I need help in identifying this ocular.

[azrabella]

I recently purchased and am eagerly awaiting arrival of a new to me (used) 17mm eyepiece that the seller (though not the user) informs me was Skywatcher's first foray into wide-angle eyepieces from c2003. It appears to have a dual fit format with a 70 degree fov, with the same configuration as a Meade 4000 Smoothside? I cannot find any reference on t'interweb, and was wondering if any of you clever slueths could identify it for me. Also if it is dual fit, then in 1.25" mode what happens to the fov, or is the inner barrel removable??? I don't have a clue. Images supplied.

Edited August 13, 2019 by azrabella

[vlaiv]

My guess is that it is this EP line:

with a slightly different housing.

Probably Chinese made EP branded under different brands. I think this line is probably the same (different only by housing and possibly QA / coatings some minor internal improvements):

https://www.teleskop-express.de/shop/product_info.php/info/p4924_TS-Optics-Eyepiece-Expanse-17-mm-Wide-Angle-1-25-and-2-inch-connection.html

Also look at Celestron Ultima LX

As for FOV - 70 degrees in 17mm FL fits 1.25" format, so FOV won't change as you are effectively not using 2". 2" connection is there for convenience - if you have 2" diagonal it just adds a bit of stability for large EP and you don't have to put in 2"/1.25" adapter if you have other 2" EPs when exchanging them.

[John]

I recognise the eyepiece - I've used the 5mm version (which also has a hybrid barrel) and it was a nice eyepiece, if a little bulky. This was about 6 or 7 years ago and the eyepiece that I used was a few years old even then.

They used to be listed by OVL, the Skywatcher importer but I'm not sure that they were made by Synta (who make Skywatcher stuff). The inner 1.25" barrel contains optical elements so don't be tempted to remove it !

Celestron might have had a version of them as well.

You probably won't be able to tie down the precise optical design without taking it to pieces. Probably 6 or 7 lens elements though. Many super wide eyepieces were a development from the Erfle eyepiece design tweaked to give better edge performance and more eye relief.

Give it a try - you may well be pleasantly surprised !

[John]

PS: 365Astronomy still seem to be listing the 3.5mm version of this eyepiece alongside the current Skywatcher SWA 70's:

https://www.365astronomy.com/3.5mm-UWA-Ultra-Wide-Angle-Eyepiece-70-degree-1.25-inch-and-2-inch.html

I've seen an 8mm in this range as well.

[rwilkey]

I used to have a couple of these SW eps.  I recall it had a twist up eyeguard which I used to think was quite clever, they were modelled on the SW LET eps (or vice versa).  I remember I had the 3.5mm, the other could have been a 5mm, I don't know, I have since sold them.  However, here is a photo of one of them that I took in 2011:

 

[F15Rules]

I agree, they did remind me of both the Ultima LX (a half decent range IMO, I owned and liked the 13mm and 22mm), and the conical top reminding me of the Skywatcher LET (a pretty poor range in my opinion, unworthy of the SW ED scopes it was often bundled with).

I enquired about this on UKABS as it was described as a SWAN eyepiece, but not like any WO Swan I've ever seen, so I didn't pursue it.

If it is similar to an Ultima LX it should prove a decent bargain

Let us know what you think!☺

Dave

[azrabella]

I will just as soon as the clouds part - don't hold your breath though, that might be some while.