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Old 11-07-2020, 08:51 AM
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OneCosmos (Chris)
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Induced pupil dilation!

Here’s a quirky one for comment.

Whilst thinking about eyepieces and exit pupil and reading about how to measure my dark-adapted pupil size, I thought I would pop in to my local optometrist to ask if there was any way to measure it for me. I knew it was unlikely I could become dark adapted first though in the shop so I asked about inducing the dilation.

They said it wouldn’t work because the drops they use to force it to happen would actually dilate the pupils way beyond what any amount of time under really dark skies could ever do and would thus not really reflect my true exit pupil.

That got me thinking though. I asked how long the effect would last and he said usually 4 or 5 hours so there is the potential to have it done one late afternoon when it promises to be clear to see if I would notice any difference. Obviously I’d have to wear super dark sunglasses whilst leaving the shop to go home but then try to stay dark until the sun goes down.

Has anyone ever tried this, perhaps simply opportunistically? Do you think you would notice any difference I.e. see fainter stars etc?
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Old 11-07-2020, 11:26 AM
glend (Glen)
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I question whether an ethical optometrist or othamologist would just put drops in your eyes for your astro pursuits. Your not suppose to drive while dilated, and my Opthomologist makes me wait, unless I have arranged to be picked up. There are various strengths of drugs used, optometrists usually have the weak stuff.

FYI, there are a range of drugs which provide dilation, but the other effects might be concerning:

Drugs and medications that can cause dilated pupils are:

Methamphetamines and other amphetamines. Antihistamines (Including cold and allergy medications) Atropine. Pseudoephedrine (Sudafed), Cocaine. Marijuana. LSD. Heroin withdrawal.

It does not change the fact that the human eye has no time exposure function, it can only detect photons at particular moment in time. You would be better off buying a camera designed for Electronically assisted astronomy (EAA).
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Old 11-07-2020, 11:52 AM
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OneCosmos (Chris)
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Drugs and medications that can cause dilated pupils are:

Methamphetamines and other amphetamines. Antihistamines (Including cold and allergy medications) Atropine. Pseudoephedrine (Sudafed), Cocaine. Marijuana. LSD. Heroin withdrawal.

Iím sure with enough Heroin you could see all nebulae perfectly and indeed visit them
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Old 11-07-2020, 02:18 PM
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Lemme guess - LSD for extra colour?
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Old 11-07-2020, 02:25 PM
DarkArts
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LSD for extra colour?
It's an alternative to the Hubble palette.

Seriously though, if you're willing to go that far for visual, maybe invest in video astronomy or a humongous Dob?
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Old 11-07-2020, 03:24 PM
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Not recommended - suggest you google acute angle closure glaucoma...

DT
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Old 11-07-2020, 07:15 PM
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Just for the record I would have absolutely no intention of actually trying it, I was merely engaging in a thought experiment about whether extreme dilation would allow people to see fainter objects.

For those that know such things is the size of your pupil during daytime an indication of how well you would see at night? I ask because the optometrist I saw did casually pass the comment that ďI can see that your pupils are on the small sideĒ ☹️
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Old 11-07-2020, 07:44 PM
Startrek (Martin)
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I was diagnosed with Positive Vitreous Detachment ( PVD ) about 18 months ago as I was experiencing flashes at night in my peripheral vision of both eyes for a week, so decided to get tested, Another sign was a lot of floaters in my vision which I still have
The drops the eye hospital used to inspect your retina, open your pupils so wide you look like an alien or a cat about to pounce on a mouse

The biggest mistake I made was not to bring sunglasses with me after the test

It was a sunny day and the glare was unbelievably painful , my eyes watered nonstop , so I shut my eyes and my wife held my hand until we got back to the car.Your pupils donít resume normal function for 1 to 2 hours.

The condition has settled but I still have floaters in both eyes and the occasional flash only in the right eye peripheral vision

I get tested once a year now plus a general eye test

If your tested and diagnosed with PVD make sure you take your sunglasses with you just in case

Cheers
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Old 11-07-2020, 08:45 PM
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Originally Posted by Startrek View Post
I was diagnosed with Positive Vitreous Detachment ( PVD ) about 18 months ago as I was experiencing flashes at night in my peripheral vision of both eyes for a week, so decided to get tested, Another sign was a lot of floaters in my vision which I still have
The drops the eye hospital used to inspect your retina, open your pupils so wide you look like an alien or a cat about to pounce on a mouse

The biggest mistake I made was not to bring sunglasses with me after the test

It was a sunny day and the glare was unbelievably painful , my eyes watered nonstop , so I shut my eyes and my wife held my hand until we got back to the car.Your pupils donít resume normal function for 1 to 2 hours.

The condition has settled but I still have floaters in both eyes and the occasional flash only in the right eye peripheral vision

I get tested once a year now plus a general eye test

If your tested and diagnosed with PVD make sure you take your sunglasses with you just in case

Cheers
Thanks for the tip and exposure of optical problems that can occur. I hope things remain stable for you.
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Old 12-07-2020, 01:19 AM
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Stonius (Markus)
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I'd be curious if anyone's tried this. And whether the optics of the human eye hold up when the pupil has been artificially widened. It may be that you get more photons, but the details are blurred.


An interesting experiment.


But in answer to the point about measuring your pupil dilation, it's easy to do yourself if you have a paper guillotine.


Just cut two narrow pieces of aluminium foil such that they taper from about 8mm to around 4mm.


One night when you are fully dark adapted close one eye, and focus on a star. Hold the 4mm end of the foil strip just in front of your eye. You should note that you can not completely block the star from view (because the foil strip is not wide enough, ie your pupil is wider).


Simply move the foil strip down until you can only just completely block the star. Then you know the width of the foil is the same as your pupil. Fold it at that point and measure later on in the light. Repeat with the other strip on the other eye.


Using this method I found that there was quite a discrepancy for me. 7mm in my left eye and 5mm in my right. So if I'm looking for something really faint I favor my left 'good' eye.


I hope that helps.


Cheers


Markus
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Old 12-07-2020, 03:13 PM
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OneCosmos (Chris)
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Quote:
Originally Posted by Stonius View Post
I'd be curious if anyone's tried this. And whether the optics of the human eye hold up when the pupil has been artificially widened. It may be that you get more photons, but the details are blurred.


An interesting experiment.


But in answer to the point about measuring your pupil dilation, it's easy to do yourself if you have a paper guillotine.


Just cut two narrow pieces of aluminium foil such that they taper from about 8mm to around 4mm.


One night when you are fully dark adapted close one eye, and focus on a star. Hold the 4mm end of the foil strip just in front of your eye. You should note that you can not completely block the star from view (because the foil strip is not wide enough, ie your pupil is wider).


Simply move the foil strip down until you can only just completely block the star. Then you know the width of the foil is the same as your pupil. Fold it at that point and measure later on in the light. Repeat with the other strip on the other eye.


Using this method I found that there was quite a discrepancy for me. 7mm in my left eye and 5mm in my right. So if I'm looking for something really faint I favor my left 'good' eye.


I hope that helps.


Cheers


Markus
Actually yes, that it a rather neat approach.
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Old 12-07-2020, 03:28 PM
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I'd be curious if anyone's tried this. And whether the optics of the human eye hold up when the pupil has been artificially widened. It may be that you get more photons, but the details are blurred.
Many years ago a friend of mine somehow got hold of some Atropine and tested whether the resultant pupil dilation assisted in the observation of dim objects.

The answer is no. It caused him to have blurred vision in that eye.
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Old 12-07-2020, 05:29 PM
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Yes, atropine will paralyse the ciliary muscles blocking accomodation or focus.

The effect of normal atropine also lasts 7+ days in the eye. There is a different stuff that is used for ophthalmic examinations that only lasts a couple of hours.

DT
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Old 15-07-2020, 06:52 AM
ad602000 (Pete)
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If anyone was thinking of trying this don't forget,
1/ you only get two eyes
2/ there are no braille eyepieces
3/ first invest in a really well trained Labrador
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Old 15-07-2020, 09:35 AM
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If anyone was thinking of trying this don't forget,
1/ you only get two eyes
2/ there are no braille eyepieces
3/ first invest in a really well trained Labrador

Come on, it's not like I'm suggesting people try observing on Meth. It's a commonly administered drug that is safe enough to be approved by the TGA. As long as it's used in accordance with medical advice they'll be fine. Just don't take it and wander around in the sun with no sunglasses on.



M
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Old 19-07-2020, 01:59 AM
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Take a photo!

Hi All,

One way to fairly accurately estimate your dilated pupil is, sit in a pitch-black room for about 20 minutes then have someone (or yourself with a cable release) take a fairly close (<50cm) flash-photo while you're holding up a ruler (for scale) very close to your eye. Must make sure the camera is focused manually before you start and that there are no "pre-flashes" -- just the one flash. You're eye won't react quickly enough to constrict before the single flash has been and gone.

I once did this many, many years ago (back in the late '80s) with a 35mm SLR film camera and found I was about 6-6.5mm. It took me about a ten goes before I managed a pic in excellent focus with appropriate illumination. The lab technician who developed the film must have been scratching his/her head, wondering the hell I was trying to achieve!

After my eye operations last year, I asked the technician who did testing afterward to measure them (under the effects of drops) and they were 6.1mm. This of course was an artificially induced dilation, but probably pretty close to real.

Best,

L.
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