118 replies to this topic

[Helvetios]

There was one of these at NEAF 2018 and it was awesome.  It's a 100mm eyepiece, so very low magnification on your typical scope.  It had very good eye relief, large FOV, and was extremely sharp. This is clearly intended for new folks to quickly settle in on a target and then switch to more typical eyepieces for observing.  No having to co-align a separate finder.  The cost on the Vixen webpage is 4,500 Yen, which is only about $45, so I can see one of these in my telescope gadget bag soon.  Here is a Google translation of the Vixen webpage listing:

 

"Eyepiece type finder:  It is a simple eyepiece with a focal length of 100 mm. It is equipped with a crosshair and can be used as a viewfinder by replacing it with an observation eyepiece. Since the focal length is long, low magnification can be obtained and a wide range that can be used as a viewfinder can be seen.  When used for a telescope with a focal length of 600 mm.  Magnification = focal length of telescope 600 ÷ focal length of finder eyepiece 100 = 6 times.

 

Since it is replaced with an eyepiece lens, it is difficult for beginners to use the optical axis of the viewfinder without difficulty and can be used immediately. After putting the target on the crosshair, replace it with the observation eyepiece and adjust the focus and observe."

[karstenkoch]

I'm inclined to believe Helvetios. I seriously doubt that the designers are that out of touch to make a pinhole AFOV. They must have added some elements to widen the AFOV. I say that because I am not knowledgeable enough to say that it can't be done, and it seems like the only way for this eyepiece to make sense.

[karstenkoch]

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

You crack me up!

[CHASLX200]

Be like looking thru a straw.

[Starman1]

I'm inclined to believe Helvetios. I seriously doubt that the designers are that out of touch to make a pinhole AFOV. They must have added some elements to widen the AFOV. I say that because I am not knowledgeable enough to say that it can't be done, and it seems like the only way for this eyepiece to make sense.

Can't make the field stop much larger than 30mm max. and that would have noticeable vignetting at 6x.

At 100mm, that's a 17° field.

In their hypothetical 600mm refractor, that would be a true field of 2.8° or so at 6x.

That's about half as wide as a typical finder scope, but you could use it as a finder.

[Maurolico]

It make sense to me just as Zen eyepiece: you will see all because you will see nothing. The crosshair is the Koan's key.

[karstenkoch]

You can hear one hand clapping if you listen with one ear. You can binoview with only one eyepiece if it's the Vixen 天体望遠鏡 ファインダーアイピース100. Listen to the babbling brook!

[rowdy388]

You can hear one hand clapping if you listen with one ear. You can binoview with only one eyepiece if it's the Vixen 天体望遠鏡 ファインダーアイピース100. Listen to the babbling brook!

  Imagine all the positive chi you can control with this eyepiece in your possession.

[gnowellsct]

I used it to point a refractor at the Vixen stand at NEAF, seemed OK, but nothing dramatic. .  But the NEAF space is an enclosed college gym and doesn't really simulate hunting for something in the sky.  

[karstenkoch]

I used it to point a refractor at the Vixen stand at NEAF, seemed OK, but nothing dramatic. .  But the NEAF space is an enclosed college gym and doesn't really simulate hunting for something in the sky.  

What's your estimate of the AFOV?

[emilslomi]

Any viewing experiences yet? Any idea where to order? I think it is available now in Japan, but I have not seen it anywhere else. 

 

Cheers, Emil

[25585]

15.4° without distortion.

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

Don't forget the 80mm 3 inch Masuyama! 

 

I would be interested in the 100's eye relief and positioning comfort more than anything.

[macdonjh]

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

"... optical engineer's total lack of practical experience."  But I then wonder where that engineer's boss (or co-workers) were?  Usually weird, impractical products get stopped during internal reviews and don't see production.

 

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

Funny, I use a tarzier as my finder.  He's quite cuddly and good company on my shoulder after he's found the object I want to observe.  My kids like him, too.

 

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

I discussed Mr. Russell's 65mm, 72mm and 80mm eye pieces after buying a scope with 5250mm focal length.  Eventually, the eye relief scared me off.  The eye relief of the 50mm eye piece I already have (Erfle?  Konig?) is already plenty.  I just wanted something that would get me less than 100x magnification.

[macdonjh]

Don't forget the 80mm 3 inch Masuyama! 

 

I would be interested in the 100's eye relief and positioning comfort more than anything.

Optical design question: since the Masuyama has a 3" barrel and can accommodate a field stop larger than 46mm, can they control the eye relief and make it something practical like 20mm?  I know I could just look up the specifications for this eye piece, but I'm really more interested in a general answer: can you have shorter eye relief in really long focal length eye pieces if you can also have a big field stop?

[25585]

Any viewing experiences yet? Any idea where to order? I think it is available now in Japan, but I have not seen it anywhere else. 

 

Cheers, Emil

I have emailed my Vixen retailer. I am interested in owning the 100, if the cost is not too high.

 

This ep makes me wonder again though, if refractors sold for Japanese domestic use are more for terrestial use from apartment and office blocks, or sight seeing, than for astronomical viewing. Their plethora of smaller aperture models and seemingly fewer larger aperture ones being the reason.  

[emilslomi]

I have emailed my Vixen retailer. I am interested in owning the 100, if the cost is not too high.

 

This ep makes me wonder again though, if refractors sold for Japanese domestic use are more for terrestial use from apartment and office blocks, or sight seeing, than for astronomical viewing. Their plethora of smaller aperture models and seemingly fewer larger aperture ones being the reason.  

The price quoted on the Japanese site is very reasonable - low enough to try the ep as a curiosity. If I remember correctly, the FOV is written to be 17deg. Nice thing about it is that if I use this ep as intended, i.e. as a finder, my orthos will look super-wide-field afterwards.

 

Cheers, Emil

[25585]

Exit pupil math is amusing. 

 

Use with long refractors could be handy lengthwise, less bending down for higher altitudes.

 

I wonder if the designers used only Vixen scopes and gear to try it out with. Not so practical with a Newtonian, OK with a SCT.

 

With its tube length, lens and weight placement will be important.

 

Interesting to note that Vixen no longer makes 2 inch eyepieces, the NLVW 30mm, 42mm LVW and 50mm NLV have all been discontinued, thus their large FL WA models. Only Masuyama (26 to 80mm) in Japan make larger than 1.25 inch eps AFAIK.   

Edited by 25585, 05 August 2018 - 09:18 AM.

[emilslomi]

Sorry, I did not remember correctly - the Japanese site lists 11 degrees as the "apparent sight", which, I guess, will be the AFOV.

 

Cheers, Emil

[Astrojensen]

Sorry, I did not remember correctly - the Japanese site lists 11 degrees as the "apparent sight", which, I guess, will be the AFOV.

 

Cheers, Emil

11° AFOV is ridiculously narrow. It will make a 40° ortho feel like a hyperwide Ethos or something. 17° is actually sorta kinda usable (I've tried it), but 11° is just too narrow.  

 

 

Clear skies!
Thomas, Denmark

[emilslomi]

Thomas - you know what, I think you are right. I'm not that curious. 100 mm - wow! - but I'll pass after all.

 

Cheers, Emil

[gezak22]

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

I think the engineers knew very well what they were doing. It was probably a non-technical manager/VP who came up with the idea and, when the engineers protested, pushed ahead anyway.

[Starman1]

Optical design question: since the Masuyama has a 3" barrel and can accommodate a field stop larger than 46mm, can they control the eye relief and make it something practical like 20mm?  I know I could just look up the specifications for this eye piece, but I'm really more interested in a general answer: can you have shorter eye relief in really long focal length eye pieces if you can also have a big field stop?

Yes, by designing an eyepiece with a smaller eye lens, for a given apparent field, the eye relief will shrink.

So it definitely is possible to design, say, a 50mm eyepiece with a 20mm eye relief.

[Starman1]

Oh, and the name of our distant relatives with the cute faces is t-a-r-s-i-e-r, with an s, not a z.

They sure are cute, though:

https://www.google.c...B912lZ79dV2b6M:

And their pupils open to enormous size.

How did that picture of Jabba the Hutt get in there?

[25585]

Yes, by designing an eyepiece with a smaller eye lens, for a given apparent field, the eye relief will shrink.

So it definitely is possible to design, say, a 50mm eyepiece with a 20mm eye relief.

31mm Naglers have for me too-short eye relief. The 35 and 41 Panoptics are just OK. Best is my TV 55mm Plossl. This is usable eye relief, not advertised.

 

Takahashi advertise 28mm eye relief for their 32mm Abbe. The eye lens is so recessed usable relief is 17mm. So the advertised amount was not the usable amount. I have read the LE ep is similar.

 

Vixen's 100 may just be a shorter FL ep with a barlow, all in one unit. And where is it made?

[The Ardent]

This is the beginning of the great revival, when narrow FOV becomes fashionable. Competition to see who can observe with the narrowest. Give it about 20 years and hyper wides will be the rage again. 

11° AFOV is ridiculously narrow. It will make a 40° ortho feel like a hyperwide Ethos or something. 17° is actually sorta kinda usable (I've tried it), but 11° is just too narrow.  

 

 

Clear skies!
Thomas, Denmark