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contedracula
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Re: Hexagon, possible? new [Re: leviathan]
      #5940000 - 06/25/13 03:27 PM

This is partly true but - if - it was totally would have bought all of us a 20" Dobson because it costs 1/10 of Big APO

There are many other factors that penalize a large mirror... all the glitters is not gold

Thanks
Gianluca


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David Gray
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Reged: 08/06/12

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Re: Hexagon, possible? new [Re: David Gray]
      #5951526 - 07/02/13 03:25 PM Attachment (27 downloads)

Possible? I have had several fair sightings this apparition so I would say yes - at least incipiently definable I venture to say! The current light surroundings (NPR) of the NP Cap perhaps giving rather unusually ideal circumstances. Details with attached recent observation.

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idp
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Reged: 08/21/09

Loc: New Haven, CT
Re: Hexagon, possible? new [Re: David Gray]
      #5951789 - 07/02/13 05:36 PM

Quote:

The current light surroundings (NPR) of the NP Cap perhaps giving rather unusually ideal circumstances. Details with attached recent observation.




Excellent remark. The edge of the North Polar Cap has been quite a high-contrast feature these months.

It looked "angular" to me at the end of May with a 10" refractor, though still nothing definite.

I wonder whether combing through archives of visual observations would yield more examples of notes like "cap edge not smooth" etc. I guess though that such observations of border-line features were easily dismissed.

Regards,

Ivano


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azure1961p
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Re: Hexagon, possible? new [Re: idp]
      #5951845 - 07/02/13 06:20 PM

David,

Beautiful work! I was wondering when you might post another Saturn. I think its pretty well a shutout detail for my 8" but its still compelling to seek it out. My treasure is is seeing the ellipse and the lighter apron of atmosphere surrounding it like a collar. Believe it or not in 6/10 seeing its a tough call with my 8" to see even that. My 70mm in similar seeing doesn't see it at all.

I noticed you got some nice condensations along the EZ along with the thin equatorial belt that bisects this zone. Nicely rendered.

Pete
Ps: your post reminds me Ive still yet put an apodizer together.

Edited by azure1961p (07/02/13 06:22 PM)


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David Gray
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Re: Hexagon, possible? new [Re: azure1961p]
      #5953198 - 07/03/13 02:05 PM Attachment (19 downloads)

Thanks Pete, Ivano.

Ivano your remarks: "I wonder whether combing through archives of visual observations would yield more examples of notes like "cap edge not smooth" etc. I guess though that such observations of border-line features were easily dismissed." led me to the following:

I have just put together some thoughts in connection to what I said last post re. NPR/NPC difficulties. Attached is a scenario where conditions may have developed more favourably for a time following the 1960 Botham White spot (NNTZ).

Note in the first drawing the huge size of the NPC: I rather regard this as a very dark NPR. Checking some reports from late 1959 there was actually a smaller dark NPC within this. Either way I am not going to accuse Dollfus of poor drawing technique!!!

Dave.

Edited by David Gray (07/03/13 02:19 PM)


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idp
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Reged: 08/21/09

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Re: Hexagon, possible? new [Re: David Gray]
      #5956575 - 07/05/13 06:55 PM

Hi Dave,

Very interesting finding and remarks, as usual. I agree that Dolfuss's drawing depicts a darkened NPR, rather than the NPC.

I'd also note that while a fine (or rather, outstanding) observer, Ruggieri was working with a just a 10" newton; even supposing that the "hexagon" was there and conditions were favorable, he may simply not have had enough of a telescope to spot it.

As for high-latitude GWSs being the root of the hexagon-like current: amateurs have only recently been able to image it, but the feature was discovered during the Voyager flybys and Cassini found it there. In other words, it seems to be rather stable, rather than connected to temporary and far-apart events. There are a few professional papers out there on the topic (such as Ingersoll at al., "Icarus", 2011), I seem to remember that the action of high-latitude GWSs was not considered but my memory could fail me.

Regards,

Ivano


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idp
sage


Reged: 08/21/09

Loc: New Haven, CT
Re: Hexagon, possible? new [Re: idp]
      #5958356 - 07/07/13 12:54 AM Attachment (19 downloads)

By the way: I stumbled upon this 1998 observation of the SPC by Richard Schmude jr, and I wonder whether this is how an observer could depict a prominent "corner". The telescope used by Schmude was a 51cm newt. f/4.5, seeing I (ant.)

Regards,

Ivano


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David Gray
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Reged: 08/06/12

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Re: Hexagon, possible? new [Re: idp]
      #5958839 - 07/07/13 12:14 PM Attachment (20 downloads)

Thanks Ivano,

Richard McKim is currently dealing with a long backlog of BAA reports on behalf of the Saturn Section. So I have my 1998 obs’ns to hand and soon found the attached! I do not know the exact date of Schmude’s drawing you attached but the similarity with my attached 1998 Oct 7 intensity sketch is striking. I had a transit for this “c. of dusky proj.(int. 4.25) n.edge of SPB 22:23 UT (SSTZ lighter (int. 2.5) f. this (3.25 p.)).” I would hesitate to say hexagon here however: the corner/vertex looks a bit extreme; but certainly suggestive!. Later in the week, when more time, I will take a longer look at my obs. around those years – I have 67 sessions for 1997/98 and 80+ for 1998/99.

I was in touch with Saturn Director Mike Foulkes re. the NPC hexagon effect recently and his response included this with regard to the SPC: “……..On a related topic, over the weekend an American observer sent out some images indicating that that there was a hexagon over the south pole in 2006. Having looked at the images and other observations at the time I find myself in the negative on this I have transformed some images from this time into polar projections and the results are inconclusive. In addition the few Cassini images that I have seen just show (to me at any rate) a regular SPR with a dark spot (the vortex) at the centre but with no hexagon. But I'm looking at other observations around these years……...

As Richard McKim now has most observers' reports for 1994 to 2001 to hand I will alert him to look out for any hexagon-like features/impressions.

Dave.


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idp
sage


Reged: 08/21/09

Loc: New Haven, CT
Re: Hexagon, possible? new [Re: David Gray]
      #5958877 - 07/07/13 12:45 PM

Hi Dave,

Schmude's observation is dated Sep. 27, 1998, 21:00 UT. He used 380x, no filters. At the time he sent copies of his observations of Saturn to the Italian Astronomical Union, that's why I have this one.

So your observations are more than 2 months apart, yet similarities are stunning. I'd give credit to Schmude's report: big telescope, seeing excellent, experienced observer. I would not venture either into interpretations, looks more like a protuberance or a DS from the drawings - but then, I guess that's how an observer would have "classified" and tried to interpret such a feature.

Thanks for yet another interesting conversation.

Ivano

Edited by idp (07/07/13 01:07 PM)


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azure1961p
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Reged: 01/17/09

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Re: Hexagon, possible? new [Re: idp]
      #5959033 - 07/07/13 02:25 PM

Very good point Ivano. That could have been how the hex was interpreted . I agree the similarities here are quite impressive. It is a little universe in its own with regard to perception when the senses are pushed this hard so its nice to see corresponding observation support these threshold features. It could have been something else too but its compelling enough to consider the hex too.

Really nice work guys.

Pete


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David Gray
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Reged: 08/06/12

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Re: Hexagon, possible? new [Re: idp]
      #5959059 - 07/07/13 02:42 PM

Ivano,

Just to check:

Using WinJUPOS I have determined my transit for the SP feature as L3 = 311.5. Schmude’s drawing CM3 = 128 deg; eye-estimating his feature at L3 = c.170 deg. I make our obs. as 10 days apart – you said 2 months so wondering if a mistake somewhere?? A second feature is a possibility assuming no error of course; even a lighter stretch of the SSTZ defined p. & f. by similar dusky features but nothing catches my eye in a rather hasty check; but a fair number of SSTB darker sections etc. However my int. sketch for 1999 Feb. 24 18:20 UT shows two n.edge undulations on the SPB and indicated “!!” and eye-estimated at L3 = c.290 deg.

From all this we might assume that certain SST/SPR activity might delude us into a hexagon interpretation. Then coming to this apparition I have seen a few comments claiming lighter patches in the already lighter NPR. So, turning things around, are the broader NPR (NPCs to NPBn) parts twixt the hexagon vertices being (mis)interpreted as discrete NPR features – seeing and lack of resolution possibly compounding things??

Dave.


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idp
sage


Reged: 08/21/09

Loc: New Haven, CT
Re: Hexagon, possible? new [Re: David Gray]
      #5959571 - 07/07/13 08:43 PM

Quote:

Ivano,

Just to check:

Using WinJUPOS I have determined my transit for the SP feature as L3 = 311.5. Schmude’s drawing CM3 = 128 deg; eye-estimating his feature at L3 = c.170 deg. I make our obs. as 10 days apart – you said 2 months so wondering if a mistake somewhere??




Of course, on my part. I read the "2013 07 07", so I thought "July 7th", but of course it was 1998! Apologies, I always have to do these things on the run and this morning it was no exception.

Ivano


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Hexagon, possible? new [Re: David Gray]
      #5962301 - 07/09/13 02:32 PM

Quote:

Possible? I have had several fair sightings this apparition so I would say yes - at least incipiently definable I venture to say! The current light surroundings (NPR) of the NP Cap perhaps giving rather unusually ideal circumstances. Details with attached recent observation.




Superb sketch, David. I'm glad you made it out. As you say, the primary problem seems lack of contrast, not resolution (since even 8-inchers have resolved it in images). Saturn is so low now that it's hard to make out even Cassini from my latitude (47-d). I'm amazed that you can see so much from the UK though you do apparently have a giant custom made aperture.

Tanveer.


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David Gray
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Reged: 08/06/12

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Re: Hexagon, possible? new [Re: TG]
      #5963589 - 07/10/13 07:13 AM

Thanks Tanveer,

Yes I am pretty well persuaded that the NPC hexagon is definable in apertures less than my 415mm D-K in the very best conditions, especially given the contrasts prevailing this apparition. I had hoped to use a 152mm off-axis stop in such circumstances but now I’ve just about lost Saturn over the rooftops by good darkness. Had it occurred to me: as the D-K has only a 19% CO (optical window – no vanes) I could have constructed some 200mm – 300mm on-axis masks and still had a CO fairly close to commonly used SCTs etc, and which might have proved informative!

A pity to lose Saturn as we have a stable high pressure over the UK now. But yes I do fairly often get good seeing low down with my apparently ‘anomalous’ local microclimate at this latitude of +54.7 deg.! In fact of late I have seen Antares B (3 nights) with ease and its at an altitude of 9 deg. here and Antares is usually just a >5” blur – the atmospheric dispersion is always gross however and have no means of reducing it below c. 15 deg.( dec.-20 deg.)- apart from stopping down of course.

I perhaps can give another indicator of a hexagon effect as on July 8 with the seeing not quite up to it I got the effect of a dark spot on the NPC which, pending checking, may well be a vertex of the hexagon – somewhat past the CM at 21:20 UT.

Yes the 415mm f/16 D-K is custom made (1977/78): optics by James Muirden, mechanical by Peter Drew. Guests have described it as giving refractor-like performance without the chromatic drawbacks, some of whom have used large/r refractors. It was last recoated in 1989 by the late David Sinden himself (formerly of Grubb Parsons). I was with him to watch the process; thanks to his skill (and the optical window) the coating still looks fresh and continues to go well past mag. 16 on a decent night (15 with the binovu). This tribute-site shows him in the very workshop where he coated my mirrors: https://sites.google.com/site/grubbparsons/home/david-sinden - the casual ease the way he handled my mirrors actually caused me some concern which amused him greatly when he saw the look on my face!!

David.

Edited by David Gray (07/10/13 07:24 AM)


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bremms
Carpal Tunnel
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Reged: 08/31/12

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Re: Hexagon, possible? new [Re: David Gray]
      #5965911 - 07/11/13 03:26 PM

Earlier this year I looked for the Hexagon in my 6" refractor. This scope does very well on planets (F10 Achro better than 1/8 wavefront) and I saw no sign of the hexagon during very good seeing, but the rings will give a slight phonograph appearance with a grooved texture. Don't think I'll have my 12.5 " F6 Newt done for this years Saturn observing. The mirror is from 1962, and tests to better than 1/10 wave and smooth. I might try the C11, but Saturn is hard to see from my house now due to trees.

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Chuck Hards
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Reged: 05/03/10

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Re: Hexagon, possible? new [Re: bremms]
      #5982261 - 07/21/13 12:35 AM

We used to call the cap Saturn's polar "hood" back in the old days. I think ALPO just calls it the Polar Region (either north or south).

Correct me if I'm mistaken, but isn't the hexagon about half the diameter of the cap (or hood) itself? So any apparent faceting of edges of the cap itself could be chalked up to the power of suggestion?

Our club has a 32" Cassegrain (812mm) and I plan to try for the Hexagon at my next opportunity. As others have noted, the best seeing may have to wait until next year, when Saturn is in the early morning sky. Right now the evening seeing is terrible from my area.


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azure1961p
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Re: Hexagon, possible? new [Re: Chuck Hards]
      #5982684 - 07/21/13 10:14 AM

Well the power of suggestion is plausible but in aperture great enough with everything thing else optimum it ought to show is my guy feeling. My observations with the 8" have me a polar spot, albeit subtlety but seeing was never good when I looked. I do believe with a degree of certainty that larger apertures like Dave's can actually do it. Maybe even a 12 newt. My guess is if I had a stellar 10 Pickering night it'd be a more defined spot but still smoothed. Lol, my humble (but loved) 70mm never showed it even a hint of a spot, nor my 6" sct - but again the 5-6 Pickering I had.

Pete

Edited by azure1961p (07/21/13 10:58 AM)


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Chuck Hards
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Re: Hexagon, possible? new [Re: azure1961p]
      #5983128 - 07/21/13 02:36 PM


I'm not going to disagree, I hope to see it myself, but it's a lofty goal.

Saturn is only about 20 arc seconds in diameter (rings are about 49 arc seconds) so the hexagon is probably less than 1.5 arc seconds across, at best, probably closer to 1 arc second, so any telescope used would have to be able to resolve sub-arc-second features. Saturn is nowhere near opposition now so the hex may be even smaller. It's also a low-contrast feature, being buried in the polar hood, both darkish features.
Secondary obstructions will work against us when trying to discern low-contrast planetary details. Fast Newtonians and most Cassegrains have very largish secondary obstructions, and it's a rare large-aperture light-bucket Newtonian mirror that is considerably better than diffraction-limited. And unfortunately extremely large APO refractors are non-existant. Even our club 32" Cassegrain has a 10" secondary, and fairly thick steel support vanes.

I'm thinking that a large Mak may have the best chance of seeing the hexagon, along with superb transparency and a very steady atmosphere. Large Maks (say 12" and higher) are a rare breed as well.

But let's keep trying, I plan to.


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David Gray
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Reged: 08/06/12

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Re: Hexagon, possible? new [Re: Chuck Hards]
      #5983302 - 07/21/13 04:55 PM Attachment (13 downloads)

Quote:

Saturn is only about 20 arc seconds in diameter (rings are about 49 arc seconds) so the hexagon is probably less than 1.5 arc seconds across, at best, probably closer to 1 arc second,




With respect I have to differ with these dimensions for the NPC/Hexagon. Attached is a graphic to scale after some recent imagery (rather than use my drawings with any inherant innaccuracies!).

Here this is based on an equatorial Saturn diameter of 17.2" and Jupiter at 35" (Equatorial). As I suspected the NPC comes out similar angular size to the GRS.

Regards,
David/Dave.


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Chuck Hards
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Re: Hexagon, possible? [Re: David Gray]
      #5983685 - 07/21/13 09:36 PM

Yes, but the hexagon is only about half the diameter of the cap itself, isn't it? I'm pretty sure the hexagon edges are well within the dark cap that we see in the telescope, judging by the Cassini imagery I've looked at. In other words, the cap itself is not the hexagon, but contains the hexagon. So my estimate of 1.5 arc seconds is probably pretty close.

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