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Saturn April 4

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#1 David Gray

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Posted 05 April 2013 - 07:37 AM

Very nice view after some weeks of dismal cloudy nights (and days)!

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#2 kenrenard

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Posted 05 April 2013 - 08:00 AM

David,
Stunning capture. I would love to see Saturn through your scope. Great Work.

Ken

#3 Jef De Wit

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Posted 05 April 2013 - 08:07 AM

Looks like a photo to me :applause:

#4 Andrev

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Posted 05 April 2013 - 08:26 AM

Wow, what a beautiful sketch. So much details. Beautiful rendering.

Andre.

#5 dweller25

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Posted 05 April 2013 - 09:07 AM

Excellent observation and sketch David, your 16" DK must be an impressive piece of kit.

#6 niteskystargazer

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Posted 05 April 2013 - 09:33 AM

David,

Very good sketches of Saturn :)

CS,KLU,

:thanx:,

Tom

#7 frank5817

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Posted 05 April 2013 - 01:44 PM

David,

That is a very, very beautiful sketch.
As Ken said, "Stunning".

Frank :)

#8 Asbytec

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Posted 05 April 2013 - 01:52 PM

Yes, stunning is just shy of being the right word. Wow, beautiful.

#9 azure1961p

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Posted 05 April 2013 - 08:21 PM

The finish is nice but what I like most is the color fidelity.

Pete

#10 Asbytec

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Posted 05 April 2013 - 11:12 PM

David, what about Enke's division, ever seen it in your 16 incher?

#11 David Gray

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Posted 06 April 2013 - 04:58 AM

David, what about Enke's division, ever seen it in your 16 incher?


If you mean the Encke Minima (what I call the ‘classical Encke’): yes on very many occasions. If the IAU Encke then on average some five or so times per apparition (edge-ons excepted!), but only during better seeing. This latter to me is the true Keeler Gap: the IAU compounding the silliness by calling an impossibly fine line even nearer Ring A’s outer edge the Keeler. Can I see the IAU Encke as a ‘black’ gap like Cassini? Definitely not. On the BAA intensity scale (0 = White/Bright; 10 = Black) I usually make it twixt 7 & 8. Appropriately it looks to me quite like a fine lead-pencil line tho’ often a little diffuse – especially on the inner edge. I can’t rule out contrast effects entirely, but in my view perhaps 60/40: and undecided which predominates: real or illusion!! Nature seems to like hiding real features, at least to some eyes, under illusion/contrast effects; Saturn’s rings seemingly being particularly prone.

Somewhere in the BAA Saturn archive is a drawing of the only time I saw IAU Encke in my 10” (1970s?) also in their Journal – will need to check.

Attached is about the best view I ever had of Saturn. The original (HB pencil drawing) is a corrected scan. Never liked my scans as they usually necessitated a lot of computer work to bring them back with the original – very stressing (and eye-abusing!). Some would call this photo-shopping, but I largely contest this as the original is there for guidance; as opposed to giving some pimply model a flawless complexion (not denying some ‘primitive’ pleasure tho’!). In line with my current practice I plan to digitally photograph this, as correction is very minimal, and redo it with the saved colour hues – some cloudy night maybe.

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#12 Kris.

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Posted 06 April 2013 - 07:48 AM

:jawdrop:

#13 azure1961p

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Posted 06 April 2013 - 08:50 AM

I think photoshoping, or other image editing software is a necessity for any imaged artwork, astronomy or not for me anyway. I havent yet found ever an image thwt stays intact from scanner or came 8ra, or iphone (surprisingly good). I may try the graphite drawing as you do and color it in photoshop if only because the color balance in my pastel drawings were , for all intent and purpose, awful. The originals Im proud of. The published end product online was awful. Like my avatar. Oil paintings fair better, my pastel planetary drawings end up with white balance shifts and muddled tones whe re there should be clarity and fine blending. And i draw jupiter with a 5" disc. This time around with Saturn imdefinately going a different route.

Superb work Dave.

Pete

#14 David Gray

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Posted 06 April 2013 - 11:07 AM

Much appreciated Pete, thanks:

One thing I quickly found when first trying the computer-colouring method is how grossly wrong the judged hue turned out to be. For example I might decide a pale lilac fill (Corel Draw pre-prepared vector) might be close for ring A, but when applied has to be desaturated considerably. This can be done by holding down control on one of the greys; left-clicking adds small increments of the chosen grey. Then the same procedure with an appropriate colour to achieve a closer hue to what was seen. In addition belts and zones (vector fills) can be adjusted against each other to get a nearer relative hue. E.g. I once judged a broad dusky band on Uranus (!!) as of warm brownish hue. Had I been using pastels would I probably have used a small amount of terra cotta + grey/brown; but after being satisfied with the relative hues the Corel colour-sampler indicated the band an olive-brown hue but it looked reddish-brown in relation to the general cyan hue on the monitor! I have a totally black work-area/background when pursuing this. The computer being in the house some 20yds away entails a lot of to-ing & fro-ing so a certain ability of carrying the general view/hues in the head is desirable, but manual drawing-media method demands much more on the memory even if you get down to it straight after – and of course there is the scanning nightmare!!

Colour work is a veritable mine-field and many many variables: futile to claim absolute colour; ball park is the best aim I feel. I have already used a lot of words to describe relatively basic/simple procedures; and it would take pages to relate what is involved with what I am seeking tinting my drawings.

I am finding a basic Kodak Easy Share camera ideal as a substitute ‘scanner’. A discard from our son Stuart after he moved to DSLR! Inserting an SD card in the PC quicker and simpler than scanning.

David/Dave (either - been called worse!)

#15 Asbytec

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Posted 06 April 2013 - 12:07 PM

David, thank you for the outstanding reply on Enke. Fascinating. I am impressed with your observation and account of it. You're description is of a true observer of planets.

I thought I observed Enke once in a 6" Mak. But after some research and a lengthy thread discussing it, I determined it was not very likely observed. Highly improbable, in fact. Enke minimum, however, will suffice.

Not to get off topic, but some manipulation to get it just right or to display well is fine. Observing is the result of long periods of careful study, it's not nice to ask your audience to do the same work studying a "realistic" sketch.

Outstanding work, David.

#16 David Gray

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Posted 06 April 2013 - 01:08 PM

I thought I observed Enke once in a 6" Mak. But after some research and a lengthy thread discussing it, I determined it was not very likely observed. Highly improbable, in fact. Enke minimum, however, will suffice.

Many thanks Norme:
If you had good faith, and with all due caution, in your observation at the time I would say stand by it. 6” scopes do remarkably well in skilled hands (S.W. Burnham: 0.2” doubles elongated etc) Some cynics conceal many explaining-aways beneath their comfort- blankets. I saw someone on the first locked Uranus (“…Season…”) thread virtually talked-out of his Uranus drawing, which accorded well with my impressions around that date.

In earlier days there was a dictum “draw only what you actually see” even if you suspect an illusion. If there is a strong feeling of illusion note it down as a cautionary: someone else may have independently recorded your ‘illusion’; then there is a chance of mutual confirmation. Taking this principle to its extreme, if one night I found that the turbulent Jovian atmosphere had produced markings that looked like “Hi There” (not impossible) I should draw it as I see it. Imagers would soon sort this one; but just to demonstrate.

Please pardon if I am telling you what you already know/practice. But simply stating my strong views.

The late Andy Hollis had strong views with this all this: note the last paragraph in his letter attached. I have hidden the name of a very experienced (still living) observer to spare his blushes!
Dave

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#17 Asbytec

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Posted 06 April 2013 - 09:36 PM

David, your sketches of Saturn speak of your ability to work at the edge of uncertainty, that realm just beyond what is physically possible for most observers. That can only come with practice and probably some genetic disposition toward observing. I recently learned to observe planets through patients and long hours at the eyepiece. Shy of any known genetic advantage, the hard work really paid off.

It is possible to observe what others cannot or might doubt. Sure, record what you see and note observations. I've tried to be aware of optical illusions such as the mach effect. But those illusions are much easier to see on an internet web site than picking the illusion from Martian maria.

Jupiter and Mars were amazing during their recent flybys. I am afraid I will miss Saturn during our short dry season and being away on travel.

#18 ericj

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Posted 07 April 2013 - 11:29 AM

Wonderful sketch as always David thank for posting it.

Best,

Eric Jamison

#19 idp

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Posted 07 April 2013 - 02:51 PM

the IAU compounding the silliness by calling an impossibly fine line even nearer Ring A’s outer edge the Keeler.


Glad to know I'm not the only one to be bothered by the silliness of the UAI nomenclature. When I wrote reports on Saturn for the Italian Astronomical Union I tended to call "Encke minumum" the large, easy shading at the center of A ring and "Encke gap" what used to be Keeler's gap, just to avoid confusion.

Saturn’s rings seemingly being particularly prone.


Indeed :)

Attached is about the best view I ever had of Saturn.


Awesome. I've always been stunned by your draftsmanship. I remember too the green hue around the polar region in 2003. I've given up trying to get a decent digitization from a scanner, I just take a digital shot - which of course has its drawbacks too.

I'm also intrigued by the bright spot in the temperate zone; how "visible" was it? Could you definitely see its rotation?

Great to see your works on this forum.

Ivano

#20 David Gray

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Posted 08 April 2013 - 05:38 AM

I'm also intrigued by the bright spot in the temperate zone; how "visible" was it? Could you definitely see its rotation?


Many thanks Ivano:

Not sure if the spot is real; but was more certain of a mainly slight scalloping of the NTB n. edge. There being a deeper more apparent indentation/bay that I followed to the CM from early in the session: NTB thicker and darker p. & f. the light ‘spot’. We are familiar with this effect on Jupiter: where any real lightness can be contrast-enhanced. So possibly illusory and perhaps made a little too apparent/light through artistic incompetence/carelessness. Actually it is less apparent on the full-res version (300 dpi) on the monitor, and the original drawing!

Encke div: I spout off about this IAU thing at any opportunity it’s had me riled for years! I got the impression those that might have had some influence just seemed to roll over and accept it – speaking to, among others, upper-level BAA people back then.

2003 drawing: I think I defined the green hue as “a duck-egg-bluish-green” or some such and it was striking to a lot of observers I recall.

Very much like your drawings too; and would like to add I feel honoured to be among some very accomplished artists on this forum – though for myself I like your term "draftsmanship"! My late mother and, very especiially, her sister Florence (Raine) (Aunt Florrie: 1892-1931 [d.tragically]) were the real artists of the family

David.

#21 idp

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Posted 08 April 2013 - 10:03 AM

Encke div: I spout off about this IAU thing at any opportunity it’s had me riled for years! I got the impression those that might have had some influence just seemed to roll over and accept it – speaking to, among others, upper-level BAA people back then.


I see. That surprises me a bit, as IAU nomenclature is first of all historically inaccurate and I'm sure BAA guys knew well about that...

though for myself I like your term "draftsmanship"!


Uhm...not a native English speaker, so "draftsmanship" might not be accurate :question: Or maybe it is American (I live in the USA now), or related to technical drawing rather than artistic, or I may just have invented it :D

Anyway, your drawings of Saturn are by far the best I see around; would love to know more about your technique. It takes both an experienced observer of the planet and a good artist.

Ivano

#22 David Gray

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Posted 08 April 2013 - 01:33 PM

[around; would love to know more about your technique.


Draftsmanship: well I am far-north English born (mainly Celtic/Viking stock here!) so draughtsmanship; but that or artistic I guess I traverse their hazy boundaries. I have been accused of trying to produce planetary works of art; but I say if you get what you see at the eyepiece accurately, then, as they are often objects of beauty, the art takes care of itself! I have to say that assorted candy-colours on planets etc. elude me: even so I find our ‘drab grey’ moon a rich palette of subtle hues!

My technique: a good HB pencil and stumps (medium & thin). I adopted a method of stump painting some years back and ‘tickle’ in darker features with the HB. To me, why draw with the pencil first then have to blend in the marks afterward. Stump first and much of the blending is done and at the eyepiece; saving time and more retaining the integrity of the drawing with it pretty much finished on site. I am attaching more details, but the reference to Staedtler Mars Lumograph EB pencils is out of date as I find they (& EE) are discontinued now. Replaced with, I think, 8B & 9B graphite. A great shame as the EB takes a fine point and is ideal for Cassini div. C ring, and shadows etc as it has considerably less sheen than graphite – glad I bought a good stock years ago!

Erasers: I do not anymore use kneaded (putty) erasers as with using the stumping technique any putty-residue on the paper will greedily grab the graphite from the stump and leave a virtually irremovable dark patch. I find a good triangular pencil-end rubber perfectly fine and convenient.

Paper: I used to use Ivorex or Bristol Board. But now use Xerox Colotech+ (100 gsm) inkjet printer paper £10 ($15) for 500 sheets some years back; and some years back got a deal on three packs for £20 ($30) and have just recently started on the second. So much more economical than the board; very smooth, white (no yellowing yet!) and damp-resistant outdoors at night. Also gives good prints!

For planets with very delicate diffuse features I prepare the drawing area by rubbing all over in small tight circles with a small wad of tissue or cotton wool. This dulls the tooth making very smooth blends possible. With Saturn I apply this more thoroughly to the rings than globe area. I use small tight circles when stumping also, unless I want to lightly reinforce a faint belt, ring div or such.

David.

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#23 idp

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Posted 08 April 2013 - 02:40 PM

Awesome tips, thanks!

Ivano

#24 azure1961p

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Posted 08 April 2013 - 11:20 PM

So these oculars deliberately showing chromatic aberration work to cancel out atmospheric dispersion colors on things particularly like Galilean moons at high power and such? Amazing .

Could you explain it a little further? Is this a standard tool or method or one you developed on your own. Its the first Im hearing of it . Particularly in Connecticut in winter, dispersion can be very degrading to the image indeed. It'd be a fine thing if I had such a thing to counter its effects.

Pete

#25 David Gray

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Posted 09 April 2013 - 01:48 AM

So these oculars deliberately showing chromatic aberration work to cancel out atmospheric dispersion colors on things particularly like Galilean moons at high power and such? Amazing .

Could you explain it a little further? Is this a standard tool or method or one you developed on your own. Its the first Im hearing of it . Particularly in Connecticut in winter, dispersion can be very degrading to the image indeed. It'd be a fine thing if I had such a thing to counter its effects.

Pete


If you have “The Planet Jupiter” (1958) by B.M. Peek then you can find my first source of information in chap. 5 (OBSERVATIONS OF COLOUR) page 38. Also Sidgwick’s classics deal pretty thoroughly with chromatic aberration in general and may touch on the Ramsden effect. If you can’t access these I will be glad to quote some passages.

Actually a narrow angle dispersion prism, as used by many imagers now, would be the ideal; but needing differing angles for varying altitudes. There are variable ones available – one I have seen retails at over £300 ($450): I am just a poor pensioner! S&T years ago gave details of H.E Dall’s Compensating Eyepiece where the crown and flint components of the field lens are uncemented and a thumbscrew (with a graduated scale) alters the position of the flint against the crown.

In principle I would not be inclined to tackle the Galileans for detail at other than a goodly altitude where the atmospheric effects would be minimal. But it would certainly bring out truer colours (ball-park!) lower down.

Whilst checking out Peek I re-read (after many years) the “Drawings of Jupiter” section - page 35 bottom half to 36 where he had described an observing technique that years later in S&T Alika K. Herring (a bio.) wrote that a seasoned U.S. observer had told him in his early years: that we should look on a planet rather than at it. Those who seek elusive detail should particularly note this apparent absurdity – my experience finds it quite logical!! Hope you can see Peek’s book: and I will have to dig out those S&Ts to check the details against my memory!






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