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unknown 4mm eyepiece

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#1 droid

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Posted 08 November 2019 - 01:58 PM

I was gifted this eyepiece by a fiend for my birthday. He doesn't know  what brand it is, or any info , other than what's on the side of it.

 

Im kinda orta thinking itll get used once or twice a year, tops with our atmosphere here.

 

Any know anything abut this eyepiece???

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#2 Sky Muse

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Posted 08 November 2019 - 02:10 PM

For one, the "UWA" stands for ultra-wide angle, but a 58° AFOV doesn't translate into what it accepted as an ultra-wide TFOV.  That would be at least an 82° AFOV, and greater.

 

Here's a BST 1.25" 4mm "UWA" 58°, and practically identical...

 

https://agenaastro.c...epiece-4mm.html

 

It's probably safe to say that it's an overseas knock-off.

 

Incidentally, I don't really consider BST to be a brand; more like a generic.

 

The one you have seems to have nice coatings, and perhaps even fully multi-coated like the BST.


Edited by Sky Muse, 08 November 2019 - 02:13 PM.

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#3 jeremiah2229

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Posted 08 November 2019 - 02:26 PM

If the upper part/half can be rotated to adjust for the eye it's a Sky-Watcher, if not adjustable then it's a BST.

 

 

Peace...



#4 Tank

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Posted 08 November 2019 - 02:26 PM

BST



#5 GalaxyPiper

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Posted 08 November 2019 - 02:27 PM

Closest Analog to that eyepiece is called a "Skywatcher", this is what I found:

 

https://www.telescop...g-eyepiece.html

 

skywatcher_planetary_uwa_eyepiece.jpg

 

Otherwise, it's maybe just another Chinese made eyepiece.

Also, here at Worthpoint:

 

https://www.worthpoi...lossl-516188291

 

skywatcher-uwa-4mm-planetary-plossl_360_

 

and also here:

 

https://www.worthpoi...ry-58-519806279

 

skywatcher-25-4mm-uwa-planetary-58_360_a

 

If you sign up with them, you might get a monetary value for it. Probably not more than say $50.00 U.S.

 

Enjoy the "Gift".


Edited by GalaxyPiper, 08 November 2019 - 03:09 PM.


#6 MikeMiller

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Posted 08 November 2019 - 02:55 PM

I wonder what this is "wide" in comparison to. :)



#7 sg6

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Posted 08 November 2019 - 02:56 PM

From shape and 4mm and UWA 58o I would say it is a reproduction of the old TMB Planetary's. Just without the usual printing around it. No idea who doesn't bother with the usual printing. However there are a number of sources of the general design.

 

Unfortunately therefore nothing overly special but a potentially usable 4mm eyepiece.



#8 CharlieB

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Posted 08 November 2019 - 03:15 PM

These were the first knock-offs of the Burgess/TMB Planetary eyepieces.  I have the 3.2mm and 5mm versions.  They work fine, but the build is not as good as the Burgess/TMBs.



#9 droid

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Posted 08 November 2019 - 03:28 PM

It does have a twist up eye cup, though I never realized it till now.

 

And yes its a an exact copy of the skywatcher eyepiece in the link

 

Thoughts on whether its good enough for a once or twice a rear usage.

 

My opinion, would be,  it beats the you know what out of looking through a 4mm plossl. Which it will replace.


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#10 GalaxyPiper

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Posted 08 November 2019 - 04:17 PM

 

Thoughts on whether its good enough for a once or twice a rear usage.

 

Should do just fine. Internally I think it is a plossl. It just has a wider field of view.

You should get some use out of it, maybe more than you think.



#11 Jon Isaacs

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Posted 08 November 2019 - 04:52 PM

Should do just fine. Internally I think it is a plossl. It just has a wider field of view.

You should get some use out of it, maybe more than you think.

 

It's actually a "negative-positive" eyepiece. If you look at the third photo you'll see a tiny lens. That's a Barlow-like telenegative lens and it functions like a Barlow. The rear section contains the positive magnifying section. Naglers are negative-positive eyepieces but somewhat more sophisticated. 

 

The rear magnifying section has a focal length much longer than 4 mm, probably 20 mm so. This way the eye piece can have the eye relief of a 20 mm eyepiece, 12-15 mm.

 

I have the 4 mm TMB. They're good eyepieces, I suspect this one is too.

 

Jon


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#12 droid

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Posted 08 November 2019 - 07:27 PM

Thanks Jon.... I don't think its a skywatcher, but it sure looks identical.

 

I also picked up a 3mm Zhumel LER ep.




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