Poll: Quality or quantity?

[parallaxerr]

I'll keep this short -

Explore Scientific 82° or Tele-Vue Delite 62°?

Scope: Skywatcher ST120.

Targets: Mostly DSO, globs & doubles.

I was settled on the ES82° but have read mixed reviews on certain FL's. The Delites are considerably more expensive but I can't find anything in between that appeals and if I'm paying more than the ES price I might as well push to the Delites...Delos/Naglers etc. are out of the question.

The ES's promise a larger FOV and associated image scale but if the Delites transmit a liitle more and sharper then maybe it's worth it?

I could buy 2.5 ES's for the price of one Delite, so therein lies the question, quality or quantity? Poll posted, I'll go with the numbers

EDIT: It's hard to keep things short here! A little more info - I'm sticking to 1.25" due to focuser travel restrictions with the scope & I don't need any of the longer FL's in 2" format as I find the image too bright above about 20mm. Also, I've missed the boat on almost EVERY 2nd hand bit of astro kit I've ever tried to buy so only considering new cost at the moment. To that end, are TV EP's too much for the humble ST120?

[Davesellars]

It may depend on the focal lengths you're looking at purchasing.

I have the ES82 6.7mm, 8.8mm and the 11mm.  Apart from the 8.8 which I've only just received the 6.7 and 11mm are great eyepieces but like yourself there was sufficient concern about the 14mm such that I have just gone for a Televue instead (at great cost).   Certainly the ES82 6.7 and 11 work very well in my ST120 I'd say go for these.  Also the ES68 range (apart from the 16mm) is very good judging by my ES68 24mm so you could go for the 20mm -> 24mm in this range for low power.

[parallaxerr]

Hi Dave,

Yes it's the 14mm I've read about. There's an element of OCD going on here too in as much as I'd like a complete set of EPs not only from one manufacturer but from one range. Shame the ES68° range doesn't have a few more in the lower FLs.

[cloudsweeper]

I've also got an ST120, and ES82 EPs - the 18 (2 inch), 14, 11, and 6.7.  (Also the 24mm 68 degree.)  I have no adverse remarks about them in terms of sharpness of image across the field, and would recommend these.  I do not have any TV EPs, so only others can say whether you'd get much better performance for a lot more outlay!

Doug.

[Moonshane]

Never used the ES but I have two Delites (11mm and 7mm) and they are in my opinion the best eyepieces I have used. When funds allow (maybe a long time as I have started binoviewing!) I think I'll be adding the rest of the set to my box. Certainly the 18.2mm, 15mm and the 9mm although I doubt I'll be binoviewing with Delites - as I'll usually be using orthos in a tracking EQ5.

What mount are you using? I think that a tracking mount to some extent negates the need for wider fields especially on things like planets and doubles.

[Moonshane]

ps one thing to bear in mind is that I seem extremely sensitive to off axis CA and with Ethos and Delos, whilst they are wonderful on all but the moon, I found that there was a lot of off axis CA manifesting itself in blotches of pink and blue, sometimes yellow, across the surface of the moon. I can recreate this by looking at a light with the eyepieces in the hand. Maybe my eyes are weird though. It does not happen in Panoptics, Delites, or the older Naglers (e.g. type 1/2) but does in the T5s.

[parallaxerr]

I've got a Nexstar SE so tracking in Alt-Az. You raise a good point about tracking and FOV, however, I was thinking more along the lines of larger image scale with the 82°'s but I suppose decreasing exit pupil will limit this to some extent. It's all a bit of a balancing act!

[Moonshane]

Indeed, everything is a compromise in some way or other.

Bear in mind that most objects will fit within a 1 degree true field although for clusters, more helps sometimes

Here's a spreadsheet I did for my current eyepieces and your scope which shows a fair mix. All eyepieces are TV other than my 18mm BCOs.

eyepieces and scopes.pdf

[parallaxerr]

18 minutes ago, Moonshane said:

ps one thing to bear in mind is that I seem extremely sensitive to off axis CA and with Ethos and Delos, whilst they are wonderful on all but the moon, I found that there was a lot of off axis CA manifesting itself in blotches of pink and blue, sometimes yellow, across the surface of the moon. I can recreate this by looking at a light with the eyepieces in the hand. Maybe my eyes are weird though. It does not happen in Panoptics, Delites, or the older Naglers (e.g. type 1/2) but does in the T5s.

I think I saw this on Jupiter once, through a TV85 fitted with a Delos. It came as a bit of a shock tbh as my ED80 with Baader Zoom showed none in direct comparison.

[Ricochet]

15 hours ago, Davesellars said:

Also the ES68 range (apart from the 16mm) is very good judging by my ES68 24mm so you could go for the 20mm -> 24mm in this range for low power.

What's wrong with the 16mm? I've got the 16 and 24 and to my eye the 16 is superior. 

[parallaxerr]

50/50 so far...

[Paul73]

Thought that the question was about the 82°??? I believe that the 82° are a bit better than the 68° range. But, they represent really good value for money.

The Delite's are also .... err, light. So they will be kind on balance. I would go for Delite for your prime planetary eyepiece and ES 82° for the rest.

Paul

[YKSE]

Have you tried your 5, 6 & 9mm LER planetary with ST 120? or Baader Zoom with/without 2.25x with ST 120? How's your impression? what is it you want to improve? I'd explect a upgrade of scope will give you better improvement than a couple of EPs.

[parallaxerr]

Yes, I've tried all the above.

The 5,6 & 9mm LER's are very nice at splitting doubles and getting in close to globs. When the planets were up I had very pleasing views of Jupiter & Mars. At 55° AFoV they feel a liitle restrictive when compared to the Zoom @ 8mm and 63°, for example.

The Zoom has been very useful in helping me understand how my eyes behave wrt exit pupil. However, at longer FL's where I'm trying to open up the exit pupil, the AFoV drops to 48-53°. I also see some pincushion with the zoom and stars trailing off at around 80%'ish depending on what FL is selected. I'm not overly satisfied with the Zoom/x2.25 barlow combination, however it has helped me to identify the benefits of a wider FoV when comparing it with the 5mm LER (Zoom @12mm w/x2.25 barlow).

These factors have lead to me wanting higher quality fixed FL EP's that have an AFoV of 60°+ and better correction across the FoV (I understand the scope may account for some of it but the better the EP the less it's exagerrated). The ES82's promise larger image scale but I think the TV's are likely to be the better corrected.

P.S.

With upgrading the scope comes upgrading the mount. I had the intention of doing this recently but funds prohibit the initial large outlay and I had no joy selling my gear. I like fracs and the ST120 is the largest I can fit on my mount so now the plan is to drip feed the EP's in over time. Maybe in time when funds become avaialble I'll upgrade to a better scope but I'm sure I can put the ST120 to good use in the mean time.

[YKSE]

You've done very carefully observation/comparison with EPs

You have everything covered with EPs, therefore the best way to use them untill your fund allows for scope/Mount update, potential gains with EP update at present is quite limited, IMHO.

For your reference, here’s some observations I’ve done or read:

1. Baader zoom’s FOV are more likely in 42° in 24mm and 70° in 8mm range

2. Pincushion in Baader zoom is quite mild, to my eye, it’s about as in Delite shown here

http://astronomyconnect.com/forums/articles/tele-vue-delite-eyepieces-first-light-review.1

 3. Televue EPs are better corrected for astigmatism, and have quite flat field, your 120ST will show quite Field Curvature(FC) because of its short focal length, EPs with opposite curvature than 120ST should show less FC than a flat field EP.

4. Off axis CA mentioned above by some is the result of wider AFOV, it shows mostly on bright objects when you try to look it at the edge. EPs with AFOV in around 70° will have much less issue with this off axis CA.

Good luck with your decision and choice.

[parallaxerr]

Thanks for that, interesting point on field curvature. I think I understand everything then another curve ball comes in! So is there a way to find out abut EP's that have opposite FC to the ST120?

I read the review you linked to and noted the Delite pincushion, I see a little more than that in my Zoom.

I would still like a range of EPs with the same AFoV's, but if the Delites are wasted in the ST then maybe I should plump for the ES82°s. They are well within budget and get mostly good reviews?

[YKSE]

Sorry for the curve ball, there may be more

Seriously, I don't think buying  EPs with specific FC to suit scopes is the right way. Better to have and understand your own preference clear before taking a plunge. e.g. If you've very keen on seen sharp stars in the edge, then you should consider your scope and EPs as a whole; or you can do like some others, with reasonable godd understanding/expectation of off-axis aberrations, do the on-axis observations most of the time, using the wider FOV as good reference and star-hopping aid.

Just to take a wild guess of Delite and ES82 (I've used none of them): Delite will show sharper stars in the edge in ST120, mostly because its much narrower AFOV than ES82.

[parallaxerr]

1 minute ago, YKSE said:

Just to take a wild guess of Delite and ES82 (I've used none of them): Delite will show sharper stars in the edge in ST120, mostly because its much narrower AFOV than ES82.

My thoughts exactly. Perhaps keeping the AFoV a little smaller will "mask" some of the inherent FC of the scope.