# Thread: Apertura 30mm superview question.

1. ## Apertura 30mm superview question.

Does anyone know the mm of the exit pupil on the 30mm superview Apertura (gso or I would assume highpoint)?

I really really like the view through this and I want to keep my exit pupil to as close to this as I can. Thanks.

2. ## Re: Apertura 30mm superview question.

The exit pupil with that eyepiece/scope combination is 6.02mm. That can be a bit large for some folks.

With my AD12, I find between 2mm and 3.5mm to be rather optimal, but of course, that can also depend upon what one is observing at the time.

3. ## Re: Apertura 30mm superview question.

The exit pupil is not a property of the eyepiece. It is the objective diameter D divided by the magnification M, where M is the ratio of focal lengths F of the objective and f of the eyepiece, so exit pupil x = Df/F . Apply that formula to choose the components that lead to that exit pupil.

4. ## Re: Apertura 30mm superview question.

Originally Posted by CamelHat
The exit pupil is not a property of the eyepiece. It is the objective diameter D divided by the magnification M, where M is the ratio of focal lengths F of the objective and f of the eyepiece, so exit pupil x = Df/F . Apply that formula to choose the components that lead to that exit pupil.
Boom ... Mind blown lol

5. ## Re: Apertura 30mm superview question.

Sooooo (2*30)/?) Lost on the last number

6. ## Re: Apertura 30mm superview question.

Wait... (2*30/4.9)??? Soo 12.22?

7. ## Re: Apertura 30mm superview question.

Originally Posted by Nomma
Wait... (2*30/4.9)??? Soo 12.22?
K.I.S.S...

If you know your focal ratio, you are halfway there.

If you know your eyepiece focal length, divide that number by your focal ratio to get the exit pupil.

If you know your desired exit pupil, multiply that number by your focal ratio to get the desired eyepiece focal length.

Easy peasy.

8. ## Re: Apertura 30mm superview question.

So... 6.02*4.9= 29.5mm okay so that's a 30mm.. but what If I was let's say a 20mm ep with an exit pupil of 6mm? Based on the equation that would be impossible?

9. ## Re: Apertura 30mm superview question.

Originally Posted by Nomma
So... 6.02*4.9= 29.5mm okay so that's a 30mm.. but what If I was let's say a 20mm ep with an exit pupil of 6mm? Based on the equation that would be impossible?
Right, although in principle a 20mm eyepiece could have a 6mm exit pupil in an f/3.33 telescope. The exit pupil is the focal length of the eyepiece divided by the f number. 20/3.33 = 6.

10. ## Re: Apertura 30mm superview question.

Originally Posted by Nomma
So... 6.02*4.9= 29.5mm okay so that's a 30mm.. but what If I was let's say a 20mm ep with an exit pupil of 6mm? Based on the equation that would be impossible?
No.

You will need to change scopes to get a 6mm exit pupil out of a 20mm eyepiece.

In your AD12, a 20mm eyepiece will yield a 4mm exit pupil.

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