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Saturn's moons in stop-go motion and a(nother) disappointing Mars

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#1 Tulloch

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Posted 11 August 2020 - 01:27 AM

Last night's forecast for zero clouds, zero wind and very low jetstream speeds all pointed to a good night's viewing. I took a few videos of Saturn and its 5 closest (significant) moons spaced around 30 minutes apart and hoped for the best. I'm pretty happy with the result shown below, you will need to click on the animation image below (150% captured size) to make it work. Since the seeing was so good I got up early with high hopes for Mars.

 

Unfortunately Mars is just not working for me at the moment, either it's the low(ish) elevation of 47* (I know), or looking right over my neighbours' rooftops, difficulty with finding something to focus on (usually just a blurry mess) or a combination of all three with the added annoyance of having to get up at stupid o'clock for the privilege. Anyway, shown below at 200% captured size is the consolation prize, it's still the best image I've managed to extract of the Red Planet so far, complete with edge rind and overblown polar ice cap.

 

Andrew

 

Equipment details: Celestron Evolution C9.25" with Tele Vue 2.5x PowerMate and ASI224MC camera. Saturn's moons processed separately and shown larger and brighter than captured.

Attached Thumbnails

  • Animation1sm150 labels_pipp_1fps.gif
  • 2020-08-10-1816_8-L-Mars_AS_F3000_l6_ap48_Driz30 Mars925FC-D r1g1b11 ps2sm200.png

Edited by Tulloch, 11 August 2020 - 01:32 AM.

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#2 troyt

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Posted 11 August 2020 - 01:34 AM

Good images Andrew, I really like the animation. waytogo.gif



#3 Foc

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Posted 11 August 2020 - 02:10 AM

Good effort. Mars has not been giving most of us a good time in Oz this year.



#4 BQ Octantis

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Posted 11 August 2020 - 03:36 AM

Very nice captures, Andrew! The seeing for your Saturns was particularly good—you clearly resolved the polar hexagon in at least a couple of the stacks. I've yet to resolve it again since 6 June. The seeing was rubbish for me last night in spite of a modest 48 m/s jet stream and a prediction of 0.8 arcsec, 4/5 seeing. I didn't bother capturing.

 

The seeing the night before was much better, but I had two families that wanted an outback sky tour (a mere 500m walk to the darkness). So naturally, I set up the 7-in for them to ogle Jupiter and Saturn (followed by the 5-in for the Carina Nebula, the Lagoon Nebula, and Omega Centauri). Unfortunately, I had to use some degreaser on my orthos for the first time once the kids were done with them!

 

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Edited by BQ Octantis, 11 August 2020 - 04:19 AM.

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#5 CPellier

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Posted 11 August 2020 - 03:41 AM

Very good Saturn indeed. Mars is not bad either although clearly less than Saturn.

To follow with your question about color balance on my Mars topic, both images look to have red in slight excess.


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#6 sunnyday

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Posted 11 August 2020 - 07:28 AM

very nice shots , thanks 



#7 dcaponeii

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Posted 11 August 2020 - 08:19 AM

Last night's forecast for zero clouds, zero wind and very low jetstream speeds all pointed to a good night's viewing. I took a few videos of Saturn and its 5 closest (significant) moons spaced around 30 minutes apart and hoped for the best. I'm pretty happy with the result shown below, you will need to click on the animation image below (150% captured size) to make it work. Since the seeing was so good I got up early with high hopes for Mars.

 

Unfortunately Mars is just not working for me at the moment, either it's the low(ish) elevation of 47* (I know), or looking right over my neighbours' rooftops, difficulty with finding something to focus on (usually just a blurry mess) or a combination of all three with the added annoyance of having to get up at stupid o'clock for the privilege. Anyway, shown below at 200% captured size is the consolation prize, it's still the best image I've managed to extract of the Red Planet so far, complete with edge rind and overblown polar ice cap.

 

Andrew

 

Equipment details: Celestron Evolution C9.25" with Tele Vue 2.5x PowerMate and ASI224MC camera. Saturn's moons processed separately and shown larger and brighter than captured.

Question:  I'm seeing much less graininess in your images as well as others when compared to the stuff I'm generating.  Is there something in post porcessing that I might be missing or is it js just still about data quality?  I suspect that I'm still missing something important after Registax.  I still know I need to sharpen less so maybe that's all of it?


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#8 Tulloch

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Posted 11 August 2020 - 05:19 PM

Thanks all for the comments and likes, I do enjoy imaging Saturn and its moons.

 

 

Very good Saturn indeed. Mars is not bad either although clearly less than Saturn.

To follow with your question about color balance on my Mars topic, both images look to have red in slight excess.

Thanks Christophe, I have sort of backed myself into a corner somewhat by insisting on some semblance of colour accuracy (or at least as close as I can), and have determined a method to obtain it (I won't bore you with the details  or here:)). So when I end up with Mars as red/orange as that, I have to accept it as being right. Now, there will be some additional red caused by the lower elevation of the planet (46 degrees vs 70 degrees for Jupiter/Saturn), but not that much. Maybe the stacking and/or sharpening process is affecting the colour balance in a non-equal way?

 

I probably should get my own Star Analyser and do the test myself, but I don't think it would work with my ASI224MC colour camera.

 

Question:  I'm seeing much less graininess in your images as well as others when compared to the stuff I'm generating.  Is there something in post porcessing that I might be missing or is it js just still about data quality?  I suspect that I'm still missing something important after Registax.  I still know I need to sharpen less so maybe that's all of it?

Yes, it's all in the post processing. I hate seeing any grain/noise in my images so I will denoise/soften/blur/whatever I have to to reduce it as much as possible, probably to the detriment of resolution. Others do not share my affliction, and are quite happy to show a degree of noise in their images that sometimes makes me recoil in horror :). But, each to their own!

 

Andrew


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#9 KiwiRay

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Posted 11 August 2020 - 05:46 PM

The Saturn is very good, and the Mars is not bad at all.  Perhaps you have backed yourself into a corner with colour, though.  It looks far too red, nothing like what I see in the eyepiece - even the white ice of the Mountains of Mitchel is orange. A colour balance in Photoshop can really improve the aesthetics of this image.  Darryl's Mars images from today aren't that much more detailed than yours, but his skill at processing has made them very pleasing to the eye anyway.  At least with Mars, letting go of some (probably unattainable) idea of objectively true colours could lead not only to nicer looking images, but more interesting ones, where subtle variation in surface colour isn't overwhelmed by a heavy layer of orange. 


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#10 Tulloch

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Posted 11 August 2020 - 06:28 PM

Thanks Ray, as I mentioned Christophe's thread, all I see in the eyepiece is an orange blurry mess, so the images I create look pretty similar smile.gif. I could be just like everybody else and manually adjust the colour balance to make something that looks good (see below for a different colour cast done manually in Registax by multiplying the Red channel by 0.85, the Green by 1.05 and the Blue by 1.25) , but it seems false to me.

 

It is interesting to note that I don't have a problem artificially brightening Saturn's moons to make them easier to see in the image, while others do not share my relaxed attitude to moon brightness and size. I justify it by saying that the moons are visible through the eyepiece anyway, and blame the dynamic range of the camera not being the same as the human eye, but it's still false.

 

Back to the colour of Mars, I'm encouraged somewhat by this article by Damian Peach, where he goes into detail about the "true" colour of Mars and how amateurs like us butcher the colour cast lol.gif .

http://www.damianpea.../marscolour.htm

 

Andrew

Attached Thumbnails

  • 2020-08-10-1816_8-L-Mars_AS_F3000_l6_ap48_Driz30 Mars925FC-D r1g1b11 ps2sm200 Regi R085G105B125.png

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#11 KiwiRay

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Posted 11 August 2020 - 06:59 PM


Back to the colour of Mars, I'm encouraged somewhat by this article by Damian Peach, where he goes into detail about the "true" colour of Mars and how amateurs like us butcher the colour cast lol.gif .

http://www.damianpea.../marscolour.htm

 

Andrew

Encouraged to persist in the quest for truth in colour?  Even Peach himself produces quite a range of colours for his images, from bright orange to almost pink. The truth might be out there, but it's apparently quite hard to find! 

 

Your colour-balanced image looks better to me, even if I know Mars probably isn't that rusty-brown colour.  Somewhere between the two might be something that's both nice to look at and close enough to accurate. 
 


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#12 Tom Glenn

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Posted 11 August 2020 - 07:20 PM

Andrew, nice images.  With regards to your thoughts on color, as you know, I've followed along in some of your other threads, and spent some time thinking more about this.  Although your calibration protocol for the ASI224mc with color charts in daylight was an impressive bit of work, I'm not sure it's particularly relevant to correctly calibrating an astro photograph.  So now I'm not sure what you're defining as "truth" in reporting.  Likely, your color corrections, while well intended to mimic daylight color accuracy, are in fact producing a "false" result as used here.  Recently, I've done some comet processing, which is really DSO style processing despite being a solar system object.  This has introduced me to a whole new world of processing, and how colors are calibrated.  The currently best recognized color calibration protocol in PixInsight is called "Photometric Color Calibration".  In this method, the software plate solves your image to place it in the correct sky location, and then samples stars in the image and balances them based upon known databases (for those exact stars).  It's not perfect, but it's the most accurate that we can do.  The results are pretty impressive, and match up fairly well with known standards, and give very different results to using an in-camera "daylight" white balance, which is what you are using.  But this only works for wide field views that can be plate solved, and include many reference stars.  For planets, we're right back to where we started.  Using Registax to "Balance RGB" probably is among the best methods out there to produce an accurate color cast, in the absence of other relevant standards.  



#13 Tulloch

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Posted 11 August 2020 - 08:19 PM

Thanks Tom, I've appreciated your thoughtful and detailed explanations on what I've been attempting to do with the images I've been getting (and I suspect that you are probably getting a little tired of telling me that it's not possible lol.gif ). The idea behind the "Photometric Color Calibration" sounds a bit like what I was trying to do with my G2V star calibration method a few months ago, which was to adjust the RGB values to be more-or-less equal for the Sun-like star. The analysis showed (or at least didn't contradict) that my method of using Wred=62, Wblue=99 and multiplying the blue channel in Registax by 1.1 produced the right colours for both the planets and the G2V calibration star. Now, there may have been more than a little confirmation bias going on in that analysis, but the results were at least consistent. Of course the planets are being illuminated by the Sun so they should be in "daylight", unlike the stars which have their own spectral characteristics. 

 

The colour balance of my Jupiter images match pretty closely the "Auto-balance" RGB settings in Registax, and they tend to match other's images of Jupiter also. Probably because of the wide colour variations and large white areas on Jupiter, Registax is able to provide a good auto-correction of the colour channels, something that is not present in other planets (especially Mars, Uranus and Neptune). This all started for me when I started taking images of the Ice Giants and wondering, how do I white balance these planets when there's nothing to balance against?

 

My key question regarding this is: If I take images using the same colour settings and with the planet at the same elevation, why should the resulting colour balance be different?

 

The only thing I can think of to answer this question is that somehow either the stacking process or the sharpening process introduce an unequal effect for the different colour channels. For instance, if the Red channel is higher than the Blue in the original image, does the sharpening push the red higher and blue lower, thus increasing the imbalance? This is something I plan to look into next.

 

I do use Registax's Colour Balance tool for looking at the overall colours of the planets, but of course the Auto-balance feature is not applicable for Mars, Neptune or Uranus (and I contend Saturn also) which is why I'm interested in a standard method. I could use the icy polar region for auto-white balancing Mars in PS, but I want to have something that is consistent. 

 

I was especially interested when Christophe posted his spectroscopic measurements of Uranus and Neptune, as these are the most definitive measurements of the "correct" colour of the planets I can imagine, the only problem is trying to then incorporate the effects of Earth's atmosphere and how that affects the overall colour balance. This is not insurmountable, but still something to consider.

 

Thanks again,

 

Andrew


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#14 Tom Glenn

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Posted 11 August 2020 - 08:59 PM

The idea behind the "Photometric Color Calibration" sounds a bit like what I was trying to do with my G2V star calibration method a few months ago, which was to adjust the RGB values to be more-or-less equal for the Sun-like star. The analysis showed (or at least didn't contradict) that my method of using Wred=62, Wblue=99 and multiplying the blue channel in Registax by 1.1 produced the right colours for both the planets and the G2V calibration star. Now, there may have been more than a little confirmation bias going on in that analysis, but the results were at least consistent. Of course the planets are being illuminated by the Sun so they should be in "daylight", unlike the stars which have their own spectral characteristics. 

The idea is the same.  Using the tool in PixInsight, the main difference is that instead of choosing a single star to calibrate on, or even several, it samples hundreds of stars (or however many are in the image).  Then it draws a line of best fit to calibrate color.  So, while still subject to all the problems we face as amateurs, it does attempt to offer something standardized.  

 

I did attempt to manually white balance some of my DSLR moon shots using the "Linear Fit" tool in Pixinsight.  You can split up an OSC color image into RGB channels, and the true raw data usually has a strong color cast.  With DSLRs it is predominately green, because of the distribution of pixels in the bayer matrix.  These are normally corrected "in camera" but doing it manually was instructive.  "Linear fit" attempts to match difference exposures, assuming that they should have similar background levels (and probably some other assumptions that I don't fully understand....much has been written about it through).  In short, linear fitting the channels and then recombining produced an accurate looking color balance, at least subjectively.  This is probably what programs like Registax already do, however, in their RGB balance tool. 


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#15 DMach

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Posted 12 August 2020 - 03:47 AM

Love that animation Andrew, congrats!


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#16 Kokatha man

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Posted 12 August 2020 - 04:37 AM

Nice animation Andrew waytogo.gif - but what can I say about colour balance?!? shrug.gif lol.gif


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