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photonovore
Moonatic
Reged: 12/24/04
Posts: 2792
Loc: tacoma wa
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Hi Mauro,
No, i understood what you were trying to show and i knew it was not that a 16" would achieve full resolution. I just don't agree that one can relate seeing aberrated point source airy pattern characteristics with the resolution of an extended target (many conflated airy patterns) and get anything meaningfully accurate as a result. Double stars yes, planets no way. I think that the relative contrast functions are the only way to effectively analyze this issue.
Re; slide 22, where the eye's line would lie between those two plotted lines is anyone's guess as no frequency data is given for either line, which would be necessary to make a meaningful interpolation.
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Mardi
4" achromat, ETX-70, 8"cat.
Whitepeak Lunar Observatory Website
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
Hi Mauro,
No, i understood what you were trying to show and i knew it was not that a 16" would achieve full resolution. I just don't agree that one can relate seeing aberrated point source airy pattern characteristics with the resolution of an extended target (many conflated airy patterns) and get anything meaningfully accurate as a result. Double stars yes, planets no way. I think that the relative contrast functions are the only way to effectively analyze this issue.
Re; slide 22, where the eye's line would lie between those two plotted lines is anyone's guess as no frequency data is given for either line, which would be necessary to make a meaningful interpolation.
A am not sure what you are meaning.
1) The Point Spread Function and the Modulation Transfer Function are two representations of the same thing, one in the space domain, the other in the frequency domain. If you prefer I can produce the MTF functions, but as I said the MTF of the larger aperture stands above (for the same reason that its PSF has less moment of inertia). In any case the image of a planet is the convolution of the PSF (every point of the source maps onto a corresponding PSF distribution, thus the more compact the PSF the lesser the original point images are smeared).
2) I do not understand your comment about slide 22. Slide 22 shows that for long time exposures the resolution achieved by a scope D=r0 il less than the asymptotic resolution (D=infinity). Resolution still improves if the diameter is greatedr than r0, but there are diminishing returns. For short term exposures returns are greater. Now, it is true that there is no line for the eye. But depending on which is the "exposure time of the eye" we can at least understand that resolution will improve somewhat in between the two curves. Thus a scope with a diametr ~2~4 r0 (where the r0 to be considered is that of top 10-20 percentile nights) is indeed exploitable. BTW I found that, at least here in the Padana plate, there are 20-30 nights per year with a ~1" seeing (average seeing between 1.5" and 2"). Thus a 20" scope is fully justified.
Edited by Mauro Da Lio (01/07/08 12:49 PM)
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ozzie
super member
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Posts: 136
Loc: Panama City, Panama
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i know i came late to the discussion... but this is a honest sketch of how do u see mars thru a 10".. at least this is what i see
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Zhumell 10" Dobsonian
Bushnell 10 x 50 Binoculars
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walt r
Post Laureate
Reged: 02/13/07
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Loc: Doylestown, PA
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That's close to what it looks like in my 18" when the seeing is steady. Great sketch Ozzie.
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Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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photonovore
Moonatic
Reged: 12/24/04
Posts: 2792
Loc: tacoma wa
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mauro, what i see you are doing is trying to dial in an encircled energy figure from static psf simulations and then derive resolution upon an extended surface from that. The problem is that while this method could possibly offer useful information for *two* 100% intrinsic contrast point sources vis a vis relative contrast *between* those points at the higher frequencies that are accessible in point source targets of such high contrast, these simulations do not relate to targets that are intrinsically _low_ contrast. The MTFs that could be generated from encircled energy plots of high intrinsic contrast targets don't offer any useful information on the contrast coefficients necessary to analyze targets lacking high intrinsic contrast. To accomplish the latter you must plot the MTFs onto an expanded scale cooresponding to the intrinsic contrast ranges actually found within the target--as i did earlier--and use that to examine the realtionships and effects of relative aberration seeing etc. You are looking at 100% intrinsic contrast relationships when you need to be looking at 10% and lower intrinsic contrast relationships (the planetary high resolution contrast range). 100% intrinsic contrast just does not exist on the planets, not even close; basing your analysis upon a range of contrast coefficients that are simply non-existent upon the targets of interest (planets) is just not a valid way to analyze the question. Simply put, it is not possible to effectively examine _low_ intrinsic contrast relationships through using *high* intrinsic contrast simulations. This is because the frequency of focal plane resolution of high intrinsic contrast targets lies around 90cycles, on the tail end of the MTF. In low intrinsic contrast targets the same resolution is found around 50 cycles and below at mid mtf and lower--all the mtf upwards from that is unresolvable. You are trying to use that range and you cannot do so--it just isn't there to use when the target has low intrinsic contrast.
Analyzing the high contrast MTF curve (or high contrast diffraction images) would indicate the highest resolution is at ~90 cycles --and below the effects of most aberration, out at the tail of the curve. Analyzing the low contrast MTF shows that the peak resolution has moved to the -middle- of the MTF curve at about 50 cycles, the region where aberration has the most deleterious effect. You should be able to imagine how misleading (by overestimation) it would be to use the high contrast curve to try and estimate the resolution of a low contrast target--and how doing so would also underestimate the effects that CO, seeing and aberration in general have upon low intrinsic contrast resolution as well. When i did the quick & dirty comparative MTF representing the low intrinsic contrast mtf range in an earlier post, i merely expanded the 10% contrast range from the thin slice on the bottom of a 100% mtf (as seen above) to the full scale in order to enable some clarity so as to be able to see more clearly what is going on.
Since seeing (along with CO and SA etc) primarily affects the belly" area of the mtf curve far more than the high frequency tail, it is to be expected that point source target resolution will be less affected by poor seeing than extended images having low intrinsic contrast. And this is just what an analysis of these comparative MTFs shows to be the case.
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Mardi
4" achromat, ETX-70, 8"cat.
Whitepeak Lunar Observatory Website
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
... these simulations do not relate to targets that are intrinsically _low_ contrast.
I showed the Point Spread Functions because I thought the were easier to understand. The MTFs are the fourier transform of those functions and holds exactly the same information, but presented in another flavour. Maybe one might prefer the latter.
The radius that holds a given amount of encircled energy does not tell much about how the light is distributed inside it (It was not my intention to point the radius of the PSFs as meanikngful, rather to point the light distribution).
Here is an example.
The first row represents a scope in bad seeing conditions, with D ~4 times r0 (based on the number of speckles). The first picture at the left is the turbulent wavefront (according to Suiter's model) as seen by the full aperture. The centre picture shows the PSF. The right picture the MTF.
The second row shows the same things but for a scope 1/4 the original diameter (D ~1 r0). As seen only a little part of the turbulent wavefront is now seen by the 1/4 aperture scope. As a consequnce the rms and ptv values of the turbulent wavefront are reduced and -note- the maximum and minimum path differences (brightest white and darkest black) are left out. In fact, as the centre picture shows, the PSF of the reduced aperture is only slightly perturbed. Yet, the light is less concentrated, both the brightest part and the fainter halos. The bottom right MTF confirms that: As seen the MTF curve of the smaller scope stands below.
The first scope could be representative of ~400 mm diamter in poor seeing conditions -barely acceptable for me- (I often see better, thus the difference is often greater). The second scope might be a 100 mm diameter in the same case.
In such poor seeing conditions the larger scope is not worse than the smaller one. But sometimes (not so rarely) seeing is better and when that happens only the big gun can show more.
Edited by Mauro Da Lio (01/08/08 05:15 PM)
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photonovore
Moonatic
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You are indicating that the smaller aperture's mtf is impacted by the given level of seeing aberration as is the larger aperture--which is *not* the case! The smaller aperture's Airy disk, being several times larger than the large aperture's, is also large enough to contain the given level of seeing aberration within it, therefore no degradation of it's Airy disk is extant.
Example: in 1" arc seeing the seeing disk is 1" arc FWHM in diameter. The Airy disk of a 4.56" telescope *contains* this level of aberration completely within it's confines. This is why a 4" telescope is not seeing aberrated in 1"arc seeing and can access its diffraction limit of resolution. But a 18" telescope, having a native airy disk diameter 4 times smaller, is extremely seeing impacted by the presence of a seeing disk four times larger than its native airy disk.
Blue line= unaberrated (seeing unlimited) MTF curve perfect unobstructed telescope of aperture x (say 18inches)
Red line= unaberrated (seeing unlimited) MTF curve perfect unobstructed of aperture x/4 or 4.5inches. (Remember, the bottom scale of the MTF represents actual resolution in lp/mm when used to plot multiple apertures.)
Black line=seeing aberrated mtf of x aperture (of blue line)
Your error lies in applying equivalent & proportionate seeing wavefront error to both the small & large apertures. In fact the seeing error at a given FWHM seeing state yields a wavefront error which is proportionate to aperture as a net wavefront error. In order for seeing to create an impact upon the MTF it must induce an error of an amplitude sufficient to exceed the diameter of the Airy disk itself.
IOW, you cannot apply a "1/4 wave of seeing"(or whatever) equally to variant apertures, as you are doing, and expect an accurate result. In 1"arc seeing the 4" aperture will suffer no degradation in it's native resolution--it's MTF will remain *unaffected* (red line) and it will be able to resolve at it's diffraction limit at all frequencies!!; whereas a 16" aperture in the same seeing will have it's resolution degraded by a factor of four, resulting in an extremely impacted mtf (black line) with a corespondent frequency dependent reduction in it's native resolution.
Above is the case of high intrinsic contrast targets (100% maximum relative contrast) Note the much increased resolution of the large aperture, even when severely seeing impacted, over the smaller aperture. This is because seeing impacts higher frequencies less than mid frequencies. (very important to recognize!) This illustrates the case of double stars. This is what you have been looking at all along--but you cannot translate this resolution relationship to extended (low intrinsic contrast) targets because it is not the same relationship:
Above we have the case of the _low_ intrinsic contrast target (max intrinsic relative contrast 10%) Note how the relative resolution of the larger aperture is now severely impacted compared to that of the smaller aperture. Note as well that is additional aberration is added to the larger aperture, it could well result in a net deficit in resolution to smaller apertures. Note also that the much reduced contrast threshold that electronic imaging allows (redraw green line in the low contrast diagram to 1-2%) results in a substantial increase in resolution advantage for the larger aperture. This accounts for the excellent performance of larger apertures as used in electronic imaging--as well as why their results in that venue cannot be conflated with their visual performance.
I am really sorry...but i think i am running out of ways to explain this any more clearly than i have... 
BTW, the entire interpretation between MTFs of varying aperture and high & low intrinsic contrast that i have been presenting all along is taken practically verbatim right out of Rutten & Venrooij's book Telescope Optics, sec. 18.7 "Obstructed Telescope's for Visual Use". The seeing/resolution/aperture relationships from Cavadore (251 * Lambda / ro (ro in mm, lambda in µm). Understand, I am not trying to reinvent or reinterpret anything in any sort of "new" way at all, but rather I have simply been trying to explain what is accepted and known in the literature on this subject.
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Mardi
4" achromat, ETX-70, 8"cat.
Whitepeak Lunar Observatory Website
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
Your error lies in applying equivalent & proportionate seeing wavefront error to both the small & large apertures
No. I first produced a wavefront according to Suiter's model (large scale eddies are stronger than smaller ones) and then sampled the corresponding part according to the aperture (see left figures: the smaller scope sees a lot less ptv and rms seeng, only the part that is intercepted by the smaller aperture, see figure).
Thus the Large scope was subject to a lot of degradation. The smaller scope only a little. But Even if it were not degradated at alla (which is not possible because any time there are large eddies there also are smalle ones) it would not be better. And that in the hypotesis that the seeing has exatly the intensity which damage the big and not the small. Worse seeing would affect both and the small will continue lagging (but who care observing in such bad conditions?). Better seeing wuold otherwise leave large gaps between the two scopes, which is what happens in many nights per year, and in many moments during the same night.
The above simulations is very unfavourable to the big gun. Here is the same situation but now I have averaged 30 frames. It is undoubtely that the light spreading of the averaged 30 frames is favourable to the big gun (this is in perfect agreement with curve of long term expoasures in said slide 22).
Quote:
IOW, you cannot apply a "1/4 wave of seeing"(or whatever) equally to variant apertures, as you are doing..
NO. I did not apply the same rms to both. The rms is different. It is whta results from the sampling of a larger turbulent wavefront. It was the rms of the part of the wavefront intersected by the aperture. If you look at the pictures to the left you see what part of the turbulent front is seen by each scope. You can even read the white and balck levels (pick rhe corresponding point on the first picture, the second has been represented with rescaled gray levels because levels are automatically mapped onto 0-22 interval by the plotting algorithm, the turbulence value are not changed) and estimate the ptv of the smaller scope compared to the larger one.
Edited by Mauro Da Lio (01/09/08 11:07 AM)
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
Note how the relative resolution of the larger aperture is now severely impacted compared to that of the smaller aperture.
This is the worst scenario where the seeing reduces the differences to a minimum (but still the big is better). I provided this scenario only to show that the smalle never can surpass the biger. That exact amount of seeing is unlikely. More means that observing is useless (in both scopes). Less means that there is a gap o 50-100% in favour of the big.
Quote:
I am really sorry...but i think i am running out of ways to explain this any more clearly than i have...
I perfectly know that for low contrast objects I have to look at values of MTF about ~0.5 (5% for an object with original contrast of 10%9. But the point is that the MTF curve of the big scope is better for any contrast level, the fact it is only marginally better in this example is because the amount of seeing was chosen to make the maximum damage to the big and the least to the small (in a word the worst scenario). Often, very often thecase is better.
Edited by Mauro Da Lio (01/09/08 06:28 AM)
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
Example: in 1" arc seeing the seeing disk is 1" arc FWHM in diameter. The Airy disk of a 4.56" telescope *contains* this level of aberration completely within it's confines. This is why a 4" telescope is not seeing aberrated in 1"arc seeing and can access its diffraction limit of resolution.
Wrong. Seeing is equivalent to lesser than perfect wavefront. Altough not enough to disrupt the diffration pattern, the imperfect wavefron lower the strehl ratio and moves light from the Airy disk to the ring. Thus the MTF goes down (a lot before the disk breaks).
The curve was computed on a perfect scope subject to the wavefront error sampled by its aperture.
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calibos
Carpal Tunnel
Reged: 11/18/07
Posts: 1744
Loc: Ireland
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I ask a simple question and get a simple answ........  This discussion has gotten so over my head its at the Zenith......where mars is at my latitude......and all I can see is a white disc.... Hey, the thread has come full circle!!
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Keith D.
16" Meade Lightbridge - See Here (Starting Re-build Soon)
Moonlite CR2 Motorized Focuser with Rigel nFocus and Filterslide (2" Orion Variable Polorizer,UHC,H-Beta,Lumicon OIII)
Stellarvue F80M2 80mm Finder
Dewbuster and DewNot Dew Control
Servocat & SkyCommander & SkyVoyager/SkyFi/iPhone Goto
Howie Glatter Holographic Laser Collimator and Blug
Televue 3.7sx,6,8,10,13,17 & 21mm Ethos + 31mm Nagler
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David Knisely
Postmaster
Reged: 04/19/04
Posts: 13646
Loc: southeastern Nebraska
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Quote:
I ask a simple question and get a simple answ........ This discussion has gotten so over my head its at the Zenith......where mars is at my latitude......and all I can see is a white disc.... Hey, the thread has come full circle!!
OK, those guys are having a "discussion" which may or may not have much to do with what you personally see. The color one sees will vary depending on the observer, as some people don't see much initially. Under really good conditions (and with enough power and some experience), you may see something kind of like what I show below, but again, it takes some time to eek-out all the detail. I hope this answers your question. Clear skies to you.
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David W. Knisely . . . . . . "If you aren't having fun in this hobby, you aren't doing it right."
Hyde Memorial Observatory
http://www.hydeobservatory.info
Prairie Astronomy Club
http://www.prairieastronomyclub.org
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walt r
Post Laureate
Reged: 02/13/07
Posts: 3611
Loc: Doylestown, PA
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That's really close David.
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Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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photonovore
Moonatic
Reged: 12/24/04
Posts: 2792
Loc: tacoma wa
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Mauro, ah, now i see what you did. My apologies. i see that the significant difference between our method/interpretations is in the estimation of seeing impact upon the smaller aperture; a bit less than perfect in yours, where i drew mine as perfect, which makes a difference, true enough. I ran this scenario through aberrator v.3 and got a similiar result to yours along the 3-5% line--better resolution for the larger scope, seeing aberration included for both. (you do realize that my analysis also showed slightly better resolution for the larger scope as well, no? Our difference turns out to be merely one of degree.)
Ok...
...until i added an obstruction (as is found on virtually any large aperture telescope.) You are comparing two unobstructed optics. The actual question here revolves around small unobstructed vs. larger obstructed. That makes a difference.
Try adding a typical 35% central obstruction to the otherwise perfect larger scope's mtf-- and let's see what happens. I already tried it using aberrator--and doing so further displaces the MTF of the larger scope to the left as one would expect. I am curious as to how much it does so-- by your calculation?
Edited by photonovore (01/09/08 07:57 PM)
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calibos
Carpal Tunnel
Reged: 11/18/07
Posts: 1744
Loc: Ireland
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Quote:
Quote:
I ask a simple question and get a simple answ........ This discussion has gotten so over my head its at the Zenith......where mars is at my latitude......and all I can see is a white disc.... Hey, the thread has come full circle!!
OK, those guys are having a "discussion" which may or may not have much to do with what you personally see. The color one sees will vary depending on the observer, as some people don't see much initially. Under really good conditions (and with enough power and some experience), you may see something kind of like what I show below, but again, it takes some time to eek-out all the detail. I hope this answers your question. Clear skies to you.
David,
My comments were just a tongue in cheek way of making light of the fact that the current "discussion" is way over my head. I wasn't trying to reclaim ownership of "my" thread. Its "a" thread not "my" thread, where my questions have been answered to my complete satisfaction to an extent that was way and above the call of duty and now the thread has become a convenient location for several optical experts to have a serious discussion/debate on the subject. I know the guys are no longer discussing these highly technical issues for my benefit. That probably didn't come across too well in my last post I guess.
Keith
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Keith D.
16" Meade Lightbridge - See Here (Starting Re-build Soon)
Moonlite CR2 Motorized Focuser with Rigel nFocus and Filterslide (2" Orion Variable Polorizer,UHC,H-Beta,Lumicon OIII)
Stellarvue F80M2 80mm Finder
Dewbuster and DewNot Dew Control
Servocat & SkyCommander & SkyVoyager/SkyFi/iPhone Goto
Howie Glatter Holographic Laser Collimator and Blug
Televue 3.7sx,6,8,10,13,17 & 21mm Ethos + 31mm Nagler
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
Mauro, ah, now i see what you did. My apologies. i see that the significant difference between our method/interpretations is in the estimation of seeing impact upon the smaller aperture; a bit less than perfect in yours, where i drew mine as perfect, which makes a difference, true enough. I ran this scenario through aberrator v.3 and got a similiar result to yours along the 3-5% line--better resolution for the larger scope, seeing aberration included for both. (you do realize that my analysis also showed slightly better resolution for the larger scope as well, no? Our difference turns out to be merely one of degree.)
Ok...
...until i added an obstruction (as is found on virtually any large aperture telescope.) You are comparing two unobstructed optics. The actual question here revolves around small unobstructed vs. larger obstructed. That makes a difference.
Try adding a typical 35% central obstruction to the otherwise perfect larger scope's mtf-- and let's see what happens. I already tried it using aberrator--and doing so further displaces the MTF of the larger scope to the left as one would expect. I am curious as to how much it does so-- by your calculation?
I used the same wavefront and then sampled it according to the apertures because every time a turbulent wavefront is (randomly) generated a slightly different effect may be obtained. So I wanted to compare the two apertures on the same wavefront. I think it is not that easy to compare two scopes with the same wavefront in aberrator (is it?).
Of course the analysis focuses on this question (the effect of CO in larger scopes is to be verifyed):
- when aperture is masked there are two opposing effects: 1) less wavefront is intercepted, 2) the interference base (diameter) shrinks and lights spreads. The question is which prevails?
The answer seems to be that the resolution always improves with diameter (according to slide 22) but when D=~ro the improvements starts to be less than proportional and then at ~3-5 r0 the returns are quickly diminishing
In the equations there are two factors that have large influence:
1) the model of turbulence. We know that, for flows far from turbulence ources the isotropic Kolmogorov model is a good description. It foresees that the power spectral density of the turbulent kinetik energy decreases according to a given function of spatial frequency. That in turn means tha the rms of turbulence wavefront errors is proportional to (D/r0)^(5/6). This holds (?!?) for the Suiter's generated turbulent wavefront (at least I corss checked and it seems true). The 400 mm was abut 0.3 rms and the 100 mm was about 0.1 (which means ~pickering 6 for the 100 mm). BTW I have rewiewed my observation logs and it seems I have pickering ~5 not so rarely in 10" scope. Which means a rough estimate of r0 as good as 16 cm. Jet stream rarely affects Northen Italy and I do not live in mountains.
What happens if the power spectral density does not follow Kolmogorov distribution (which may happen, especially between building etc).
2) the actual value of r0. Chosing r0 we tend to flatten the performance of larger scopes towards r0. So we actually minimize the differences of scopes larger than r0 and make them similar to r0 (only slightly better). That was the case of the example. However r0 varies moment to moment and night to night. So it seems reasonable to choose scope diameter according to the 20-30 quantiles of better nights. In that case there may hppen moments in which we can exploit the larger diameter,
Edited by Mauro Da Lio (01/10/08 04:41 AM)
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walt r
Post Laureate
Reged: 02/13/07
Posts: 3611
Loc: Doylestown, PA
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Quote:
Try adding a typical 35% central obstruction to the otherwise perfect larger scope's mtf-- and let's see what happens.
Since this thread was discussing a large aperture Newtonian, how about using a realistic CO of 18 to 20%. A 35% CO is more like a SCT or other catadioptric scope.
Interesting discussion.
--------------------
Walt
Obsession 18" f/4.45 #1370 AN/SC
MK67 Deluxe 6" f/12 Mak-Cass, Super Polaris GEM, JMI MicroMax DSC
DIY 60mm f/6 Achromat
Cookbook 245 CCD
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Mauro Da Lio
sage
Reged: 09/12/04
Posts: 382
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Quote:
Try adding a typical 35% central obstruction to the otherwise perfect larger scope's mtf-- and let's see what happens. I already tried it using aberrator--and doing so further displaces the MTF of the larger scope to the left as one would expect. I am curious as to how much it does so-- by your calculation?
The picture at upper left shows (better to worse) a) full aperture 0.3 rms; b) same as a but 20% obstruction (we are speaking of large dobs) ; c) 1/4 aperture.
That is what is produced for a given randomly generated wavefront. However, another try might produce the extreme case at upper right. In fact, every time a wavefront is produced, its effect may change depending on its actual shape and also, for the reduced aperture, it might happen that the relevant cross section is lucky compared to the full wavefont.
Thus the bottom picture shows 10 different frames, to get an idea of how the mtf changes for the three pupils.
The balck line is the full aperture non obstructed scope. The dashed red nearby line is the same wavefront but with 20% CO. There also is a corresponding green line that represents the mtf for the same wavefront but limited to 1/4 diameter.
As seen the small aperture has lesser variations (frame to frame) than the bigger ones. On average the obstructed scopes are a bit worse than the corresponding non-obstructed case.
But, and here are the interesting points:
a) the best lucky cases of the reduced aperture (green curves), are far from the mean mtf of the large scopes.
b) for the large scopes there are "lucky" moments that the small one cannot hope. Even if these moments are not considered, the average mtf is better.
c) at the highest contrast levels (0.7-1) , spatial frequencies 0-0.05 the worst case of the big scope is better than best case of the small one; in the medium contrast levels (0.5-0.7) there is only 1 case of the obstructed scope that is worse than the *best* case for the small.
How better is the big gun? If we look, for exmple, at the contrast level 0.5, we see that the small scope resolution ranges from 0.075 to 0.1 (spatial frequancy). The big scope ranges from 0.085 to 0.23. The ratio between the lucky moments is 0.23/0.10 = 2.3 times!! The ratio between the unfortunate moments is 0.085/0.075 = 1.1.
And all this happes for the amount of turbulence which most flattens the differences.
Edited by Mauro Da Lio (01/10/08 09:55 AM)
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Rick Woods
Postmaster
Reged: 01/27/05
Posts: 11940
Loc: Inner Solar System
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Calibos,
For Mars, maybe you should be looking into a couple of good quality planetary eyepieces. TV plossls and UO orthos are reasonably priced, and very highly regarded. You want high contrast and few glass elements. Hyperions may be great, but they have 8 elements - way too much for a planetary EP.
Your scope is what it is - none of the graphs shown here will change that. But eyepieces, you can change. I'm not sure what sizes the TV plossls come in; but if you can snag a 5mm or 6mm plossl or ortho, it might help a lot.
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- Rick
14" LX200
Cactus Patch Observatory
"The four points of the compass be logic, knowledge, wisdom, and the unknown. Some do bow in that final direction. Others advance upon it. To bow before the one is to lose sight of the three."
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calibos
Carpal Tunnel
Reged: 11/18/07
Posts: 1744
Loc: Ireland
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Quote:
Calibos,
For Mars, maybe you should be looking into a couple of good quality planetary eyepieces. TV plossls and UO orthos are reasonably priced, and very highly regarded. You want high contrast and few glass elements. Hyperions may be great, but they have 8 elements - way too much for a planetary EP.
Your scope is what it is - none of the graphs shown here will change that. But eyepieces, you can change. I'm not sure what sizes the TV plossls come in; but if you can snag a 5mm or 6mm plossl or ortho, it might help a lot.
I have a 10mm Sirius Plossl that came with the scope and a barlow 2x. I thought I tried them in combo for 5mm. Can you beleive I am not sure!! Maybe I tried that combo on Saturn. Don't remember it making a difference there but then again the colours on Saturn are supposed to be a lot fainter anyway. Will try the combo again on Mars tonight if the Skies co-operate.
[Sigh] What I wouldn't give to see the level of colour and contrast displayed in Davids and Ozzies simulated views above!! 
--------------------
Keith D.
16" Meade Lightbridge - See Here (Starting Re-build Soon)
Moonlite CR2 Motorized Focuser with Rigel nFocus and Filterslide (2" Orion Variable Polorizer,UHC,H-Beta,Lumicon OIII)
Stellarvue F80M2 80mm Finder
Dewbuster and DewNot Dew Control
Servocat & SkyCommander & SkyVoyager/SkyFi/iPhone Goto
Howie Glatter Holographic Laser Collimator and Blug
Televue 3.7sx,6,8,10,13,17 & 21mm Ethos + 31mm Nagler
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