Upgrade from Nagler T6 3.5mm to...

[iPeace]

Scope: TV85, 85mm, f/7.

Ethos 3.7mm: FOV + X-factor

Delos 3.5mm: mag + eye relief + cheeky defiance of X-factor

All pundits welcome

[Piero]

It's a tough call...!  And to make things harder for you there is a new Delos at £195 sold by Okularum on astrobuysell! I bought the 8mm from them. Eyepiece and service were perfect.  

For your 85mm F7, I think you are fine with both, but if you plan to get a larger fast telescope maybe the extra FOV might turn useful for tracking. On my 200mm F6, the fov of my "Delos 4" and "Delos 3.2" (8mm plus 2x or 2.5x telextenders) is sufficient for my needs. It depends on your priorities, fov or eye relief, I think.

In any case, they will deliver great views, no doubt! 

[GavStar]

I have a tv85 and found the Delos 3.5mm gave me too many problems with floaters due to the small 0.5 exit pupil. I much prefer the 4.5mm Delos for the tv85.

[iPeace]

1 minute ago, Gavster said:

I have a tv85 and found the Delos 3.5mm gave me too many problems with floaters due to the small 0.5 exit pupil. I much prefer the 4.5mm Delos for the tv85.

Fair comment and most welcome. I have the 4.7mm Ethos and love it, but find myself downshifting to the 3.5mm Nagler or the Nagler 3-6 Zoom too often to leave it at that.

[A McEwan]

Hi,

 

I'm curious as to what aspect you are hoping to "upgrade"?

 

Is there a problem with the T6 3.5mm that needs to be solved by buying a different eyepiece of similar focal length?

[iPeace]

1 minute ago, A McEwan said:

Hi,

 

I'm curious as to what aspect you are hoping to "upgrade"?

 

Is there a problem with the T6 3.5mm that needs to be solved by buying a different eyepiece of similar focal length?

Well, I am looking for improved quality of the view itself (I realize this will be marginal at best, but it's where I am at the moment) and either more FOV or more eye relief (as those seem to be my choices). I lean towards FOV but owe it to myself and to all of you to invite your input on this most trivial of dilemmas.

[John]

I used to have the 3.5mm T6 Nagler. It was a great eyepiece and I really enjoyed using it. About the shortest FL that does not show the floaters in my eye too much.

My eyepiece at that focal length is currently the 3.5mm Pentax XW. Slightly smaller AFoV, quite a bit larger / taller, and with very comfortable 20mm of eye relief plus 96% transmission. The XW shows a little less light scatter than the Nagler did.

I'm also really enjoying my 4.7mm Ethos so I may well stump up for a 3.7mm from that range as well but I'll probably keep the XW 3.5 because I like the way that the 10mm and shorter Pentaxes from that range do things. The Delos will be very "XW" like I reckon.

Over to you again !

PS: I've also got the 2mm-4mm Nagler Zoom that covers that focal length. Thats a great eyepiece as well but I tend to use it as my binary splitter more than anything else as the zoom function is so useful for that.

[iPeace]

Thanks so far gents.

I still have my Nagler 3-6 Zoom and may keep it...star splitting sounds like great fun.

Perhaps mainly looking for some reason to deviate from 'blindly' completing the Ethos range...

I appreciate the learned following that Pentax has in this respect; wonder if anyone has experience with these in combination with a Televue refractor?

[Piero]

My TV60 has never been combined with a Pentax XW, but I have two Vixen SLV which are considered quite close to the Pentax XW, apart from the field of view. To me, the SLVs work very well, so I would think that the Pentax XW will be at least as good as the SLVs. 

The only thing to bear in mind is that the SLVs and the Pentax XW come to focus at different position compared to the Delos / Nagler T6. Not a big deal though. If this is a concern for you, you can add a ring to the eyepiece barrel to make them almost parfocal. I think Mod Michael did so.

[GavStar]

I have some Pentax xw (including the 3.5mm which I don't use very often for the reasons explained above) - they work great in my tv85 - very much recommended - very comfortable eyepieces.

[John]

With the 2" barrel extender removed, the 4.7 and 3.7 Ethos are par focal with the Nagler T6's, TV Plossls etc (part of TV's "B" par focal group). With the barrel extender in place the short Ethos are way off most other eyepieces in an outward direction.

The XW's reach focus around 8mm further inwards than the TV's "B" group which is actually closer to where most non-TV eyepiece reach focus.

I've given up with worrying too much about par-focalness (is that a word ?) these days but it can be annoying to have to make major focus adjustments when viewing at high power I agree.

I've had my XW 5mm and 3.5mm for a long time and was very happy indeed with them. I recently bought the 7mm and 10mm to go with them (bought new, which is unusual for me).

When the 4.7mm Ethos came up (used but mint) at a good price I decided to try it thinking that I could move it on if it did not suit me but, so far, it's not put a foot wrong even compared with my favourite XW, the 5mm.

I don't use Tele Vue refractors though. I guess my Vixen ED102SS and Skywatcher ED120 at F/6.5 and F/7.5 are reasonable substitutes for comparison purposes though ?

 

[iPeace]

Not bothered with eyepieces being parfocal (nice but not essential). Somewhere in the back of my mind is a memory of reading a piece by a fellow astronomer saying he didn't much like the combination of certain Pentax eyepieces with his Televue scope, so that's my only reason for asking. Good to get your take on this (that's all of you). The make of scope is certainly not essential when it comes to the value of your input.

As I am also enjoying my 4.7mm Ethos very much it makes sense to follow that road; not taking anything for granted however, as 3.5mm seems to be right on the edge of what works well for me in this scope.

[John]

You can always find a report somewhere from someone who does not like a particular eyepiece or eyepiece / scope combination. Eyepieces seem to be very personal choices and what one person enjoys another may loathe.

In focal lengths longer than 10mm the Pentax XW's show some field curvature which some don't like in certain scopes. Others either don't see it or find that it does not bother them.

Tele Vue use certain optical compromises to ensure a non-astigmatic field even with scopes as fast as F/4. Some though don't like the compromise that they use which is to allow some pin cushion distortion.

As far as I know there is no such thing as the perfect eyepiece  

 

[scarp15]

I particularly enjoy using my 5mm Pentax XW with my TV76 (96X) and had (occasionally still do) considered including a 3.5mmXW. However based on some of the reasoning already mentioned and a desire for a smaller increase in magnification, I would prefer as a next in line, 4mm. For this reasoning I am hoping and awaiting patiently to see whether TeleVue introduce a 4mm DeLite into the line next year. This would yield 120X in my scope and provide excellent eye relief, combined with the current DeLite line-up receiving very favourblae reviews this particular e.p - should it one day exist, will become an attractive option. Additionally the 4mm would be useful occasionally with my F6 200mm dob. 

[Don Pensack]

I agree with the assessment that the only real reason to change is for extra eye relief (which no one would need with that small an exit pupil), or an increased field size.

And going from 82° to 110° is a big change.  The 3.7mm is a fine eyepiece.  I use it in my own scope at 493X to see the moons of Uranus, or size differences on the Galilean moons of Jupiter.

You won't see any difference in axial sharpness compared to the Nagler, but I found that reddish stars in clusters stood out better.  I think the Ethos may be a little flatter response into the deep red.

At any rate, I haven't seen a finer sub 4mm eyepiece with a field anywhere near as wide, so I'd vote for the Ethos SX.

[A McEwan]

When I had a TV85 I had 5.2mm, 10.5mm and 14mm Pentax XL's. I had no problems using them in that scope, and they worked very, very well.

I hate to be slightly negative, but can I suggest you do not sell your T6 Nagler 3.5mm until you've tried all the other eyepieces you're thinking of as "replacements". That way you will still have it and not need to rebuy it again.

 

[Stu]

I used to have a TV85, and tried most of the combinations you are considering; 3.5mm Type 6, 3.5mm Delos, 3 to 6 Nag zoom and 3.7mm Ethos SX.

I used to find that floaters became an issue for me with the 3.5mm eyepieces, and I tended to use the zoom at somewhere between 3 and 4mm, but closer to 4, so that was a very scientific way of establishing that I needed a 3.7e! That gives an exit pupil of just over 0.5mm, and I start to struggle below that.

If I had to rank them in ascending order of quality I would say Zoom, Nag, then Delos/Ethos tied. The Nag is very close but there is just something about the 'Os'es that wins it.

So how did I get on with the Ethos SX? Initially I was wowed by it, and probably posted on here words to that effect. Being able to take in the whole moon at x162 was pretty amazing, and the clarity is second to none. However, I struggled with the eye relief. I am one of those weird people who need to see the field stop otherwise I feel like I'm missing out on something! I didn't really enjoy having to sort of climb inside the exit lens and look around, plus pushing my eye in towards the lens meant that I spent as much time looking at my clearly very long eyelashes as the target!

I eventually sold it as I didn't use it as much as I expected, and put the cash towards something else. In some ways I wish they would make a 3.7mm Delos, the focal length is perfect as a max for planetary on these scopes, and with the eye relief and contrast/scatter control of the Delos it would be superb. Perhaps they could make a Delite in that f/l?

The trouble with opinions of eyepieces is that they are so personal. John loves his 4.7mm, and I'm sure would love the 3.7. I guess it's all to do with face shape, eyesight and probably a number of intangibles.

What was the question? ?

[John]

You sayin' that I got an Ethos shaped face pal ?

 

 

[iPeace]

Thanks again to all; have learned a bit and it is great to have you weigh in on this. I have yet to sell an eyepiece - though that day must surely come - so most likely I will still have the 3.5mm Nagler, as well as the Zoom, by the time a replacement arrives so comparison will happen.

[iPeace]

And the winner is...

3.7mm Ethos!