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Saturn – Came Good This a.m.....

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#1 David Gray

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Posted 16 May 2019 - 04:24 PM

Been having some great steady seeing for some weeks now; but with all the low-lying morning mist Saturn was just too dim even for the D-K – even Jupiter was. 

 

At last this early dawn I did not get out of bed in vain (these many morns now). Too late for Jupiter.....was too close to the houses.  Saturn at first affected by tremulous air, but of the kind that long experience has taught often comes good – stunning when it did.  Much like I briefly caught Jupiter two mornings ago.......soon thwarted by cloud that time tho’....

 

A marked indent in the south edge of Saturn's NEB(S) was seemingly caused by an indefinite light oval in the EZ(N)

 

With all the recent steady (misty) conditions a lot of double star stuff has been recorded – many, normally very tough ones, fell to the D-K – and not forgetting the mighty old 3-incher.....When time will maybe put a few together and post here........when/if time.......tongue2.gif

 

Had hoped to add Jupiter to this report post-midnight but looking like cloud – maybe showers – coming.........so off to bed after a long – busy as ever – day; but might get Jupiter and/or Saturn if it clears before dawn.....tongue2.gif......... 

 

Dave.

SAT 2019 May 16.jpg


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#2 frank5817

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Posted 16 May 2019 - 11:27 PM

David excellent sketching,

 

The north polar region is just covering the back of the rings.

 

Frank :)



#3 Special Ed

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Posted 17 May 2019 - 09:32 AM

Beautiful, Dave.  smile.gif   Lots and lots of subtle detail.  bow.gif 

 

How can retired people be so busy all the time?  lol.gif 


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#4 niteskystargazer

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Posted 17 May 2019 - 02:05 PM

Dave,

 

Very nice sketches of  Saturn – (Came Good This a.m.....) smile.gif .

 

CS,KLU,

 

thanx.gif ,

 

Tom



#5 Ivan Maly

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Posted 17 May 2019 - 08:33 PM

Great work!! What kind of apodizer is that?



#6 stanislas-jean

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Posted 18 May 2019 - 04:47 AM

ADC use makes in addition excellent views under moderate seeing.

Excellent report David, very detailed. Here with 4-5° more elevation this is still poor in a 150mm.

Good skies.

Stanislas-Jean



#7 David Gray

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Posted 18 May 2019 - 08:45 AM

Many Thanks Frank, Michael, Tom, Ivan, Stan and those who Liked.......

 

Ivan Maly: will get back asap about the apodizer when I locate some files for a photo.

 

Seems we are in for a prolonged cloudy spell here; so given the low position of the planet, this nice view could be my highlight of the apparition.  Systematic following of activity and/or developments is near hopeless at <15º-20º altitude

 

Why I’m saying highlight is after seeing the linked views on ALPO-Japan: those first two (Ohsugi & Kanagawa) are one rotation earlier than mine; which seem to indicate that EZ(N)/NEB(S) indentation/bay I described.........

 

“A marked indent in the south edge of the NEB(S) was seemingly caused by an indefinite light oval in the EZ(N)”.  Initially I had noted this as a darker hump on the belt then better moments allowed sight of the weaker leading/leftward one with a possible ghostly EZ(N) light oval suggested.

 

http://alpo-j.asahik...19/s190515z.htm

 

This seems more confirming when comparing at Kanagawa’s image, ~25 minutes after Ohsugi’s apparently showing the feature having moved past the CM.

 

Here attached the original rendering with the ‘oval’ outlined.

SAT 2019 May 16 II.jpg

As Stan indicates the ADC (Atmospheric Dispersion Corrector) is proving a boon to continue my quest for rendering colours more surely – NB I didn’t say *exactly*: a futile pursuit....!!  But I am now getting more localized hue-differentiating that I would have given up on by now with the low altitude.

 

A Link to a recent thread here shows nicely with the Jupiter animation how we can judge a belt as too red or blue.  https://www.cloudyni...w/#entry9372547

 

The dispersion not only affects disk-edges but wherever there is a light/dark interface - add some seeing effects......!  Even worse with finer detail where hue-modification manifests in unseen ways.......

 

Edit: just to add there is other hue modification - lo-altitude reddening effects that the ADC does not correct but will convey faithfully!  That reddening was minimal on the date reported here; to witness that variation note the rising/setting Sun/Moon over a period of days/nights!

 

Dave.


Edited by David Gray, 18 May 2019 - 09:12 AM.

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#8 Special Ed

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Posted 18 May 2019 - 09:16 AM

Dave,

 

Nice catch on that oval causing that indentation on the NEBs--the images from ALPO-Japan confirm it to my eye.  smile.gif 


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#9 Susan H

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Posted 18 May 2019 - 09:19 AM

Excellent work, David. Great detail of the gas giant and it’s rings. Saturn is one of my favorite targets when viewing. When people look at it through my scope it just blows them away. Keep up the good work. Clear skies. 


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#10 David Gray

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Posted 18 May 2019 - 09:38 AM

Thanks Michael, Susan.........

 

Catching Saturn that morning, the magic still not jaded by the many

hours/years of viewing it telescopically..........nearly two orbits now.

 

Dave.


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#11 David Gray

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Posted 18 May 2019 - 09:44 AM

Great work!! What kind of apodizer is that?

Thanks Ivan........

 

By chance I was led to a description and photo of the apodizer on an earlier thread.

 

https://www.cloudyni...iges/?p=8511339

 

Also detailed is my method of cancelling dispersion just prior to getting the ADC into use.

 

Dave.



#12 Ivan Maly

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Posted 18 May 2019 - 01:52 PM

Thanks! So it's a ring suppressor, I see. Very cleverly implemented. I should try stuffing that material into the dew shield of my Mak.



#13 Magnetic Field

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Posted 18 May 2019 - 02:06 PM

Been having some great steady seeing for some weeks now; but with all the low-lying morning mist Saturn was just too dim even for the D-K – even Jupiter was. 

 

At last this early dawn I did not get out of bed in vain (these many morns now). Too late for Jupiter.....was too close to the houses.  Saturn at first affected by tremulous air, but of the kind that long experience has taught often comes good – stunning when it did.  Much like I briefly caught Jupiter two mornings ago.......soon thwarted by cloud that time tho’....

 

A marked indent in the south edge of Saturn's NEB(S) was seemingly caused by an indefinite light oval in the EZ(N)

 

With all the recent steady (misty) conditions a lot of double star stuff has been recorded – many, normally very tough ones, fell to the D-K – and not forgetting the mighty old 3-incher.....When time will maybe put a few together and post here........when/if time.......tongue2.gif

 

Had hoped to add Jupiter to this report post-midnight but looking like cloud – maybe showers – coming.........so off to bed after a long – busy as ever – day; but might get Jupiter and/or Saturn if it clears before dawn.....tongue2.gif......... 

 

Dave.

attachicon.gif SAT 2019 May 16.jpg

Very impressive.

 

Aperture rules!

 

Are you in the UK then. Typed in Ower Yonder. Not so far away were I am. So much to the old tale that a large aperture will always suffer from mediocre seeing.


Edited by Magnetic Field, 18 May 2019 - 02:18 PM.


#14 David Gray

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Posted 18 May 2019 - 02:54 PM

<"Thanks! So it's a ring suppressor,">

 

Yes Ivan suppressing the Airy rings, where most of the seeing agitation is in mid-scale seeing, steadies the image.

 

For some time due to some experimenting I have become convinced that a domed/hemispherical mesh such as a food strainer is the ‘proper apodizer’.  The stepped 3-layer one being a 2D compromise: the dome as the scope sees it is smoothly graduated/dimming toward its edge due to foreshortening.

 

Here is one of a few discussions I’ve had......still not made one...........

 

https://www.cloudyni...ies…/?p=7205376

 

Cheers,
Dave.


Edited by David Gray, 18 May 2019 - 02:57 PM.

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#15 Tyson M

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Posted 18 May 2019 - 03:47 PM

Superb observations! 



#16 David Gray

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Posted 18 May 2019 - 05:59 PM

Thanks Tyson M..........

 

Also to expand on Apodizing I should perhaps add........

 

I should have clarified *mid-scale seeing*: being that where there is still a discernible/steadier central disk as with Pickering 4-7 but still some significant disturbance of the rings.  In short no clear (over-agitated) central disk no real apodizing gain; and better than Pickering 7 little further improvement other than as a neutral filter – which at the other end might also help in some types of poor seeing.

 

To get the gist see Damian Peach’s, now classic, seeing animation.........http://www.damianpea...m/pickering.htm

 

What that has to do with planets is that the scope renders them as a multitude of overlapping Airy Disks.  In the main the device does not work well with the Moon as there is too much overlap of apodizing diffraction effects from the disparate brighter regions in the field reducing contrast – think of having a dozen Jupiters in the field........!  But I have determined that the ring suppressing is in effect by noting the apparent stilling-degree of the seeing albeit offset by the aforesaid contrast loss.  Tho’ regions on the terminator or crescent cusps (isolated mountains etc.)  have been seen sharpened to advantage with the device.

 

I suspect not taking account of the type seeing explains why some have dismissed the gain as imagined or whatever: it's not an omnipotent magic cure!  Of course some just do not like the surrounding diffraction 'mess'........I'm too concentrated on eking out planetary detail to care or even notice it......If I want to see a pretty/'truer' scene (or faint moons) I take it off - easy as it just drops-in/lifts-out-of the end of the scope - no affixing needed and weighs a few ounces.

 

As I have said before: the guys who do the numbers are missing something somewhere - learned dissent or not........

 

Dave.


Edited by David Gray, 18 May 2019 - 06:08 PM.


#17 Ivan Maly

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Posted 18 May 2019 - 11:32 PM

I think all of this is pretty clear. Not sure who did what wrong numbers; if need be, I could easily simulate the whole thing on a computer precisely, but qualitatively there is nothing mysterious or equivocal about the effect of apodizers, at least the radially monotonic ones like you have, and how the ring suppression interacts with turbulence and object size. What I did not know is that someone in the amateur world actually put it into practice so simply and successfully!


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#18 David Gray

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Posted 19 May 2019 - 07:43 AM

Thanks Ivan, so refreshing to read your remarks and insights: I was soon coming to realize your knowledge on the matter, but thought it as well to aim my clarifying at the wider audience here - as with some of this........

 

The guys missing something in their critique I suspect is possibly failure to evaluate over a range of seeing.  As I found it usually starts to fail in poor/very poor seeing and offers decreasing gain in the better end of the scale.  It’s that mid-scale where I find it works most effectively. I say *mid-scale* to avoid the more ambiguous *average seeing* which would vary location to location.  As it happens, in my location mid-scale is the average seeing..........!!  

 

As a Secondary School (UK) Non-Diploma drop-out I do not possess the science of those guys – purely empirical/suck-it-and-see being my approach.

 

A history of my apodizing experience..........

1963 (serendipity!): looking at Jupiter (3” scope) from the stair-landing window the wind blew the hitched-back net curtain across the scope and I was astonished/intrigued by the sharpened view. As the curtain fluttered the *rainbow* Diffraction ‘Mess’ varied from striking to gross but as long as Jupiter was  bright enough it remained tack-sharp.

1991: that curtain effect being in my mind to follow up on all those years then one night with Mars & Jupiter out of sheer whim I hung the fireguard over the end of the 16.3” D-K and WOW!!  So a piece cut out of the guard (we had a spare) became the apodizer for a few years.  Then an edge-damaged 18” (perfect drop-in fit!) stainless steel flour sieve (see attached pic) got years of use till the proper 3-layer one I still use. 

 

Now of course the domed mesh (~1mm +/- 0.2mm as in other versions) in prospect – when time.....

 

Shortly after the fireguard experience I sent BAA veteran Alan W. Heath (then Saturn Section Director) a piece of net curtain and he swore it seemed to tame the seeing and still uses it to date on his 10” Newt.

 

His successor David Graham, on a visit, got a look through the D-K at Saturn with the apodizer (flour sieve) applied and immediately exclaimed “It works!!!”  Both are very seasoned critical observers of planets – Alan started when I was still at school (1953)!

 

Dave.

DK Apods.jpg


Edited by David Gray, 19 May 2019 - 07:47 AM.


#19 Ivan Maly

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Posted 19 May 2019 - 12:20 PM

Makes sense too. Mesh, in addition to being a material (not that I ever thought about this possibility before!) that you can fashion an apodizer from (apodization as such being achieved through graded aperture shading), is also a multi-edge aperture mask that can work by diffraction even if it's just one layer of uniform mesh over the aperture. This and the ring suppression by apodization are two different effects, but both can work in theory against turbulence under specific conditions. The diffraction especially does not improve the total view in the eyepiece (kind of like low-Strehl optics), but can pull intensity out of the central pip and into a relatively smooth blur that doesn't boil with the turbulence because it is larger than the turbulence. So the contrast may be down even within a small planet disk, but the signal to noise as perceived by the observer may at the same time be up. To achieve the uniform diffraction pull, a hexagonal mesh should be better than a rectangular one, and overlapping layers of hexagonal mesh should be about ideal. Which is exactly what I see in your pictures!

 

So a mesh apodizer may not just be a low-tech solution to the problem of manufacturing an apodizer, but in this application actually doubly clever.


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#20 azure1961p

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Posted 21 May 2019 - 05:32 PM

Dave, This is beautiful.   

 

Something that goes unmentioned a lot of times with the big scope is the resolution of the outter edge of the A ring.  Smaller scopes will show a more subdued A ring where it tends to terminate with less certainty than you show here.  Infact exactly where Enckes Division is, is exactly where it tends to lose it's punch right before deep space.  Not to say that the rings don't focus beautifully sharp in say, my C90 or 70mm achro, just that upon closer high power inspection, just when you need that extra light at that magnification, the dimness belies the limits of the very small aperture.  Conversely, the big 16+ shows it's outter edge brightening before deep space - just as it truly does.

 

A great study and ever your ability to lock into fleeting details in challenging altitudes.

 

Pete



#21 David Gray

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Posted 22 May 2019 - 04:21 AM

Thanks Pete.....

 

Not sure if you ‘ve seen it yet but a deep discussion going on in the Refractor Forum – sort of the D-K vs 3”-4” apos...........(Thread not mine!).
https://www.cloudyni...d-4-apochromat/

 

Just posted, last night, some of my take on, among a lot more, the Encke Gap...........an extract......

 

“As to the Encke Gap (IAU) we need be very cautious of that seeming detected as a similar effect is caused by that narrow brighter edge of Ring A giving an apparent dark – contrast-induced - line   In fact the whole planet can be a minefield of contrast effects. When I’ve seen it in pristine conditions there is a more sureness that contrast effects are not the main player but even then, at some level, still involved I feel......gut-feel!

Also the broader Encke Minima, more of a band, can take on a sharp linear appearance against the lighter inner Ring A irradiating against Cassini.  No denying there are real features there, but just happen to lay where dark/light interfaces play their tricks......

Unfortunately lower-res apertures can fall into that with their seeming pristine/crisp views.  That brighter dark-sky-contrasting Ring A rim has some connotations with the Terby Spot; that notorious contrast-effect, that imagers also suffer, against the globe shadow (ShG/R).  Tried to find decent clarifying Link but maybe others will succeed – like many things now: seemingly fading into the mists............thus we encounter confused newbies (and not-so newbie!) 

The attached is a couple of better views (confident-Encke) when the planet was riding high here.  The ring south-face on view and the SPC in evidence – no hexagon-shape ever reported for that.

The Encke gap these recent apparitions (& Ring B minor divs.) I’ve recorded a few times and more muted and far fewer times than those hi-alt south-face views not because of any differences twixt the faces.......Simply because even with, the less frequent, steady air low down, we northerners have to contend with viewing through a much longer path of airborne particulates which will often damage contrasts and fine detail regardless of steady seeing.  What I call the second seeing effect: *The crispness factor*; when all else comes good that gets to be the decider.

 

Dave.




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