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Mars 2018-07-22

dslr imaging Maksutov planet
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#1 BQ Octantis

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Posted 22 July 2018 - 09:14 AM

I've done better. Blast this storm!

 

frames2-4.jpg

Mars 2018-07-22 12:54 UTC, 52˚ elevation

Skywatcher 180 (2700mm f/15 Cass-Mak)
Kokusai Kohki 12.5mm orthoscopic

Canon T3i Live View capture

Scale = 3.3 pixels per Airy disk

Outback Northern Territory, Australia

Seeing = 4/5, jet stream = 18 m/s

 

BQ


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#2 SpectralMike

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Posted 22 July 2018 - 03:14 PM

Cool! Hellas in the south...At least you were able to get some detail to come through .I like it!


Edited by SpectralMike, 22 July 2018 - 03:17 PM.


#3 BQ Octantis

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Posted 23 July 2018 - 03:15 AM

Cool! Hellas in the south...At least you were able to get some detail to come through .I like it!

Thanks, mate! I took another stab at it—I did a red-channel only stack and sharpened; I then used that as a luminosity channel on an unenhanced RGB stack. A higher gamma helped make the noise less obvious, too. The southern polar ice cap is a bit reddish, but I'm otherwise happier with the result. Here it is with a comparison to some sort of ground truth:

 

frame1.jpg

 

Cheers,

BQ


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#4 Ed D

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Posted 23 July 2018 - 04:53 AM

The second image is really nice.  I have been "stabbing" away at my Mars image from July 4th, learning and improving along the way.

 

Nice work!  waytogo.gif

 

Ed D


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#5 BQ Octantis

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Posted 23 July 2018 - 02:47 PM

The second image is really nice.  I have been "stabbing" away at my Mars image from July 4th, learning and improving along the way.

 

Nice work!  waytogo.gif

 

Ed D

Thanks Ed. This is my first year of processing Mars through the 7", and it's a very different beast than Jupiter or Saturn. The dust storm has only added to the challenge…

 

BQ



#6 BQ Octantis

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Posted 25 July 2018 - 03:50 AM

Ok, one more try on this one. Thanks to Brent's luminosity comments on his 23 July image, I realized I needed to severely fix my white balance before processing to get the detail in the southern polar ice cap. The blue channel was simply way too low, so I brought it up considerably. This helped immensely on the RGB align, too. My Saturn processing from the 22nd found the seeing to be much worse than advertised, too, so I was more selective in restacking Mars and did a 3-frame derotation. It didn't improve the details on the disk, but the southern polar ice cap is much nicer:

 

frames124a.jpg

 

Cheers,

BQ

 

 


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#7 HentySky

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Posted 25 July 2018 - 03:56 AM

Hi BQ, your polar cap is now looking a lot better than the earlier images.  I find if you use the Red channel for luminance then a lot of the contast on the pole is lost.



#8 BQ Octantis

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Posted 25 July 2018 - 04:23 AM

Hi BQ, your polar cap is now looking a lot better than the earlier images.  I find if you use the Red channel for luminance then a lot of the contast on the pole is lost.

Agreed! Thanks again for the hint.

 

BQ



#9 BQ Octantis

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Posted 26 July 2018 - 05:41 AM

Since the 22nd it's either been cloudy or I've been too busy to shoot, so I've spent a bit of time on trying to eek out what I can from my Mars capture from the 22nd. I had an epiphany today: my blue channel is way too compressed with daylight white balance—indeed, it covers less than half the levels of the red spectrum.

 

Screen Shot 2018-07-26 at 7.51.38 PM.png

 

This makes it the primary source of noise on the disk. I decided to try aligning the RGB histogram peaks before going headlong into sharpening to perhaps reduce this. It worked for the good contrast areas on the south pole, but not so much on the disk:

 

frames1-4.jpg

 

A look at the blue channel further illustrates the trouble with trying to expand the bit resolution by 100%:

 

blue.jpg

 

I think I might try using auto white balance this weekend—this should spread the histogram evenly across all the colors.

 

BQ

 

P.S. I got a better result on eliminating the edge rind in PS5 by removing it by channel (in a separate document, and then pasting the fix back into the RGB). I created a curved path along the center of the rind and did a simple path stroke on a new lighten layer (15 pixels 0% hardness, 15% flow); I then used layer opacity to fix the darkest spot and then used a 50 pixel brush on a layer mask to feather the lighter areas.


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