#21
|
|||
|
|||
The following flash photograph method was the easiest, simplest, and
most accurate method for me. This was suggested in a post in this usenet group by someone else a few months ago: Take a nap with the house darkened. Pre-position an ordinary disposable flash camera in front of the bathroom mirror and practice holding it next to your face and taking a flash picture. You will need to be proficient enough in operating the camera to take a flash picture in total darkness. When you wake up in the darkened room, go to the mirror and take the picture. Your exit pupil does not react fast enough to the flash bulb to alter the measurement. Measure the developed photo using measure calibers, or if digital, the pixels coordinates displayed in picture editing software. Measure the physical dimensions of your eyebrows, nose, eye "whites", or iris. A little proportional math is then used to find the size of the your exit pupil in the photograph. One drawback of this method is that there is some uncertainty in measuring the fuzzy border of exit pupil in a small photo, this seems to be the most accurate of various alternative methods. Study of the relative size of your dark adapted exit pupil, using a very-low-intensity red light and a small hand mirror, when you dark-adapted at a dark sky site, was also helpful. One advantage of this method is that it can be performed reliably with truly dark adapted eyes. The photographic method seemed the be the simplest and most effective, out of a variety of options, e.g. - the triangular S&T pupil gauge, allen wrenches, drill bits, having a friend measure the exit pupil with measuring calipers when dark adapted at a dark sky site, using the measuring calipers at a dark sky site in a small hand mirror, etc. - Canopus56 Exit_pupil_dia_physical = ( Exit_pupil_dia_photo * Eyebrow_ln_physical ) / (Eyebrow_ln_photo) |
#22
|
|||
|
|||
canopus56 wrote:
The following flash photograph method was the easiest, simplest, and most accurate method for me. This was suggested in a post in this usenet group by someone else a few months ago: Take a nap with the house darkened. Pre-position an ordinary disposable flash camera in front of the bathroom mirror and practice holding it next to your face and taking a flash picture. You will need to be proficient enough in operating the camera to take a flash picture in total darkness. When you wake up in the darkened room, go to the mirror and take the picture. Your exit pupil does not react fast enough to the flash bulb to alter the measurement. Measure the developed photo using measure calibers, or if digital, the pixels coordinates displayed in picture editing software. Measure the physical dimensions of your eyebrows, nose, eye "whites", or iris. A little proportional math is then used to find the size of the your exit pupil in the photograph. One drawback of this method is that there is some uncertainty in measuring the fuzzy border of exit pupil in a small photo, this seems to be the most accurate of various alternative methods. Study of the relative size of your dark adapted exit pupil, using a very-low-intensity red light and a small hand mirror, when you dark-adapted at a dark sky site, was also helpful. One advantage of this method is that it can be performed reliably with truly dark adapted eyes. The photographic method seemed the be the simplest and most effective, out of a variety of options, e.g. - the triangular S&T pupil gauge, allen wrenches, drill bits, having a friend measure the exit pupil with measuring calipers when dark adapted at a dark sky site, using the measuring calipers at a dark sky site in a small hand mirror, etc. - Canopus56 Exit_pupil_dia_physical = ( Exit_pupil_dia_photo * Eyebrow_ln_physical ) / (Eyebrow_ln_photo) Turn the "red eye reduction" feature off on your camera, or else you'll be seeing spots for no reason. :-) Shawn |
#23
|
|||
|
|||
|
#24
|
|||
|
|||
ROM SPACE KNIGHT NURSE wrote:
I'm going to buy binocs. I've read the ten power require a tripod due to the natural shakiness of hands, but the 7 power not. Is that extra 3-power worth the extra $$ for a tripod and adaptor? If you have steady hands get the 10x, otherwise 7x. The higher power can make a difference for some objects, particularly planets. Get the widest field you can find in either power but don't expect the focus to be good at the edge of the field unless they have very good optics. Have you considered a zoom binocular, like a 7x-15x/50mm? |
#25
|
|||
|
|||
Florian wrote:
This is my method for measuring pupil size... I use a set of metric Allen wrenches. Go out at night and wait a minute or two for your pupils to fully open. Hold an Allen wrench one at a time close to your eye and look at a medium bright star. I rest the wrench on my cheek. With small sizes you will see two stars, one on each side of the wrench. Work up until you only see one star, on one side of the wrench or the other. I've heard some people can see two stars when using a regular wooden pencil. That's about 7mm. To me a pencil looks like a board! I can just see two stars with a 3mm wrench and only see one with a 4mm thus my pupil is 4mm or less. Sky & Telescope magazine sells a little gauge for measuring nighttime pupils as well. It's a piece of mylar with paired holes from 1mm to 9mm apart. It works on the same principal as my Allen wrench method. You can also use drill bits or strips of black paper cut to various widths. -Florian Would that work for wearers of glasses? You couldn't get the allen wrench so close to the pupil for the test. |
#26
|
|||
|
|||
thanks to all posters for the info...Rom
MY HALLIBURTON BOARD OF DIRECTORS RIGHT OR WRONG! |
#27
|
|||
|
|||
Would that work for wearers of glasses? You couldn't get the allen
wrench so close to the pupil for the test. Yes, will work if you wear glasses. The wrench doesn't have to be right at your eye. A few inches away should give similar readings. -Florian |
#28
|
|||
|
|||
Zoom binoculars have historically been optically inferior to fixed
power bioculars. So the fixed power binos have always been recommended over zoom types. The same has usually held true with fixed versus zoom telescope eyepieces. Perhaps the high-end zoom eyepieces have broken the rule? Regarding allen wrenches (UK allen keys) I supopose you have noticed they are hexagonal? It seems too obvious to point out that they must be larger across the "points" than they are across the flats. Presumably deliberately laying the "handle" flat on one's cheek largely eliminates this error? ;-) Chris.B |
#29
|
|||
|
|||
On Tue, 25 Jan 2005 01:19:29 -0500, starman wrote:
Would that work for wearers of glasses? You couldn't get the allen wrench so close to the pupil for the test. Stars are so distant that the rays of light are parallel; therefore, the distance from the eye to the allen wrench doesn't matter. The effect of spectacles is that the rays of light diverge or converge after they pass through the lens, depending on your prescription, which affects the apparent size of your pupil. You can take off your glasses and still get your pupil diameter, assuming you can still see the star. |
#30
|
|||
|
|||
I brought the tripod first and then the 8X56's.
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Erfahrungen mit Bresser Corvette 10x50 oder 16x50? | Srdjan Boskovic | Amateur Astronomy | 0 | August 2nd 04 07:27 AM |
Some good 10x50 binocs?? | K S Aldebaraan | Amateur Astronomy | 7 | May 21st 04 07:59 AM |
BSA 10x50 binoculars arrive 9-29-03 | Pete Rasmussen | Amateur Astronomy | 3 | September 30th 03 01:12 PM |