Binoculars with near 70deg AFOV? (1 Viewer)

[Binastro]

I have tried using Orion belt stars to measure binocular real fields.

It is like watching paint dry.

Firstly, one has to ensure the star crosses the centre of the field.
It probably won't.

But after a few tries one gets a good reading, unless the clouds turn up.

Cosine of 1 or 2 degrees is above 0.999 so Orion belt stars are good.
I think it should be sidereal time.

I didn't see any Perseid meteors last night because of cloud after a clear sunny day.
If you have a clear dark sky tonight should be good also.

Regards,
B.

 

[bockos]

Swarovski NL Pure 8x42 има 159m FOV и 69 ° AFOV ... Интересното е, че 12x42NL има 113m.FOV и 71 ° AFOV ... Следователно виждаме тези 113m (в 12x42) някак по -широки в 71 ° зрително поле ... ... отколкото 159m FOV .. при 69 ° при 8x42. Правилно ли разбирам това? Благодаря.

 

[Conndomat]

Swarovski NL Pure 8x42 има 159m FOV и 69 ° AFOV ... Интересното е, че 12x42NL има 113m.FOV и 71 ° AFOV ... Следователно виждаме тези 113m (в 12x42) някак по -широки в 71 ° зрително поле ... ... отколкото 159m FOV .. при 69 ° при 8x42. Правилно ли разбирам това? Благодаря.

translate...
"Swarovski NL Pure 8x42 has 159m FOV and 69 ° AFOV ... Interestingly, 12x42NL has 113m. FOV and 71 ° AFOV ... So we see this 113m (in 12x42) somehow wider in 71 ° field of view ... ... than 159m FOV .. at 69 ° at 8x42. Do I understand this in the right manner? Many Thanks."

 

[Conndomat]

Правилно ли разбирам това?

yes...

Andreas

 

[Northman]

Ranked for Tanget AFOV




Just imagine what they can do with a x50 or x56 objective lens.
16x56?
18x56?

 

[Binastro]

The AFOV has little to do with objective size.

It is the eyepiece that determines the AFOV, although in binoculars this is complicated by the IPD.

There is a Russian 8x30 binocular with a 13 degree field.

There are Russian 15x105 and 15x110 binoculars with 6 degree real fields.

I have 7x32 and 8x42 binoculars with over 13 degree and over 11 degree fields, but the aberrations give me a headache.

I don't like eyepieces with more than 90 degree AFOV.

However, there are several 100 degree eyepieces that fit suitable binoculars.

The 120 degree eyepieces are probably too large as they fit 2 inch fit eyepiece holders.
It is claimed that without field stops some are 140 degree AFOV.

It is possible that someone with a wide IPD may be able to use a 120 degree AFOV binocular, although I don't know if the brain would like the image.

Our eyes have a sideways view of about 170 degrees.

With very wide AFOV eyepieces, the focal length must be short to work in a binocular, which means the magnification must be high or very high.

B.

P.S.
The Koehler 120 degree eyepiece was used in submarine periscopes in the 1940s.

The Hill's Cloud camera with a 180 degree lens was introduced in 1923.

Nikon had a 220 degree lens.

 

[Mark9473]

I noticed that Zeiss "Subjective Viewing Angle" specs for the SF and HT models appear to be accurate measurements. Only the Conquest models use the simple calculation. A case of the right hand not knowing what the left hand is doing?

Henry

For my 10x42 HT, Zeiss specify:
FOV = 110m / 1000m, which is 6.3°, and AFOV = 63°, so it appears they did the simple calculation.

 

[Northman]

View attachment 1400358

The AFOV has little to do with objective size.

It is the eyepiece that determines the AFOV, although in binoculars this is complicated by the IPD.

Yes.
My admittedly narrow understanding of binocular construction, is of course eyepiece designs with higher mag, equals smaller exit pupil, and results in larger tAFOV. So looking at what Swarovski did/does with the 12x42. It has a 3,5mm exit pupil, and gets 68deg tAFOV.

A 56mm objective with 3,5mm exit pupil, gives 16x
Or narrowing it down to 3,11mm exit pupil with 18x could give a 70-75deg tAFOV?

 

[wllmspd]

Lower powers risk needing larger field stops and thus larger diameter eyepieces. So minimum power can end up wi narrower views. For medium to high power it’s upto the designer what AFOV they want. I can pop different eyepieces of the same power, but vastly different AFOV into my big astro bins.

peter