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Saturn-A Good night for Ring Details, Animation

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#1 Rouzbeh

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Posted 14 August 2019 - 02:46 PM

Reprocessed data from a few weeks ago. I was lucky to come across good seeing even though transparency was below average.

 

It was one of those unexpected nights when everything worked well together.

 

The Hexagonal feature at the north pole was clear and I was very excited about the dark areas near the outer ring and wasn't sure if it was the Encke gap.

 

Blowing up the scale and comparing it to probe data I figured it must be. Also visible is the F ring in the blow-up

 

Attached Thumbnails

  • 2019-07-25-1905_6-R100-RGB-LRGB tu2 take2.jpg
  • 2019-07-25-1905_6-R derot 1847 to 1924-RED.jpg

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#2 kevinbreen

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Posted 14 August 2019 - 02:48 PM

Flipping wonderful image!


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#3 Rouzbeh

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Posted 14 August 2019 - 02:49 PM

scaling up the rings.

You can make out the F ring on the extreme right.

 

The overlay scale may be off a bit, also the angles don't match but enough to give an approx idea of where the rings are.

Attached Thumbnails

  • 2019-07-25-1905_6-R derot 1847 to 1924-Sat ring ca sm.jpg

Edited by Rouzbeh, 14 August 2019 - 02:51 PM.

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#4 JimNaySeeUm

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Posted 14 August 2019 - 02:53 PM

Dang, that is incredible, makes me want to quit trying as I do not think I will ever get an image that clear and detailed. Great job!!!
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#5 Rouzbeh

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Posted 14 August 2019 - 03:02 PM

  • I was surprised at the resolution that night.

 

Here is a comparison from a Pic Du Midi 105cm Cassegrain image posted on the Baader site (I'm using their filters).

 

https://www.baader-p...ly-17-aperture/

Attached Thumbnails

  • picdumidi.jpg

Edited by Rouzbeh, 14 August 2019 - 03:06 PM.

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#6 Tom Glenn

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Posted 14 August 2019 - 03:05 PM

Rouz, a very nice image!  I will, however, direct you to a post explaining that the F-ring is not visible from Earth, even from Hubble.  From time to time there are posts here in which people claim to have the F-ring, but it's always a result of sharpening artifacts.  You can read more about it in the other link, and look at the Hubble images, and images from Pic du Midi, but there is no F-ring visible.  Many imagers choose to get rid of the artifact by either masking or black clipping, although many people don't mind it and just leave it as is.  But it's not a real ring feature, at least not from Earth based images.  

 

https://www.cloudyni...ng-f/?p=9504033


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#7 Rouzbeh

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Posted 14 August 2019 - 03:09 PM

Animation

 

https://youtu.be/jiPTdlqu5ls

 

Some nice details near the north pole.


Edited by Rouzbeh, 14 August 2019 - 03:11 PM.

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#8 Rouzbeh

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Posted 14 August 2019 - 03:39 PM

Tom, thanks for letting me know.

 

There is definitely something on the lower right side of the outer ring. Not sure what it is? Can't be an artifact only there. I'll do some more digging.

 

Boosted the levels and Tethys and its motion is visible. Really fascinating stuff. 

 

Radius: 531 km
Orbital period: 45 hours
Gravity: 0.145 m/s²
Distance to Earth: 1.272 billion km

 

 

 

 

Attached Thumbnails

  • 2019-07-25-1905_6-R derot 1847 to 1924-Sat_lapl8_ap68_Drizzle15_AI_Dcv_70 moon T.jpg

Edited by Rouzbeh, 14 August 2019 - 03:40 PM.


#9 Tom Glenn

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Posted 14 August 2019 - 04:01 PM

Rouz, I can't say much about the peculiarities of the artifact, but from your image above (which overall nicely shows the absence of artifact!), you can tell the trajectory of the artifact is not following that of a ring feature.  The true F-ring would appear to have the greatest separation near the extremes of the ring ansae, and then almost disappear as you move away from the ansae, due to perspective.  Your feature has its origin near the ansae on the right side, and then proceeds to increase its separation from the main rings before disappearing.  That's not what any real feature would do.  

 

This sort of false ring also appears on the limb of the Moon after processing, but it also tends to occur somewhat randomly on some regions of the limb but not others.  I'm sure it comes down to the way in which the raw data reacts to the processing, with some regions more prone to generate an artifact than others. Similar to how some regions of the globe, or the main rings themselves, will react differently to the same level of sharpening.  For example, your image above shows a strong contrast separation between the C ring and B ring, but this is strongest towards the front of the rings, near where they meet the globe, and fading elsewhere .  Each part of the image behaves a bit differently.  

 

Very nice images, and the polar hexagon is looking really good!  


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#10 Rouzbeh

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Posted 14 August 2019 - 04:55 PM

Here are Tethys and Mimas.

 

There seems to be another satellite along with Tethys, don't know what that is. Tethys doesn't have its own satellite as far as I know?

 

I initially thought it was noise but a video sequence shows its orbiting Saturn.

 

 

https://youtu.be/Re4Y7sa5V4s

 

 

Attached Thumbnails

  • 2019-07-25-1905_6-R-Sat_Moons marked bright.jpg

Edited by Rouzbeh, 15 August 2019 - 06:18 AM.


#11 MatthewTKK

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Posted 14 August 2019 - 05:09 PM

Pretty much the entire image has artefacts down and right of bright features - see the arcs outside the A ring and on the edge of the B ring, as well as the "echo" of the planet limb on the C ring. That has shown up as a dot below Tethys as well. Maybe there is a reflection somewhere in your light path? or something on the optics?



#12 Rouzbeh

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Posted 14 August 2019 - 05:26 PM

I have increased the levels abnormally to show faint objects. Its not what Id do for regular images.

I do see noise specs but they don't orbit so can rule those out.

No artifacts near Mimas though. I'm not completely convinced whats next to Tethys is an artifact. Its in every frame.

Will reprocess that data again tomorrow and have a closer look at Tethys.

#13 Rouzbeh

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Posted 15 August 2019 - 06:22 AM

Did some more processing, with a lot of levels brightening and sharpening you can make out a faint circular pattern around Tethys. I concluded it's the airy disk.

 

Here's a closeup with sharpening and exaggerated levels:

 

Attached Thumbnails

  • Airy.jpg

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#14 DMach

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Posted 15 August 2019 - 06:29 AM

Possibly a collimation artefact?

 

Excellent images regardless, congrats!


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#15 Rouzbeh

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Posted 15 August 2019 - 06:34 AM

Rouz, I can't say much about the peculiarities of the artifact, but from your image above (which overall nicely shows... 

 

Overall an interesting session, always good to learn anything new. 

That Tethys shadow was really bugging me, glad I found the cause.

 

I'll most probably go for that 183 cooled cam. Might be useful with smaller pixels and perhaps when longer exposures are required. It will be beneficial when chip temps reach 50DegC.

Ill get some DIY bits to TEC cool (at least keep it under control) that 290mm chip, its quite easy.



#16 Rouzbeh

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Posted 15 August 2019 - 06:37 AM

Possibly a collimation artefact?

 

Excellent images regardless, congrats!

 

Thanks.

 

I can make out the airy disk surrounding the moon. I rarely get a perfect ringed circle around the stars also. Seeing affects it I have noticed.



#17 Rouzbeh

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Posted 15 August 2019 - 10:00 AM

Some interesting numbers:

 

C14 theoretical resolution:

Resolution (Rayleigh) 0.39 arc seconds

Resolution (Dawes) 0.33 arc seconds

 

The 2 moons:

Tethys: 10.5mag  0.159" Apparent Diameter - Actual Diameter 1,060 kilometres (660 mi)

Mimas: 13.2mag  0.06" Apparent Diameter - Actual Diameter 396 kilometres (246 mi)

 

I'm sure the atmosphere spreads the light out though and it ends up being bigger. Tethys is 7-8 pixels across, approx 0.4 arc seconds.



#18 AstroDan2015

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Posted 15 August 2019 - 08:54 PM

Hi Rouz,

 

Stunning image!


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#19 DMach

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Posted 16 August 2019 - 06:02 AM

Thanks.

 

I can make out the airy disk surrounding the moon. I rarely get a perfect ringed circle around the stars also. Seeing affects it I have noticed.

 

For sure seeing makes the Airy disk jump around, but hopefully it all evens out. I'm a huge convert to MetaGuide is fantastic for this reason - as you get closer to collimated, you can increase the stack time and average out the jumping around due to seeing, wind etc.

 

But an even Airy disk does seem to be a fragile and sensitive beast as aperture increases ... it seemed so much more robust (let alone easier to see) back when I was using a 6" SCT lol.



#20 aeroman4907

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Posted 16 August 2019 - 08:15 AM

For sure seeing makes the Airy disk jump around, but hopefully it all evens out. I'm a huge convert to MetaGuide is fantastic for this reason - as you get closer to collimated, you can increase the stack time and average out the jumping around due to seeing, wind etc.

 

But an even Airy disk does seem to be a fragile and sensitive beast as aperture increases ... it seemed so much more robust (let alone easier to see) back when I was using a 6" SCT lol.

Alas, I can't make MetaGuide see my QHY183C camera.  I've installed the necessary drivers from QHY, but the application that will throw the video to the 'web cam' just doesn't work.



#21 Rouzbeh

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Posted 16 August 2019 - 09:42 AM

Yes I used Metaguide to collimate it as best as I could. I must say those mirror locks work like a charm. Solid stainless, and hold collimation for a long time.

Although things to jump around a lot on screen at 7m FL.

 

That's a bit annoying that the 183 doesn't work with Metaguide. 

 

Thanks, Astrodan :)



#22 Kokatha man

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Posted 16 August 2019 - 07:37 PM

...a well-formed & evenly-illuminated Airy Disk through a C14 is a rare event in our experiences Rouz - full sets of even & well-illuminated diffraction rings extending from the Poisson Point outwards on a (very) slightly de-focused star is about as good as it gets 99% of the time: our final check is to come to full focus & watch everything collapse into the P.P. which should happen in a uniform fashion, where the single D.R. takes on that uniform illumination (rarely!) or something nearest to this in the form of flares that are evenly-distributed & illuminated. 


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#23 Rouzbeh

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Posted 17 August 2019 - 05:49 AM

...a well-formed & evenly-illuminated Airy Disk through a C14 is a rare event in our experiences Rouz - full sets of even & well-illuminated diffraction rings extending from the Poisson Point outwards on a (very) slightly de-focused star is about as good as it gets 99% of the time: our final check is to come to full focus & watch everything collapse into the P.P. which should happen in a uniform fashion, where the single D.R. takes on that uniform illumination (rarely!) or something nearest to this in the form of flares that are evenly-distributed & illuminated. 

Yes, I can never get it perfectly even no matter what. Stacked some frames too  and sharpened and stretched.

 

With metaguide and lots of tinkering pretty much impossible. After a point you probably do more harm than good. I took a few screenshots last time.

Attached Thumbnails

  • Metaguide collimation.png
  • 2019-05-14-1738_0-IR-coli_surface_lapl4_ap1 wv.jpg
  • 2019-05-14-1725_4-IR-coli_surface 2_lapl8_ap49 wv tu.jpg



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