Preferred focal length spacing for your eyepiece collection?

[Rob_UK_SE]

5 minutes ago, Louis D said:

I went with a large and deep Pelican-style case so I could store my eyepieces upright.  It allows many more eyepieces in a single case.  One downside is I have to have the layout memorized since many eyepieces look the same from the top in the dark.  Another is it allows for the weight to creep as I've added more heavy eyepieces.  The case is over 20 pounds now.

That’s an interesting idea, Louis. At 20lbs, that’s quite some eyepieces case!

My Peli case isn’t deep enough to support this option, but I also think I’m close to my comfortable weight limit. I can certainly feel the weight difference with it fully loaded up. Having just checked it on some scales, it is now up to 7.3kg (16lbs). 

[Don Pensack]

1 hour ago, Stardaze said:

Interesting Don! Out of interest, having got the APM 20 and 13, how improved did you find the Ethos variants? 

The 21mm Ethos has a bit better star images and contrast than the 20APM (it's not 3x greater, though)

The 13mm Ethos was definitely sharper than the 13 APM, but contrast was the same or even maybe a tad better in the APM.  It was hard to tell.  They were close.

By the way, there is a 7mm APM XWA coming in December (+/-).

[Don Pensack]

On 03/09/2020 at 12:00, Rob_UK_SE said:

A quick update...

Firstly, thank you all for sharing your insight with this. I ended up making the decision to close the gaps in my available focal lengths (expanding on the 21E, 13E, 8E and 6E quartet) and, in particular, have something else to complement the 21E for lower power / wide field views. Below is the updated case which now includes a 30mm XW and a 10mm XW. This will be my main case as it covers focal lengths from 30mm to 3mm.

 

After spending some initial hours with the XW eyepieces, I have found them to be extremely comfortable and very easy to use in terms of eye placement. I will evaluate their optical performance over a series of nights and don’t want to jump to conclusions, but I have certainly been pleased with the views, so far. For the reasons of comfort and accessibility primarily (so that my son can enjoy higher power views too), I have decided to expand my higher magnification set and complement my 3-6mm Nagler zoom with the XWs. I’m starting to see why you enjoy using these eyepieces with your refractors, John.

This arrived today. Can you see the emerging theme here... (another case might be required)😀

Ironically, my observing partner (who also reads through the posts on SGL) ended up purchasing your recommendation, Don, for the 30mm APM ultra flat. I had, regrettably, already ordered the 30mm XW before your recommendation. I will therefore look forward to a bit of a ‘shoot out’ between these two heavyweights: the 30mm XW and the 30mm ultra flat.  

Ferrari is better than Lamborghini.

No, Lamborghini is better than Ferrari!

What about a Bugatti?

Or a McLaren?

When you're at that level, little nuances in character determine what you do or don't prefer.

And, at low power, contrast is probably more important than sharpness, since our eyes have limited resolution with night vision.

But here's some things to look for:

Date__________________Scope______________

Eyepiece_______________________________Day  Night

1.       spherical aberration_________________________________________________________

2.       coma_____________________________________________________________________

3.       astigmatism________________________________________________________________

4.       field curvature______________________________________________________________

5.       distortion--type and amount___________________________________________________

6.       chromatic aberration--axial and lateral___________________________________________

7.       apparent field_______________________________________________________________

8.       eye relief___________________________________________________________________

9.       light scatter control--field and star outside field (glare)______________________________________________________________________

10.   SAEP_______________________________________________________________________

11.   CAEP_______________________________________________________________________

12.   Tint________________________________________________________________________

13.   Vignetting___________________________________________________________________

14.   Transmission_________________________________________________________________

15.   thermal issues________________________________________________________________

16.   field stop focus_______________________________________________________________

17.   impression of contrast_________________________________________________________

18.   EOFB_______________________________________________________________________

19.   Sharpness on axis/50%/edge____________________________________________________

Other comments about eyepiece____________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

Edited September 6, 2020 by Don Pensack

[Rob_UK_SE]

9 minutes ago, Don Pensack said:

Ferrari is better than Lamborghini.

No, Lamborghini is better than Ferrari!

What about a Bugatti?

Or a McLaren?

When you're at that level, little nuances in character determine what you so or don't prefer.

And, at low power, contrast is probably more important than sharpness, since out eyes have limited resolution with night vision.

But here's some things to look for:

Date__________________Scope______________

Eyepiece_______________________________Day  Night

1.       spherical aberration_________________________________________________________

2.       coma_____________________________________________________________________

3.       astigmatism________________________________________________________________

4.       field curvature______________________________________________________________

5.       distortion--type and amount___________________________________________________

6.       chromatic aberration--axial and lateral___________________________________________

7.       apparent field_______________________________________________________________

8.       eye relief___________________________________________________________________

9.       light scatter control--field and star outside field (glare)______________________________________________________________________

10.   SAEP_______________________________________________________________________

11.   CAEP_______________________________________________________________________

12.   Tint________________________________________________________________________

13.   Vignetting___________________________________________________________________

14.   Transmission_________________________________________________________________

15.   thermal issues________________________________________________________________

16.   field stop focus_______________________________________________________________

17.   impression of contrast_________________________________________________________

18.   EOFB_______________________________________________________________________

19.   Sharpness on axis/50%/edge____________________________________________________

Other comments about eyepiece____________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

Thank you, Don, for sharing all of this - it’s very generous of you. You mentioned your 20 point review in another thread and I have wondered what you include towards reaching such well-informed conclusions. 👍

In terms of the cars, I quite like the Jay Leno approach...why not have one of each!

Edited September 3, 2020 by Rob_UK_SE

[RickEm]

5 hours ago, Don Pensack said:

I never took to the 21mm because it had a slightly poorer outer field correction in the 12.5" than the other Ethos focal lengths.

Axial sharpness was excellent, as was contrast but it was obvious to me why TeleVue didn't stretch the focal length past 21mm.

Even using my glasses to completely correct astigmatism (I see none at 31mm with the glasses on), the edge of the field displayed some visible astigmatism when running through

focus from one side to the other.

Granted, it is WAY out in the field, but the 17mm was simply sharp to the edge, as was the 13mm.

Compared to the 22mm Nagler, the Nagler seems to have a flatter field (not field curvature per se, but the presentation of the field to the eye), and a slightly easier exit pupil to acquire and hold.

I just find the 22mm more comfortable to use.

 

I find it ironic that in comparisons I've done of all the focal lengths in the ES 100° series and the APM XWA series, that the poorest edge correction in each of those lines is with the 20mm as well.

[well, except the 25mm ES 100°, which is a "bridge too far" in my opinion]

I don't really expect perfection in an eyepiece, but I came to the 21mm Ethos after 12 years with the 22mm Nagler, and just never got comfortable with the 21mm Ethos.

In contrast, the 17mm was an example of everything an eyepiece should be.  It ended up being my most-used low power eyepiece. Because of the nature of the targets I observe,

which are usually small, my most-used eyepieces are in the 6-11mm (166-304x) range, so I use any eyepiece in the 15-30mm range primarily for the very largest targets at low power.

 

I certainly recommend the 21mm Ethos over those other two, and I used it for 10 years.  It was only when I found I needed glasses to observe that I went back to the 22mm Nagler.

Otherwise, I'd still be using it.  A 95% score is still an A grade.

 

 

 

As usual, Don, a very thorough explanation.  It’s much appreciated!  I notice that in the discussion you recommended the APM 30mm UFF over the 31 Nagler.  Was that simply for reasons of cost and weight?

[Don Pensack]

On 03/09/2020 at 14:04, Rob_UK_SE said:

Thank you, Don, for sharing all of this - it’s very generous of you. You mentioned your 20 point review in another thread and I have wondered what you include towards reaching such well-informed conclusions. 👍

In terms of the cars, I quite like the Jay Leno approach...why not have one of each!

Having one of each works with eyepieces, too (spoken from experience).😀

[Don Pensack]

On 03/09/2020 at 15:28, RickEm said:

As usual, Don, a very thorough explanation.  It’s much appreciated!  I notice that in the discussion you recommended the APM 30mm UFF over the 31 Nagler.  Was that simply for reasons of cost and weight?

Another example of personal preference.  The 30mm APM has just a bit more eye relief than the 31mm Nagler, so was easier to use with glasses on.

I also found the contrast in the 30mm APM to be a bit better (more than a 1mm focal length difference could account for).

But the difference I preferred was the "map-flat" field in the APM, compared to the "concave" field presentation in the Nagler.  That may be purely a psychological interaction with the eyepiece,

where the wider field just seems to be a bit closer to the eye at the edge than in the center.  I'm not sure what it is, but I preferred the flat field presentation.

[Note: neither eyepiece has field curvature per se, and stars are tiny points to the edge in both.  I'm talking about how the field appears to the eye.]

In fairness, the 30mm APM has 9 elements for a (measured) 72° field, where the Nagler has 7 elements for an 82° field, and an eyepiece designer has more options when more lenses are used.

And it wouldn't surprise me if, in a lab, the APM did not have quite as high a transmission as the Nagler.  But at 59-61x in my 12.5" scope, light transmission isn't the

primary factor influencing one's impression of an eyepiece.

The Nagler's field is 10.5% wider than the APM, so those trying to maximize true field might prefer the Nagler.

The APM yields 1.19° in my scope, however, which I find wide enough for pretty much everything except a handful of giant targets, on which I can scan back and forth as necessary.

I have a 102mm refractor for when I want truly enormous fields of view.

 

As for the 30mm XW, though it is very comfortable to use (again, a personal comment, not an optical one), I found in my scope that the edge wasn't as well corrected as either the 

Nagler or the APM.  Contrast is excellent, though, and it makes an excellent daylight eyepiece in my refractor at 24X, with a nice bright image, so transmission is also quite high.

Field of view was similar to the APM.  At this level, small nuances make the difference.  No one is losing out to have any of them.

Edited September 6, 2020 by Don Pensack

[RickEm]

1 hour ago, Don Pensack said:

Another example of personal preference.  The 30mm APM has just a bit more eye relief than the 31mm Nagler, so was easier to use with glasses on.

I also found the contrast in the 30mm APM to be a bit better (more than a 1mm focal length difference could account for).

But the difference I preferred was the "map-flat" field in the APM, compared to the "concave" field presentation in the Nagler.  That may be purely a psychological interaction with the eyepiece,

where the wider field just seems to be a bit closer to the eye at the edge than in the center.  I'm not sure what it is, but I preferred the flat field presentation.

[Note: neither eyepiece has field curvature per se, and stars are tiny points to the edge in both.  I'm talking about how the field appears to the eye.]

In fairness, the 30mm APM has 9 elements for a (measured) 72° field, where the Nagler has 7 elements for an 82° field, and an eyepiece designer has more options when more lenses are used.

And it wouldn't surprise me if, in a lab, the APM did not have quite as high a transmission as the Nagler.  But at 59-61x in my 12.5" scope, light transmission isn't the

primary factor influencing one's impression of an eyepiece.

The Nagler's field is 10.5% wider than the APM, so those trying to maximize true field might prefer the Nagler.

The APM yields 1.19° in my scope, however, which I find wide enough for pretty much everything except a handful of giant targets, on which I can scan back and forth as necessary.

I have a 102mm refractor for when I want truly enormous fields of view.

 

As for the 30mm XW, though it is very comfortable to use (again, a personal comment, not an optical one), I found in my scope that the edge wasn't as well corrected as either the 

Nagler or the APM.  Contrast is excellent, though, and it makes an excellent daylight eyepiece in my refractor at 24X, with a nice bright image, so transmission is also quite high.

Field of view was similar to the APM.  At this level, small nuances make the difference.  No one is losing out to have any of them.

Thanks, Don, for the analysis.

[popeye85]

I hope the op won't mind me hijacking the thread for a bit 😁😁😁

I'm also in a bit of a muddled state about upgrading my eyepieces and could do with the help of you fine people!

I've just upgraded to a 12"dob and want to get some eyepieces that will do it justice-at the minute I just have a Mish-mash set of basic eyepieces.

I am looking at the explore scientific 82° set at the minute mainly due to the wide FOV and it sits perfectly into my current budget. Although may upgrade again in a few years. 

The FL in the range come in at. 

4.7.     6.7.   8.8.   11.   14.    18.   24.    30

 

I'm thinking 4 or 5 ep's for the set but struggling to pick which ones-any advice you could offer would be greatly appreciated! 

Thanks.

Popeye.

P.s happy to look at other brands but the budget is £120-150.

[Timebandit]

47 minutes ago, popeye85 said:

I hope the op won't mind me hijacking the thread for a bit 😁😁😁

I'm also in a bit of a muddled state about upgrading my eyepieces and could do with the help of you fine people!

I've just upgraded to a 12"dob and want to get some eyepieces that will do it justice-at the minute I just have a Mish-mash set of basic eyepieces.

I am looking at the explore scientific 82° set at the minute mainly due to the wide FOV and it sits perfectly into my current budget. Although may upgrade again in a few years. 

The FL in the range come in at. 

4.7.     6.7.   8.8.   11.   14.    18.   24.    30

 

I'm thinking 4 or 5 ep's for the set but struggling to pick which ones-any advice you could offer would be greatly appreciated! 

Thanks.

Popeye.

P.s happy to look at other brands but the budget is £120-150.

 

 

From the focal length range of eyepiece you mention. Then I would opt for the 

4.7   8.8   14   24

Why ,this will give you a good range from high mag power for planet, mid power and lower range power for DSO. Depending on the exact focal ratio of your scope. But from an initial answer from the information provided then this would give you a good spread of eyepiece powers for observation.

 

 

[popeye85]

20 hours ago, Timebandit said:

 

 

From the focal length range of eyepiece you mention. Then I would opt for the 

4.7   8.8   14   24

Why ,this will give you a good range from high mag power for planet, mid power and lower range power for DSO. Depending on the exact focal ratio of your scope. But from an initial answer from the information provided then this would give you a good spread of eyepiece powers for observation.

 

 

Cheers. What about a ultra wide field ep?

[Louis D]

On 19/09/2020 at 08:32, popeye85 said:

Cheers. What about a ultra wide field ep?

As in ultra wide true field of view?  You didn't specify the focal ratio of the 12" Dob's mirror.  Assuming an f/5, that would mean 7*5=35mm would be about your longest focal length based on maxing out your exit pupil.  You could go with a 30mm ES-82 or 31mm Nagler T5.  The 35mm Aero ED won't be as well corrected at f/5, but it will present a slightly wider TFOV and be much lighter and cheaper.