Eye Pupil dilation

[bomberbaz]

I hear an awful lot about this and it is of course very important that we match eyepiece exits to our eye maximum dilation to avoid wasted light.

For those not sure if the exit pupil is bigger than your dilated pupil it will simply lead to a duller view often referred to as washed out.

I personally own a very over sized eyepiece but as its used purely as a spotter eyepiece I accept this.

The rule of thumb for exit pupils is 7mm but as we get older, this tends to shrink in most of us although some are luckier than others.

Another thing is smokers tend to have worse night vision but thats a different story.

Anyway, I found a table of test results and though by no means a definate guide, its might give a few of you some insight into what you can expect.

This particulary applies to users of faster scopes F5 and above.

RESULTS: Two-hundred sixty-three individuals participated. For participants aged 18 to 19 years (n=6), the mean darkadapted
pupil diameter was 6.85 mm (range: 5.6 to 7.5 mm); 20 to 29 years (n=66), 7.33 mm (range: 5.7 to 8.8 mm); 30 to
39 years (n=50), 6.64 mm (range: 5.3 to 8.7 mm); 40 to 49 years (n=51), 6.15 mm (range: 4.5 to 8.2 mm); 50 to 59 years
(n=50), 5.77 mm (range: 4.4 to 7.2 mm); 60 to 69 years (n=30), 5.58 mm (range: 3.5 to 7.5 mm); 70 to 79 years (n=6), 5.17
mm (range: 4.6 to 6.0 mm); and 80 years (n=4), 4.85 mm (range: 4.1 to 5.3 mm).

One of the most surprising results to me is the range difference, see them for yourselves.

You can either go to an optician to figure out your own pupils or try the DIY method I also found online below:

i hope this helps

Steve

To determine what your personal pupillary diameter is you need a method to measure it.

 

Take a piece of paper card stock (about 1 x 5 inches) and draw two slightly diverging lines on it. Then use a needle or safety pin to put several pairs of holes along the lines, about ½ inch apart. With care, most pairs will turn out to be of differing separations varying from about 8 or 9 millimeters, down to about 2 or 3 in roughly half-millimeter steps. Measure the separation of the holes, not from center to center, but from inner edge to inner edge. The use of a good ruler and a magnifier is required to measure them accurately. Label the pairs with their separation distances.

To use the thing, just hold it up to your eye and peer through the holes. Select the pair that appears as if the holes merge to the point that their inner edges just touch but don't overlap. Your pupillary diameter is then read from your pre-marked labels.

From a dark site the sky should provide just enough light to do the trick. If not, look through the device at a faintly illuminated object like a white car or the side of a building.

You now have a baseline for determining the lowest usable magnification for your telescope that won't waste aperture.

[John]

That data seems what I'd have expected. I'm 54 and my largest exit pupil with my kit is 5.8mm. About right.

Even with that I've seen the sky looking washed out reasonably often and opted for a 3.9mm exit pupil and a bit more magnification to get a darker background sky.