118 replies to this topic

[Astrojensen]

Unusual, to say the very least. Was rummaging around Vixens homepage, when I came across this:

 

https://www.vixen.co...roduct/35203_6/

 

A 100mm focal length 1.25" eyepiece... Purpose: To be used as a finder eyepiece in the main telescope, instead of using a separate finderscope. 

 

Errm - a 100mm 1.25" eyepiece has an AFOV of something like 17° - 18°. And the TFOV is not larger than, say, a 32mm 1.25" plössl. How the heck is that going to be any better as a finder eyepiece than just a 32mm plössl? Am I missing something? It does look pretty well made and it's not expensive, so I might actually buy one, just to try it out. 

 

One thing is for sure: Images in it are going to be BRIGHT, also on longer f/ratio scopes. Magnification on my 63/840mm Zeiss Telemator is only going to be 8.4x! Exit pupil 7.5mm! But the TFOV is, again, not going to be larger than my 32mm plössl, my 40mm plössl, my 24mm ES68 or my 40mm Zeiss huygenian. It is actually going to be drastically less than my 40mm ES68.

 

I'm scratching my head a bit over this one. 

 

 

Clear skies!
Thomas, Denmark 

[star drop]

Perhaps the low magnification makes for steadier views during an earthquake.

[junomike]

Translated page

I see  their principle but without a "Finder" for most people has a large FOV also.

This is merely minimizing the image scale and IMO one would be better off with a 24mm 68° eyepiece.

[csrlice12]

Binoview it!

[Starman1]

Unusual, to say the very least. Was rummaging around Vixens homepage, when I came across this:

 

https://www.vixen.co...roduct/35203_6/

 

A 100mm focal length 1.25" eyepiece... Purpose: To be used as a finder eyepiece in the main telescope, instead of using a separate finderscope. 

 

Errm - a 100mm 1.25" eyepiece has an AFOV of something like 17° - 18°. And the TFOV is not larger than, say, a 32mm 1.25" plössl. How the heck is that going to be any better as a finder eyepiece than just a 32mm plössl? Am I missing something? It does look pretty well made and it's not expensive, so I might actually buy one, just to try it out. 

 

One thing is for sure: Images in it are going to be BRIGHT, also on longer f/ratio scopes. Magnification on my 63/840mm Zeiss Telemator is only going to be 8.4x! Exit pupil 7.5mm! But the TFOV is, again, not going to be larger than my 32mm plössl, my 40mm plössl, my 24mm ES68 or my 40mm Zeiss huygenian. It is actually going to be drastically less than my 40mm ES68.

 

I'm scratching my head a bit over this one. 

 

 

Clear skies!
Thomas, Denmark 

15.4° without distortion.

Egads, and I thought the Russell 2" 85mm Plössl was a bit odd (31° field)

[Jon Isaacs]

I thought maybe it was a misprint but the eyepiece certainly looks like a 100 mm eyepiece. 

 

It makes no sense to me.  Being an engineer type myself,  it seems to me it must be the result of some optical engineer's total lack of practical experience. .

 

It's probably sharp to the edge and truly orthoscopic.. 

 

Jon

[CrazyPanda]

It's in case you have a tarzier as an observing companion. 

Edited by CrazyPanda, 30 March 2018 - 09:31 PM.

[Moravianus]

After short sale it will become a collector's eyepiece

[M57Guy]

and I thought the Russell 2" 85mm Plössl was a bit odd (31° field)

It is, but the 65 and 72 are almost do-able, provided you have a ladder for the eye relief.

[Simon B]

Could it show a larger TFOV than a 32mm plossl, but simply vignette? As in, it slowly fades to black around the edge of the field of view?

 

For e.g., a C5 can show a larger TFOV than a 32 plossl (1.25°), but it will simply vignette (out to about 2°)

[Jon Isaacs]

Could it show a larger TFOV than a 32mm plossl, but simply vignette? As in, it slowly fades to black around the edge of the field of view?

 

For e.g., a C5 can show a larger TFOV than a 32 plossl (1.25°), but it will simply vignette (out to about 2°)

When the stop is at the focal plane, the vignetting will be a sharp cut off.  With a 27mm field stop in a 28mm barrel there will be additional vignetting caused by the barrel but a 28mm field stop is about maximum in a 1.25 inch barrel.  

 

With the C-5, the rear baffle/rear port is out of focus.

 

Jon

[garret]

1 April fools day

Edited by garret, 31 March 2018 - 07:38 AM.

[garret]

I found a '40' mm Plössl with Google...

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[faackanders2]

Translated page
I see  their principle but without a "Finder" for most people has a large FOV also.
This is merely minimizing the image scale and IMO one would be better off with a 24mm 68° eyepiece.

I would rather have a 40mm 70 AFOV 2" University Optice MK-70 Koenig for maximum TFOV in a 2" at the highest power possible.

[faackanders2]

It's in case you have a tarzier as an observing companion.

Or a Great Horned Owl

[junomike]

I would rather have a 40mm 70 AFOV 2" University Optice MK-70 Koenig for maximum TFOV in a 2" at the highest power possible.

Agreed although I rarely need the extra FOV of the 40mmm SWA, thus my 31T5 usually wins out.

[Simon B]

When the stop is at the focal plane, the vignetting will be a sharp cut off.  With a 27mm field stop in a 28mm barrel there will be additional vignetting caused by the barrel but a 28mm field stop is about maximum in a 1.25 inch barrel.  

 

With the C-5, the rear baffle/rear port is out of focus.

 

Jon

Thanks, makes sense! I'm always learning

 

So, it really does seem like a rather pointless eyepiece 

[lylver]

I did a 33° 80mm for 2", this one is keyhole

[Astrojensen]

 

So, it really does seem like a rather pointless eyepiece 

Indeed. I wonder what they were thinking. Perhaps smoking something good? 

 

 

Clear skies!

Thomas, Denmark

[Starman1]

Uh, you guys be OK with my NOT adding this to the Eyepiece Buyer's Guide?

[Astrojensen]

Uh, you guys be OK with my NOT adding this to the Eyepiece Buyer's Guide?

You could add it, but mention that it was introduced in early April 2018. 

 

 

Clear skies!
Thomas, Denmark

[CrazyPanda]

Uh, you guys be OK with my NOT adding this to the Eyepiece Buyer's Guide?

You could start an eyepiece avoiders guide as a supplemental companion to the buyer's guide

Edited by CrazyPanda, 01 April 2018 - 11:57 AM.

[csrlice12]

Put it in a 60mm scope and look thru the scope objective lens....

[Disciplus55]

Is it a April Fool joke ? Could be...

[Astrojensen]

Is it a April Fool joke ? Could be...

I don't think so, as I saw it several days before april 1st, but I guess it's not impossible. 

 

 

Clear skies!
Thomas, Denmark