Searching For A New Eyepiece

[LDW1]

I am looking for a recommendation for a 42-50mm eyepiece, from actual experiences, with as wide a FOV as possible.  Cost is not an issue.

[Mr Spock]

With a 2” fitting the 42mm LVW is as wide as you’ll get. Lovely eyepiece to look through. 
I have a thread on here somewhere about it. 
I’ll have a look for it when I get back to my pc. 

[Louis D]

The 40mm Pentax XW has a measured 46.3mm to 46.5mm field stop, so also about as wide as possible with the field stop within the insertion barrel.  It's not quite as sharp to the edge as the 40mm ES-68/Maxvision/Meade 5000 SWA, but's it's a lot lighter and more ergonomic for both eyeglass wearers and non-eyeglass wearers.

Why do you want to go up to a 50mm eyepiece?  Are you planning on using it in a slow scope like an SCT?

[LDW1]

6 minutes ago, Louis D said:

The 40mm Pentax XW has a measured 46.3mm to 46.5mm field stop, so also about as wide as possible with the field stop within the insertion barrel.  It's not quite as sharp to the edge as the 40mm ES-68/Maxvision/Meade 5000 SWA, but's it's a lot lighter and more ergonomic for both eyeglass wearers and non-eyeglass wearers.

Why do you want to go up to a 50mm eyepiece?  Are you planning on using it in a slow scope like an SCT?

I already have a Russell Optics 5? and 65mm eps but I am looking for another brand to play around with in my scopes. I had a WO 40mm SWAN, 72° that performed well but I gave it away.

[Mr Spock]

Here's the topic on eyepieces I mentioned. The LVW has a 48mm field stop and is as wide as you get. You'll see from my report it's only 42mm in the centre but is as wide as you can get in a 2" fitting. The 72° field is comfortable to see too. Not much point going longer than this, unless you are working at f15 - f20. If you are using a shorter focal length the 31mm Nager may even be preferable.

I don't know why the link above is showing someone else's image - must be a forum bug.

[Don Pensack]

6 hours ago, LDW1 said:

I am looking for a recommendation for a 42-50mm eyepiece, from actual experiences, with as wide a FOV as possible.  Cost is not an issue.

If cost is no object: TeleVue Panoptic 41mm.  You won't find a better eyepiece, optically, in or around that focal length.  It has a 46mm field stop.

[Louis D]

4 hours ago, Mr Spock said:

The LVW has a 48mm field stop and is as wide as you get.

Is the field stop well above the insertion barrel requiring lots of in focus?  48mm is the outside diameter of the insertion barrel, so it must be quite a trick to make the insertion barrel wall as thick as foil.

[Mr Spock]

Yes, the field stop is inside.

[LDW1]

3 hours ago, Don Pensack said:

If cost is no object: TeleVue Panoptic 41mm.  You won't find a better eyepiece, optically, in or around that focal length.  It has a 46mm field stop.

Price may not be a concern but I think the weight is, lol.  For me ie 2+ lbs, you have to be kidding, lol ?

[Mr Spock]

Big, high quality eyepieces, have a lot of glass. They all have significant weight.

[bosun21]

Some are heavier than 2lbs. The 40mm ES 68 degree is 1.2kg. That’s over 2 1/2lbs

[Mr Spock]

My 42mm LVW is 542g as weighed just now.

[LDW1]

1 hour ago, Mr Spock said:

Big, high quality eyepieces, have a lot of glass. They all have significant weight.

I know, I had 2-2" Luminos they were heavy enough and they weren't particularly expensive. Weight might be my hang up.

[LDW1]

1 hour ago, Mr Spock said:

My 42mm LVW is 542g as weighed just now.

A big difference between 1 lb and 2 lb when it comes to ep's and comfort and logistics.

[Louis D]

As I said above, you'd probably like the 40mm Pentax XW at 24.7 oz. (700g).

Has anyone done a comparo between the 40mm Pentax XW and the 42mm Vixen LVW since both are relative lightweights at this focal length?

[Dan_Paris]

Which f/ratio are your scopes?

[LDW1]

2 hours ago, Dan_Paris said:

Which f/ratio are your scopes?

I am not worried about the f of my 5 scopes, when / if I find an interesting ep I will buy one and test it out.  Sometimes the f ratio concerns can be deceiving when it comes to performance unless the astronomer is very technical.

Edited June 15, 2022 by LDW1

[great_bear]

On 10/06/2022 at 20:25, Don Pensack said:

If cost is no object: TeleVue Panoptic 41mm.

I found the field curvature on the Panoptic 24mm unbearable (one of the reasons I sold it on) - does the 41mm also suffer from that?

[Don Pensack]

Jeremy,

 

A clarification: the 24mm Panoptic has a flat field and near zero field curvature.  The edge stars are sharply focused at the same time as the center, even at f/4-f/5.

What you're probably remarking about is its positive rectilinear distortion (i.e. pincushion distortion), which is noticeable if the eyepiece is panned

or if the telescope has a long enough focal length the passage of the field is fairly rapid.  It results in straight lines moving across the field as ) | ( 

That the eyepiece has, in abundance--perhaps stronger than other eyepieces in the size.

 

The 41mm is the same design, just larger and with a wider field stop.  If the RD in the 24mm bothers you, the 41 might not be the best choice.

Though, the much lower magnification does mean that field drift through the eyepiece is a lot slower, so it largely depends on whether the eyepiece is panned across the sky.

 

It does depend, also, on what you want the eyepiece to do.  If you want a good eyepiece for terrestrial use, suppressing rectilinear distortion and allowing some angular magnification distortion may be a better choice (e.g. 24mm APM UFF).

Or, for use in an astronomical scope that tracks, the RD would be unnoticeable (just as AMD is unnoticeable (e.g. 12.5mm Docter/Noblex).

But, in a scope that doesn't track, many people would prefer a smaller amount of RD. 

 

You're not going to beat the sharpness of the 41mm Panoptic at its focal length, though.  So it does depend on the observer's preferences.

 

 

[great_bear]

Apologies - I must be getting it confused with something else I had in that focal length that was like the starfield was wrapped on a tennis ball. 

[Louis D]

8 hours ago, great_bear said:

Apologies - I must be getting it confused with something else I had in that focal length that was like the starfield was wrapped on a tennis ball. 

It could very well be the eyepiece appeared to make the star field appear wrapped on a tennis ball and yet have no field curvature.  Stars appearing to be wrapped on a ball is a form of distortion.  The field appears curved onto a ball, but that does not mean it has a curved field.  Curved field means that the field of focus is not flat center to edge.  Stars focused in the center get progressively blurrier toward the edge, regardless of whether they appear wrapped on a ball or not.

Did stars stay nice and sharp center to edge as they traversed the apparent ball shape?  If so, it had a flat field, not a curved field, with distortion.

[great_bear]

It was definitely field curvature. 

You could rack the focuser in/out and the stars in focus would change from being the ones around the edge to the being the ones in the centre (and everything in-between as you racked in/out)

I thought it was the Panoptic 24, but can’t rule out being mistaken. 

[Don Pensack]

1 hour ago, great_bear said:

It was definitely field curvature. 

You could rack the focuser in/out and the stars in focus would change from being the ones around the edge to the being the ones in the centre (and everything in-between as you racked in/out)

I thought it was the Panoptic 24, but can’t rule out being mistaken. 

Short focal length refractors have strongly curved focal planes.

If a flat field eyepiece is used in such a scope, the field curvature seen is due to the scope.

Pictographically, it looks like this:

) + | = )  a flat eyepiece in a curved field scope.

| + | = |  a flat eyepiece in a flat field scope

| + ) = )  a curved field eyepiece in a flat field scope

) + ) = |  a curved field eyepiece in a curved field scope where the curvatures match.

and ) + ( = severe field curvature.  The field curvatures of scope and eyepiece don't match.

[great_bear]

It would either have been in the Mak 180 Pro (F15) or the standard SkyWatcher 130P (F5) - I can't remember which.

Edited June 22, 2022 by great_bear

[great_bear]

On 10/06/2022 at 13:45, LDW1 said:

I am looking for a recommendation for a 42-50mm eyepiece, from actual experiences, with as wide a FOV as possible.  Cost is not an issue.

The TMB Paragon 40mm has become a bit of a classic (also known as the Sky Watcher Aero ED40) - and not particularly expensive either.

Unfortunately it's getting harder to find these days. I have one, and it's a keeper; I'm never selling mine (and I'm ridiculously fussy when it comes to eyepieces).

https://www.harrisontelescopes.co.uk/acatalog/skywatcher-aero-40mm-ed-eyepiece-2.html (out of stock, regrettably).

Edited June 23, 2022 by great_bear