2" Low Power Eyepiece Options...

[Ian McCallum]

I really like my SW 28mm 2" LET eyepiece, but would like something with less magnification, for wider views.  There's two budget eyepieces from @FLO that have caught my eye.

https://www.firstlightoptics.com/stellalyra-eyepieces/stellalyra-50mm-2-superview-eyepiece.html

Astro Essentials Plossl 56mm version...

Has anyone any experience of these eyepieces?🤔

[Louis D]

First off, what are you going to be using them in?  Assuming you want to avoid going over a 7mm exit pupil, you wouldn't want to use a 50mm eyepiece in a scope faster than f/7 and a 56mm eyepiece in a scope faster than f/8.

[Don Pensack]

52 minutes ago, Ian McCallum said:

I really like my SW 28mm 2" LET eyepiece, but would like something with less magnification, for wider views.  There's two budget eyepieces from @FLO that have caught my eye.

https://www.firstlightoptics.com/stellalyra-eyepieces/stellalyra-50mm-2-superview-eyepiece.html

Astro Essentials Plossl 56mm version...

Has anyone any experience of these eyepieces?🤔

What Louis said.

If the scope is an f/6, and the pic looks a little like it is, then 42mm is the longest you want to go.

That's OK, since 40-42mm eyepieces have the same size true fields in 2" as longer focal length eyepieces.

[Ian McCallum]

39 minutes ago, Louis D said:

First off, what are you going to be using them in?  Assuming you want to avoid going over a 7mm exit pupil, you wouldn't want to use a 50mm eyepiece in a scope faster than f/7 and a 56mm eyepiece in a scope faster than f/8.

Either my Sky-Watcher 200P or more likely my Sky-Watcher Evostar 120 refractor. 

[Mr Spock]

The 42mm Superview would be a better choice. The 50s are better in f8-f10 scopes.

Or if you wanted to spend more, you could get 65° https://www.firstlightoptics.com/stellalyra-eyepieces/stellalyra-40mm-2-kitakaru-rpl-eyepiece.html 

I have a Helios 120mm (early Skywatcher) and that works great with my 42mm LVW.

[Louis D]

The 35mm Aero ED would work well as a near widest field eyepiece if you can still find one in stock.  It's pretty sharp in the inner 75% of the field of view at f/6.  It gradually gets more abberrated toward the edge.

The 40mm Pentax XW works really well at f/6, but is quite a bit over your budget.

[Ian McCallum]

5 hours ago, Louis D said:

The 35mm Aero ED would work well as a near widest field eyepiece if you can still find one in stock.  It's pretty sharp in the inner 75% of the field of view at f/6.  It gradually gets more abberrated toward the edge.

The 40mm Pentax XW works really well at f/6, but is quite a bit over your budget.

What's in stock and what's in budget is the key. 😉

[John]

I had the 30mm and 40mm Aero ED's for a while recently. The 40mm is a better corrected eyepiece than the 30mm in scopes faster than around F/8. It was actually pretty well corrected almost across the whole field of view even in my F/5.3 12 inch dobsonian.

I understand that the 35mm is also a better corrected eyepiece than the 30mm but I've not used that one.

Edited December 21, 2021 by John

[Louis D]

It's unfortunate that no vendor has stepped forward to purchase a new production run of the 40mm TMB Paragon clone (Aero ED/Paragon ED/Titan II/Paracor/Sky Rover).  The only change I would make would be to bring the eye lens up to being closer to the top of the upper barrel to make it more eyeglasses friendly.  Since the clone comes with a really nice twist up eye cup, why not?

[vlaiv]

https://www.firstlightoptics.com/ovl-eyepieces/panaview-2-eyepieces.html

good for 120 Evostar, not so much for Dob.

In essence same eyepiece - maybe a bit lighter

https://www.teleskop-express.de/shop/product_info.php/info/p957_TS-Optics-38-mm--2----70--Wide-Angle-Eyepiece.html

Good in both F/6 and F/7.5 - Aero ED clones - no longer available at FLO - but can be sourced elsewhere - 35mm version:

https://www.teleskop-express.de/shop/product_info.php/info/p2334_TS-Optics-35-mm-2--UFL-Eyepiece---69--Field-of-View---6-Element-Design.html

And 40 mm from Lacerta:

https://tavcso.hu/en/product/LA40ed

Maybe this one (costing a bit more):

https://www.teleskop-express.de/shop/product_info.php/info/p9549_Explore-Scientific-62--LER-Eyepiece-40-mm--argon-purged.html

 

[Louis D]

I have the Meade 5000 Plossl 40mm 60 degree version of the ES-62 40mm.  While it's exceptionally sharp in the center and almost totally devoid of field distortion, it is only sharp at f/6 in the inner 50% and falls off beyond that.  It has a 42.7mm field stop by my measurements, so not quite as wide as the Aero ED 35mm at 44.4mm.  For comparison, the Pentax XW 40mm has a 46.2mm field stop.  I'll have to check if I have an updated image that includes the XW.

Here's my comparison images of 32mm to 42mm eyepieces in an AT72ED f/6 refractor imaged with a Samsung Galaxy S7 camera:

[Voyager 3]

The 35mm ED does look special from your image Louis . Did you use a field flattener for this ? If no , this actually looks like a terrific deal!

 

[Louis D]

Yes, I forgot to mention I have a TSFLAT2 spaced 15mm in front of the 2" GSO dielectric diagonal to flatten the field.  Since I have no focus accommodation anymore, it was maddening trying to take in the entire field at once when vast portions of it were completely out of focus to my eye.  Younger folks might never notice the field curvature of a short refractor.

[Louis D]

Here's the updated 32mm-42mm image which includes the 40mm Pentax XW.  I have returned again and again on different occasions to try to capture a better image, but they all turn out similarly, so I went with the one shown.  As you can see, it's not perfect to the edge by any means.  Even with the field flattener, slight curvature remains, but the camera lens has enough depth of field in my experience to counteract it, so that's not the issue.  It's mostly just residual astigmatism.  It's not bad, but it is there.

 

 

Edited December 22, 2021 by Louis D

[Don Pensack]

On the 40XW, in my 12.5" Dob with Paracorr 2 (so operating at f/5.75 = 1826mm focal length), I don't see FC in the 40mm XW,

but there is a bit of astigmatism in the outer 5°+ of field.  That may be what is blurring the edge in your photo.

The resultant exit pupil was way too large for my older eye, and I didn't see any increase in brightness from a 27mm Panoptic.

Ah, to have younger eyes and larger pupils.

Too bad the 35mm Scopos is no longer available.

[Louis D]

Yeah, the 35mm Scopos is a special eyepiece.  I may have bought the last of the remaining new old stock when I bought it from Europe since they showed as unavailable after that.

It is extremely pin sharp in the inner 75% or so of the field and not very much worse beyond that.  I mean really sharp compared to my other 32mm+ eyepieces.  Stars are just teeny tiny pinpoints.  Sometimes I'll pop it in on a rich star field just to soak in the view because its so awe inspiringly well corrected.  There's no field curvature and plenty of eye relief.  Given its 47mm diameter eye lens and ~17mm of eye lens recession (IIRC), it could have had much, much more usable eye relief.  I once screwed off the top cover with the eyepiece vertical just to check.  Sure enough, even with eyeglasses, it was very difficult to hold the exit pupil because the eye relief is so long, and there was no reference point to touch with my nose or eye socket.

The downside is that it is my second heaviest eyepiece (behind only the 17mm ES-92) at 37.8 ounces or 1072g.  However, if I balance for the ES-92s, it's a natural to use it as my finder eyepiece before swapping to them.

[Carl Au]

On 21/12/2021 at 20:24, vlaiv said:

https://www.firstlightoptics.com/ovl-eyepieces/panaview-2-eyepieces.html

good for 120 Evostar, not so much for Dob.

In essence same eyepiece - maybe a bit lighter

https://www.teleskop-express.de/shop/product_info.php/info/p957_TS-Optics-38-mm--2----70--Wide-Angle-Eyepiece.html

Good in both F/6 and F/7.5 - Aero ED clones - no longer available at FLO - but can be sourced elsewhere - 35mm version:

https://www.teleskop-express.de/shop/product_info.php/info/p2334_TS-Optics-35-mm-2--UFL-Eyepiece---69--Field-of-View---6-Element-Design.html

And 40 mm from Lacerta:

https://tavcso.hu/en/product/LA40ed

Maybe this one (costing a bit more):

https://www.teleskop-express.de/shop/product_info.php/info/p9549_Explore-Scientific-62--LER-Eyepiece-40-mm--argon-purged.html

 

TS in Germany still have them. I bought the 30mm for use in a fl7 refractor. I have no complaints whatsoever, I don't see any aberrations at all, none. Both scope and ep made by UO. I don't know if that makes a difference or not.