USING THE TELESCOPE EXIT PUPIL
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- เผยแพร่เมื่อ 8 ก.ย. 2024
- What is the exit pupil, how do you calculate it, what does it do, and why does it matter? In this video I will answer all of those questions and explain how using the right exit pupil will maximize your telescope's aperture and what you see with your telescope in the night sky.
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This is one of those rare amazing videos that only a handful of people know how to explain! Thanks!
Thank you for your very nice comment. I appreciate it.
Excellent video on exit pupil. I never heard it explained so well, nor how to calculate it or determine your own. Thank you!
Thank you, Elray.
This video is “old school” in all the best ways. What a refreshing and informative presentation! I wish I could subscribe more than once!
What a nice comment. Thank you so much.
Great video of a subject that rarely if ever gets covered.
Clear skies!
Chris
Thanks, Chris. I can see why it's rarely covered as it was difficult to present it in an interesting engaging way without putting the audience to sleep.
Hi Tsula! Great video on exit pupil ! I love determining exit pupil for diffrent eyepieces with different scopes. It kinda tells you what too expect out of your eyepiece. Most beginners don't understand or care about exit pupil. I know I didn't at first a long time ago. Clear Skies forever.
Thanks, Eric. I used to never pay attention to the exit pupil either until one of the viewers told me I should. Now I always do.
Terrific presentation, Tsula, and some great information! Thanks so much for putting together a super video on a subject not often discussed.
Thanks, Greg. Now if these darn clouds will clear up I will go put it to practical use.
@@tsulasbigadventuresUgh, don't I know it, Tsula! The weather here has been awful as well. Wonder how they're coming along on developing that filter that can let us see through the clouds? 🤣
This is a lot of information to unpack. Thank you for this video. I'll keep watching it til I'm able to absorb all this and understand it all comfortably.🎉❤
Thanks Walter. I hope it becomes clear after a while. Thanks for watching.
@@tsulasbigadventures it will. I usually take 2 or 3 times to fully absorb everything but it was an excellent presentation. Thank you so much. I'm very new to this.
@@walteredwards544 Thank you. I appreciate the feedback.
Thank you. Great info.
Thank you.
Interesting and very useful presentation Tsula and useful for myself as I've just setup one of my refractors for visual use. Just waiting on a clear night now.
Cheers Ollie.
Thanks, Ollie. I'm glad to hear that. I hope it clears up for you and me. Cheers.
SOOooooo gooood !!! explanation !!!!
Thank you so much.
Excellent information! Thank you!
Thank you. I appreciate it.
So helpful! Thank you.
Thank you and thanks for watching.
The smallest exit pupil that I have is 2mm on my Zeiss 5x10 Mini Quick monocular although using high power eyepieces I may be able to reduce on that with some of my telescopes although I haven't worked that out.5mm is suppose to be the average exit pupil for most people over 30.
I'm sure you could on your telescope but the question is should you and most of the time the atmosphere will dictate that.
Loved the idea of using hex wrenches to measure dilated pupils. Always enjoy your videos. Have you tried EAA?
Thank you. No, I have not unless you include looking at the back of my camera or the laptop image on Sharpcap while making videos of the planets. Is it like that? I don't even know.
It’s not quite like that. It’s using the live stacking facility in Sharpcap with very short exposures. It’s pretty amazing.
@@g3cwi_Radio_Adventures I've never used it. I currently have an aversion to all things electronic.
You would cover a subject which has always made my head spin! 🙂 (I had no idea, until a few minutes ago, that the "entrance pupil" is simply the lens aperture - that's correct, isn't it?) So I can't add anything to the discussion except to note that a Sky & Telescope article (which missed, by the way, your hex-wrench trick) suggests the once much-maligned and seemingly redundant Barlow lens as an alternative to using eyepieces with too little exit pupil and eye relief.
The excellent movie KINSEY (2004) has a very good joke about the pupil of the eye and, speaking of movies, it looks like our friend Ridley Scott has outdone himself in incompetence with his Napoleon bomb. May I recommend instead the superb CROMWELL (1970), freely available on TH-cam?
This was a hard topic to cover without sounding pedantic or being soporific. The entrance pupil is the human dark-adapted pupil. I have never heard of referring to the telescope's aperture as the "entrance pupil." I just read the article in Sky & Telescope you are referring to and he made a mistake at the beginning by saying the aperture of the telescope is the entrance pupil. The entrance pupil is your own eye's pupil. Also, when he said to use a barlow lens he was just saying to use a barlow with another eyepiece that has good eye relief in order to get better eye relief; it's not going to improve your exit pupil at all though. The exit pupil would be the same with a 12mm eyepiece or a 2x Barlow with a 24mm eyepiece but each eyepiece will have a different eye relief with the 12mm eyepiece having less eye relief. I didn't like the example he used about minimum magnification and telescope apertures; it's not just the aperture that matters but also the focal length of the telescope. I don't know if I have time for Cromwell. I am so busy right now listening to an audio book Relativity and reading an excellent book about the "Computers" at the Harvard Observatory called Glass Universe. I don't know if you know about the Computers. That's what they called the severely underpaid women who examined glass plates to measure star's spectra and find variable stars and other things. It's a really good book. But I'm only 50% through.
@@tsulasbigadventures Thanks! Yes, it’s a big topic even without covering why the exit pupils of binoculars can be calculated simply from aperture and magnification (because binoculars generally don’t have interchangeable eyepieces) and why microscopes have smaller exit pupils than telescopes (because microscopes can be supplied, artificially, with as much light as needed) - not to mention that some binoculars, particularly the compact ones, are intended for daytime rather than nighttime (generally astronomical) use, hence determining the size of the exit pupils built into them.
A second watch of your video made things clearer - and made me notice the brief excerpt from Holst’s wonderful piece 🙂 - but I was still confused by the graph. I’d never seen one with two sets of data on the X-axis, and where one of those data sets (the focal ratio) turns a corner and descends on the Y-axis. That yellow dashed line - it seems to me that if it sloped toward, say, a focal ratio of f/10, it wouldn’t come anywhere near intersecting with your dark-adapted entrance pupil of 6 mm.
I read NPR’s review of the book about the Harvard “computers.” I’d never heard of them, but I was aware that women were employed in many similar tasks before the advent of practical machines. And by the “Relativity” book, do you mean the one of Einstein, in which he tried to popularize his theories? There’s a (free) Librivox version of it.
@@waltergold3457 Walter: I was wondering if you noticed that I included Holst's Planets. Only 10 seconds. No, the audio book is one of those Great Courses series. It's called Einstein's Relativity and the Quantum Revolution. It's very good and makes it very easy to understand for non-physicists like myself. I'm sorry about the confusing graph. I should have explained that to use it you draw a line diagonally toward your f ratio.
@@tsulasbigadventures "Jupiter" is in my humble opinion the finest work of English classical music - I exclude Handel because he wasn't from England. I've read that during the premiere, the maids in the basement of the hall, waiting to clean it after the concert, danced with their brooms and mops as the piece played overhead.
I understand the part about drawing the diagonal line but I'm not sure what it would mean if drawn to one of the longer f-ratios. In such a case, the line couldn't intersect with your ideal entrance pupil of 6 mm - which means, I think, that you can't get a rich field with a long f-ratio. That would make sense.
PS: Speaking of bad movies (and popularized science), THE MARVELS - Disney's latest franchise bomb, a catastrophic one - has Captain Marvel "reigniting" a star by flying through it, core and all. The science nerds on TH-cam are having a field day with it.
@@waltergold3457 Beethoven said Handel was the greatest composer (before Beethoven came along) and I agree. You can get a richest field with a long f ratio but it would take a very long eyepiece. For my f/10 telescope I would need a 60mm eyepiece to reach a 6mm exit pupil. I'm not sure they make one that long and I don't own one. I think the longest one I own is 56mm but that's close enough. I would never go to that movie, The Marvels.
At what exit pupil do you get floaters Tsula?
I read in the Observer's Handbook that you can see floaters but I have never personally seen them to my knowledge.
Is that a Rolex?