Don Pensack

The 17mm T4, though, is the only Tele Vue eyepiece I've seen EOFB (edge of field brightening) in.

It's sharp enough and comfortable enough, and, with glasses, doesn't have any pupil acquisition sensitivity (one of the advantages of wearing glasses),

But I couldn't abide the EOFB, which the 17mm Ethos is free from.

I've said many times that if eyepieces as good as the Starguiders came with telescopes there would be a lot less upgrading of eyepieces in telescopes.

2 hours ago, clydie said:

At the end of last year I got a Sky-Watcher Classic 200p, and it's a brilliant telescope. Much better than my last one. However, I haven't been able to use it properly yet (travelling, and now it's too bright at nighttime where I live), and I never got around to finding out (even when I had my old one) what is the best eyepiece-wise? I have two that came with the telescope but they are just labelled "SUPER 25" and "SUPER 10" which, along with how they look and feel, means they are not the best option, even if they work well enough.

When it gets dark again I'll mostly be using it for planetary observation, though I would like to try looking at deep-sky objects too. I specified middle of the range in the title because I'm not really willing to spend more than £60 on anything.

Thank you!

^ The moon through the SUPER 25 eyepiece, and my phone camera. (not exactly representative of the actual quality haha)

Judging from the prices of eyepieces in general, £60 is a low-end price, but you are fortunate there are many eyepieces at low prices today.

Given your scope, and what might be useful, I would look at at eyepiece in the 6-7mm range.

It would be usable for double stars, small planetary nebulae, small globular clusters, planets, Moon, and small open clusters.  In the 170-200x range.

High power, but not so high that seeing will be a constant issue.

On 15/06/2024 at 11:43, Legalpusher said:

Thanks for the advice.  I opted to buy the 12.5 Morpheus to fill the gap between 16.5 and 8.  It is a nice eyepiece at a reasonable cost.  It fills my need quite nicely.  I am quite pleased with the view and built quality. It has its own distinctive quality as compared to the Pentax and Tele-Vue eyepieces.

I am trying to decide if I should buy the 2x Powermate now, or save up for the 4.7mm or 3.7mm Ethos for planetary viewing.  Another option would be the 4.7 Williams Optic.  I heard it is just as good for half the price.  Please share your views.

If you are referring to the XWA 110° eyepiece, a few notes:

1. It's actually a 4.8mm focal length.

2. It's very sharp, even as low as f/4.

3. William Optics hasn't offered that eyepiece for many years.  Its top was hard to use and later versions of the eyepiece have had a better design of the eye lens end.

4. There are other brand names the 4.8mm is sold under.  Just search for "XWA eyepieces" to catch all the labels the eyepiece is sold under.  You can also find my 2024 Eyepiece Buyer's Guide on cloudynights.com on the Eyepieces Forum to see all the labels, including the factory house brand label, Sky Rover.

5.You could do a lot worse than the Ethos SX eyepieces.  They are even excellent planet eyepieces.

It's not unusual to find particles inside the Baader Zoom.

Your last line says it all: "Fixed eyepieces (even mid budget) remain the king if optical performance is priority. "

It's the reason I don't own a zoom, even the Leica.

My friend Daniel Mounsey and I chatted about eyepieces and observing recently:

I do NOT recommend the Svbony filter.

If you are on a tight budget, the nebula filter to get is the Orion Ultrablock.

It often goes on sale and it is 10x as effective at contrast enhancement as the Svbony filter.

You buy a nebula filter to look at emission nebulae with improved contrast, and the cheap, wide bandwidth, ones simply don't perform.

Why enhance the nebula only a little bit when, for only a little more, you can get high-end enhancement?

Right now, the Ultrablock is only $79.99 in the 1.25" size, but it performs right there with the filters that cost $130-$150.

yes.

When the field is completely flat and free of astigmatism, only then do you realize how small is the amount of coma at f/5. 

It also helps the eyepiece is 70°.  Coma becomes more visible the wider the apparent field.

To find the exact in between magnification, sum the magnification of the 8mm and 16.5mm, then divide by two.

Divide the focal length of the scope by that number to get the center focal length of eyepiece.

If you would prefer even % jumps between eyepieces, 23/1.4 = 16.43mm i.e.16.5mm.

Divide 16.5mm by 1.4 and you get 11.78mm, 

or around 11 or 12 to get the even jump in %.

Or, if you'd simply like a focal length in the middle, a 12-12.5mm would be fine.  And a Morpheus would be a good choice.

6 hours ago, Legalpusher said:

I am new to astronomy.
While searching for suitable eyepieces for my newly acquired Dobsonian,  I came across the Pentax 16.5 and 23mm  My experiences with Pentax in my youth prompted me to buy them.  Compared with the OEM Celestron Omni 32mm,  I was happy with the purchase, and added the 40mm XW as well.  They were comfortable enough to use with glasses, although is much more comfortable without the glasses in between.  A months later, I bought a Tele-Vue Ethos 8mm, the 100 degrees AFO blew me away, I bought the 6mm as well.  They were comparable in comfort and view quality.  The wider view gave them a unique feel.  Don’t think I’ll be buying the 4.7mm soon.  The lack of funding, a common condition since I acquired the hobby, & the weather doesn’t favor its use, maybe later in the fall.  
The 4.7 TeleVue at 110 degree of apparent field of view probably won’t be used frequently due to condition limitations.  Should I buy a less costly alternative like a Nagler, Pentax XW, or skipping it totally?  May be a Powermate?  Having 4 mm and 3 mm eyepieces with the same field of view at the cost of 1/2 an Ethos is appealing.  What pitfalls am I not aware of? If any?
Waiting for a $40, 100mm Vixen eyepiece to replace my OEM red dot finder.  My arthritis prevents me from using it since day 1 totally.   How anyone able to use it on a Dobsonian is beyond my comprehension.  Can’t wait to see how it works out.   May be I should replace the red dot with a right angle finder for $80 instead?

 

 

So you have 6mm, 8mm, 16.5mm and 23mm.

You lack an eyepiece in between the 16.5mm and 8mm.  Beyond that is merely personal taste.

11mm would be ideal, but 10mm would be fine as well.  The best choice would be a 10mm Ethos.  With ultrawide fields,  the choices at 10-11mm are limited, but the 11mm Explore Scientific 82° is a possibility, or, if you could find one, the 11mm Tele Vue Type 6 Nagler.

If talking used eyepieces like the 11mm T6,  the ultimate is the Tele Vue Apollo 11, but a 10mm Ethos would be cheaper.

Tianhu is a big maker of astro goods in China, but is not KunMing United Optics, so it is likely a sub-contracted piece made for KUO under their Sky Rover house brand.

The Baader 32mm Plossl is only 45° and does not have a "full" 1.25" field.  It does have good optics, though, and a glasses friendly eye relief.

Other 32mm Plossls will have a wider true field.  Look for a 27mm field stop or larger.

Get the 24mm UFF:

sharper in outer 50% of field

a bit more eye relief

more elements- better corrected

more true field

lower distortion

better contrast

For glasses, 24mm, and widest field, it is the one.  APM's version has a smooth lower barrel.  I'm not sure any of the others does--maybe Svbony.

On 09/05/2024 at 19:38, Louis D said:

@Naughty NealWhat do you think of the 22mm Angeleyes 70 degree eyepiece?  Someone on CN reported it as having chromatic aberrations (turning stars into rainbows).  That's what my 13mm Astro-Tech AF70 (Redline) has in spades.  It's really annoying to the point of making it unusable.

The AF70 and all the current rebrands of it vary so much from focal length to focal length.

The 22mm is excellent, but the 13 is a dog--the worst EOFB of any eyepiece I've ever seen..  Go figure.

4 hours ago, John said:

The odd thing is that you don't hear any complaints about eye relief from owners of Zeiss ZAO ortho, TMB Supermonocentric or Pentax XO eyepieces, which are very tight in the shorter focal lengths. Presumably the optical performance of these legends is so good that the effort required to use them is worthwhile 🙂

They are used only for planets or close double stars, so the eye is held back far enough the field size is reduced.

Only recommended in scopes that track.

I found reviews of them going all the way back to 2013:

https://www.google.com/search?client=opera&q=reviews+Explore+Scientific+52°+eyepieces&sourceid=opera&ie=UTF-8&oe=UTF-8

Note that there are reviews on Cloudynights.com and StarGazersLounge.com

electronic eyepieces that capture the image for download to a viewing device have been around for decades.

They did not incorporate the viewing screen into the eyepiece, and I recall them being wired, not wireless.

This might be the first example of an eyepiece that has an internal screen and can project the image wirelessly to a tablet, phone, or computer.

I saw a MallinCam on a big dob with a small tablet view screen hung on the scope in maybe the '90s?

This is only a very small step from that.

The 24mm Hyperion has a true field 33% wider than the 17.5mm Morpheus.

If you have a 2" focuser, though, a 30mm UltraFlatField makes a better jump from the 17.5mm Morpheus and yields a true field 68% wider than the 17.5mm Morpheus.

It was speculated the EOFB was due to its angular magnification distortion, except the Docter/Noblex 12.5mm has no EOFB and has strong AMD as well.

Baffles?  Lens polish at the edges of the lens? Field stop too large?  Unknown cause.

But I lent the eyepiece to five other observers, and they all saw the same thing.

If your circumstances don't allow it to be seen, keep it, because though tests show it's edge is only average at f/4, its other problem, FC, is very minor, and it was quite sharp at f/5.75.

I find the APM 12.5 to have noticeable and objectionable edge of field brightening.

That's too bad, since otherwise it's fine.

The 12.5mm Morpheus is a great eyepiece--sharp, great contrast, easy to use.  It's also lighter than the APM.

It's an easy choice, IMO.

5 hours ago, Mr Spock said:

That isn't the finding of people who are using it. I find it just a little behind the 3.3mm TOE at the 3mm (3.5mm) setting.

The center and 50% points are very good.  It's only at the edge the eyepiece image quality suffers.

As exemplified by the Moon photos and Ernest's measurements.

However, the figures at f/10 are very reminiscent of many inexpensive eyepieces.

It's only by f/4 (and likely f/5) that the eyepiece really falls down in edge quality, and then, likely outside the center 50% of the field.

1 hour ago, Louis D said:

Has anyone discussed theories on the optical and mechanical organization of the Televue Nagler Zooms and the Svbony 3-8mm zoom?  My theory, they have a 4 element image forming positive group up top and a 2 element negative, Smyth, group down in the insertion tube.  To increase magnification, they simply move the two groups apart like a varifocal eyepiece such as my Speers-Waler 5-8mm "zoom".  This also maintains the size of the AFOV as in the S-W.  The mechanical trick to maintain near parfocality is to move the negative lens group downward during zooming in (higher power).  I have to do this with the focuser knob to maintain focus while zooming in with the S-W.

In order to maintain parfocality, the upper and lower sections must move apart but one moves up while the other moves down.

That's why they look like mushrooms at the shortest focal lengths.

The Nagler Zoom has 5 elements in a 3 segment upper and 2 segment lower.

Al Nagler told me once that he could make a 15-30 zoom with an 82° field in the same manner, but it would be too expensive to sell, too heavy to use, and very fragile.

From Ernest Maratovich's test of this zoom:

The first column shows the focal lengths at the click stops (actual measured focal lengths in parentheses).

The next column is the field stop at each click stop.  No mystery here, because focal length = field stop at 57.3° apparent field, and this is very close.

The next column is calculated field stops based on stated (and actual) focal lengths with no distortion.  You can use these figures in Astronomy tools to get an accurate answer, or in TF = AF/M.

The next column is the measured apparent field (what we actually see). Roughly 57-60°.

Then 3 columns of spot size at f/4 (center/mid/edge) and 3 columns of spot size at f/10 (center/mid/edge). 5 is considered by most books to be perfect.  10 is fine as long as the spot stays round.  15 is OK and like many eyepieces at the edge. >20 is so-so.

The last column is the nature of the aberrations at that focal length, listed in importance from most to least, followed by a distortion %, if measured.

Conclusions: FC dominates from 5-7mm settings. Astigmatism is present from one end to the other.  Distortion is fairly high for the narrow fields.

f/10 performance is better than f/4, but not remarkably so except from the 3mm to 4mm settings.

It has much better performance than most inexpensive eyepieces except at the 3mm setting.

4 hours ago, Highburymark said:

Yes indeed Don - but this has always made me wonder why we don’t see more people having field curvature issues with the many brands of flat field eyepieces (APM, Altair, Lunt, SVBony etc)? As there’s field curvature inherent in many telescopes. I haven’t used any of that range myself, and I don’t doubt they are excellent, but why buy flat field eyepieces unless your scope has a perfectly flat field?

One reason I can think of is to reduce the amount of visible field curvature.

| + ) = )  You might be able to focus half way to the edge and accommodate the entire field.

| + | = |  This is ideal, and reflectors of 1200+mm focal length are pretty flat, so this will work.

) + ) = |  And this works if the eyepiece and scope have nearly identical curvatures,

) + ( = bad field curvature, and this can happen with a mismatch of eyepiece FC and scope FC.

Since we don't know (the manufacturers don't tell us) whether the FC in an eyepiece is positive or negative, the lowest risk is a flat field eyepiece.

But, alas, to the owner of a flat field scope, it doesn't matter whether the FC in the eyepiece is positive or negative--it'll be curved.

But, like the person with a flat eyepiece and curved focal plane scope, it might be possible to accommodate the curve, so the degree of FC is important as well.

I don't really under stand how short f/ratio refractors of 50-80mm don't see serious FC with nearly all eyepieces, though.

My 12.5" has a radius of curvature of ~1600mm.  An 80mm f/6 refractor has a ROC of 160mm!!  How any eyepiece wider than an ortho functions in such a scope is a mystery.