened AT72ED.

Edited March 24, 2019 by Louis D
Added telescope type, cleaned up images gaps, lined up names

[alan potts]

Nice idea there, I see why TV cost what they do but the field curve really shows but sharp.

[Piero]

Yes, I agree, interesting idea.

My es30 82 Deg was also good, but oh man, if it was heavy and large! I replaced it with a 35 pan, which was an outstanding eyepiece but still a bit too heavy for me. So it was replaced by a maxvision 40mm. Decloacking it worked, although it was still heavier than the 35 Pan (which was used for comparisons). So I got a 42 Vixen LVW. It's size was perfect, but the edge of the one I got was not great with my f7.4 refractor. Finally, I got the APM UFF 30mm, which replaced them all. Yes, it loses in terms of fov, but the field is outstanding and shape/weight just perfect with my other eyepieces. It's one of the best eyepieces I've ever tried. So comfortable too. 

I sometimes think that a 26 TV nagler could replace both the 30mm UFF and 20mm HDC. These last two work just so well though, to make me forget the thought quite quickly.

Edited March 24, 2019 by Piero

[John]

Interesting comparison Louis

It's a case of "pick your aberration" with wide angle eyepieces - go for the trade off that you can live with

[Paul73]

Thanks for posting. Fascinating stuff and a great way of comparing eyepieces.

I’ve just got in trouble for spending the last 20 mins staring at my phone when I “should be doing useful stuff”.....

Paul 

[John]

1 hour ago, Paul73 said:

..I’ve just got in trouble for spending the last 20 mins staring at my phone when I “should be doing useful stuff”.....

Paul 

I get told off by my other half for "talking to your little friends". Having met some of you, thats not quite an accurate description

 

[Louis D]

2 hours ago, Paul73 said:

I’ve just got in trouble for spending the last 20 mins staring at my phone when I “should be doing useful stuff”.....

As I've said before, my SO scornfully admonishes me, "Are you on AstroPorn again?" every time she catches me on here.  I need to find somewhere better to hide while online with y'all.

[Geoff Barnes]

14 minutes ago, Louis D said:

As I've said before, my SO scornfully admonishes me, "Are you on AstroPorn again?" every time she catches me on here.  I need to find somewhere better to hide while online with y'all.

You need to spend more time in the bathroom Louis! ?

Edited March 24, 2019 by Geoff Barnes

[Louis D]

I just cleaned up the gaps between images in each of the uploads.  I also lined up the eyepiece names better.  I don't know why some of the images came out narrower when they all came from the same camera without horizontal cropping or resizing.  It might have something to do with the image rotation since I had to shoot corner to corner to maximize the camera's field of view.

I also added the 22mm Astro Tech AF70 which somehow got overlooked yesterday.  It comes amazingly close to the 22mm Nagler T4, just with a narrower AFOV and much less distortion.  It's also hard to choose between them under the stars.  The AT has better eye relief than the Nagler if you want to see the entire field since they have practically the same diameter eye lenses.

I find it interesting how I lived for years with the 38mm Rini MPL since that was first "max TFOV" eyepiece for finding objects.  It's pretty bad, really.  I then tried the 29mm Rini MPL which pushed things to a 95 degree AFOV, but which is obviously really bad long before that.  Next I tried the 42mm Rini Erfle, which greatly widened my TFOV over the 38mm MPL, but was actually no better corrected.

I then got the 40mm Meade 5000 SWA when they were on their blowout sale for $125.  Talk about a massive improvement.  I doubt the 41mm Panoptic would yield as big an improvement again for another $400.

The 35mm OVL Aero ED may not be perfect edge to edge, but notice how much better it is than the 42mm Rini Erfle with nearly as wide of a TFOV.  The 40mm Meade 5000 Plossl might actually degrade at a narrower AFOV.  It's still not bad compared to the 42mm Erfle or 38mm MPL.  It's difficult to choose between them.  The Meade has massively better eye relief, though.  This is either a plus or minus depending on whether or not you wear eyeglasses at the eyepiece.

The 35mm (might be 32mm) military surplus eyepiece does pretty well for a 1940s to 1970s design.  It's some sort of periscope eyepiece.  It's an early negative/positive design with a huge eye lens.  I haven't been able to liberate it from its housing to use it under the stars.  It was balanced on the 2" diagonal for this test.

The 35mm Baader Scopos Extreme is actually quite a bit better than it came out looking.  It's really sharp and contrasty in the center falling off only in the last 10% of the field.

The 30mm Agena UWA 80 came out better looking than it really is, probably due to the camera lens stopping down its f-stop improving its ability to bring all of the massively curved field of the eyepiece into focus at once.  It is a very sharp eyepiece in the center, though.  If the designers added a field flattener to it, it would be right up there with the 35mm Aero ED, perhaps better, with much better eye relief and a wider AFOV.

The 30mm ES-82 is pretty well corrected to the last 10% of the field where it degrades a bit due to chromatism that is difficult to pick up here.  However, that wide field is a joy to behold.

The 30mm APM UFF is clearly sharp pretty much to the edge with just the slightest degradation in the last 5%.  Notice how much wider it is than the 27mm Panoptic despite yielding only 10% less power.  That's distortion at work right there.

The 27mm Panoptic has field curvature that is not that apparent for the same reasons that the 30mm UWA 80 looks good.  However, refocused, it is sharp at the edge, unlike the UWA 80.

[Louis D]

Here are my collected thoughts for the 1.25" maximum field eyepieces:

The 24mm APM UFF could have been near perfect to the edge if it had only attempted to be as wide the 25mm Meade HD-60.  As it is, the edge performance is just awful.

The 25mm HD-60 is just about as good and has a better edge, though obviously narrower AFOV and TFOV, but not by a lot.  The question is, is it worth the extra money to get a wider field of the APM UFF if the edge is awful?  That's why I'm having a difficult time making up my mind about the 24mm APM UFF.

The 23mm Vite (Svbony) 62 Aspheric is not bad at all for $10 while being slightly wider than the 25mm HD-60.  In a slower scope or barlowed binoviewer, the gap narrows even further.  That, and my nose fits easily between two of them.

As long as I have a 2" focuser, I'm going to continue using either the 22mm Nagler T4 or 22mm AT AF70 in that focal length range.  They're just so much better than the 1.25" offerings.  That's why I included them for comparison.  The 17mm ES-92 is just slightly narrower in TFOV than the 22mm AT AF70 and yet has a much more engaging view, so I typically use it instead for objects framed by that field stop size.  Just look at how much bigger the yardstick appears to be.  Astro objects get that same boost.  That's helped tip the 22mm choice toward the Nagler which is slightly wider in TFOV than either the AF70 or ES-92 despite the Nagler's obvious edge distortion.

The venerable 32mm GSO Plossl is nearly perfect to the edge and is just slightly narrower than the 24mm APM UFF.  Is that extra magnification and smaller exit pupil worth the terrible edge performance of the APM UFF?

The 35mm Rini MPL actually manages to squeeze in a good chunk more TFOV without compromising edge performance too much by using oversized lenses set well above the 1.25" barrel.  I think it's probably closer to 32mm than 35mm looking at the yardstick height.  However, in the end, I use 2" eyepieces at this focal length, so it is relegated to the Z-team case along with my other Rini eyepieces as sentimental reminders of a time when I could only afford $30 to $50 eyepieces.

[Louis D]

I compared the 35mm Baader Scopos Extreme to the 35mm OVL Aero ED last night on rich star fields in my 8" f/6 Dob with GSO coma corrector.  It was no contest.  The Scopos is sharp right out to the field stop while the Aero ED degrades slightly starting at 50% out and gets noticeably astigmatic from 75% out to the edge.  The Scopos is also quite a bit sharper.  I could detect slight granulation in M22 in the Scopos on axis, but could not in the Aero ED.  The sharpest part of the Aero ED is a fraction of the Scopos's sharp field.  The eye relief is very generous on the Scopos and very tight on the Aero ED.  Win goes to the Scopos last night.

[John]

Interesting Louis.

Of the Aero ED and clones, the 40mm is clearly the best performing focal length. I find the 30mm shows more astigmatism than I'd like at F/6.5 and clearly the 35mm is of a similar disposition.

I've not used a Baader Scopos but your feedback reminded me that I had read in the past somewhere that the 35mm is the best of the 2 focal lengths in that range.

 

[Louis D]

1 hour ago, John said:

I've not used a Baader Scopos but your feedback reminded me that I had read in the past somewhere that the 35mm is the best of the 2 focal lengths in that range.

Agreed.  With the introduction of the 30mm APM UFF, there's no reason to hunt down a 30mm Baader Scopos Extreme.  I may still pick up a 35mm Panoptic someday if I come across one with the flush mounted eye lens for a good price.

[Mike_S]

Wow. Looks like I picked a good one for my "finder piece" which is the ES 82 degree's 30mm. It's clearly more than just that.

[John]

29 minutes ago, MSammon said:

Wow. Looks like I picked a good one for my "finder piece" which is the ES 82 degree's 30mm. It's clearly more than just that.

They are very good eyepieces. I have the Nagler 31 which is very similar.

I picked up an Aero ED 40mm to get the max FoV from my refractors although it only shows a touch more sky than the 31mm Nagler. 40mm is just a bit too long for the 12 F/5.3 dob though - too large an exit pupil for my moderealy light polluted skies.

 

 

[MarsG76]

Looks like the Astro Tech and the Televue have the edge... The TV Nagler looking the best to me... that's why they cost a Kidney, an arm and a leg...