Meade 5000 21mm 100 deg Mega Wide Angle

[25585]

Has anyone tried or bought the Meade 100 deg MWA 21mm eye piece. 

Costs a lot less than the TV Ethos, is it as good? Heavy and is advertised as having eye relief of 20mm. 

[John]

I read a few reports on another forum when these 1st came out. Apparently they don't deliver a full 100 degree AFoV (closer to 90), have tighter eye relief than advertised, had a tendancy to "kidney bean" and showed edge of field brightening in the outer 20% of the field of view. I sort of lost interest after that ....

[Louis D]

Go for the 20mm 100 degree eyepieces like the Lunt/WO/Myriad XWA/HDC lines.  It is lighter than the 21mm Ethos and 20mm ES-100, and several folks on CN are finding them to be at least as good.

[John]

If I did not already have the Ethos 21 I'd certainly be strongly considering the Lunt 21. The Myriad and WO XWA were also great but I found the thick, wide eye cup didn't quite work for me ergonomically.

 

[Paul73]

Mega Wide Angle?? Sounds like a step too far for Mead.

We really must stop comparing everything to the 21mm Ethos. It’s like comparing a nice top of the range Audi with a Bentley. Then complaining when the Audi isn’t quite as good. However......... having owned an Ethos 21mm, I can’t help but feel a tiny bit let down by other 100° 20mm(ish) examples, despite them being splendid eyepieces.

Haven't tried the Lunt yet...

Paul

[25585]

Too good to be true! Oh well, still got the new Orion 20mm 80 degree LER to try out. 

@John might be a CN thread you read which corroborates what you wrote. They did like the ES 92 in comparison. 

[Louis D]

5 hours ago, Paul73 said:

Mega Wide Angle?? Sounds like a step too far for Meade.

And yet, the older Meade XWA line was considered equivalent to the ES-100 line, if not a lot uglier.

[Paul73]

47 minutes ago, Louis D said:

And yet, the older Meade XWA line was considered equivalent to the ES-100 line, if not a lot uglier.

Interesting point. The ES 100° 20mm is a decent eyepiece.

Has the quality suffered in the push for the extra eye relief? ES could only squeeze 92° from their long eye relief offering. TV 15mm eye relief from their 100° range, or 72° from their Delos 20mm eye relief range. TV can be a tad conservative, staying away from the absolute limits to conserve there ‘quality of image at all costs’ reputation. ES do push the boundaries more. So I’m guessing that there is a good reason why you don’t see many 100° 20mm eye relief offerings.

Paul

[John]

To get a full 20mm of eye relief while also being able to see a full 100 degree AFoV I understand that the eye lens needs to be a certain diameter. There are some complex threads on the CN forum from Don Pensack, amongst others, explaining the formula.

ES did push the 100 degree / 2" format out to 25mm although there were some slight optical compromises with doing that when folks eventually got to try out the design. Tele Vue have stated that they won't exceed 21mm with the Ethos because they were not happy with making the compromises needed.

I think Meade had to find new manufacturing sources for many of their ranges a couple of years back and seem to have lost a bit of ground in that process

 

 

[Louis D]

11 minutes ago, John said:

To get a full 20mm of eye relief while also being able to see a full 100 degree AFoV I understand that the eye lens needs to be a certain diameter. There are some complex threads on the CN forum from Don Pensack, amongst others, explaining the formula.

It's just basic right angle trigonometry using tagents.  The eye relief is the adjacent side, the radius (half diameter) of the eye lens is the opposite side.  The angle formed is half the apparent field of view angle.  So, tan(AFOV/2)=(eye lens diameter/2)/(eye relief).  Rearranging, the necessary eye lens diameter for a given eye relief and AFOV is 2*(eye relief)*tan(AFOV/2).  Filling in the variables for 20mm eye relief and 100 AFOV, we get about 48mm for the minimum diameter needed for an eye lens.  The Ethos eye lenses are only 30mm across while the ES-92s are 43mm across.  So, the ES-92 need about 42mm to achieve 20mm and 92 degrees, and they do.  However, the Ethos need 36mm eye lenses for 15mm and 100 degrees.  Clearly, there's a disconnect between what's claimed and reality.  Ethos can only have either 12.6mm of eye relief at 100 degree AFOV or a 90 degree AFOV at 15mm eye relief.

24 minutes ago, John said:

I think Meade had to find new manufacturing sources for many of their ranges a couple of years back and seem to have lost a bit of ground in that process

Yes, this all went down with Ningbo Sunny buying Meade in 2013.  Jinghua Optical (JOC), the owner of ES, was the provider of most Meade branded eyepieces at that time.  I'm guessing NS didn't want to buy from a competitor (JOC) and cancelled orders leading to the Maxvision line and the Meade MWA line.

[Paul73]

Good explanation about manufacturers and lense size.

I guess that this is why you have to virtually climb into an Ethos 21 to get the full fov (the eye relief seems a bit shorter than the advertised 15mm).

Paul

[John]

22 minutes ago, Paul73 said:

Good explanation about manufacturers and lense size.

I guess that this is why you have to virtually climb into an Ethos 21 to get the full fov (the eye relief seems a bit shorter than the advertised 15mm).

Paul

When I had the ES 20 / 100 I needed to roll down the eye cup to see the full FoV. With the Ethos 21 I don't have to do that so my conclusion is that the Ethos has a little more useable eye relief than the ES 20 / 100.

 

[YKSE]

1 hour ago, John said:

To get a full 20mm of eye relief while also being able to see a full 100 degree AFoV I understand that the eye lens needs to be a certain diameter. There are some complex threads on the CN forum from Don Pensack, amongst others, explaining the formula.

Actually, the ER discussion was on the very Eyepieces when it just came out The picture may be of help to understand the trigonometry calculation.

 

[Louis D]

40 minutes ago, John said:

When I had the ES 20 / 100 I needed to roll down the eye cup to see the full FoV. With the Ethos 21 I don't have to do that so my conclusion is that the Ethos has a little more useable eye relief than the ES 20 / 100.

 

It's pretty clear from this image that the 20mmm ES-100 has a fairly deeply inset eye lens robbing it of some usable eye relief.  By contrast, the 20mm WO XWA and 21mm Ethos have nearly flush mounted eye lenses, maximizing usable eye relief, so your experience fits with this.  The 20mm Lunt HDC is also nearly flush mounted.  The ES-92 are recessed a couple of millimeters to my slight annoyance.

[Ruud]

In the animations below I've ignored the size of the exit pupil. For a 7mm exit pupil, the eye lens needs to be 7mm wider than shown here. The diameter of the eye lens is shown in cm.

I made the animation to see when glasses would bump into an eyepiece, especially when the wearer looks at the edge of the field. If you want to play with the sliders yourself, this is the makefile for the animation: glasses and UWA.ggb 

You'll need the Geogebra program to open the file: https://www.geogebra.org/download. Geogebra is a free maths tool.

This is the size of the eye lens (cm), needed for 2 cm eye relief:

This is how your glasses might bump into the eye lens:

[Louis D]

3 hours ago, Ruud said:

In the animations below I've ignored the size of the exit pupil. For a 7mm exit pupil, the eye lens needs to be 7mm wider than shown here. The diameter of the eye lens is shown in cm.

Very cool animations.  Now I just feel like a dinosaur doing all my calculations manually, though I do skip the trig tables nowadays with scientific calculators.

[25585]

I think looking at a whole FOV, rather than through a lens giving a whole FOV, i.e. seeing an image projected out a few mm, is better if surroundings allow. This is why standard Barlows appeal, long ER allows easier visibility of a FOV, if the eye piece is right maybe.