184 replies to this topic

[Starman1]

Don, why did they discontinue the 26 T5 with 16mm E/R?

Very slow sales.

[Starman1]

Serious question about a “gap”:

 

I have the 31mm T5 (40x magnification in my AD10) and have ordered the 14mm T7 (89x).

 

Would you feel the need to have something in between?  The 19mm T7 would give me 66x.

 

I like LER — old eyes, cataract surgery, eyeglass wearer (though normally not at the eyepiece).

I wouldn't go for an in-between in a 10" scope.  Gaps of 50x are fine.

[ClsscLib]

Consider a used 22 Panoptic...or the 24mm if you want a max 1.25" afov eyepiece.

Why do you recommend those over the 19mm T7?

 

At 52x and 57x, both seem fairly close to my 31mm T5 (40x).

 

 I also prefer not having to switch back and forth between 2” and 1-1/4” EPs.

 

 I might well be missing something, though.

[SeattleScott]

Why do you recommend those over the 19mm T7?

At 52x and 57x, both seem fairly close to my 31mm T5 (40x).

I also prefer not having to switch back and forth between 2” and 1-1/4” EPs.

I might well be missing something, though.

“If” you want to stay 1.25” format. Clearly you don’t care, and if anything prefer 2” format. So you can disregard the Panoptic suggestion.

[SeattleScott]

I do not wear glasses, but advancing age and cataract surgery made me uncomfortable with the shorter eye relief eyepieces. I replaced my 13mm Ethos with the Docter 12.5mm, the 10 and 8 Ethos with the 9mm Morpheus, and the 6mm Ethos with a Delos. After trying these changes for a year, I passed my wonderful Ethos on to others who can better use and enjoy them.

Now after also enjoying the view through the TV Apollo 11, I have ordered a couple of T7 Naglers and expect them to give me the slightly wider field I like, with the same comfortable view.

Cheers,

Ron

The field stop of the 9T7 is 13 versus 11.5 for the 9 Morpheus. So it should give a noticeably wider view.

The field stop of the 5.5T7 is 8.1 compared to 6 Delos at 7.6, so a bit wider, with a bit more magnification. It is only 6-7% wider, but you get a little more magnification, and the viewing angle is wider.

Edited by SeattleScott, 19 May 2025 - 01:19 PM.

[jrmacl]

That's quite obvious. 

 

But the real question is, how to fill that "huge gap" between the 19 mm T7 and the 20 mm T5?

 

Jon

Easy, you just have to pull your 41mm Pan up a little in your 2X Big Barlow

[RAKing]

The field stop of the 9T7 is 13 versus 11.5 for the 9 Morpheus. So it should give a noticeably wider view.

The field stop of the 5.5T7 is 8.1 compared to 6 Delos at 7.6, so a bit wider, with a bit more magnification. It is only 6-7% wider, but you get a little more magnification, and the viewing angle is wider.

 

Yup - that fits my calculations, too.  The shorter 5.5mm should also have a slightly darker background due to the smaller exit pupil.  It's probably not much, but at these short focal lengths, it might help on my double stars.

 

Ron

[Mike W]

Very slow sales.

For some reason I envisioned the 26t5 the same as the 16t5 when it's a pound heavier!

[scotsman328i]

For some reason I envisioned the 26t5 the same as the 16t5 when it's a pound heavier!

I have the 26T5 and did own the 16T5, that’s pretty much the way it is! lol

[Procyon]

Serious question about a “gap”:

I have the 31mm T5 (40x magnification in my AD10) and have ordered the 14mm T7 (89x).

Would you feel the need to have something in between? The 19mm T7 would give me 66x.

I like LER — old eyes, cataract surgery, eyeglass wearer (though normally not at the eyepiece).

Compare the 31 and 14 views. If you have every other gap or scope filled and have a lot of change left over, may as well get the 19 T7 if you find the views between the 31 and 14 differ. It will be an expensive minor gap filler though.

I have some expensive minor gap fillers too, best is to find a specific use for them, to justify their existence and cost lol. In your case, maybe it could be used as a Nebula, Asterism and Comet eyepiece.

Edited by Procyon, 20 May 2025 - 07:00 AM.

[Jon Isaacs]

I wouldn't go for an in-between in a 10" scope.  Gaps of 50x are fine.

 

Personally, I want something between a 31mm and a 14mm.  that's a jump of 2.2x in magnification while the images (of extended objects) are 1/5th as bright.  

 

Jon

[25585]

To me the question is, would I replace my ES92s with T7s, the latter being 14mm and 19mm.

 

The answer would be I might add T7s to join my 92s, but I would not replace the ESs which are proven. (Likewise my Long Perng LER 80 AFOV and my Docter/Noblex would stay).

 

For any T7, I would need to try one before paying for it, TV fool me twice shame on me. 

[C0rs4ir_]

Here's a thought.

I am thinking of replacing a 13mm Ethos with 14mm Type 7 Nagler.

Is this a good move?

Would performance improve with new coatings and maybe better polish?

I am not needing the 20mm eye relief at this point.

Never. The Ethos are just too perfect to be replaced by a narrower field ep - be it 5% better aberration controlled or not. Simply life long keepers.

Edited by C0rs4ir_, 20 May 2025 - 06:47 AM.

[scotsman328i]

Personally, I want something between a 31mm and a 14mm.  that's a jump of 2.2x in magnification while the images (of extended objects) are 1/5th as bright.  

 

Jon

Definitely Jon, that’s a big gap of magnifications between a 31mm and 14mm.

 

Most of my observing done on a regular basis is done between 30mm and 10mm.

 

I’ve filled my ‘higher end’ medium power gap (between 10mm and 20mm) with a 10 Ethos, 13 Ethos and a 17 Nagler Type 4. Ive filled the ‘lower end’ of that medium power gap (between 20mm and 30mm) with a 20NagT5, 22NagT4, 24 Panoptic and a 26NagT5. Pretty much most every viewing session I’ve found myself using 20mm-26mm a real luxury to have when studying nebula, open clusters, star fields and brighter galaxies. At a 20mm to 10mm step down, I’ve found owning a 17mm and 13mm ocular the perfect steps to 10mm and greater magnification.

 

The 17NagT4, 13 and 10 Ethos, either Pentax 7XW or Nikon 7NAV-SW and Nikon 5NAV-SW are fantastic for planetary, lunar, star splitting, planetary nebs and glob cores mostly every observing session. My Pentax 3.5 is mostly used for planetary and lunar observing, and tougher doubles when the seeing is good enough.  

[Starman1]

Personally, I want something between a 31mm and a 14mm.  that's a jump of 2.2x in magnification while the images (of extended objects) are 1/5th as bright.  

 

Jon

You are only thinking brightness, and brightness is only one parameter of increasing magnification.

I am thinking significant magnification difference in appearance.

 

When you view something at low power, it has a certain size and resolution.

If you just bump the power a little bit, the image is about the same size and has about the same resolution and the background sky in the eyepiece is just a little bit darker.

 

If the object looks the size of a dime, I don't see that making it the size of a nickel provides a different view.  Making it the size of a quarter *barely* does.  Making it the size of a half dollar

makes it look larger, better resolved, and quite different than the dime.

 

I've owned 32 scopes, and my feeling in each of them is that when I bump the magnification from low power to the next one up, I want to see a different view of the object.

I want it to be larger, to resolve details in it better, and for it to appear different and for the background sky to be a lot darker.

 

To accomplish that at low power means a bump in power that is a much larger % than it would be at medium or high power, like a difference of 100% in magnification.

In my 8", that was a jump from a 40mm eyepiece to a 20mm eyepiece.  In my 12.5", that was a jump from a 30mm eyepiece to a 14mm eyepiece.

Ever since my first scope in 1963, I have made the mistake in purchasing an eyepiece that was in between low power and a doubling of that power, and in every scope I've owned, that eyepiece

got very little use.  I would switch to it, only to discover I wanted more power and a different view of the object.

Even objects like the Veil Nebula, which looks great at a low power with a good O-III filter, has 10x as much detail in a higher power, and that higher power has always been at least double the magnification of the lowest power.

 

Where that in-between eyepiece has gotten use is as a substitute low power eyepiece, using it as the lowest power and just not using the lowest power eyepiece.

When I've done that, I can see a somewhat smaller % jump to the next power up.  But if starting at low power, a 50% increase just doesn't do it.

 

Of course, at high power, a small % change can result in a different appearance.

But we are talking about 40x to 89x in a 10" scope, a difference of 49x.  I would put that in the "noticeable change" category.  a 40x to 66x change would be in the "I can see a slight difference, but it isn't enough" category.

[russell23]

To add to what Don is saying, and I'm in no way assuming he would agree with this, but I agree with what he is saying here and this is my take with my refractors:

 

I generally use a magnification in the 30-50x range as my lowest main observing magnification.  This is a great magnification range for framing deep sky objects while having a nice combination of bright exit pupil and image resolution.

 

For example, last night that was 49x in my AT115EDT.  What is the purpose in going higher than 49x?  Is the purpose to get a dimmer image?  No.  The purpose is to increase image scale and resolution of details. So in my AT115EDT I could go to 96x with my 20mm XW and a barlow or 151x with the 20mm XW and a different barlow.  What purpose then, does 100x serve?   It is less resolution than 151x and a dimmer, smaller TFOV image than 49x.   So I'll go right from 49x to something in the range 130-150x.  

 

Sure, the magnifications between 49x and 151x will increase resolution, but you lose image brightness and TFOV compared to 49x and you have inferior resolution to 151x. 

 

Why stop at 151x?   That is in the exit pupil range (0.7-0.8mm) below which the image becomes too dim for DSO for my tastes. 

 

This is a shorter version of my latest post on the 3 eyepieces 90% of the time thread.

 

Dave

Edited by russell23, 20 May 2025 - 10:05 AM.

[davidgmd]

I replaced my Delos 6 with an Ethos 6 rather than the NT7 5.5 since at that exit pupil I don't need glasses.

[Procyon]

Is it different with refractors? I like looking at Asterisms or Open Clusters at 12x with a 48mm Brandon. Than I switch to a 38mm Panaview for 16x or a 31.5mm for 19x. I kind of like the difference it makes on Open Clusters. Maybe I'm just a refractor noob, I dunno. Afterwards I like making a jump to a 17mm for 35x.

[scotsman328i]

Is it different with refractors? I like looking at Asterisms or Open Clusters at 12x with a 48mm Brandon. Than I switch to a 38mm Panaview for 16x or a 31.5mm for 19x. I kind of like the difference it makes on Open Clusters. Maybe I'm just a refractor noob, I dunno. Afterwards I like making a jump to a 17mm for 35x.

In the grand scheme of things, it doesn’t matter, Bro. What you like is what you like. If your set up works for you and you’re happy with the magnification steps, that’s all that matters. As you trial and error with your refractor, you’ll check out other eyepieces in the focuser through possibly your club or other friends who observe, the you can decide if you want to fill that gap or not. It’s all relative, my man! 

[RichD]

Definitely agree with Don about a decent sized jump up from low power, but 49x to 151x a bit too far for me. I'd happily go 49x, 100x, 151x for purposes of framing objects as much as anything. But everyone is different

[russell23]

Is it different with refractors? I like looking at Asterisms or Open Clusters at 12x with a 48mm Brandon. Than I switch to a 38mm Panaview for 16x or a 31.5mm for 19x. I kind of like the difference it makes on Open Clusters. Maybe I'm just a refractor noob, I dunno. Afterwards I like making a jump to a 17mm for 35x.

Not necessarily.  This is what I like to do.  I explained the reasons.  I used to spend a lot more time fishing my way for the best view trying all my magnification stops.  What I found is that most deep sky objects either are best observed at 30-50x with a 1.5 - 2 deg TFOV or alternatively at a 0.7-0.9mm exit pupil which with my refractors is generally in the 130x-150x range.  A handful of larger diameter objects benefit from a lower than 30x wider TFOV view.

 

I just find it wasteful to work my way through all of the intermediate  magnifications in the 60x-120x range.  Usually either the wider field of the lower magnification or better resolution of the higher magnification wins out over magnifications in the 60-120x range.  

 

In the context of the Nagler T7 series, with my AT115 they would give:

 

19mm --> 42x

14mm --> 58x

9mm --> 89x

5.5mm --> 146x

 

So the 19mm and the 5.5mm fit perfectly into my preferred ranges with that scope.  There is no need to get all four focal lengths.  The 14mm and 9mm would not get a lot of use.

 

The 9mm would get more use with my 102mm f/11 where it would give 125x and a 0.82mm exit pupil.

 

Obviously not everyone will agree with my approach. Many don't.  And that is ok.  But the thing I have found is that if I trim the magnification options down to about 3 or 4 I feel like I spend more time observing than if I'm constantly swapping around comparing views. 

Edited by russell23, 20 May 2025 - 11:53 AM.

[PKDfan]

Is it different with refractors? I like looking at Asterisms or Open Clusters at 12x with a 48mm Brandon. Than I switch to a 38mm Panaview for 16x or a 31.5mm for 19x. I kind of like the difference it makes on Open Clusters. Maybe I'm just a refractor noob, I dunno. Afterwards I like making a jump to a 17mm for 35x.

Yup. Definitely Procyon.

I get 10.1X with 40XW and all the way to 13.1X with 30XW and if i want to get really crazy i drop in a 20mm for an insanely high 20X.

You guys who do really high gaps need to realize the aesthetics of all the powers below 50X.

9Morpheus is a blistering 45X in my 400mm scope and every one of those views to me is dramatically different ethos.

YMMV. lol.

CSS
Lance

[Procyon]

It's a lil different with my 11 SCT, hated going to 40mm ep's except from a darksite. Even 32mm. I just start with 25mm, to 20mm for closer look at oc's, than 17mm for Galaxies, 10-14mm for Planets, Globulars.... 5-9mm for major closeups of PN's, Planets, Globs and Lunar if I ever look at it...

I may go a little nuts and add a 19mm T7 if it has great transparency % or throughput, although would have preferred an 18mm for Galaxies, and replace the 9mm XWA with a 9mm T7. Only if they're Delos like though, no point otherwise. Ain't spending 700 for an 82 with less than Delos performance. That's Ethos and Nikon HW territory in $.

Edited by Procyon, 20 May 2025 - 01:23 PM.

[areyoukiddingme]

I also like a large jump from a ~30mm to a 14 or 12.5mm using ~F6.

 

While the magnification change is worth taking into account, so too is the logarithmic response of the visual system to brightness changes.

 

We see brightness changes that are less dramatic than would be expected compared to the physical differences.

 

And while fixed steps in magnifications or exit pupils are fine for producing a line of eyepieces, I find myself constantly wanting to tinker with the steps because something more uneven in steps more closely approximates what I find I prefer--i.e, a big step from lowest power, to smaller steps at higher powers.

[areyoukiddingme]

For the physical difference, take 5, 2, and 1mm exit pupils. The physical brightness differences would be referenced to the 1mm.

 

The 5mm would be 25x brighter, and the 2mm is 4x brighter than the 1mm (they are squares).

 

For perceptual difference, it follows a logarithm or power function (I think the latter is the better fit, but it has been a very long time since I looked at that).

 

Asking Grok, with scotopic conditions, an exponent of .33 is likely appropriate on the intensity. And that gives:

 

5mm is 25**.33 = ~2.9

 

2mm is 4**.33 = ~1.5

 

1mm is the baseline = 1mm. 

 

Physically, a 5mm exit pupil is about 6x brighter than the 2mm exit pupil, but perceptually it's approximately 2x.

 

There's probably not an exact number that can be placed on the perceptual difference, as it will depend on sky conditions, individual dark adaptation, and perhaps individual differences in sensitivity, not to mention the approximate nature of the power law.