90x Per Inch!!...How?

[Starwatcher2001]

On 11/08/2020 at 01:10, Geoff Barnes said:

Are they lemons? I see them as eggs! 🤔

Use averted vision.

[jetstream]

On 11/08/2020 at 06:26, andrew s said:

I have set myself the personal goal of researching the science of visual astronomy with the aim of trying to satisfy myself  that if all the relevant science is taken into account does it explain the claims of skilled visual observers or not. 

I think a lot of the issue is that partial explanations from limited fields  (say just optics) is used and often out of context. An example might be that "a 1mm exit pupil is optimum" without context or qualifications. 

Regards Andrew 

Somewhere I have an article discussing exit pupil and the eye regarding "resolution" . After reading it I went on a mission to find what works for me using the text as a guideline- I found that around an .8mm exit pupil is a sweet spot for me,eventhough I can use lower. When designing my 15" I had this in mind and it gives 457x at this eye illumination.

This is a very useable mag here which gives mind blowing views of Jupiter, Saturn and the moon. Mind you this scope has used double this mag on occasion on the moon (barlowed Vixen HR).

[jetstream]

This is interesting... try seeing the "17"

https://www.imatest.com/docs/sqf/#csf

[John]

Then what ?

(the 17 popped out a little easier for me when I removed my reading glasses)

 

 

[Geoff Barnes]

Are there folks on here who can't see the number? It seems very obvious to me.  🤔

[iPeace]

4 hours ago, jetstream said:

around an .8mm exit pupil is a sweet spot for me

Calculating in hindsight, I'm inclined to agree!

[andrew s]

Moving it slightly made it pop out for me. Regards Andrew 

I just noticed it was very clear when scrolling the page. The diagonal line blur and it leaps out.

Edited August 13, 2020 by andrew s

[Saganite]

5 hours ago, jetstream said:

This is interesting... try seeing the "17"

https://www.imatest.com/docs/sqf/#csf

Not at normal reading distance with specs, but moving back 30" from screen it was pretty clear. Interesting.

[Pixies]

If I tilt my head so the lines are horizontal - the 17 pops out. Also, if I remove my specs (very short sighted)

[chiltonstar]

I'd agree with Andrew S - clear when scrolling the page, or indeed if I move my head from side to side and look at it.

Chris

[JeremyS]

6 hours ago, John said:

Then what ?

(the 17 popped out a little easier for me when I removed my reading glasses)

 

 

Me too: I can't see the 17 at all with my reading glasses on, but when I take them off it is obvious.

[vlaiv]

While not the best example - depends highly on computer screen calibration, it is very good example for what it is supposed to show.

It's not the point in looking at it like this, on SGL. Point is to open the image in another empty tab. That way it will be shown full size (about x3 the size of the image embedded here on SGL) - try seeing 17 on that image!

If you can't - then you need to slowly step back from the screen until you find size (magnification) that will yield the most contrast.

Scrolling is cheating by the way - Many computer screens "flicker" when scrolling high frequency signal. It has to do with gray to gray response time of computer displays.

[vlaiv]

Btw, interesting fact - if I open image in another tab, I can't see it with my healthy eye, but I can with my far sighted / highly astigmatic eye (without glasses).

[JeremyS]

4 minutes ago, vlaiv said:

Scrolling is cheating by the way

Is it though? We were originally considering visual acuity in a telescope, rather than on a computer screen. It's well known that it's often easier to see an object if the field of view is moving, e.g. if the telescope is tapped.

[Stu]

22 minutes ago, vlaiv said:

While not the best example - depends highly on computer screen calibration, it is very good example for what it is supposed to show.

It's not the point in looking at it like this, on SGL. Point is to open the image in another empty tab. That way it will be shown full size (about x3 the size of the image embedded here on SGL) - try seeing 17 on that image!

If you can't - then you need to slowly step back from the screen until you find size (magnification) that will yield the most contrast.

Scrolling is cheating by the way - Many computer screens "flicker" when scrolling high frequency signal. It has to do with gray to gray response time of computer displays.

That makes it much more interesting Vlaiv, at full red I can’t see the 17 close up, but Nice it away a certain distance and I can.

[vlaiv]

14 minutes ago, JeremyS said:

Is it though? We were originally considering visual acuity in a telescope, rather than on a computer screen. It's well known that it's often easier to see an object if the field of view is moving, e.g. if the telescope is tapped.

There might a bit of that, but I believe that dominant effect is screen flicker when scrolling.

Check out this page:

http://www.lagom.nl/lcd-test/clock_phase.php

When you scroll it, depending on your computer screen it might flicker quite a bit.

[vlaiv]

This one is even better for showing effect (at least on my screen):

http://www.lagom.nl/lcd-test/sharpness.php

When I scroll this page - chart "flickers" all over the place

[John]

I'm going to make it full screen, put my lap top on a hill about 50 km away and observe it at 500x with my Tak

@mikeDnight would still see more detail in it than I would

 

 

[andrew s]

33 minutes ago, vlaiv said:

This one is even better for showing effect (at least on my screen):

http://www.lagom.nl/lcd-test/sharpness.php

When I scroll this page - chart "flickers" all over the place

It would be good to test @mikeDnight observation on vertical v horizontal resolution. Do you loose resolution differently with the two sets of lines in the first image in the link as you recerd from it? Pick the high contrast pairs next to each other.

I get a difference. 

Regards Andrew 

Edited August 13, 2020 by andrew s

[vlaiv]

2 minutes ago, andrew s said:

It would be good to test @mikeDnight observation on vertical v horizontal resolution. Do you loose resolution differently with the two sets of lines in the first image in the link as you recerd from it?

Regards Andrew 

Not really sure if this is valid test. Have you seen screen pixels under magnification?

Most displays have it like that, but some have it in different configuration, like this:

Green carries the most brightness out of three R, G and B colors and in above image - there is greater separation between vertical lines then horizontal lines with respect to green light alone (as pixel is vertical triplet).

 

[andrew s]

Just now, vlaiv said:

Not really sure if this is valid test. Have you seen screen pixels under magnification?

Most displays have it like that, but some have it in different configuration, like this:

Green carries the most brightness out of three R, G and B colors and in above image - there is greater separation between vertical lines then horizontal lines with respect to green light alone (as pixel is vertical triplet).

 

I did it with the screen in both orientations and got the same result. But ideally a printed gray scale would be best.

Regards Andrew 

[JeremyS]

Aren't we getting off track here? I thought we were trying to understand visual acuity at the eyepiece, not monitor resolution and performance....

[andrew s]

7 minutes ago, JeremyS said:

Aren't we getting off track here? I thought we were trying to understand visual acuity at the eyepiece, not monitor resolution and performance....

Sorry, it was just a quick test to see if as @mikeDnight  said he could resolve the plants better with the detail vertical rather than horizontal.  This was intended as a quick test. I had not considered the display characteristics influencing it.

Regards Andrew 

[chiltonstar]

10 minutes ago, JeremyS said:

Aren't we getting off track here? I thought we were trying to understand visual acuity at the eyepiece, not monitor resolution and performance....

Indeed - isn't the fundamental point essentially (pin out of grenade) can paying lots of money for an expensive refractor really beat the laws of physics?

Chris

[mikeDnight]

2 hours ago, chiltonstar said:

Indeed - isn't the fundamental point essentially (pin out of grenade) can paying lots of money for an expensive refractor really beat the laws of physics?

Chris

Unlike man made laws, paying lots of money can't alter physical laws. However, considering first the different qualities of various scope designs, then choosing to pay for the best optics available in that design, will result in superior performance on nights of good seeing and transparency. On mediocre nights you may see scopes of similar design give similar performance, but when the conditions for high performance allow for it, the higher end optics will pull away from the good but run off the mill optics. And as many can attest, mere aperture is no guarantee of superior performance.