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General Astronomy >> General Observing and Astronomy

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dpwoos
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Reged: 10/18/06

Loc: United States
Re: Pupil Size new [Re: Tony Flanders]
      #5640890 - 01/24/13 03:05 PM

Let's be clear - my contention is that one's pupils contract and dilate in response to the brightness of what is seen through the eyepiece, and that other chemical stuff is going on is not in dispute. I also am claiming that when folks target a certain exit pupil for observing the Moon, or Jupiter, or M42, or M13, etc. they really have no idea what will be the actual diameter of their eye's pupil as it responds to the brightness of that exit pupil. So, it seems to me that I need to determine 1) the brightness levels of the exit pupils of various targets (e.g. by using a sky meter), and 2) the response of my pupil to those brightness levels in terms of pupil diameter.

The hard part will be controlling for pupil contraction/dilation from other sources: Pavlovian conditioning, fear, sexual attraction, etc. I will have to stay cool, calm and collected. Not my strong suit.


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Jon Isaacs
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Reged: 06/16/04

Loc: San Diego and Boulevard, CA
Re: Pupil Size new [Re: dpwoos]
      #5640910 - 01/24/13 03:22 PM Attachment (12 downloads)

Quote:

. they really have no idea what will be the actual diameter of their eye's pupil as it responds to the brightness of that exit pupil. So, it seems to me that I need to determine 1) the brightness levels of the exit pupils of various targets (e.g. by using a sky meter), and 2) the response of my pupil to those brightness levels in terms of pupil diameter.




Dennis:

First, lets eliminate Jupiter and the moon, these are bright targets and normally observed at exit pupils smaller than the diameter of the eye during the day.

Then I suggest just measuring the diameter of your dilated pupil under a variety of low light conditions. I think you will find that the dilated diameter of you pupil does not change. There is so little light from the night sky that the pupil is always at it's maximum dilate if the skies are at all dark.

I just followed Tom's suggestion and photographed my dilated eye in a closet. I waited about a minute for the immediate dark adaptation finish. The flash wouldn't work without the LCD display turned on so it was not all that dark. Under those circumstance, my pupil was very close 7mm.

Jon


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dpwoos
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Re: Pupil Size new [Re: Jon Isaacs]
      #5641005 - 01/24/13 04:29 PM

Quote:

There is so little light from the night sky that the pupil is always at it's maximum dilate if the skies are at all dark.




I do not accept that because a sky is "dark" means that all exit pupils will be (even nearly) as dark, and I know you don't either as you specifically want to treat the Moon and Jupiter as exceptions though they reside in a dark sky. However, we don't have to settle this here and now. I am going to measure the brightness of some exit pupils and post the results. Then, if the data so warrants, we can subject ourselves to further cruel but necessary experiments (I see you have already begun) to determine our pupil's responses to these levels of brightness.

One other thing I have learned is that the pupils work together - a light producing a constriction of the pupil of one eye will produce a consensual constriction of the pupil of the other eye. This further complicates my testing, as I have to be careful that my bad eye doesn't taint the results by looking at something that it oughtn't.


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GeneT
Ely Kid
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Reged: 11/07/08

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Re: Pupil Size new [Re: csa/montana]
      #5641021 - 01/24/13 04:39 PM

Great advice!

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derangedhermit
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Reged: 10/07/09

Loc: USA
Re: Pupil Size new [Re: Jon Isaacs]
      #5641034 - 01/24/13 04:44 PM

http://www.ncbi.nlm.nih.gov/pubmed/15030828

http://www.ncbi.nlm.nih.gov/pubmed/22179219


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derangedhermit
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Reged: 10/07/09

Loc: USA
Re: Pupil Size new [Re: derangedhermit]
      #5641052 - 01/24/13 04:54 PM

As far as the apparent advantage of filling the pupil with light: aberrations increase dramatically (and variably on a per-eyeball basis) with larger pupil. In a number of people large enough that it makes it worth mentioning, a further increase in exit pupil results in a loss of resolution by the eye, due to the additional light at larger off-axis angles hurting the image more than it helps.

During daytime, the pupil ranges from around 3.75mm for young adults (on average, add disclaimers, ...) down to around 2.25mm for 60 year olds, where it apparently levels off as one ages further (on average, dah dah dah). Even this is large enough that some eyes' resolution benefits from a reduced pupil.


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Tony Flanders
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Reged: 05/18/06

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Re: Pupil Size new [Re: dpwoos]
      #5641079 - 01/24/13 05:13 PM

Quote:

Let's be clear - my contention is that one's pupils contract and dilate in response to the brightness of what is seen through the eyepiece.




Quite so. But do you have any evidence for that contention?

It's mighty hard to test, because one's pupils react to changes so quickly.


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Jon Isaacs
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Reged: 06/16/04

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Re: Pupil Size new [Re: dpwoos]
      #5641095 - 01/24/13 05:22 PM

Quote:


I do not accept that because a sky is "dark" means that all exit pupils will be (even nearly) as dark, and I know you don't either as you specifically want to treat the Moon and Jupiter as exceptions though they reside in a dark sky.




There is some confusion here.

The reason I want to treat Jupiter and the Moon differently is that one's pupil dilation does not matter, exit pupils that are reasonable for observing these objects will always be smaller than the dilated pupil, it doesn't matter if you pupil is dilated to 4 mm or 6mm or 3mm, the exit pupil of the eyepiece will be smaller than this.

- One has to distinguish between looking through the eyepiece at an object and the object being present in the sky. Jupiter being in the night sky will not affect the dilated diameter of your eye. It probably won't even affect it when you look directly at it in the eyepiece.

When it comes to Deep Space Objects, there is not enough light to cause a change in the dilation of the eye. As Tony and others have said, the eye dilates to it's maximum diameter quickly and it doesn't need to be very dark for it to happen. Go in a dark closest for a couple of minutes and watch your eye dilate.

Jon Isaacs


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Tom Polakis
Carpal Tunnel
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Reged: 12/20/04

Loc: Tempe, Arizona
Re: Pupil Size new [Re: Tony Flanders]
      #5641108 - 01/24/13 05:28 PM

Quote:

Quote:

Let's be clear - my contention is that one's pupils contract and dilate in response to the brightness of what is seen through the eyepiece.




Quite so. But do you have any evidence for that contention?

It's mighty hard to test, because one's pupils react to changes so quickly.





I don't think it's all that difficult to test. Simply use an extreme range of brightness levels, and take flash photos. I am going to go out into my extra-bright backyard observatory, where the zenith sky brightness is around 18 mag/arcsec^2. Heck, I'll even let the light of Jupiter flood my vision. While I'm staring at the bright sky, I'll take the photo. Then I'll photograph my eyes in my pitch-black background, and see if the pupil diameter is larger. If my pupil size is equally large looking at my backyard sky, then it's safe to say that it doesn't vary while looking at much dimmer objects through an eyepiece.

Having mentioned my backyard observatory, we are currently entering a period of four or five days of likely overcast in Arizona, which is following one of the clearest months of Winter I have ever experienced. So maybe I won't be out there looking up at the rain tonight after all.

Tom


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dpwoos
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Re: Pupil Size new [Re: Tony Flanders]
      #5641128 - 01/24/13 05:41 PM

No, I don't have any evidence. Seems obviously true to me and I thought that most other folks would find it so as well, but I guess not! Now that I know that the pupils constrict in tandem, I am thinking it is possible to monitor the pupil size of the non-dominant eye while observing with the dominant one. That would be a pretty cool gadget - webcam, IR illumination, headband - maybe get one of my sons to test it for me? Just kidding, of course. After many years they still talk about how I made them and their friends ride around with me in our car in the dark with paper bags over their heads to do star counting. I think they are actually sorry that the state police didn't spot us. Anyways, simpler is to record the brightness of the exit pupil when observing a collection of targets (e.g. with a sky quality meter), and then to separately measure my pupil diameter when my eyes are exposed to the same light level.

What do you think?


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TexasRed
scholastic sledgehammer


Reged: 05/17/11

Loc: East Texas
Re: Pupil Size new [Re: Tom Polakis]
      #5641149 - 01/24/13 05:51 PM

Thanks to the original poster for starting this interesting thread. I had the exact same experience at my optometrist's a few weeks ago, except she said my dark adapted pupils measured about 6.5 mm at the age of 62, which beat the average of about 5.7 mm for my age. I had the same questions about the accuracy and validity of that.

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Tom Polakis
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Reged: 12/20/04

Loc: Tempe, Arizona
Re: Pupil Size new [Re: TexasRed]
      #5641753 - 01/24/13 11:52 PM Attachment (19 downloads)

This is one of the weirder things I have posted on a forum.

Here are my and my wife's pupils fully dilated after five minutes in a black, indoor room. In addition to the scale, the white lines superimposed on all four pupils are 7mm long. Mine are just slightly shy of 7mm, and my wife's just more than 6mm.

Tom


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BlueGrass
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Reged: 07/25/09

Loc: Wasatch Front, UT
Re: Pupil Size new [Re: Tom Polakis]
      #5642027 - 01/25/13 07:21 AM

I've rethought my post and I'm going to try this. I'm on the downside of 55 and this could be something I can use at my next optometrist visit ...

Edited by BlueGrass (01/25/13 12:13 PM)


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Widespread
professor emeritus


Reged: 05/11/11

Loc: Bowling Green, Kentucky
Re: Pupil Size new [Re: BlueGrass]
      #5642217 - 01/25/13 09:46 AM

Page 52 of RASC's 2013 Observer's Handbook has a great exit-pupils diagram. According to the diagram, the average exit pupils by age are as follows:

Age 10: 7.7mm
Age 20: 7.3mm
Age 30: 6.9mm
Age 40: 6.5mm
Age 50: 6.1mm
Age 60: 5.7mm
Age 70: 5.3mm
Age 80: 4.9mm

Best,
David


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Mark Peterman
super member


Reged: 08/07/12

Loc: Texas
Re: Pupil Size new [Re: BlueGrass]
      #5642223 - 01/25/13 09:49 AM

Thanks to everyone who responded to my original question. I guess I was a bit suprised to learn that I am at least a 6mm. For some reason I had figured it would be less.

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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: Pupil Size new [Re: Widespread]
      #5642821 - 01/25/13 03:36 PM

Quote:

Page 52 of RASC's 2013 Observer's Handbook has a great exit-pupils diagram. According to the diagram, the average exit pupils by age are as follows:

Age 10: 7.7mm
Age 20: 7.3mm
Age 30: 6.9mm
Age 40: 6.5mm
Age 50: 6.1mm
Age 60: 5.7mm
Age 70: 5.3mm
Age 80: 4.9mm

Best,
David



It is common for a person to have several tenths of a millimeter difference from the average age. I guess that's why people measure their own.


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derangedhermit
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Reged: 10/07/09

Loc: USA
Re: Pupil Size new [Re: Tom Polakis]
      #5642840 - 01/25/13 03:44 PM

Quote:

This is one of the weirder things I have posted on a forum.

Here are my and my wife's pupils fully dilated after five minutes in a black, indoor room. In addition to the scale, the white lines superimposed on all four pupils are 7mm long. Mine are just slightly shy of 7mm, and my wife's just more than 6mm.

Tom



Pupils contract at near focus as part of the accommodation process. You need to be focusing on a distant object, say on the other side of the room (15-20 ft away).

Please tell your wife for us that she has pretty eyes


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dpwoos
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Reged: 10/18/06

Loc: United States
Re: Pupil Size new [Re: derangedhermit]
      #5642889 - 01/25/13 04:09 PM

So when I look through an eyepiece is it near or far focus?

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Mr. Bill
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Reged: 02/09/05

Loc: Northeastern Cal
Re: Pupil Size new [Re: dpwoos]
      #5642907 - 01/25/13 04:19 PM

Quote:

So when I look through an eyepiece is it near or far focus?




The ep creates a virtual image that is (as far as the eyes concerned) at infinity.


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Tom Polakis
Carpal Tunnel
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Reged: 12/20/04

Loc: Tempe, Arizona
Re: Pupil Size [Re: derangedhermit]
      #5642936 - 01/25/13 04:32 PM

Quote:

Quote:

This is one of the weirder things I have posted on a forum.

Here are my and my wife's pupils fully dilated after five minutes in a black, indoor room. In addition to the scale, the white lines superimposed on all four pupils are 7mm long. Mine are just slightly shy of 7mm, and my wife's just more than 6mm.

Tom



Pupils contract at near focus as part of the accommodation process. You need to be focusing on a distant object, say on the other side of the room (15-20 ft away).





The room was completely black, so there really was nothing to focus on. What do eyes do in this situation? I know that they have a problem coming to focus on a blank sky (looking for Venus in the daytime, for example). Do you know if they also contract in complete darkness?

Tom


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