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Saturn+ASI120MM, Good Seeing&Lotsa Detail+Wjupos!!

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#126 Mitchell Duke

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Posted 03 February 2013 - 04:02 PM

Congrats Darryl!

#127 Kokatha man

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Posted 03 February 2013 - 05:16 PM

Thanks for your comments Lars, Jim and Mitchell. :)

It's a fairly long read (which of my posts isn't?!? :lol:) but for those interested here's some correspondence between myself, Mike Foulkes (BAA Saturn Section Director) and John Rogers (BAA Jupiter Section Director) wher John initially commented on Ring A's seeming transparency at certain points in my image - something I think Paul (Toxman) commented upon specifically earlier on.....initially I replied with the observation that it has been a feature of numerous imagers' Saturn images from Damian Peach down.....here's the main parts of the commentary so far...with some slight editing. :)

Mike Foulkes: "Ring A is certainly translucent. This was first demonstrated by a stellar occultation observed visually in 1917. The start faded by quite a bit but was still visible when it passed behind ring A. It returned to full brightness when it passed behind the Cassini's division. This effect was seen in subsequent occultations. And the Shadow of the Rings on the Globe can be seen through Ring C with the appropriate observing geometry.

I have seen the effect shown on your images in a number of other images.

I have had a look at a few images in the archive taken when the south face was presented to the Earth. On some images there is a slighly brighter patch on Ring A coincident to where each of the limbs would be. This gives the impression that the limb is visible through Ring A - not only in monochrome images but in some colour images as well.

On some images Cassini's division appears dark where visible, except close to one limb where this patch seems to have spilled over onto the division. This gives the impression that one limb is visible through cassini's division but not at the other.

This was not always visible on images taken by the same observer."



John: "My memory from visual obs'ns and from many images, is that Ring A is not generally transparent/ translucent. However, the absolute reference must be Cassini images, and two are attached.

As you see, Ring A was clearly translucent in one image (closeup with Ring A at bottom of field), but not in the other (taken with the sun directly behind the camera; the rainbow colours in the sun reflection must be due to the spacecraft movement between the R,G,B images).

I suppose the ring is translucent in the right conditions, but not when at lower inclination nor lower phase angle (i.e. near opposition, when the glare masks features behind). Indeed it appears weakly translucent in some amateur images, inc. Damian's best-quality ones, so there could well be some reality in the appearance on your image -- my surprise was probably over-stated.

However, it looks as though it has been enhanced in your image by processing, which is also evident in other features of the image: the 'Terby spot', and dark bands parallel to the edge of the planet and the rings, and multiple bands within the rings (inc. in images by Damian, but not by Cassini)

These are common on most observers' Saturn images, and I suppose that they are due to the very high contrast across these sharp boundaries, combined with the strong processing needed to bring out small low-contrast features on the planet."


Darryl: "Hi Mike - thanks for replying: John's response and my reply are in this email - I don't want to start any "turf wars" :) but it seems to be similar to your own response.....anything else you might feel you wish to add, please feel free to do so if you have the time..."

Darryl: "Hi John - thanks for the reply.....something to think about ths morning over tea & toast after 3 straight mornings of clouds appearing out of nowhere just after collimating rituals following 3:30am risings and setting up procedures....! :(

I thought this place (just outside of "Palmer") must've been named after somewhere in England because of the weather this morning (one of my less colourfull mutterings! :) ) but I see I'm wrong on that one!

Anyway, it sounds like another of those artefacts induced through processing that is a product of "natural" illumination parameters - my paraphrasing of your more detailed explanation, just as the "Brightside artefact/rind" is most often visible on processed Mars' images unless dealt with in post-processing, and sometimes on Jupiter too - although with Jove it usually indicates "strong" processing...as you noted for this particular Saturn image for the selfsame reasons you articulated at the end of your email.

Thanks once again and I appreciate the comments you've made here as well as those Mike has sent me also.....something to reflect upon as we sit out this little run of frustrating weather.....oh for a "cloud filter!!!"
:)

#128 wenjha

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Posted 03 February 2013 - 09:00 PM

I really have interesting to build one 14" or 16"scope this year.maybe start from the small one 14" at first :grin:

#129 Mike Phillips

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Posted 04 February 2013 - 10:09 AM

Here's a great HST animation that shows the feature's subtleness quite well.

http://youtu.be/gvptWeFPWIg

Mike

#130 lcd1080

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Posted 04 February 2013 - 12:19 PM

Thanks Mike, the interesting thing is that when one pauses the HST animation the hexagon isn't immediately obvious. Only when the animation is running or when viewing a polar projection does the hexagon "jump out" at the viewer.

Pete

#131 Mike Phillips

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Posted 04 February 2013 - 01:47 PM

Thanks Mike, the interesting thing is that when one pauses the HST animation the hexagon isn't immediately obvious. Only when the animation is running or when viewing a polar projection does the hexagon "jump out" at the viewer.

Pete


Agreed, and I'm sure there's cassini animations to back up the mighty HST's congruent assessment to ours!

#132 Kokatha man

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Posted 04 February 2013 - 04:29 PM

Looking at the blog again, it's evident to me that other parts of Saturn's cloud structure have flat segments as well. Not just the north pole. I suspect that this has already been noted and studied by the Cassini folks.
JimC


Good point Jim - we noted ourselves that the demarkations between bands displayed various segment shapes.....I joked that Pat was seeing "semi-hexes" almost everywhere! :lol:

#133 Kokatha man

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Posted 04 February 2013 - 04:35 PM

Here's a great HST animation that shows the feature's subtleness quite well.

http://youtu.be/gvptWeFPWIg

Mike


Very nice image animation Mike..!

Has me wondering what wavelength(s) this was images in..? :lol:

Used different filters with some nice seeing this morning for Saturn and expect some interesting outcomes when processing is finished...but tomorrow morning holds more promise so we'll stay till then and return home to finish of all the processing..!

It was quite something as the session ended with the scope pointing almost vertically skyward - an indication of the elevation we're starting to enjoy down here now!!! :)

#134 bunyon

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Posted 04 February 2013 - 04:51 PM

I had that skyward view of Jupiter from the Keys in December. It is, indeed, weird. In a good way. Have tomorrow.

#135 Fogboundturtle

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Posted 04 February 2013 - 05:17 PM

The camera is great but I believe the operator was greater. That's a picture I would probably never achieve in my lifetime. just simply amazing.

#136 Trevor Durity

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Posted 04 February 2013 - 08:00 PM

Awesome images!!! I just logged into the forum to see if there were any opinions on the 120 before I purchase one, and seeing your results have dispelled all fears. Gotta get me one of these! It'll be quite a step up from the ol' Toucam ;-)

Amazing work Darryl!

#137 Kokatha man

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Posted 05 February 2013 - 12:41 AM

.....it (Saturn) was at 67 degrees for our last iR run Paul: atm it hits around 68 degrees about 7am. :)

OperaterS fbt - my wife Pat is an integral half of our imaging.....we're definitely a team and I really believe this gives some crucial advantages, especially as I've done my share of solo imaging practise! :grin:

Being very particular I guess I make the final call on everything (typical male I hear Pat & all women retort!!! :shocked: :grin:) but for feedback and some timely reminders about possible alternative opinions/points, as well as a fantastic background as a retired professional gun IT "fixer" it adds up to a lot of extra advantage.....and the company sure is nice! :)

I reckon this camera is a great choice Trevor, I "moved up" imo from the Flea3 so that is saying something as far as I'm concerned.....especially because I was involved with this camera from very early in its development. :)

Took 6 sets of rgb's this morning in "goodish" seeing again, each channel for 3 sets consisting of the obligatory 7000 frames @ 50fps.

The other 3 sets were iR-rgb sets of 5000 frames per channel where we split the 420 seconds total run into 4 channels each 105 seconds.....iR742nM's show interesting extra detail with "The Hex" standing out strongly in said: maybe some real possibilities for WinJupos stacking of multiple sets this time and am starting preliminary processing right now to finish off at home in front of the pc - but we'll stay and image tomorrow morning to see what it's like.....after that it might be a bit of a rest for a week or so! :)

Our battery banks have worked miracles these last few nights and are (along with dc-dc convertors for the laptop) indispensable! :grin:

#138 Fogboundturtle

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Posted 05 February 2013 - 01:23 AM

I didn't mean any disrespect to your wife. If I could only find a significant other that share my passion, I would be a happy man.

I hope one day I will get the chance to go down under and experience the majestic southern hemisphere. Until then I can view your threads on CN.

#139 Kokatha man

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Posted 05 February 2013 - 02:20 AM

None taken brother! Just thought I should give her the credit due to her for her input on the images - good insurance also..!:question: :4 :flower: :lol:

#140 GeorgeInDallas

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Posted 30 March 2013 - 11:38 AM

Hi,

I am enjoying reviewing your excellent Saturn images, in particular your most recent post. I notice that you have included a screen shot of your collimation image in the lower left hand corner of the image on the first post of this thread. Could you please explain how you made that collimation image. Do you have a web page or forum thread that discusses your collimation technique. I am aware of Therry Legault's page on collimation, but have been frustrated by my inability to produce anything that resembles his (computer generated) collimation images. Any help or explanations would be greatly appreciated.

Thanks,
George Hall
http://georgeastro.w....com/index.html

#141 Kokatha man

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Posted 30 March 2013 - 08:10 PM

Heck George, you could've just provided a link to this thread to illustrate your questions.....it's like a "blast from the past" and looking at the main images makes me want to go and repro them again..!!! :lol:

But at its' time it was very exciting to be sure.....collimation is no "mystery art" tbh but there's a coupe of things you must do..!

First off, NEVER collimate with any so-called collimating device - they're for visual obbing at best: you need to collimate onscreen using the imaging train you'll image with naturally.....anything else will include compromises!

Naturally the need to centre the star you're using in the centre of the FOV etc is critical, but once you take the star out-of-focus on a night of reasonable seeing you should see those nice patterns that Thierry Legault demonstrates.....unfortunately seeing defficiencies create scintillation that makes it more difficult to ascertain the true nature of their state, as do heat plumes from a scope that isn't cooled sufficiently. :(

Sometimes in these circumstances (as in the pik you refer to) I do an "on the fly" capture of the diffraction rings appearance to help gauge collimation adjustments etc.....ie, a short capture of a few hundred frames that I process then & there to get the image you saw.....that particular image demonstrated that I still had to tighten the secondary screw at the 3 o'clock position in my C14 because the rings are compressed on that side most specifically in that position: I was judging with an "extra-focus" set of Diffraction Rings, if I had used an "intra-focus" setting, meaning the star was moved out of focus by moving the focus inwards from the focus position, these rings would've needed that particular screw loosened...

Contrary to some information there is nothing wrong with loosening a secondary screw on an SCT if you remember not to keep on loosening one screw indiscriminantly - you need to make compensatory tightening of the others if you loosen one more than a half a turn or so imho...

Of course, there might not have actually been a screw located at 3 o'clock to tighten, in which case it would've possibly been a screw at 9 o'clock to loosen.....or to work with screws that might've been positioned at 2 & 5 o'clock etc, etc!

Another advantage of onscreen collimating is that it is much easier for a person to collimate because all you need to do is turn the laptop screen to face you as you twiddle the collimation! :)

The collimation that night was a disappointment but at that stage we looked over our shoulders and saw a huge cloudbank racing across the sky so we just went for it then and there.....and only got that one rgb set in before total cloud-out.....so in hindsight it was a very lucky grab and the results far exceeded expectations: but you can be sure the image would've been very considerably better had we the time to finish the collimation properly that time..!!!

#142 GeorgeInDallas

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Posted 30 March 2013 - 09:52 PM

Thanks for your prompt and detailed reply.

I do collimate my 12" LX200GPS using the imaging configuration and camera (2.5x PowerMate, Flea3). Like you suggest I monitor the laptop display as I adjust the collimation knobs. I usually must have the star out of focus by a considerable amount to make it large enough to see the image from the small three step ladder that I use to reach the collimation knobs. My scope is on wheeley bars and a large field tripod. Using this technique I am never quite certain that I have the out of focus star image centered quite properly. Is the collimation image that you posted the actual size that you utilize to collimate? Do you have examples showing a "good" collimation that you could post?

When you talk about an "on the fly" capture and processing of the collimation image, do you use Registax to do the processing? Will Registax align the collimation images correctly? How many collimation images do you stack? Do you do any type of post-stacking processing?

Thanks for your help,
George Hall

#143 Timthelder

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Posted 30 March 2013 - 10:15 PM

Maybe I'm behind...(per usual) But I just thought I would say, "Nice image Daryl" via my latest S&T magazine issue.

Congrat's Mate!

Tim

#144 Kokatha man

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Posted 30 March 2013 - 10:46 PM

Thanks for your prompt and detailed reply.

I do collimate my 12" LX200GPS using the imaging configuration and camera (2.5x PowerMate, Flea3). Like you suggest I monitor the laptop display as I adjust the collimation knobs. I usually must have the star out of focus by a considerable amount to make it large enough to see the image from the small three step ladder that I use to reach the collimation knobs. My scope is on wheeley bars and a large field tripod. Using this technique I am never quite certain that I have the out of focus star image centered quite properly. Is the collimation image that you posted the actual size that you utilize to collimate? Do you have examples showing a "good" collimation that you could post?

When you talk about an "on the fly" capture and processing of the collimation image, do you use Registax to do the processing? Will Registax align the collimation images correctly? How many collimation images do you stack? Do you do any type of post-stacking processing?

Thanks for your help,
George Hall


Hi George & Tim! - Sean is sending me a copy or 2 as we don't get the US version of S&T where I live.....looking forward to seeing it. :)

George, "on the fly" means we do a quick capture and process in Registax5 (easiest) and "yes" it will align the Diffraction Rings (best to use "Centre of gravity" alignment mode.....minimal amount of wavelets applications (around 20 or so with #1 slider, that's all the post-processing necessary) and that image would be (possibly) half-scale :question:

...maybe stacking 100 or 200 out of 500-1000 frames, it doesn't take many seconds to capture that many for us.....this "on the fly" testing shouldn't really be necessary for nights of good seeing where it is easy to judge good collimation - although it is an extra check.

No examples that I can lay my hands on atm but is is important to try and keep the enlarged (out of focus) image as small as you can work with although this isn't allways feasible, but do try and keep the image as centred as possible on the screen to ensure most effective and accurate gauging of optical alignment/collimation. :)






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