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TG
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Reged: 11/02/06

Loc: Latitude 47
Hexagon, possible?
      #5820749 - 04/24/13 08:20 PM

Now that the hexagon is showing up in images taken with scopes as small as 10", has anyone spotted it visually? Is it even possible?

Tanveer.


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azure1961p
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Re: Hexagon, possible? new [Re: TG]
      #5821016 - 04/24/13 10:54 PM

The only fringy glimpses that have come visually from responsible observers appears to show that its demanding of large aperture with no slam dunk about it. I'd have doubts with a ten inch but Im an optimist too.
Hope this helps.

Pete


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TG
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Reged: 11/02/06

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Re: Hexagon, possible? new [Re: azure1961p]
      #5822735 - 04/25/13 06:14 PM

Quote:

The only fringy glimpses that have come visually from responsible observers appears to show that its demanding of large aperture with no slam dunk about it. I'd have doubts with a ten inch but Im an optimist too.
Hope this helps.

Pete




I haven't actually heard anybody say they saw it. Perhaps I hang out with the wrong crowd.

It's going to be clear and steady tonight (knock on wood) and I'm going to see what I can do with my 7-incher.

Tanveer.


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David Gray
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Re: Hexagon, possible? new [Re: TG]
      #5823412 - 04/26/13 12:02 AM

This is part of my response to a query by idp/Ivano [13 04 21 03:06 PM] on the Sketching Forum:

“…….. and I fear I spent an inordinate, futile, amount of time chasing that NPC hexagon (smooth oval to me) i.e. beyond my detection!” (415mm D-K x270 & x365).

Its possible one of the hexagon’s flat faces was central at the time: I would reckon that a ‘corner’ would look like a south-edge projection/bulge when well onto the disk. So not deterred - yet!

The thread is here:
http://www.cloudynights.com/ubbthreads/showflat.php/Cat/0/Number/5810485/page...


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MikeBOKC
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Re: Hexagon, possible? new [Re: David Gray]
      #5823846 - 04/26/13 09:12 AM

Considering that the polar hexagon wasn't even discovered until the Voyager flyby, after many decades of professional observations and photographs of Saturn from earth by some pretty large telescopes, I would be doubtful that it is a visual possibility absent quite large aperture and a rare night of near perfect seeing. I'd certainly be thrilled to see it in my 14 incher, but I would suspect it would only be achievable in 20 inches and up.

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David Gray
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Re: Hexagon, possible? new [Re: MikeBOKC]
      #5823933 - 04/26/13 09:51 AM

This was the first serious attempt at the hexagon; although I have been aware of it since Voyager days; and an active contributor to the BAA Saturn Section since 1968.

Used the 415mm D-K since 1978, and have had very many fine views, but have never seriously considered attempting it all this time! Of course when the NPC is well presented the planet is always pretty low from here – as its getting now.

If you don't look you don't see!


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azure1961p
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Re: Hexagon, possible? new [Re: David Gray]
      #5825938 - 04/27/13 09:40 AM

Visual astronomy is peculiar in the respect that true threshold details can literally be arc seconds away from where you are looking but unless they get their own due attention its a no show. The peripheral emergence if other details hat grab attention are the easier things. The true fringe of contrast-detail detection has these specific attention demands that's always been a little surprising to me. I've missed nearby things simply because I didn't pour myself at it. That's what Ive found anyway.

What's daunting is when a known threshold feature still doesn't budge no matter how hard I try!

Pete


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Hexagon, possible? new [Re: azure1961p]
      #5850199 - 05/09/13 02:52 PM

We've had a string of nights with good seeing so I've been observing Saturn. I've realized two things: (1) Saturn is going to be a wash from our latitude (47*), getting increasingly worse every year for the next several years, and (2) there's no hope of my seeing the hexagon from here as it probably needs super steady 9/10 seeing and at its low altitude that's just not going to happen. That said, I was able to notice a dark gray/bluish polar cap but I wonder if I would ever spot it if I didn't know it was there.

Powers used were 200-300x in a C11HD and banding on the disk, Cassini and the C ring were visible, Cassini being visible about 1/2 the way around. I also saw what looked like ring shadow on the disk but am not absolutely sure whether it was a band instead. Also thought I saw the shadow of the disk on the rings but I suspect this may be an illusion as it's still too close to opposition.



Tanveer.


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leviathan
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Reged: 11/29/11

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Re: Hexagon, possible? new [Re: TG]
      #5851185 - 05/10/13 12:11 AM

No, it's a ring shadow, you are right. Shadow of the planet on the rings is also visible already.

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azure1961p
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Re: Hexagon, possible? new [Re: leviathan]
      #5851462 - 05/10/13 07:24 AM

Well Id imagine some filtering of the Crepe is adding to this as well. I saw it repeatedly with my 70mm refractor in the better moments though the upper latitudes was a wash with no detail gradients tho seeing wasn't great.

Tanveer don't rule out low elevation observing in summer. Some of the best Saturns Ive ever seen were 30 degrees elevation in balmy hot muggy summer night air. Cool (wet out) your local observing g latch with a hose and it can make a big difference.

Pete


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TG
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Reged: 11/02/06

Loc: Latitude 47
Re: Hexagon, possible? new [Re: azure1961p]
      #5852238 - 05/10/13 03:45 PM

Quote:

Tanveer don't rule out low elevation observing in summer. Some of the best Saturns Ive ever seen were 30 degrees elevation in balmy hot muggy summer night air. Cool (wet out) your local observing g latch with a hose and it can make a big difference.

Pete




Last night we had very good seeing so I dragged out* Tiny to the end of the backyard so it had an expanse of dripping wet grass around it (I'm in the PNW and grass is always drippin wet at night) and Saturn was amazing. Multiple banding on the surface, Cassini visible most of the way around, the C ring, shadow of the rings, and a clearly visible blue-gray polar cap. I think I went up to 400x and there was some blue/red fringing from atmospheric dispersion so the best views were had at about 300x.

I tried both binoviewers and single eyepieces and it's amazing how good the Mark V + AP 2x barlow is. There was practically no difference between using this combination with 17mm plossls and a 7.5mm Ultrascopic directly though I could see the polar cap a hair clearer without the BV.

Tanveer.

(*) literally! it's on a ScopeBuggy


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Hexagon, possible? new [Re: leviathan]
      #5852241 - 05/10/13 03:46 PM

Quote:

No, it's a ring shadow, you are right. Shadow of the planet on the rings is also visible already.




Thanks for confirming. I could see it clearer last night but was still not sure if it was an optical illusion or not.

Tanveer.


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azure1961p
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Re: Hexagon, possible? new [Re: TG]
      #5852518 - 05/10/13 06:50 PM

You've hot a pair of Mark Vs????? Very nice!

Pete


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TG
Pooh-Bah


Reged: 11/02/06

Loc: Latitude 47
Re: Hexagon, possible? new [Re: azure1961p]
      #5853150 - 05/11/13 01:19 AM

Quote:

You've hot a pair of Mark Vs????? Very nice!

Pete




Yes, they're expensive but well worth the price. I had a pair of very good Sieberts but the Mark V is on a different level.

Tanveer.


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leviathan
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Reged: 11/29/11

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Re: Hexagon, possible? new [Re: TG]
      #5926823 - 06/18/13 03:25 AM

Yes, it's possible. I saw it few days ago on 600mm observatory telescope (not amateur aperture, isn't it ?) on 535x.

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dscarpa
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Re: Hexagon, possible? new [Re: TG]
      #5927434 - 06/18/13 12:28 PM

Saw it last night in my IM715 mak! Seeing was almost excellent and I was using a 10 XW for 290X and a 8 LVW for 360X. The hexagon was a small spot on the pole that was much darker than any other features. I couldn't tell that it was a hexagon however. Tonight my C9.25 gets a crack at it. David

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idp
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Re: Hexagon, possible? new [Re: dscarpa]
      #5929905 - 06/19/13 07:13 PM

On May 28th the polar cap appeared rather "angular" to me in a 10" refractor at 430x... Definitely not a hexagon, but I would not have described it as a smooth ellipse either.

Of course I was aware of the hexagon thing etc., so I tried to convince myself what I was seeing was just a an ellipse. I remained unconvinced.

Ivano


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dscarpa
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Re: Hexagon, possible? new [Re: TG]
      #5930218 - 06/19/13 10:30 PM

It didn't look smooth to me either. Last night the clouds rolled in but tonight looks to be clear to midnight or so. My C9.25 is out on the patio with an excellent selection of high power eyepieces deployed on the counter by the door! David

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dweller25
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Reged: 08/30/07

Loc: Lancashire, UK
Re: Hexagon, possible? new [Re: dscarpa]
      #5931337 - 06/20/13 01:45 PM Attachment (36 downloads)

Agree with dscarpa, in a 7" the hexagon just looks like a darker area at the pole - even in excellent seeing.......

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JasonBurry
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Reged: 04/27/12

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Re: Hexagon, possible? new [Re: dweller25]
      #5931381 - 06/20/13 02:13 PM

Nice sketch. Looks rather like what I saw last night with my 8" (specifically, the "hexagon" polar feature), though I found the cloud bands to be a touch more obvious in moments of good seeing.

J


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dscarpa
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Re: Hexagon, possible? new [Re: TG]
      #5931595 - 06/20/13 04:16 PM

I had very good seeing here last night and used the C9.25 with a 9mm Astro Hutech ortho for 300X and a 7XW for 370X. The hexagon as was the case with my mak was easy and looked a lot like your excellent drawing but the big cat was pulling in a quite a bit of fine belt detail of various colors. The rings and moons were quite the sight as well. David

Edited by dscarpa (06/20/13 04:18 PM)


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t.r.
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Re: Hexagon, possible? new [Re: dscarpa]
      #5932751 - 06/21/13 10:26 AM

I'll try tonight with my C11XLT.

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dscarpa
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Re: Hexagon, possible? new [Re: TG]
      #5932776 - 06/21/13 10:44 AM

I'll give my WO ZS-110 a shot at it, was observing with it last week with not quite as good conditions and didn't see it. Then again on a night with the same seeing the mak didn't show it either. Had the C9.25 on it last night with only the 7 XW, love seeing Saturn like that! David

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Achernar
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Re: Hexagon, possible? new [Re: TG]
      #5933906 - 06/21/13 11:18 PM

I have seen it as a much darker area right at the pole, but the hexagon shape wasn't visible through the 10 and 15-inch Dobs I use. The seeing is often good during the warmer months, but not good enough at 400X and above for me to see the hexagon shape of this feature, if that is even possible from Earth with a 15-inch Dob. I have noticed white patches near the pole that seem to be clouds quite near it, as well as the remanants of that storm that occurred in 2010. As for the color of the polar region, it looks to me like a blend of olive drab and brown though my larger telescopes at 300 to 425X.

Taras


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dscarpa
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Re: Hexagon, possible? new [Re: TG]
      #5934426 - 06/22/13 11:26 AM

The ZS-110 showed it! It didn't stand out as much as it did when using the cats but it definitely was there at the higher powers. I was using my 5X Powermate with a 16 WO UWAN at 240X-270X and 13 Ethos for 300X. Conditions were once again very good. David

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azure1961p
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Re: Hexagon, possible? new [Re: dscarpa]
      #5935123 - 06/22/13 06:29 PM

So it wasn't a smooth polar ellipse but an faceted hexagon?

Pete


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E_Look
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Re: Hexagon, possible? new [Re: azure1961p]
      #5935209 - 06/22/13 07:32 PM

I wonder what combination of forces could cause that effect!

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contedracula
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Re: Hexagon, possible? new [Re: E_Look]
      #5936348 - 06/23/13 12:56 PM

I've used at same time three telescope in the last 2 weeks, 14" SC, 10" MakNewton and 180mm Refractor.
Seeing II Antoniadi Mark V and a lot of eyepieces but impossible to resolve the Hexagon shape, only as polar circle.

Cheers
Gianluca


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azure1961p
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Re: Hexagon, possible? new [Re: contedracula]
      #5936709 - 06/23/13 04:35 PM

It IS quite the testament to modern imaging these days. I think even an 8" aperture can resolve the hex but based on my experience is slippy seeing anyway and everyone else's experiences it would seem to be seriously difficult for any scope.

Pete


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leviathan
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Reged: 11/29/11

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Re: Hexagon, possible? new [Re: azure1961p]
      #5937382 - 06/24/13 01:20 AM

So what is the theoretically minimum aperture we need to resolve shape of Hexagon visually ? David Knisely's answer will be interesting.

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contedracula
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Re: Hexagon, possible? new [Re: leviathan]
      #5937763 - 06/24/13 10:44 AM

I believe the really problem not is the only resolution but expecially the contrast.
Through my C14HD I resolve the polar zone but NOT like AP180EDT or MN106 in these last two telescopes I see very well the edge of polar Storm but never in this season the shape of the sides as hexagon.

Thanks
Gianluca


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leviathan
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Re: Hexagon, possible? new [Re: contedracula]
      #5937880 - 06/24/13 11:54 AM

The reason I'm asking because I saw it only once in 600mm telescope, and David Gray was reporting about shape of it using 400mm. Seems that something like 400mm+ is needed together with good to excellent seeing to be able to resolve it.

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contedracula
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Reged: 10/11/11

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Re: Hexagon, possible? new [Re: leviathan]
      #5937983 - 06/24/13 12:55 PM

All of us have a conscience very influenceable and especially when we look an object previously seen easily become fool by the imagination ...

I'm not referring to your specific example, but I've read in many forums a lot of "fantasy objects" observed through the Dobson 600mm

My opinion, the BIG Dobson is the BEST PERFORMER for deep sky but for Hi Res Planetary it's really a problem to do long night of observation with hi magnification at 10 feet by the ground and manual tracking

Cheers
Gianluca


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leviathan
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Re: Hexagon, possible? new [Re: contedracula]
      #5938058 - 06/24/13 01:46 PM

Gianluca, telescope I've used was not a deepsky Dobsonian, but observatory Zeiss-600 Cassegrain 100 feet above the ground under dome. And it was not the first time that I've looked through it.

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contedracula
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Reged: 10/11/11

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Re: Hexagon, possible? new [Re: leviathan]
      #5938092 - 06/24/13 02:06 PM

For this reason, I repeat, my last message was not referring about your example, to have those diameters for us, amateur astronomer, is possible only with dobson.

Thanks
Gianluca


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azure1961p
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Re: Hexagon, possible? new [Re: contedracula]
      #5938848 - 06/24/13 10:41 PM

Well yeah but -

A "deepsky Newtonian" of immense size in dob form can be beyond any resolution you'll ever get out of a Mak newt or apo or C14. There is the problem of matching the sky conditions to the mirrors potential resolution envelope but the notion that because its a dob for example instead of a cassegrain or some such holds no water. Well maybe a drop. Standing on a ladder hand guiding a dob is just not that bad!!!!

Pete
-no I don't own a huge dob but I ve seen what they can do.

Edited by azure1961p (06/24/13 10:43 PM)


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mikey cee
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Re: Hexagon, possible? new [Re: azure1961p]
      #5938990 - 06/25/13 12:19 AM

Boy if I lived near the 30th parallel I could see all kinds of stuff...without qustion!! Mike

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contedracula
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Reged: 10/11/11

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Re: Hexagon, possible? new [Re: mikey cee]
      #5939243 - 06/25/13 07:42 AM

If I buy a Ferrari or a Lamborghini I cannot expect to heat the tires on 5th av. because the road is not adequate.

If I have a Dobson that gives me a lot of resolution but the seeing will allow it once per year is better to prefer a Telescope that makes a strong contrast almost every nights because the human eye needs LIVE CONTRAST, we don't have Photoshop during observation, a large obstruction waste too much contrast.

Today the market offers more items for astrophotography better than to observers, this has allowed to sell more economic and portable instruments forgetting there are telescopes created for a specific amateur activity.

Kindly regards
Gianluca


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Achernar
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Re: Hexagon, possible? new [Re: mikey cee]
      #5939292 - 06/25/13 08:27 AM

Indeed, I routinely look at Omega Centauri from a site near Mobile Alabama. Most of the sky is accessible from the 30th parallel in either hemisphere. That would be where I would want to put a major observatory, or as close to it as possible.

Taras


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leviathan
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Re: Hexagon, possible? new [Re: contedracula]
      #5939619 - 06/25/13 12:05 PM

Quote:

If I have a Dobson that gives me a lot of resolution but the seeing will allow it once per year is better to prefer a Telescope that makes a strong contrast almost every nights because the human eye needs LIVE CONTRAST, we don't have Photoshop during observation, a large obstruction waste too much contrast.



You can make aperture mask or use lower magnifications on those nights. Anyway smaller aperture will not show planet better and brighter that bigger one.


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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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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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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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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
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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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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
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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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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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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
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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
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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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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
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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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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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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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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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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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Re: Hexagon, possible? new [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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Re: Hexagon, possible? new [Re: Chuck Hards]
      #5983742 - 07/21/13 10:11 PM

The polar hexagon is currently *just* under 4", at about 3.8 to 3.9". When near the CM a 'flat' of the hexagon is about 2" long. This is based on the current 17.1" equatorial diameter of Saturn from WinJupos, and some measurements of recent images I've taken.

So the hexagon is certainly large enough, but I think the trick is to detect how far the vertices of the hexagon project vs. what would be the edge of a hypothetical 'smooth' polar region, and of course those are only fractions of an arcsecond. But the contrast between the dark hexagon and it's brighter immediate surroundings is strong, which certainly helps. I believe this within the range of David's scope and his visual skills. Possibly even with a somewhat smaller scope in excellent conditions.


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Re: Hexagon, possible? new [Re: Chuck Hards]
      #5983830 - 07/21/13 11:19 PM

Chuck I think you are merging that central vortice with the hex. David's diagram amply shows the hexagon shape as that dark polar spot. The hex isn't within that but that is it in its entirety. Now within that in the dead center - that's another phenomenon I don't think any observer can possibly see with any scope that central vortex . Though CCD is something altogether different.

Pete

Edited by azure1961p (07/21/13 11:20 PM)


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Re: Hexagon, possible? new [Re: azure1961p]
      #5984069 - 07/22/13 07:05 AM Attachment (15 downloads)

It became evident to me a while back that some of us were talking of different things. In particular when I see a statement claiming to see the “hexagon” but not the hexagon shape: i.e. they have seen the North Polar Cap (NPC).

Over the years there has been a lot of confusion with the polar regions: e.g. a very dark S/N Polar region being described as a very large S/NPC (or Hood); particularly if the Cap-proper is not detected. In general the edges of the NPR & NPC are near latitudes +60 & +75 repspectively.

Pete, Polar Vortexes: the NPC one may well be beyond visual - being similar in size to Rhea’s shadow which is often difficult against a much lighter background than the NPC usually offers. The SPC Vortex I believe has been spotted, perhaps at least as far back as Lassell in the mid 19th century. Several, including me. have drawn dark (and sometimes light) spots centred on the S Pole: this storm being considerably larger than Titan.

Back in the 1960s-70s I have on occasion described the SPC as variegated (10” Newt.) as have others. As we can see from Cassini imagery these regions are very dynamic and perhaps on occasion the relative contrasts are more accommodating!

Anyhow we’ll not see the S. Pole for some years; but next apparitions the NPC will be increasingly better presented tho’ the planet not favourably placed for many north of the equator sadly! Also will the unusual surrounding NPR lightness endure? I have thought it already progressively duller in the later weeks of this apparition.

To avoid ambiguity each year I include a diagram adapted from one of my drawings with my end-of-apparition report to the BAA, a copy is here attached. I happen to have this to hand, being done earlier for another enquirer!

Dave.

Edited by David Gray (07/22/13 07:20 AM)


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Re: Hexagon, possible? new [Re: David Gray]
      #5984096 - 07/22/13 07:44 AM

Well, when I'm wrong, I'm wrong. I concede my error after doing a bit more research. The dark cap we see in the telescope does seem to demarcate the edge of the hexagon.

The good news is that it's not as small as my pessimistic first thoughts.

I also found this while web surfing the hexagon subject, it may be old news to some of you:

http://www.planetary.org/blogs/guest-blogs/2013/0201-fletcher-saturns-hexagon...


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Re: Hexagon, possible? new [Re: TG]
      #5984740 - 07/22/13 04:34 PM

The hexagon was a lot smaller and darker than the cap. When the air was a bit unsteady it looked like a small dent in the top. Saw it again in my C9.25 and IM715 last week. David

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idp
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Re: Hexagon, possible? new [Re: dscarpa]
      #5988027 - 07/24/13 03:57 PM

Quote:

The hexagon was a lot smaller and darker than the cap. When the air was a bit unsteady it looked like a small dent in the top. Saw it again in my C9.25 and IM715 last week. David




Uh? I don't understand, both in CCD images and drawings it clearly coincides with the NPC. Indeed, it IS the NPC that happens to have that particular shape.

David is right, we should all remember and use the good old standard nomenclature, especially visual observers. But I fear it won't happen.

By the way, David: sorry for the OT, but I noticed you sketched Encke/Keeler as a rather broad darkening of the outer edge of the "classic" Encke. That's how I happened to see it once or maybe twice with my old 8" newton (rings wide open and great seeing, to be sure). May it be just a contrast phenomenon, rather than having to do with the actual gap?

Regards,

Ivano


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Re: Hexagon, possible? new [Re: idp]
      #5989125 - 07/25/13 08:39 AM

Quote:

By the way, David: sorry for the OT, but I noticed you sketched Encke/Keeler as a rather broad darkening of the outer edge of the "classic" Encke. That's how I happened to see it once or maybe twice with my old 8" newton (rings wide open and great seeing, to be sure). May it be just a contrast phenomenon, rather than having to do with the actual gap




Encke/Keeler: my own feeling on the contrast issue is that one enhances the other to a degree. We know we have a real feature mingled with this and I suspect if there were no division the sky/ring contrast ‘interface’ would be the weaker therein. I have seen it darker and sharper than shown here but never as a thinner version of the Cassini. Touching very slightly on my Uranus in twilight thread: my finest views of the division were in twilight with near perfect seeing when Saturn was at high n. declination. Here we have the sky not a stark black against the ring edge surely minimizing/muting any contrast effects.

OT ( this not my thread of course): I never want to come across as pedantic on this. It would be a shame if the rules were to be applied so rigidly that it were to detract from the richness of discussion. It is one thing, as you have done, to go down a ‘side-alley’ of the planet in discussion as opposed to going into warp-drive to the inner part of the Solar System!

If we were to hair-split then I may well be guilty too and indeed have even expressed my concern in that regard on the recent Cassini div. thread when it diverted to apodizers!

Slyly taking it back to the hexagon (!) I think contrast is a factor there too. I have never recorded the intensity of the edge/rim of the NPC as dark (8.5) as at this apparition and feel some of this at least is down to the unusually bright NPR- surround.

Regards,
Dave.

Edited by David Gray (07/25/13 08:41 AM)


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Re: Hexagon, possible? new [Re: David Gray]
      #5991928 - 07/26/13 08:29 PM

Quote:

Touching very slightly on my Uranus in twilight thread: my finest views of the division were in twilight with near perfect seeing when Saturn was at high n. declination. Dave.




Apropos the fine seeing at twilight comment- When SL-9 hit Jupiter in '94, I noticed that the best seeing was after sunset but with a still bright sky- very blue. Many times during those observing runs, there was a brief period of exceptional stillness of the air, lasting anywhere from 10 to 30 minutes, after which the turbulence returned for several more hours. I was using a 10" f/5.6 Newtonian and the air was so still that I could run up the magnification to over 400X at times, with no degredation. I've heard it explained that after sundown, there can be a period of thermal equilibrium between the air and the ground, but it is temporary as the ground soon begins to release the thermal energy it accumulated during the day. Since then I've noticed it on other planets and the moon on many occassions. When it happens, it is extraordinary, as if the atmosphere almost disappears. Incredible sharpness for an all-too-brief period.


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