Dobsonian 200/F6 | Maksutov 180/F15 | Binocular 12x50
Quote:Can anyone shed any further light as to why there is so much variation of opinion on this subject, when there ought to be a specific value we can all agree on?
Quote:Generally, there's a formula of...
APM 105/650 Travelling Visual Observer
Quote:an exit pupil of about 0.8mm offers maximum resolution of lower contrast features.
Quote: (instant disqualification for the first person who states "everyone's eyes are different" since I don't believe anyone's eyes are able to help them defy the laws of physics and it's scientific fact I am searching for here, since I want to drive subjectivity out of the issue once and for all!...)
Quote:The underlying assumption in your question is that there should be one optimal magnification that works for all observers for a given object in a given telescope regardless of any differences in an individual's eye.
My eyepieces are made from the waste product of exploding stars.
10XTi 102XLT ST80A(2" Focuser); President, Eypieces Anonymous, Denver Chapter (Hello, I'm an eyepiece junky, what's your excuse?)
DAS Dark Site
Quote:with years of observing planets and DSO's, your eyes probably percieve more detail then when you were younger with possibly better vision and less eyepiece time.
Quote: I want to drive subjectivity out of the issue once and for all!
"You're not afraid of the dark, are you?" - Riddick "The best scientists are humble. They seek to understand, not to ensure their legacy, but merely to understand." - Mori
Perhaps Jon, my question might be better phrased (for the more experienced of understanding such as yourself) as "What's the minimum scope-relative magnification that will resolve for human eyes all possible detail?"
Whenever I have come into large sums of money in my life, I always put half of it aside to spend on fast cars and the pursuit of loose women.
I put aside the other half to spend frivolously.
SyedTeeter STS 11 f/4.3 Zambuto | XT8i | XT8g | XLT 150 | C90 | EON 80mmAT Voyager and Nexstar SLT mountsEyepieces: Mostly TeleVue and PentaxDenk II BV'er, Earthwin PFS-SE, Pentax 10x50 PCF WP II
Quote:The image never breaks down wtih magnificiation.. The image always is exactly what it is. The only thing that changes it the power of the magnifiying glass you are using to inspect the image.
Quote:And with binoviwers, I find that I don't even need 1.3x. I am doing a lot more observations with less power and seeing detail more easily.
C10NGT, Z8, 150 Rumak, XLT 150, C6, C5, SW5 Newt, 4.5 Ball, C102GT, C90, ST80, A70LF; 15x70, 25x100; Burgess BV; Paracorr II; T6 2.5, XO 2.58/5.1, Ethos-SX 3.7, Delos 4.5, TV Plossl 7.4-26, BCO 10, Hutech HC 12.5, Sterling 12.5-25, ES100 14, CZJ H 16/25, CZJ O 16, M5k UWA 24, T5 31, Ultrascopic 35, Titan-II 40; Bino Pairs M5k UWA 6.7, Baader Zoom 8-24, M5k SWA 24, TV Plossl 26, RKE 28.7; Zooms NZ 2-4, NZ 3-6, Leica ASPH 8.9-17.8, Baader 8-24; Baader Zoom Barlow, VIP Barlow
Quote:What are the issues with the eye that might affect the magnifications we can use?Well, at the low end it's pupil diameter and astigmatism of the eye. Nearly everyone has some "whole eye" astigmatism, so an exit pupil slightly smaller than the pupil of the eye, while not the optimum for brightness, might be the optimum for a combination of brightness and sharpness.As the exit pupil shrinks and magnification goes up, there is a "eutectic" point of the balance between magnification and the eye's resolution that gets crossed. This seems to be, from all I've read, when the magnification yields an exit pupil of 1.8 to 2.5mm (and even larger, up to 4mm, with some individuals). My favorite eyepiece in each of the 23 scopes I've owned has always settled into the 1.8-2.5mm range.When the exit pupil gets smaller, smaller details become apparent due to increasing size (lab tests show an effective size of 2 degrees is the point of maximum noticeability) but only up to the point where the Airy disc begins behaving like an extended object (i.e. has a visible size). After that, increased magnification will not yield improved resolution, because the brightness of point sources will star declining, but increased size may still yet improve noticeability.This point does not have a set physiological limit, but most references say this occurs around a 1mm exit pupil with average vision (whatever average vision is--I see a spread in visual acuity that is a HUGE span, not a small difference), or slightly higher (maybe as small as a 0.8mm exit pupil.The problem for humans is that this begins to be the point where the image begins to be bothered by floaters in the eye. Floaters are small protein agglomerations in the vitreous humor of the eye. They always seem to fall in front of the small detail on a planet or the moon when you are examining that detail at small exit pupils.Due to huge variations in seeing conditions, the maximum limit is relatively undefined. I read 50X/inch often. In the old days it was 60X/inch. I've used 160X/inch (!) in a marvelous large refractor on an incredible night of seeing. Experimentation, though, showed the image of Saturn to be equally as detailed at 100X/inch, though all present preferred the image at that power to one at 65X/inch. It was easy to see details in the rings (did you know they were "grooved" like an old LP?) at those ridiculous magnifications that simply weren't seen at lower powers. It wasn't a matter of resolution, it was a matter of size of the details we sought to view.[it was the first and only time I saw the ring features known as "spokes"]The Sparrow Limit is about half the size of the Rayleigh limit in double star viewing. It is when a double star is overlapped and the image of the double is oval and may begin to have a slight pinched waist in the oval star image (normally, just oval). To see to that level requires incredibly good seeing and optics, but hardcore double star observers do do it. It's about 2.8"/aperture in inches (0.35" on an 8" scope). That is probably the physical (and physiological) limit for double star separation. For a person with decent visual acuity, that might be seen at 60X/inch--otherwise higher. That's probably where the 60x/inch I read in my youth came from.Does it have any relevance for extended objects? Probably not if the detail being perceived is a dark feature next to a brighter detail. And it's probably too severe for equally-bright details side by side. And yet, I have heard and read of lunar observers seeing details at 100x/inch and higher that they could not see at lower powers. The Moon's features yield very high contrasts--more so than on planets--so this should not surprise us.I really don't think there is a maximum magnification that is not limited by:1.seeing2.optical quality3.personal visual issues4.personal tasteThese days, I seldom go above 25X/inch, but it's not because of any factor other than #4. On one superb night, I used 58X/inch just to see if the image held up, and it was OK, though I far preferred the quality and brightness of the image at 36X/inch.De gustibus, non est disputandum.
Quote:The above then, places my experience of maximum useful magnification as lying somewhere between:
33x - 40x p.i. (equivalent to exit pupil range 0.78mm - 0.63mm)
The opinions expressed herein are solely mine as an amateur astronomer hobbyist & consumer. Information herein was correlated from experience, discussions with others, & research from multiple sources freely available at time of posting. All reasonable care & skill was used, but no warranty is made as to accuracy, & liability cannot be accepted for errors/omissions. This is for information only and not intended nor implied to be a substitute for professional advice.
Quote: the eyepieces relationship with it - and critically its position in relation to both image and to the inner-telescope environment is quite different at one extreme compared to the other.
Quote:Ever noticed: the more experienced the observer, the less magnification typically used? Says more than any rule or conceptual theory.
Quote:In the same way as an overly-large exit pupil (when masked by the observer's iris) becomes increasingly dominated by the shadow of the secondary (in a newt/sct), conversely, the area surrounding smaller exit pupils become increasingly dominated by the inside surfaces of the OTA - be they shiny (in the case of a poor telescope) or inky-black (in the case of a flocked/well-baffled one). That's what leads to the loss of contrast at higher magnifications where the exit pupil is appreciably smaller than the dilated iris of the observer.