Which are the best 2in Wide Field Eyepieces, avoiding excessively Big and Heavy Eyepieces.

[johnturley]

My widest 2in eyepieces are currently a Meade 56 mm Plossl, and a Baader 36 mm Aspheric. The former with a 52 degree apparent field of view gives just a slightly larger actual field of view than the latter with a 72 degree APFOV, and my experience indicates that these quoted APFOV’s unlike those quoted by some manufacturers such as StellaLyra are more or less correct. I should add that the 56 mm Meade is one of the original 5 element smoothside, (made in Japan) Plossls, similar I understand to the Masuyama, and not a true Plossl. 

I have looked into bettering these, but there do not seem to be many alternatives available, especially as I wanted to avoid excessively big and heavy eyepieces as my 14 in Newtonian on which my Esprit 150 is piggybacked is quite balance sensitive, and you can’t lock the dec axis. The Meade 56 mm weighs 550g, and the 36 mm Aspheric is quite a lightweight for a 2in eyepiece at 400g.

Although it is really too low a power to use in a f5 Newtonian, the 56mm Meade Plossl gives a surprisingly good edge performance in this instrument.  On the other hand the 36 mm Aspheric whilst giving quite good edge performance with the f7 Esprit, it is not so good with the f5 Newtonian. The edge performance with the latter can be improved by using a Coma Corrector, but the problem is not so much that the edge of field displays a lot of coma, but that the centre and the edge focus at different points, i.e. if you focus on the edge, the centre is out of focus, and vice versa.

One problem however with the 56mm Meade is that you have to hold your eye a few centimetres away from the eyepiece when viewing, and with being an old eyepiece does not have a rubber eyecup. I did wonder how this eyepiece would compare with the current Tele Vue 55mm Plossl, but I did have the chance to compare it 30 years ago with the then Tele Vue product, and thought that the Meade was sharper, but this was comparing a 5 element to a 4 element design. The current Meade version does have a rubber eyecup, but is now only a 4 element (made in China) version, and suspect it would not perform as well. Incidentally the original Meade 5 element (made in Japan) Plossls were priced similar to the Tele Vue Plossls, but the current 4 element (made in China) versions are about half the price. The current 5 element 50 mm Masuyama would probably be better, but priced at £499 it is a high price to pay for something that might only be marginally better. When I first saw the 50 mm StellaLyra eyepieces with a quoted APFOV of 60 degrees advertised, I thought that this might be a suitable alternative, but it turned out that the actual APFOV was only around 48 degrees, and gave a significantly smaller actual field of view.

Looking for something superior to the 36 mm Aspheric, eyepieces such as 35 and 41 mm Panoptics, plus the 31 Nagler spring to mind, but they are all big, heavy, and very expensive eyepieces.

Would be interested to hear about other people’s views and experiences, and any other recommendations.

John

Edited November 23, 2020 by johnturley

[globular]

By better to you mean wider or less aberrations?  (I imagine you want both!)
I can say a bit on FOV (but not on optical quality).

I think your Meade 56mm probably has a field stop of around 46mm and so will give you around 1.48 degrees TFOV in your 14" F5.
Your Baader 36mm is (if the 72 AFOV is accurate) giving you around 1.45 degrees.

The maximum TFOV you can get with a 2" barrel is an eyepiece with a 47mm field stop - like the Masuyama UltraWideField 32mm which would give 1.51 degrees.  A lot more magnification but only slightly more sky than the Meade.  It weighs 450g so is quite light.  As I say, I can't speak for it's optical quality.

Larger than 47mm field stop and vignetting will occur - meaning the extra sky on display will not be worth looking at anyway.

The next biggest (usable) field stop is 46.5mm and these include Pentax XW40 and Masuyama 60mm. They will give you 1.50 degrees.

All other 2" eyepieces have a field stop at or below 46mm (most quite a lot below) and so give you no more sky than your Meade.  Eg the Tele Vue Plossl 55mm has a 46mm field stop giving you 1.48 degrees. 

In summary you are not likely to get more sky at your eye with another eyepiece - but you can certainly get the same amount of sky at higher magnifications and probably better optically corrected too - but I'll leave other more knowledgeable SGLers to advise on that.

Edited November 23, 2020 by globular
typo

[johnturley]

26 minutes ago, globular said:

 

The maximum TFOV you can get with a 2" barrel is an eyepiece with a 47mm field stop - like the Masuyama UltraWideField 32mm which would give 1.51 degrees.  A lot more magnification but only slightly more sky than the Meade.  It weighs 450g so is quite light.  As I say, I can't speak for it optical quality.

 

The Masuyama UltraWideField 32mm looks promising on paper with a quoted APFOV of 85 degrees, and about half the price and weight of the 31 mm Nagler, but wonder what the edge performance of the 5 element modified Plossl design of the Masuyama would be compared to the latter. 

John 

[John]

2 minutes ago, johnturley said:

The Masuyama UltraWideField 32mm looks promising on paper with a quoted APFOV of 85 degrees, and about half the price and weight of the 31 mm Nagler, but wonder what the edge performance of the 5 element modified Plossl design of the Masuyama would be compared to the latter. 

John 

https://www.cloudynights.com/topic/562496-masuyama-32mm-85-deg/

https://www.cloudynights.com/topic/585719-31mm-nagler-type-5-vs-32mm-masuyama-85-degree-at-f7/

 

Edited November 23, 2020 by John

[John]

I found the Aero ED 40 a really nice eyepiece even in my F/5.3 12 inch dob. Not perfect but surprisingly well corrected across the field of view for a relatively low cost super wide 2 inch.

I recently sold it though because I find that I just don't use that longer focal length under my skies. The 31mm Nagler and the 21mm Ethos work better for me with regards to background sky darkness and DSO contrast. Hugely more expensive though and much heavier eyepieces.

For the £60 or so that the Aero ED 40 cost me pre-owned it was a great performer though.

 

 

Edited November 23, 2020 by John

[johnturley]

8 minutes ago, John said:

https://www.cloudynights.com/topic/562496-masuyama-32mm-85-deg/

 

Thanks John

It looks like that it would have some shortcomings in an f5 Newtonian like the Baader Aspheric

[johnturley]

3 minutes ago, John said:

I found the Aero ED 40 a really nice eyepiece even in my F/5.3 12 inch dob. Not perfect but surprisingly well corrected across the field of view for a relatively low cost super wide 2 inch.

I recently sold it though because I find that I just don't use that longer focal length under my skies. The 31mm Nagler and the 21mm Ethos work better for me with regards to background sky darkness and DSO contrast. Hugely more expensive though and much heavier eyepieces.

For the £60 or so that the Aero ED 40 cost me pre-owned it was a great performer though.

 

 

Thanks John

Is the quoted 68 degree APFOV of the Aero ED genuine, it looks very compact compared to the Panoptic especially in the 40 mm focal length.

I would probably however more likely go for the 35 mm as a replacement for the Baader Aspheric 36mm, may however wait until Rother Valley Optics showroom re-opens (hopefully sometime in the spring), so that I can look at one before deciding whether to purchase.

John 

[John]

3 minutes ago, johnturley said:

Thanks John

Is the quoted 68 degree APFOV of the Aero ED genuine, it looks very compact compared to the Panoptic especially in the 40 mm focal length.

I would probably however more likely go for the 35 mm as a replacement for the Baader Aspheric 36mm, may however wait until Rother Valley Optics showroom re-opens (hopefully sometime in the spring), so that I can look at one before deciding whether to purchase.

John 

I didn't measure the AFoV of the Aero ED40 but it sure looked like a 68 degree AFoV to me. I have Pentax XW's, a 24mm Panoptic and a couple of Delos eyepieces with AFoV's around this figure and the Aero ED40 seemed to offer something very similar.

 

[vlaiv]

Problem of course being that one can't get new Aero ED 40mm - it is just unavailable wherever I look.

 

[Saganite]

I also have the Meade 56mm 5 element 'smoothie' for use in my 5" f15 where it gives me the widest FOV that I can get, within fiscal restraint, and at this it excels.  I have also been reading other peoples views and decided that at f5.3 the APM 30mm UFF would be a good bet for my Dob, so hopefully this thread that you have started will prove to be timely.....

[John]

15 minutes ago, vlaiv said:

Problem of course being that one can't get new Aero ED 40mm - it is just unavailable wherever I look.

 

I should have sold mine for more then !

[globular]

2 hours ago, John said:

The 31mm Nagler and the 21mm Ethos work better for me [than the Aero ED 40] with regards to background sky darkness and DSO contrast.

What's the mechanism at work here?

Is it the larger exit pupil in the Aero ED 40 that caused the skies to appear brighter?  So with a different F ratio scope the Aero ED 40 could give a nice dark sky?

Or is it the magnification?  So with a different focal length the Aero ED 40 could work better?

Or is it something within the eyepiece design. So this eyepiece is doomed to give poor contrast?

Edited November 23, 2020 by globular

[John]

It's not the eyepiece. My skies have some moderate light pollution so I find that using more magnification helps darken the background sky. I've owned a number of eyepieces of 40mm and even 50mm focal length but always ended up using the shorter FL ones more. I'm a bit of an occularholic though so sometimes get tempted to try longer ones again if one pops up at a good price

 

[vlaiv]

14 minutes ago, globular said:

What's the mechanism at work here?

Is it the larger exit pupil in the Aero ED 40 that caused the skies to appear brighter?  So with a different F ratio scope the Aero ED 40 could give a nice dark sky?

Or is it the magnification?  So with a different focal length the Aero ED 40 could work better?

Or is it something within the eyepiece design. So this eyepiece is doomed to give poor contrast?

It is exit pupil - which is related to focal length and aperture.

With increased telescope focal length - magnification is increased and for the same aperture - brightness of background sky goes down, but if F/ratio is maintained, then larger aperture offsets effects of increased magnification and brightness remains the same.

Since all of these quantities are tied together in one way or another - we say that exit pupil is thing that governs background sky brightness but in reality it is aperture + focal length or magnification used.

[cloudsweeper]

50 minutes ago, globular said:

What's the mechanism at work here?

 

I go by a rule of thumb that the exit pupil needs to be about 4mm or less for decent contrast in fairly polluted skies.  Much above 4mm and the view is washed out.  That of course is not a huge problem for brighter objects, and it still enables you get a wide view for finding your way round.  I often start observing with an exit pupil of around 6mm.

Doug.

BTW - to answer the original question, I use a 42mm Revelation Superview and a Baader 36mm Aspheric.  Very usable, light, 2" EPs.

Edited November 23, 2020 by cloudsweeper

[globular]

I've been working along the same lines... but at a slightly higher figure of 5mm max exit pupil because my skies are not that highly polluted.

My XW40 in my F/10.5 scope gives exit pupil of 4.8mm and looks great to my eyes in my garden.  So that seems to fit.

If John finds 21mm Ethos and 31 Nagler are the limit then I guess that means he must be using scopes around the F/6 mark and/or more polluted skies.

[faulksy]

i would definately consider these apm eps they are very very good. they also do a 30mm. i have the 20mm 100* and at f4 its as good as a ethos

https://www.apm-telescopes.de/en/optical-accessories/eyepieces/more-74-ultra-wide-angle/apm-lunt-eyepieces/apm-hdc-xwa-20-mm-100-eyepiece

[John]

24 minutes ago, globular said:

I've been working along the same lines... but at a slightly higher figure of 5mm max exit pupil because my skies are not that highly polluted.

My XW40 in my F/10.5 scope gives exit pupil of 4.8mm and looks great to my eyes in my garden.  So that seems to fit.

If John finds 21mm Ethos and 31 Nagler are the limit then I guess that means he must be using scopes around the F/6 mark and/or more polluted skies.

My scopes are F/5.3, F/6.5, F/7.5, F/9 and F/9.25.

My skies are probably not bad for the edge of a large town and with two major cities within 15 miles of me. I've seen the Horsehead Nebula from my back garden when things have been at their best.

Most of my faint target observing is with the 12 inch F/5.3 dobsonian. The other scopes are refractors from 100mm to 130mm and I don't often use the 21 Ethos or 31 Nagler with those. The exception is the 31 Nagler in my Vixen ED 102mm F/6.5 refractor when I want to observe the whole of the Veil Nebula.

I really liked the Aero ED 40 but I decided to have a bit of a clear out a couple of months back and the 30mm and 40mm Aero ED's were not getting much use so I let them go to new homes.

 

[globular]

Seems to fit. The 21 Ethos @ F/5.3 is 4mm exit pupil, the 31 Nagler @ F/6.5 is 4.8mm.  Aero ED 40 would give 7.5mm and 6.2mm pupils in those scopes, so unless the skies were very dark you'd get washed out views.

[globular]

So bringing this all back on topic for you @johnturley;

In your F/5 scope you should get a big contrast improvement over your Meade 56mm (which has an exit pupil of 11mm) by using a shorter fl eyepiece with a wider AFOV. 

You should perhaps target something around 4 to 5mm exit pupil = focal length of 20 to 25mm.  Maybe you can push it to 6mm pupil = 30mm fl as you have such a large aperture?

To give a similar TFOV to your Meade they would need to be hyper wide - which makes them heavy and expensive.

A better compromise is probably to give up a little TFOV to save weight and cost.

[Louis D]

For improved edge of field performance at higher magnification and reasonable weight, you might try to pair the 40mm Pentax XW-R at 667g with a 46.2mm field stop and the 30mm APM UFF at 548g with a 36.4mm field stop.

[johnturley]

16 hours ago, globular said:

 

You should perhaps target something around 4 to 5mm exit pupil = focal length of 20 to 25mm.  Maybe you can push it to 6mm pupil = 30mm fl as you have such a large aperture?

To give a similar TFOV to your Meade they would need to be hyper wide - which makes them heavy and expensive.

A better compromise is probably to give up a little TFOV to save weight and cost.

I wasn't looking for an eyepiece with a smaller exit pupil, I already have a 24 mm Explore Scientific 82 degree eyepiece, just eyepieces around 50mm and 35mm to provide a wider field and/or less aberrations than my existing Meade 56mm Plossl and Baader 36 mm Aspheric.

I thought at first that the 50 mm StellaLyra Superview eyepiece with a stated APFOV of 60 degrees might provide an improvement over the 56 mm Meade, and although the level of aberrations appeared acceptable, it turned out that the actual APFOV was only around 48 degrees or less, giving a resultant actual field of view that was significantly smaller than both the Meade 56mm Plossl and Baader 36 mm Aspheric. There does not appear to be much available around 50 mm that might be better than the Meade, the Masuyama 50 mm might be slightly better, but at £499 it is a high price to pay for something that at best would only be marginally better.

At around 35 mm, there are more options, the Masuyama 32 mm looks good on paper, but it appears that the 85 degree APFOV from a 5 element design will result in a lot of aberrations towards the edge of the field, especially in a f5 instrument. The 35 mm Aero according to some reports might be an improvement over the 36 mm Baader, and at a relatively modest price of £105, or the 30 mm APM Ultra Flat, although the actual field of view of the latter will be significantly smaller than the 36 mm Baader.

John 

[Louis D]

The 35mm Aero isn't going to be much, if any, better than the 36mm Baader Aspheric.  The older 35mm Baader Scopos is significantly better, but narrower.  It's also heavier than the 12mm ES-92.

[John]

26 minutes ago, Louis D said:

The 35mm Aero isn't going to be much, if any, better than the 36mm Baader Aspheric. 

Having owned a 36mm Baader Aspheric and not found it brilliant even at F/12, I'm a little surprised to read this. The 40mm Aero ED is certainly a much better corrected eyepiece than the Baader Aspheric IMHO.

 

[vlaiv]

There is so much conflicting reports on these 2" large AFOV eyepieces.

I want something with 46mm of field stop - to get maximum sky and I don't really care much about focal length - as long as it is up to 40-42mm. I don't want overly large exit pupil.

EP will be used at F/10 and possibly F/7 scope.

Currently, this is candidate number one:

https://www.teleskop-express.de/shop/product_info.php/info/p957_TS-Optics-38-mm--2----70--Wide-Angle-Eyepiece.html

(being the same as SW Panaview 38mm - maybe a bit lighter).

Problem is of course that I keep reading: "It is ok in F/7" and "It is not good even at F/7" - all over the place . I'm fairly sure it will be acceptable at F/10, and I'm also aware that Aero ED will be better corrected - problem of course being that Aero ED is no longer available in 40mm FL - only 35mm and that has 10% smaller FOV if I'm not mistaken - about 42-43mm, right?

Further problem is that some of these reports depend on people using short FL refractor scopes - sometimes having more issues due to field curvature of the scope rather than correction of the eyepiece. Other times it is newtonian scopes that have coma.