Orion LHD Lanthanum 80 degree UWA Eyepieces

[AstroStudentUSQ]

Does anyone have first hand experience with the Orion LHD Lanthanum 80 degree UWA eyepieces?

Cannot find an independent review of these eyepieces anywhere!

Claims I am keen to see if they live up to are long eye relief (with large surface lenses - I hate squinting through pin head sized lenses!) and their claim for the Lanthanum eliminating colour fringing (or rather, not unduly introducing it).

Do share your thoughts!

Cheers,
Mark

[Wavytone]

Another type well worth trying are the Vixen SSW, I have 3, all with 20mm eye relief. Much overlooked IMHO and 60% of the price of the LHD ones.

[MortonH]

According to the specs I've seen the SSW have 13mm eye relief.

[Wavytone]

Ah yes you're right. Actually doing the maths I don't think anyone makes eyepieces with 80 degree AFoV and 20mm ER, the eye lend would have to be ginormous.

[AstroStudentUSQ]

https://www.bintel.com.au/product/orion-lhd-lanthanum-ultra-wide-eyepieces/

20mm Eye relief and 30mm lens diameter for the Orions.


Wavytone, have you noticed any CA in the outer 10% or so of those Vixens? I did read one review that mentioned this, keen to hear of users views on them as this is one of the brands I am closely looking at.

Cheers,
Mark

[Wavytone]

Mark, I acquired a 14mm secondhand and found it to be excellent and bought the 7 and 10mm as well.

I don’t think any eyepiece is perfect and any comparison depends on the eye of the beholder and the specific scope you’re using.

IMHO they’re well worth the outlay. I just wish vixen made one more at about 25mm.

[bigjoe]

If the original Long Perng version comes out it should be much cheaper..they do makes quality gear for sure.

http://www.longperng.com.tw/goods.php?act=list&catId=34&page=1

Also make the lenses for other manufacturers..
Including lenses for 120mm SW ED and ESPRIT line..Quite extraordinary indeed!
bigjoe.

[glend]

Is it actual Lanthanum glass or a Lanthanum coated regular glass, there is a difference. Given the high cost and very limited availability of Lanthanum glass i suspect its just coated.

[Wavytone]

ED elements have to be solid lanthanum glass to be effective - coating is pointless.

And hence the price of the LHD series. Ditto TV Panoptics which also use it, and FWIW the Vixen LVW42 which is huge lump of glass.

[Don Pensack]

80° requires a minimum of 33.6mm of eye lens diameter for 20mm of eye relief
30mm of eye lens diameter and 20mm of eye relief means a maximum of 73.7° apparent field.
If these eyepieces do indeed have an apparent field of 80° then the eye relief is really 17.9mm. That's still pretty long for an 80° eyepiece.

If you want to work the math for yourself:
tan0.5ApparentField = 0.5lens diameter / eye relief

One adjustment to that: the depth of the concavity of the eye lens is added to the eye relief so calculated. If the LHD has an eye lens that is 1mm concave, then eye relief could be 18.9mm.
If the eye lens is convex, the convexity amount is subtracted from the calculated eye relief.

[Don Pensack]

Well, coating isn't pointless, but it isn't lanthanum glass, either.
I'm sure these are broadband anti-reflection coating (BBAR)
For coatings to be effective, they do have to match the refractive index of the glass, however.

[AstroStudentUSQ]

Excellent points and very useful info re-equation, thank you Don!

Cheers,
Mark